Fix obsolete comment regarding FSM truncation.

[PostgreSQL.git] / src / backend / catalog / heap.c

/*-------------------------------------------------------------------------
 *
 * heap.c
 *        code to create and destroy POSTGRES heap relations
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *        $PostgreSQL$
 *
 *
 * INTERFACE ROUTINES
 *              heap_create()                   - Create an uncataloged heap relation
 *              heap_create_with_catalog() - Create a cataloged relation
 *              heap_drop_with_catalog() - Removes named relation from catalogs
 *
 * NOTES
 *        this code taken from access/heap/create.c, which contains
 *        the old heap_create_with_catalog, amcreate, and amdestroy.
 *        those routines will soon call these routines using the function
 *        manager,
 *        just like the poorly named "NewXXX" routines do.      The
 *        "New" routines are all going to die soon, once and for all!
 *              -cim 1/13/91
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/sysattr.h"
#include "access/transam.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/heap.h"
#include "catalog/index.h"
#include "catalog/indexing.h"
#include "catalog/pg_attrdef.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_inherits.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_statistic.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_type.h"
#include "catalog/pg_type_fn.h"
#include "catalog/storage.h"
#include "commands/tablecmds.h"
#include "commands/typecmds.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/var.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_relation.h"
#include "storage/bufmgr.h"
#include "storage/freespace.h"
#include "storage/smgr.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/relcache.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/tqual.h"


static void AddNewRelationTuple(Relation pg_class_desc,
                                        Relation new_rel_desc,
                                        Oid new_rel_oid, Oid new_type_oid,
                                        Oid relowner,
                                        char relkind,
                                        Datum reloptions);
static Oid AddNewRelationType(const char *typeName,
                                   Oid typeNamespace,
                                   Oid new_rel_oid,
                                   char new_rel_kind,
                                   Oid new_array_type);
static void RelationRemoveInheritance(Oid relid);
static void StoreRelCheck(Relation rel, char *ccname, Node *expr,
                                                  bool is_local, int inhcount);
static void StoreConstraints(Relation rel, List *cooked_constraints);
static bool MergeWithExistingConstraint(Relation rel, char *ccname, Node *expr,
                                                                                bool allow_merge, bool is_local);
static void SetRelationNumChecks(Relation rel, int numchecks);
static Node *cookConstraint(ParseState *pstate,
                           Node *raw_constraint,
                           char *relname);
static List *insert_ordered_unique_oid(List *list, Oid datum);


/* ----------------------------------------------------------------
 *                              XXX UGLY HARD CODED BADNESS FOLLOWS XXX
 *
 *              these should all be moved to someplace in the lib/catalog
 *              module, if not obliterated first.
 * ----------------------------------------------------------------
 */


/*
 * Note:
 *              Should the system special case these attributes in the future?
 *              Advantage:      consume much less space in the ATTRIBUTE relation.
 *              Disadvantage:  special cases will be all over the place.
 */

static FormData_pg_attribute a1 = {
        0, {"ctid"}, TIDOID, 0, sizeof(ItemPointerData),
        SelfItemPointerAttributeNumber, 0, -1, -1,
        false, 'p', 's', true, false, false, true, 0
};

static FormData_pg_attribute a2 = {
        0, {"oid"}, OIDOID, 0, sizeof(Oid),
        ObjectIdAttributeNumber, 0, -1, -1,
        true, 'p', 'i', true, false, false, true, 0
};

static FormData_pg_attribute a3 = {
        0, {"xmin"}, XIDOID, 0, sizeof(TransactionId),
        MinTransactionIdAttributeNumber, 0, -1, -1,
        true, 'p', 'i', true, false, false, true, 0
};

static FormData_pg_attribute a4 = {
        0, {"cmin"}, CIDOID, 0, sizeof(CommandId),
        MinCommandIdAttributeNumber, 0, -1, -1,
        true, 'p', 'i', true, false, false, true, 0
};

static FormData_pg_attribute a5 = {
        0, {"xmax"}, XIDOID, 0, sizeof(TransactionId),
        MaxTransactionIdAttributeNumber, 0, -1, -1,
        true, 'p', 'i', true, false, false, true, 0
};

static FormData_pg_attribute a6 = {
        0, {"cmax"}, CIDOID, 0, sizeof(CommandId),
        MaxCommandIdAttributeNumber, 0, -1, -1,
        true, 'p', 'i', true, false, false, true, 0
};

/*
 * We decided to call this attribute "tableoid" rather than say
 * "classoid" on the basis that in the future there may be more than one
 * table of a particular class/type. In any case table is still the word
 * used in SQL.
 */
static FormData_pg_attribute a7 = {
        0, {"tableoid"}, OIDOID, 0, sizeof(Oid),
        TableOidAttributeNumber, 0, -1, -1,
        true, 'p', 'i', true, false, false, true, 0
};

static const Form_pg_attribute SysAtt[] = {&a1, &a2, &a3, &a4, &a5, &a6, &a7};

/*
 * This function returns a Form_pg_attribute pointer for a system attribute.
 * Note that we elog if the presented attno is invalid, which would only
 * happen if there's a problem upstream.
 */
Form_pg_attribute
SystemAttributeDefinition(AttrNumber attno, bool relhasoids)
{
        if (attno >= 0 || attno < -(int) lengthof(SysAtt))
                elog(ERROR, "invalid system attribute number %d", attno);
        if (attno == ObjectIdAttributeNumber && !relhasoids)
                elog(ERROR, "invalid system attribute number %d", attno);
        return SysAtt[-attno - 1];
}

/*
 * If the given name is a system attribute name, return a Form_pg_attribute
 * pointer for a prototype definition.  If not, return NULL.
 */
Form_pg_attribute
SystemAttributeByName(const char *attname, bool relhasoids)
{
        int                     j;

        for (j = 0; j < (int) lengthof(SysAtt); j++)
        {
                Form_pg_attribute att = SysAtt[j];

                if (relhasoids || att->attnum != ObjectIdAttributeNumber)
                {
                        if (strcmp(NameStr(att->attname), attname) == 0)
                                return att;
                }
        }

        return NULL;
}


/* ----------------------------------------------------------------
 *                              XXX END OF UGLY HARD CODED BADNESS XXX
 * ---------------------------------------------------------------- */


/* ----------------------------------------------------------------
 *              heap_create             - Create an uncataloged heap relation
 *
 *              Note API change: the caller must now always provide the OID
 *              to use for the relation.
 *
 *              rel->rd_rel is initialized by RelationBuildLocalRelation,
 *              and is mostly zeroes at return.
 * ----------------------------------------------------------------
 */
Relation
heap_create(const char *relname,
                        Oid relnamespace,
                        Oid reltablespace,
                        Oid relid,
                        TupleDesc tupDesc,
                        char relkind,
                        bool shared_relation,
                        bool allow_system_table_mods)
{
        bool            create_storage;
        Relation        rel;

        /* The caller must have provided an OID for the relation. */
        Assert(OidIsValid(relid));

        /*
         * sanity checks
         */
        if (!allow_system_table_mods &&
                (IsSystemNamespace(relnamespace) || IsToastNamespace(relnamespace)) &&
                IsNormalProcessingMode())
                ereport(ERROR,
                                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                                 errmsg("permission denied to create \"%s.%s\"",
                                                get_namespace_name(relnamespace), relname),
                errdetail("System catalog modifications are currently disallowed.")));

        /*
         * Decide if we need storage or not, and handle a couple other special
         * cases for particular relkinds.
         */
        switch (relkind)
        {
                case RELKIND_VIEW:
                case RELKIND_COMPOSITE_TYPE:
                        create_storage = false;

                        /*
                         * Force reltablespace to zero if the relation has no physical
                         * storage.  This is mainly just for cleanliness' sake.
                         */
                        reltablespace = InvalidOid;
                        break;
                case RELKIND_SEQUENCE:
                        create_storage = true;

                        /*
                         * Force reltablespace to zero for sequences, since we don't
                         * support moving them around into different tablespaces.
                         */
                        reltablespace = InvalidOid;
                        break;
                default:
                        create_storage = true;
                        break;
        }

        /*
         * Never allow a pg_class entry to explicitly specify the database's
         * default tablespace in reltablespace; force it to zero instead. This
         * ensures that if the database is cloned with a different default
         * tablespace, the pg_class entry will still match where CREATE DATABASE
         * will put the physically copied relation.
         *
         * Yes, this is a bit of a hack.
         */
        if (reltablespace == MyDatabaseTableSpace)
                reltablespace = InvalidOid;

        /*
         * build the relcache entry.
         */
        rel = RelationBuildLocalRelation(relname,
                                                                         relnamespace,
                                                                         tupDesc,
                                                                         relid,
                                                                         reltablespace,
                                                                         shared_relation);

        /*
         * Have the storage manager create the relation's disk file, if needed.
         *
         * We only create the main fork here, other forks will be created on
         * demand.
         */
        if (create_storage)
        {
                RelationOpenSmgr(rel);
                RelationCreateStorage(rel->rd_node, rel->rd_istemp);
        }

        return rel;
}

/* ----------------------------------------------------------------
 *              heap_create_with_catalog                - Create a cataloged relation
 *
 *              this is done in multiple steps:
 *
 *              1) CheckAttributeNamesTypes() is used to make certain the tuple
 *                 descriptor contains a valid set of attribute names and types
 *
 *              2) pg_class is opened and get_relname_relid()
 *                 performs a scan to ensure that no relation with the
 *                 same name already exists.
 *
 *              3) heap_create() is called to create the new relation on disk.
 *
 *              4) TypeCreate() is called to define a new type corresponding
 *                 to the new relation.
 *
 *              5) AddNewRelationTuple() is called to register the
 *                 relation in pg_class.
 *
 *              6) AddNewAttributeTuples() is called to register the
 *                 new relation's schema in pg_attribute.
 *
 *              7) StoreConstraints is called ()                - vadim 08/22/97
 *
 *              8) the relations are closed and the new relation's oid
 *                 is returned.
 *
 * ----------------------------------------------------------------
 */

/* --------------------------------
 *              CheckAttributeNamesTypes
 *
 *              this is used to make certain the tuple descriptor contains a
 *              valid set of attribute names and datatypes.  a problem simply
 *              generates ereport(ERROR) which aborts the current transaction.
 * --------------------------------
 */
void
CheckAttributeNamesTypes(TupleDesc tupdesc, char relkind)
{
        int                     i;
        int                     j;
        int                     natts = tupdesc->natts;

        /* Sanity check on column count */
        if (natts < 0 || natts > MaxHeapAttributeNumber)
                ereport(ERROR,
                                (errcode(ERRCODE_TOO_MANY_COLUMNS),
                                 errmsg("tables can have at most %d columns",
                                                MaxHeapAttributeNumber)));

        /*
         * first check for collision with system attribute names
         *
         * Skip this for a view or type relation, since those don't have system
         * attributes.
         */
        if (relkind != RELKIND_VIEW && relkind != RELKIND_COMPOSITE_TYPE)
        {
                for (i = 0; i < natts; i++)
                {
                        if (SystemAttributeByName(NameStr(tupdesc->attrs[i]->attname),
                                                                          tupdesc->tdhasoid) != NULL)
                                ereport(ERROR,
                                                (errcode(ERRCODE_DUPLICATE_COLUMN),
                                                 errmsg("column name \"%s\" conflicts with a system column name",
                                                                NameStr(tupdesc->attrs[i]->attname))));
                }
        }

        /*
         * next check for repeated attribute names
         */
        for (i = 1; i < natts; i++)
        {
                for (j = 0; j < i; j++)
                {
                        if (strcmp(NameStr(tupdesc->attrs[j]->attname),
                                           NameStr(tupdesc->attrs[i]->attname)) == 0)
                                ereport(ERROR,
                                                (errcode(ERRCODE_DUPLICATE_COLUMN),
                                                 errmsg("column name \"%s\" specified more than once",
                                                                NameStr(tupdesc->attrs[j]->attname))));
                }
        }

        /*
         * next check the attribute types
         */
        for (i = 0; i < natts; i++)
        {
                CheckAttributeType(NameStr(tupdesc->attrs[i]->attname),
                                                   tupdesc->attrs[i]->atttypid);
        }
}

/* --------------------------------
 *              CheckAttributeType
 *
 *              Verify that the proposed datatype of an attribute is legal.
 *              This is needed because there are types (and pseudo-types)
 *              in the catalogs that we do not support as elements of real tuples.
 * --------------------------------
 */
void
CheckAttributeType(const char *attname, Oid atttypid)
{
        char            att_typtype = get_typtype(atttypid);

        if (atttypid == UNKNOWNOID)
        {
                /*
                 * Warn user, but don't fail, if column to be created has UNKNOWN type
                 * (usually as a result of a 'retrieve into' - jolly)
                 */
                ereport(WARNING,
                                (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
                                 errmsg("column \"%s\" has type \"unknown\"", attname),
                                 errdetail("Proceeding with relation creation anyway.")));
        }
        else if (att_typtype == TYPTYPE_PSEUDO)
        {
                /*
                 * Refuse any attempt to create a pseudo-type column, except for a
                 * special hack for pg_statistic: allow ANYARRAY during initdb
                 */
                if (atttypid != ANYARRAYOID || IsUnderPostmaster)
                        ereport(ERROR,
                                        (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
                                         errmsg("column \"%s\" has pseudo-type %s",
                                                        attname, format_type_be(atttypid))));
        }
        else if (att_typtype == TYPTYPE_COMPOSITE)
        {
                /*
                 * For a composite type, recurse into its attributes.  You might think
                 * this isn't necessary, but since we allow system catalogs to break
                 * the rule, we have to guard against the case.
                 */
                Relation        relation;
                TupleDesc       tupdesc;
                int                     i;

                relation = relation_open(get_typ_typrelid(atttypid), AccessShareLock);

                tupdesc = RelationGetDescr(relation);

                for (i = 0; i < tupdesc->natts; i++)
                {
                        Form_pg_attribute attr = tupdesc->attrs[i];

                        if (attr->attisdropped)
                                continue;
                        CheckAttributeType(NameStr(attr->attname), attr->atttypid);
                }

                relation_close(relation, AccessShareLock);
        }
}

/*
 * InsertPgAttributeTuple
 *              Construct and insert a new tuple in pg_attribute.
 *
 * Caller has already opened and locked pg_attribute.  new_attribute is the
 * attribute to insert.
 *
 * indstate is the index state for CatalogIndexInsert.  It can be passed as
 * NULL, in which case we'll fetch the necessary info.  (Don't do this when
 * inserting multiple attributes, because it's a tad more expensive.)
 */
void
InsertPgAttributeTuple(Relation pg_attribute_rel,
                                           Form_pg_attribute new_attribute,
                                           CatalogIndexState indstate)
{
        Datum           values[Natts_pg_attribute];
        bool            nulls[Natts_pg_attribute];
        HeapTuple       tup;

        /* This is a tad tedious, but way cleaner than what we used to do... */
        memset(values, 0, sizeof(values));
        memset(nulls, false, sizeof(nulls));

        values[Anum_pg_attribute_attrelid - 1] = ObjectIdGetDatum(new_attribute->attrelid);
        values[Anum_pg_attribute_attname - 1] = NameGetDatum(&new_attribute->attname);
        values[Anum_pg_attribute_atttypid - 1] = ObjectIdGetDatum(new_attribute->atttypid);
        values[Anum_pg_attribute_attstattarget - 1] = Int32GetDatum(new_attribute->attstattarget);
        values[Anum_pg_attribute_attlen - 1] = Int16GetDatum(new_attribute->attlen);
        values[Anum_pg_attribute_attnum - 1] = Int16GetDatum(new_attribute->attnum);
        values[Anum_pg_attribute_attndims - 1] = Int32GetDatum(new_attribute->attndims);
        values[Anum_pg_attribute_attcacheoff - 1] = Int32GetDatum(new_attribute->attcacheoff);
        values[Anum_pg_attribute_atttypmod - 1] = Int32GetDatum(new_attribute->atttypmod);
        values[Anum_pg_attribute_attbyval - 1] = BoolGetDatum(new_attribute->attbyval);
        values[Anum_pg_attribute_attstorage - 1] = CharGetDatum(new_attribute->attstorage);
        values[Anum_pg_attribute_attalign - 1] = CharGetDatum(new_attribute->attalign);
        values[Anum_pg_attribute_attnotnull - 1] = BoolGetDatum(new_attribute->attnotnull);
        values[Anum_pg_attribute_atthasdef - 1] = BoolGetDatum(new_attribute->atthasdef);
        values[Anum_pg_attribute_attisdropped - 1] = BoolGetDatum(new_attribute->attisdropped);
        values[Anum_pg_attribute_attislocal - 1] = BoolGetDatum(new_attribute->attislocal);
        values[Anum_pg_attribute_attinhcount - 1] = Int32GetDatum(new_attribute->attinhcount);

        tup = heap_form_tuple(RelationGetDescr(pg_attribute_rel), values, nulls);

        /* finally insert the new tuple, update the indexes, and clean up */
        simple_heap_insert(pg_attribute_rel, tup);

        if (indstate != NULL)
                CatalogIndexInsert(indstate, tup);
        else
                CatalogUpdateIndexes(pg_attribute_rel, tup);

        heap_freetuple(tup);
}
/* --------------------------------
 *              AddNewAttributeTuples
 *
 *              this registers the new relation's schema by adding
 *              tuples to pg_attribute.
 * --------------------------------
 */
static void
AddNewAttributeTuples(Oid new_rel_oid,
                                          TupleDesc tupdesc,
                                          char relkind,
                                          bool oidislocal,
                                          int oidinhcount)
{
        Form_pg_attribute attr;
        int                     i;
        Relation        rel;
        CatalogIndexState indstate;
        int                     natts = tupdesc->natts;
        ObjectAddress myself,
                                referenced;

        /*
         * open pg_attribute and its indexes.
         */
        rel = heap_open(AttributeRelationId, RowExclusiveLock);

        indstate = CatalogOpenIndexes(rel);

        /*
         * First we add the user attributes.  This is also a convenient place to
         * add dependencies on their datatypes.
         */
        for (i = 0; i < natts; i++)
        {
                attr = tupdesc->attrs[i];
                /* Fill in the correct relation OID */
                attr->attrelid = new_rel_oid;
                /* Make sure these are OK, too */
                attr->attstattarget = -1;
                attr->attcacheoff = -1;

                InsertPgAttributeTuple(rel, attr, indstate);

                /* Add dependency info */
                myself.classId = RelationRelationId;
                myself.objectId = new_rel_oid;
                myself.objectSubId = i + 1;
                referenced.classId = TypeRelationId;
                referenced.objectId = attr->atttypid;
                referenced.objectSubId = 0;
                recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
        }

        /*
         * Next we add the system attributes.  Skip OID if rel has no OIDs. Skip
         * all for a view or type relation.  We don't bother with making datatype
         * dependencies here, since presumably all these types are pinned.
         */
        if (relkind != RELKIND_VIEW && relkind != RELKIND_COMPOSITE_TYPE)
        {
                for (i = 0; i < (int) lengthof(SysAtt); i++)
                {
                        FormData_pg_attribute attStruct;

                        /* skip OID where appropriate */
                        if (!tupdesc->tdhasoid &&
                                SysAtt[i]->attnum == ObjectIdAttributeNumber)
                                continue;

                        memcpy(&attStruct, (char *) SysAtt[i], sizeof(FormData_pg_attribute));

                        /* Fill in the correct relation OID in the copied tuple */
                        attStruct.attrelid = new_rel_oid;

                        /* Fill in correct inheritance info for the OID column */
                        if (attStruct.attnum == ObjectIdAttributeNumber)
                        {
                                attStruct.attislocal = oidislocal;
                                attStruct.attinhcount = oidinhcount;
                        }

                        InsertPgAttributeTuple(rel, &attStruct, indstate);
                }
        }

        /*
         * clean up
         */
        CatalogCloseIndexes(indstate);

        heap_close(rel, RowExclusiveLock);
}

/* --------------------------------
 *              InsertPgClassTuple
 *
 *              Construct and insert a new tuple in pg_class.
 *
 * Caller has already opened and locked pg_class.
 * Tuple data is taken from new_rel_desc->rd_rel, except for the
 * variable-width fields which are not present in a cached reldesc.
 * We always initialize relacl to NULL (i.e., default permissions),
 * and reloptions is set to the passed-in text array (if any).
 * --------------------------------
 */
void
InsertPgClassTuple(Relation pg_class_desc,
                                   Relation new_rel_desc,
                                   Oid new_rel_oid,
                                   Datum reloptions)
{
        Form_pg_class rd_rel = new_rel_desc->rd_rel;
        Datum           values[Natts_pg_class];
        bool            nulls[Natts_pg_class];
        HeapTuple       tup;

        /* This is a tad tedious, but way cleaner than what we used to do... */
        memset(values, 0, sizeof(values));
        memset(nulls, false, sizeof(nulls));

        values[Anum_pg_class_relname - 1] = NameGetDatum(&rd_rel->relname);
        values[Anum_pg_class_relnamespace - 1] = ObjectIdGetDatum(rd_rel->relnamespace);
        values[Anum_pg_class_reltype - 1] = ObjectIdGetDatum(rd_rel->reltype);
        values[Anum_pg_class_relowner - 1] = ObjectIdGetDatum(rd_rel->relowner);
        values[Anum_pg_class_relam - 1] = ObjectIdGetDatum(rd_rel->relam);
        values[Anum_pg_class_relfilenode - 1] = ObjectIdGetDatum(rd_rel->relfilenode);
        values[Anum_pg_class_reltablespace - 1] = ObjectIdGetDatum(rd_rel->reltablespace);
        values[Anum_pg_class_relpages - 1] = Int32GetDatum(rd_rel->relpages);
        values[Anum_pg_class_reltuples - 1] = Float4GetDatum(rd_rel->reltuples);
        values[Anum_pg_class_reltoastrelid - 1] = ObjectIdGetDatum(rd_rel->reltoastrelid);
        values[Anum_pg_class_reltoastidxid - 1] = ObjectIdGetDatum(rd_rel->reltoastidxid);
        values[Anum_pg_class_relhasindex - 1] = BoolGetDatum(rd_rel->relhasindex);
        values[Anum_pg_class_relisshared - 1] = BoolGetDatum(rd_rel->relisshared);
        values[Anum_pg_class_relkind - 1] = CharGetDatum(rd_rel->relkind);
        values[Anum_pg_class_relnatts - 1] = Int16GetDatum(rd_rel->relnatts);
        values[Anum_pg_class_relchecks - 1] = Int16GetDatum(rd_rel->relchecks);
        values[Anum_pg_class_relhasoids - 1] = BoolGetDatum(rd_rel->relhasoids);
        values[Anum_pg_class_relhaspkey - 1] = BoolGetDatum(rd_rel->relhaspkey);
        values[Anum_pg_class_relhasrules - 1] = BoolGetDatum(rd_rel->relhasrules);
        values[Anum_pg_class_relhastriggers - 1] = BoolGetDatum(rd_rel->relhastriggers);
        values[Anum_pg_class_relhassubclass - 1] = BoolGetDatum(rd_rel->relhassubclass);
        values[Anum_pg_class_relfrozenxid - 1] = TransactionIdGetDatum(rd_rel->relfrozenxid);
        /* start out with empty permissions */
        nulls[Anum_pg_class_relacl - 1] = true;
        if (reloptions != (Datum) 0)
                values[Anum_pg_class_reloptions - 1] = reloptions;
        else
                nulls[Anum_pg_class_reloptions - 1] = true;

        tup = heap_form_tuple(RelationGetDescr(pg_class_desc), values, nulls);

        /*
         * The new tuple must have the oid already chosen for the rel.  Sure would
         * be embarrassing to do this sort of thing in polite company.
         */
        HeapTupleSetOid(tup, new_rel_oid);

        /* finally insert the new tuple, update the indexes, and clean up */
        simple_heap_insert(pg_class_desc, tup);

        CatalogUpdateIndexes(pg_class_desc, tup);

        heap_freetuple(tup);
}

/* --------------------------------
 *              AddNewRelationTuple
 *
 *              this registers the new relation in the catalogs by
 *              adding a tuple to pg_class.
 * --------------------------------
 */
static void
AddNewRelationTuple(Relation pg_class_desc,
                                        Relation new_rel_desc,
                                        Oid new_rel_oid,
                                        Oid new_type_oid,
                                        Oid relowner,
                                        char relkind,
                                        Datum reloptions)
{
        Form_pg_class new_rel_reltup;

        /*
         * first we update some of the information in our uncataloged relation's
         * relation descriptor.
         */
        new_rel_reltup = new_rel_desc->rd_rel;

        switch (relkind)
        {
                case RELKIND_RELATION:
                case RELKIND_INDEX:
                case RELKIND_TOASTVALUE:
                        /* The relation is real, but as yet empty */
                        new_rel_reltup->relpages = 0;
                        new_rel_reltup->reltuples = 0;
                        break;
                case RELKIND_SEQUENCE:
                        /* Sequences always have a known size */
                        new_rel_reltup->relpages = 1;
                        new_rel_reltup->reltuples = 1;
                        break;
                default:
                        /* Views, etc, have no disk storage */
                        new_rel_reltup->relpages = 0;
                        new_rel_reltup->reltuples = 0;
                        break;
        }

        /* Initialize relfrozenxid */
        if (relkind == RELKIND_RELATION ||
                relkind == RELKIND_TOASTVALUE)
        {
                /*
                 * Initialize to the minimum XID that could put tuples in the table.
                 * We know that no xacts older than RecentXmin are still running, so
                 * that will do.
                 */
                new_rel_reltup->relfrozenxid = RecentXmin;
        }
        else
        {
                /*
                 * Other relation types will not contain XIDs, so set relfrozenxid to
                 * InvalidTransactionId.  (Note: a sequence does contain a tuple, but
                 * we force its xmin to be FrozenTransactionId always; see
                 * commands/sequence.c.)
                 */
                new_rel_reltup->relfrozenxid = InvalidTransactionId;
        }

        new_rel_reltup->relowner = relowner;
        new_rel_reltup->reltype = new_type_oid;
        new_rel_reltup->relkind = relkind;

        new_rel_desc->rd_att->tdtypeid = new_type_oid;

        /* Now build and insert the tuple */
        InsertPgClassTuple(pg_class_desc, new_rel_desc, new_rel_oid, reloptions);
}


/* --------------------------------
 *              AddNewRelationType -
 *
 *              define a composite type corresponding to the new relation
 * --------------------------------
 */
static Oid
AddNewRelationType(const char *typeName,
                                   Oid typeNamespace,
                                   Oid new_rel_oid,
                                   char new_rel_kind,
                                   Oid new_array_type)
{
        return
                TypeCreate(InvalidOid,  /* no predetermined OID */
                                   typeName,    /* type name */
                                   typeNamespace,               /* type namespace */
                                   new_rel_oid, /* relation oid */
                                   new_rel_kind,        /* relation kind */
                                   -1,                  /* internal size (varlena) */
                                   TYPTYPE_COMPOSITE,   /* type-type (composite) */
                                   TYPCATEGORY_COMPOSITE, /* type-category (ditto) */
                                   false,               /* composite types are never preferred */
                                   DEFAULT_TYPDELIM,    /* default array delimiter */
                                   F_RECORD_IN, /* input procedure */
                                   F_RECORD_OUT,        /* output procedure */
                                   F_RECORD_RECV,               /* receive procedure */
                                   F_RECORD_SEND,               /* send procedure */
                                   InvalidOid,  /* typmodin procedure - none */
                                   InvalidOid,  /* typmodout procedure - none */
                                   InvalidOid,  /* analyze procedure - default */
                                   InvalidOid,  /* array element type - irrelevant */
                                   false,               /* this is not an array type */
                                   new_array_type,              /* array type if any */
                                   InvalidOid,  /* domain base type - irrelevant */
                                   NULL,                /* default value - none */
                                   NULL,                /* default binary representation */
                                   false,               /* passed by reference */
                                   'd',                 /* alignment - must be the largest! */
                                   'x',                 /* fully TOASTable */
                                   -1,                  /* typmod */
                                   0,                   /* array dimensions for typBaseType */
                                   false);              /* Type NOT NULL */
}

/* --------------------------------
 *              heap_create_with_catalog
 *
 *              creates a new cataloged relation.  see comments above.
 * --------------------------------
 */
Oid
heap_create_with_catalog(const char *relname,
                                                 Oid relnamespace,
                                                 Oid reltablespace,
                                                 Oid relid,
                                                 Oid ownerid,
                                                 TupleDesc tupdesc,
                                                 List *cooked_constraints,
                                                 char relkind,
                                                 bool shared_relation,
                                                 bool oidislocal,
                                                 int oidinhcount,
                                                 OnCommitAction oncommit,
                                                 Datum reloptions,
                                                 bool allow_system_table_mods)
{
        Relation        pg_class_desc;
        Relation        new_rel_desc;
        Oid                     old_type_oid;
        Oid                     new_type_oid;
        Oid                     new_array_oid = InvalidOid;

        pg_class_desc = heap_open(RelationRelationId, RowExclusiveLock);

        /*
         * sanity checks
         */
        Assert(IsNormalProcessingMode() || IsBootstrapProcessingMode());

        CheckAttributeNamesTypes(tupdesc, relkind);

        if (get_relname_relid(relname, relnamespace))
                ereport(ERROR,
                                (errcode(ERRCODE_DUPLICATE_TABLE),
                                 errmsg("relation \"%s\" already exists", relname)));

        /*
         * Since we are going to create a rowtype as well, also check for
         * collision with an existing type name.  If there is one and it's an
         * autogenerated array, we can rename it out of the way; otherwise we can
         * at least give a good error message.
         */
        old_type_oid = GetSysCacheOid(TYPENAMENSP,
                                                                  CStringGetDatum(relname),
                                                                  ObjectIdGetDatum(relnamespace),
                                                                  0, 0);
        if (OidIsValid(old_type_oid))
        {
                if (!moveArrayTypeName(old_type_oid, relname, relnamespace))
                        ereport(ERROR,
                                        (errcode(ERRCODE_DUPLICATE_OBJECT),
                                         errmsg("type \"%s\" already exists", relname),
                           errhint("A relation has an associated type of the same name, "
                                           "so you must use a name that doesn't conflict "
                                           "with any existing type.")));
        }

        /*
         * Validate shared/non-shared tablespace (must check this before doing
         * GetNewRelFileNode, to prevent Assert therein)
         */
        if (shared_relation)
        {
                if (reltablespace != GLOBALTABLESPACE_OID)
                        /* elog since this is not a user-facing error */
                        elog(ERROR,
                                 "shared relations must be placed in pg_global tablespace");
        }
        else
        {
                if (reltablespace == GLOBALTABLESPACE_OID)
                        ereport(ERROR,
                                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                                         errmsg("only shared relations can be placed in pg_global tablespace")));
        }

        /*
         * Allocate an OID for the relation, unless we were told what to use.
         *
         * The OID will be the relfilenode as well, so make sure it doesn't
         * collide with either pg_class OIDs or existing physical files.
         */
        if (!OidIsValid(relid))
                relid = GetNewRelFileNode(reltablespace, shared_relation,
                                                                  pg_class_desc);

        /*
         * Create the relcache entry (mostly dummy at this point) and the physical
         * disk file.  (If we fail further down, it's the smgr's responsibility to
         * remove the disk file again.)
         */
        new_rel_desc = heap_create(relname,
                                                           relnamespace,
                                                           reltablespace,
                                                           relid,
                                                           tupdesc,
                                                           relkind,
                                                           shared_relation,
                                                           allow_system_table_mods);

        Assert(relid == RelationGetRelid(new_rel_desc));

        /*
         * Decide whether to create an array type over the relation's rowtype. We
         * do not create any array types for system catalogs (ie, those made
         * during initdb).      We create array types for regular relations, views,
         * and composite types ... but not, eg, for toast tables or sequences.
         */
        if (IsUnderPostmaster && (relkind == RELKIND_RELATION ||
                                                          relkind == RELKIND_VIEW ||
                                                          relkind == RELKIND_COMPOSITE_TYPE))
        {
                /* OK, so pre-assign a type OID for the array type */
                Relation        pg_type = heap_open(TypeRelationId, AccessShareLock);

                new_array_oid = GetNewOid(pg_type);
                heap_close(pg_type, AccessShareLock);
        }

        /*
         * Since defining a relation also defines a complex type, we add a new
         * system type corresponding to the new relation.
         *
         * NOTE: we could get a unique-index failure here, in case someone else is
         * creating the same type name in parallel but hadn't committed yet when
         * we checked for a duplicate name above.
         */
        new_type_oid = AddNewRelationType(relname,
                                                                          relnamespace,
                                                                          relid,
                                                                          relkind,
                                                                          new_array_oid);

        /*
         * Now make the array type if wanted.
         */
        if (OidIsValid(new_array_oid))
        {
                char       *relarrayname;

                relarrayname = makeArrayTypeName(relname, relnamespace);

                TypeCreate(new_array_oid,               /* force the type's OID to this */
                                   relarrayname,        /* Array type name */
                                   relnamespace,        /* Same namespace as parent */
                                   InvalidOid,  /* Not composite, no relationOid */
                                   0,                   /* relkind, also N/A here */
                                   -1,                  /* Internal size (varlena) */
                                   TYPTYPE_BASE,        /* Not composite - typelem is */
                                   TYPCATEGORY_ARRAY, /* type-category (array) */
                                   false,               /* array types are never preferred */
                                   DEFAULT_TYPDELIM,    /* default array delimiter */
                                   F_ARRAY_IN,  /* array input proc */
                                   F_ARRAY_OUT, /* array output proc */
                                   F_ARRAY_RECV,        /* array recv (bin) proc */
                                   F_ARRAY_SEND,        /* array send (bin) proc */
                                   InvalidOid,  /* typmodin procedure - none */
                                   InvalidOid,  /* typmodout procedure - none */
                                   InvalidOid,  /* analyze procedure - default */
                                   new_type_oid,        /* array element type - the rowtype */
                                   true,                /* yes, this is an array type */
                                   InvalidOid,  /* this has no array type */
                                   InvalidOid,  /* domain base type - irrelevant */
                                   NULL,                /* default value - none */
                                   NULL,                /* default binary representation */
                                   false,               /* passed by reference */
                                   'd',                 /* alignment - must be the largest! */
                                   'x',                 /* fully TOASTable */
                                   -1,                  /* typmod */
                                   0,                   /* array dimensions for typBaseType */
                                   false);              /* Type NOT NULL */

                pfree(relarrayname);
        }

        /*
         * now create an entry in pg_class for the relation.
         *
         * NOTE: we could get a unique-index failure here, in case someone else is
         * creating the same relation name in parallel but hadn't committed yet
         * when we checked for a duplicate name above.
         */
        AddNewRelationTuple(pg_class_desc,
                                                new_rel_desc,
                                                relid,
                                                new_type_oid,
                                                ownerid,
                                                relkind,
                                                reloptions);

        /*
         * now add tuples to pg_attribute for the attributes in our new relation.
         */
        AddNewAttributeTuples(relid, new_rel_desc->rd_att, relkind,
                                                  oidislocal, oidinhcount);

        /*
         * Make a dependency link to force the relation to be deleted if its
         * namespace is.  Also make a dependency link to its owner.
         *
         * For composite types, these dependencies are tracked for the pg_type
         * entry, so we needn't record them here.  Likewise, TOAST tables don't
         * need a namespace dependency (they live in a pinned namespace) nor an
         * owner dependency (they depend indirectly through the parent table).
         * Also, skip this in bootstrap mode, since we don't make dependencies
         * while bootstrapping.
         */
        if (relkind != RELKIND_COMPOSITE_TYPE &&
                relkind != RELKIND_TOASTVALUE &&
                !IsBootstrapProcessingMode())
        {
                ObjectAddress myself,
                                        referenced;

                myself.classId = RelationRelationId;
                myself.objectId = relid;
                myself.objectSubId = 0;
                referenced.classId = NamespaceRelationId;
                referenced.objectId = relnamespace;
                referenced.objectSubId = 0;
                recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);

                recordDependencyOnOwner(RelationRelationId, relid, ownerid);
        }

        /*
         * Store any supplied constraints and defaults.
         *
         * NB: this may do a CommandCounterIncrement and rebuild the relcache
         * entry, so the relation must be valid and self-consistent at this point.
         * In particular, there are not yet constraints and defaults anywhere.
         */
        StoreConstraints(new_rel_desc, cooked_constraints);

        /*
         * If there's a special on-commit action, remember it
         */
        if (oncommit != ONCOMMIT_NOOP)
                register_on_commit_action(relid, oncommit);

        /*
         * ok, the relation has been cataloged, so close our relations and return
         * the OID of the newly created relation.
         */
        heap_close(new_rel_desc, NoLock);       /* do not unlock till end of xact */
        heap_close(pg_class_desc, RowExclusiveLock);

        return relid;
}


/*
 *              RelationRemoveInheritance
 *
 * Formerly, this routine checked for child relations and aborted the
 * deletion if any were found.  Now we rely on the dependency mechanism
 * to check for or delete child relations.      By the time we get here,
 * there are no children and we need only remove any pg_inherits rows
 * linking this relation to its parent(s).
 */
static void
RelationRemoveInheritance(Oid relid)
{
        Relation        catalogRelation;
        SysScanDesc scan;
        ScanKeyData key;
        HeapTuple       tuple;

        catalogRelation = heap_open(InheritsRelationId, RowExclusiveLock);

        ScanKeyInit(&key,
                                Anum_pg_inherits_inhrelid,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(relid));

        scan = systable_beginscan(catalogRelation, InheritsRelidSeqnoIndexId, true,
                                                          SnapshotNow, 1, &key);

        while (HeapTupleIsValid(tuple = systable_getnext(scan)))
                simple_heap_delete(catalogRelation, &tuple->t_self);

        systable_endscan(scan);
        heap_close(catalogRelation, RowExclusiveLock);
}

/*
 *              DeleteRelationTuple
 *
 * Remove pg_class row for the given relid.
 *
 * Note: this is shared by relation deletion and index deletion.  It's
 * not intended for use anyplace else.
 */
void
DeleteRelationTuple(Oid relid)
{
        Relation        pg_class_desc;
        HeapTuple       tup;

        /* Grab an appropriate lock on the pg_class relation */
        pg_class_desc = heap_open(RelationRelationId, RowExclusiveLock);

        tup = SearchSysCache(RELOID,
                                                 ObjectIdGetDatum(relid),
                                                 0, 0, 0);
        if (!HeapTupleIsValid(tup))
                elog(ERROR, "cache lookup failed for relation %u", relid);

        /* delete the relation tuple from pg_class, and finish up */
        simple_heap_delete(pg_class_desc, &tup->t_self);

        ReleaseSysCache(tup);

        heap_close(pg_class_desc, RowExclusiveLock);
}

/*
 *              DeleteAttributeTuples
 *
 * Remove pg_attribute rows for the given relid.
 *
 * Note: this is shared by relation deletion and index deletion.  It's
 * not intended for use anyplace else.
 */
void
DeleteAttributeTuples(Oid relid)
{
        Relation        attrel;
        SysScanDesc scan;
        ScanKeyData key[1];
        HeapTuple       atttup;

        /* Grab an appropriate lock on the pg_attribute relation */
        attrel = heap_open(AttributeRelationId, RowExclusiveLock);

        /* Use the index to scan only attributes of the target relation */
        ScanKeyInit(&key[0],
                                Anum_pg_attribute_attrelid,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(relid));

        scan = systable_beginscan(attrel, AttributeRelidNumIndexId, true,
                                                          SnapshotNow, 1, key);

        /* Delete all the matching tuples */
        while ((atttup = systable_getnext(scan)) != NULL)
                simple_heap_delete(attrel, &atttup->t_self);

        /* Clean up after the scan */
        systable_endscan(scan);
        heap_close(attrel, RowExclusiveLock);
}

/*
 *              RemoveAttributeById
 *
 * This is the guts of ALTER TABLE DROP COLUMN: actually mark the attribute
 * deleted in pg_attribute.  We also remove pg_statistic entries for it.
 * (Everything else needed, such as getting rid of any pg_attrdef entry,
 * is handled by dependency.c.)
 */
void
RemoveAttributeById(Oid relid, AttrNumber attnum)
{
        Relation        rel;
        Relation        attr_rel;
        HeapTuple       tuple;
        Form_pg_attribute attStruct;
        char            newattname[NAMEDATALEN];

        /*
         * Grab an exclusive lock on the target table, which we will NOT release
         * until end of transaction.  (In the simple case where we are directly
         * dropping this column, AlterTableDropColumn already did this ... but
         * when cascading from a drop of some other object, we may not have any
         * lock.)
         */
        rel = relation_open(relid, AccessExclusiveLock);

        attr_rel = heap_open(AttributeRelationId, RowExclusiveLock);

        tuple = SearchSysCacheCopy(ATTNUM,
                                                           ObjectIdGetDatum(relid),
                                                           Int16GetDatum(attnum),
                                                           0, 0);
        if (!HeapTupleIsValid(tuple))           /* shouldn't happen */
                elog(ERROR, "cache lookup failed for attribute %d of relation %u",
                         attnum, relid);
        attStruct = (Form_pg_attribute) GETSTRUCT(tuple);

        if (attnum < 0)
        {
                /* System attribute (probably OID) ... just delete the row */

                simple_heap_delete(attr_rel, &tuple->t_self);
        }
        else
        {
                /* Dropping user attributes is lots harder */

                /* Mark the attribute as dropped */
                attStruct->attisdropped = true;

                /*
                 * Set the type OID to invalid.  A dropped attribute's type link
                 * cannot be relied on (once the attribute is dropped, the type might
                 * be too). Fortunately we do not need the type row --- the only
                 * really essential information is the type's typlen and typalign,
                 * which are preserved in the attribute's attlen and attalign.  We set
                 * atttypid to zero here as a means of catching code that incorrectly
                 * expects it to be valid.
                 */
                attStruct->atttypid = InvalidOid;

                /* Remove any NOT NULL constraint the column may have */
                attStruct->attnotnull = false;

                /* We don't want to keep stats for it anymore */
                attStruct->attstattarget = 0;

                /*
                 * Change the column name to something that isn't likely to conflict
                 */
                snprintf(newattname, sizeof(newattname),
                                 "........pg.dropped.%d........", attnum);
                namestrcpy(&(attStruct->attname), newattname);

                simple_heap_update(attr_rel, &tuple->t_self, tuple);

                /* keep the system catalog indexes current */
                CatalogUpdateIndexes(attr_rel, tuple);
        }

        /*
         * Because updating the pg_attribute row will trigger a relcache flush for
         * the target relation, we need not do anything else to notify other
         * backends of the change.
         */

        heap_close(attr_rel, RowExclusiveLock);

        if (attnum > 0)
                RemoveStatistics(relid, attnum);

        relation_close(rel, NoLock);
}

/*
 *              RemoveAttrDefault
 *
 * If the specified relation/attribute has a default, remove it.
 * (If no default, raise error if complain is true, else return quietly.)
 */
void
RemoveAttrDefault(Oid relid, AttrNumber attnum,
                                  DropBehavior behavior, bool complain)
{
        Relation        attrdef_rel;
        ScanKeyData scankeys[2];
        SysScanDesc scan;
        HeapTuple       tuple;
        bool            found = false;

        attrdef_rel = heap_open(AttrDefaultRelationId, RowExclusiveLock);

        ScanKeyInit(&scankeys[0],
                                Anum_pg_attrdef_adrelid,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(relid));
        ScanKeyInit(&scankeys[1],
                                Anum_pg_attrdef_adnum,
                                BTEqualStrategyNumber, F_INT2EQ,
                                Int16GetDatum(attnum));

        scan = systable_beginscan(attrdef_rel, AttrDefaultIndexId, true,
                                                          SnapshotNow, 2, scankeys);

        /* There should be at most one matching tuple, but we loop anyway */
        while (HeapTupleIsValid(tuple = systable_getnext(scan)))
        {
                ObjectAddress object;

                object.classId = AttrDefaultRelationId;
                object.objectId = HeapTupleGetOid(tuple);
                object.objectSubId = 0;

                performDeletion(&object, behavior);

                found = true;
        }

        systable_endscan(scan);
        heap_close(attrdef_rel, RowExclusiveLock);

        if (complain && !found)
                elog(ERROR, "could not find attrdef tuple for relation %u attnum %d",
                         relid, attnum);
}

/*
 *              RemoveAttrDefaultById
 *
 * Remove a pg_attrdef entry specified by OID.  This is the guts of
 * attribute-default removal.  Note it should be called via performDeletion,
 * not directly.
 */
void
RemoveAttrDefaultById(Oid attrdefId)
{
        Relation        attrdef_rel;
        Relation        attr_rel;
        Relation        myrel;
        ScanKeyData scankeys[1];
        SysScanDesc scan;
        HeapTuple       tuple;
        Oid                     myrelid;
        AttrNumber      myattnum;

        /* Grab an appropriate lock on the pg_attrdef relation */
        attrdef_rel = heap_open(AttrDefaultRelationId, RowExclusiveLock);

        /* Find the pg_attrdef tuple */
        ScanKeyInit(&scankeys[0],
                                ObjectIdAttributeNumber,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(attrdefId));

        scan = systable_beginscan(attrdef_rel, AttrDefaultOidIndexId, true,
                                                          SnapshotNow, 1, scankeys);

        tuple = systable_getnext(scan);
        if (!HeapTupleIsValid(tuple))
                elog(ERROR, "could not find tuple for attrdef %u", attrdefId);

        myrelid = ((Form_pg_attrdef) GETSTRUCT(tuple))->adrelid;
        myattnum = ((Form_pg_attrdef) GETSTRUCT(tuple))->adnum;

        /* Get an exclusive lock on the relation owning the attribute */
        myrel = relation_open(myrelid, AccessExclusiveLock);

        /* Now we can delete the pg_attrdef row */
        simple_heap_delete(attrdef_rel, &tuple->t_self);

        systable_endscan(scan);
        heap_close(attrdef_rel, RowExclusiveLock);

        /* Fix the pg_attribute row */
        attr_rel = heap_open(AttributeRelationId, RowExclusiveLock);

        tuple = SearchSysCacheCopy(ATTNUM,
                                                           ObjectIdGetDatum(myrelid),
                                                           Int16GetDatum(myattnum),
                                                           0, 0);
        if (!HeapTupleIsValid(tuple))           /* shouldn't happen */
                elog(ERROR, "cache lookup failed for attribute %d of relation %u",
                         myattnum, myrelid);

        ((Form_pg_attribute) GETSTRUCT(tuple))->atthasdef = false;

        simple_heap_update(attr_rel, &tuple->t_self, tuple);

        /* keep the system catalog indexes current */
        CatalogUpdateIndexes(attr_rel, tuple);

        /*
         * Our update of the pg_attribute row will force a relcache rebuild, so
         * there's nothing else to do here.
         */
        heap_close(attr_rel, RowExclusiveLock);

        /* Keep lock on attribute's rel until end of xact */
        relation_close(myrel, NoLock);
}

/*
 * heap_drop_with_catalog       - removes specified relation from catalogs
 *
 * Note that this routine is not responsible for dropping objects that are
 * linked to the pg_class entry via dependencies (for example, indexes and
 * constraints).  Those are deleted by the dependency-tracing logic in
 * dependency.c before control gets here.  In general, therefore, this routine
 * should never be called directly; go through performDeletion() instead.
 */
void
heap_drop_with_catalog(Oid relid)
{
        Relation        rel;

        /*
         * Open and lock the relation.
         */
        rel = relation_open(relid, AccessExclusiveLock);

        /*
         * Schedule unlinking of the relation's physical files at commit.
         */
        if (rel->rd_rel->relkind != RELKIND_VIEW &&
                rel->rd_rel->relkind != RELKIND_COMPOSITE_TYPE)
        {
                RelationDropStorage(rel);
        }

        /*
         * Close relcache entry, but *keep* AccessExclusiveLock on the relation
         * until transaction commit.  This ensures no one else will try to do
         * something with the doomed relation.
         */
        relation_close(rel, NoLock);

        /*
         * Forget any ON COMMIT action for the rel
         */
        remove_on_commit_action(relid);

        /*
         * Flush the relation from the relcache.  We want to do this before
         * starting to remove catalog entries, just to be certain that no relcache
         * entry rebuild will happen partway through.  (That should not really
         * matter, since we don't do CommandCounterIncrement here, but let's be
         * safe.)
         */
        RelationForgetRelation(relid);

        /*
         * remove inheritance information
         */
        RelationRemoveInheritance(relid);

        /*
         * delete statistics
         */
        RemoveStatistics(relid, 0);

        /*
         * delete attribute tuples
         */
        DeleteAttributeTuples(relid);

        /*
         * delete relation tuple
         */
        DeleteRelationTuple(relid);
}


/*
 * Store a default expression for column attnum of relation rel.
 */
void
StoreAttrDefault(Relation rel, AttrNumber attnum, Node *expr)
{
        char       *adbin;
        char       *adsrc;
        Relation        adrel;
        HeapTuple       tuple;
        Datum           values[4];
        static bool nulls[4] = {false, false, false, false};
        Relation        attrrel;
        HeapTuple       atttup;
        Form_pg_attribute attStruct;
        Oid                     attrdefOid;
        ObjectAddress colobject,
                                defobject;

        /*
         * Flatten expression to string form for storage.
         */
        adbin = nodeToString(expr);

        /*
         * Also deparse it to form the mostly-obsolete adsrc field.
         */
        adsrc = deparse_expression(expr,
                                                        deparse_context_for(RelationGetRelationName(rel),
                                                                                                RelationGetRelid(rel)),
                                                           false, false);

        /*
         * Make the pg_attrdef entry.
         */
        values[Anum_pg_attrdef_adrelid - 1] = RelationGetRelid(rel);
        values[Anum_pg_attrdef_adnum - 1] = attnum;
        values[Anum_pg_attrdef_adbin - 1] = CStringGetTextDatum(adbin);
        values[Anum_pg_attrdef_adsrc - 1] = CStringGetTextDatum(adsrc);

        adrel = heap_open(AttrDefaultRelationId, RowExclusiveLock);

        tuple = heap_form_tuple(adrel->rd_att, values, nulls);
        attrdefOid = simple_heap_insert(adrel, tuple);

        CatalogUpdateIndexes(adrel, tuple);

        defobject.classId = AttrDefaultRelationId;
        defobject.objectId = attrdefOid;
        defobject.objectSubId = 0;

        heap_close(adrel, RowExclusiveLock);

        /* now can free some of the stuff allocated above */
        pfree(DatumGetPointer(values[Anum_pg_attrdef_adbin - 1]));
        pfree(DatumGetPointer(values[Anum_pg_attrdef_adsrc - 1]));
        heap_freetuple(tuple);
        pfree(adbin);
        pfree(adsrc);

        /*
         * Update the pg_attribute entry for the column to show that a default
         * exists.
         */
        attrrel = heap_open(AttributeRelationId, RowExclusiveLock);
        atttup = SearchSysCacheCopy(ATTNUM,
                                                                ObjectIdGetDatum(RelationGetRelid(rel)),
                                                                Int16GetDatum(attnum),
                                                                0, 0);
        if (!HeapTupleIsValid(atttup))
                elog(ERROR, "cache lookup failed for attribute %d of relation %u",
                         attnum, RelationGetRelid(rel));
        attStruct = (Form_pg_attribute) GETSTRUCT(atttup);
        if (!attStruct->atthasdef)
        {
                attStruct->atthasdef = true;
                simple_heap_update(attrrel, &atttup->t_self, atttup);
                /* keep catalog indexes current */
                CatalogUpdateIndexes(attrrel, atttup);
        }
        heap_close(attrrel, RowExclusiveLock);
        heap_freetuple(atttup);

        /*
         * Make a dependency so that the pg_attrdef entry goes away if the column
         * (or whole table) is deleted.
         */
        colobject.classId = RelationRelationId;
        colobject.objectId = RelationGetRelid(rel);
        colobject.objectSubId = attnum;

        recordDependencyOn(&defobject, &colobject, DEPENDENCY_AUTO);

        /*
         * Record dependencies on objects used in the expression, too.
         */
        recordDependencyOnExpr(&defobject, expr, NIL, DEPENDENCY_NORMAL);
}

/*
 * Store a check-constraint expression for the given relation.
 *
 * Caller is responsible for updating the count of constraints
 * in the pg_class entry for the relation.
 */
static void
StoreRelCheck(Relation rel, char *ccname, Node *expr,
                          bool is_local, int inhcount)
{
        char       *ccbin;
        char       *ccsrc;
        List       *varList;
        int                     keycount;
        int16      *attNos;

        /*
         * Flatten expression to string form for storage.
         */
        ccbin = nodeToString(expr);

        /*
         * Also deparse it to form the mostly-obsolete consrc field.
         */
        ccsrc = deparse_expression(expr,
                                                        deparse_context_for(RelationGetRelationName(rel),
                                                                                                RelationGetRelid(rel)),
                                                           false, false);

        /*
         * Find columns of rel that are used in expr
         *
         * NB: pull_var_clause is okay here only because we don't allow subselects
         * in check constraints; it would fail to examine the contents of
         * subselects.
         */
        varList = pull_var_clause(expr, false);
        keycount = list_length(varList);

        if (keycount > 0)
        {
                ListCell   *vl;
                int                     i = 0;

                attNos = (int16 *) palloc(keycount * sizeof(int16));
                foreach(vl, varList)
                {
                        Var                *var = (Var *) lfirst(vl);
                        int                     j;

                        for (j = 0; j < i; j++)
                                if (attNos[j] == var->varattno)
                                        break;
                        if (j == i)
                                attNos[i++] = var->varattno;
                }
                keycount = i;
        }
        else
                attNos = NULL;

        /*
         * Create the Check Constraint
         */
        CreateConstraintEntry(ccname,           /* Constraint Name */
                                                  RelationGetNamespace(rel),    /* namespace */
                                                  CONSTRAINT_CHECK,             /* Constraint Type */
                                                  false,        /* Is Deferrable */
                                                  false,        /* Is Deferred */
                                                  RelationGetRelid(rel),                /* relation */
                                                  attNos,               /* attrs in the constraint */
                                                  keycount,             /* # attrs in the constraint */
                                                  InvalidOid,   /* not a domain constraint */
                                                  InvalidOid,   /* Foreign key fields */
                                                  NULL,
                                                  NULL,
                                                  NULL,
                                                  NULL,
                                                  0,
                                                  ' ',
                                                  ' ',
                                                  ' ',
                                                  InvalidOid,   /* no associated index */
                                                  expr, /* Tree form check constraint */
                                                  ccbin,        /* Binary form check constraint */
                                                  ccsrc,        /* Source form check constraint */
                                                  is_local,     /* conislocal */
                                                  inhcount); /* coninhcount */

        pfree(ccbin);
        pfree(ccsrc);
}

/*
 * Store defaults and constraints (passed as a list of CookedConstraint).
 *
 * NOTE: only pre-cooked expressions will be passed this way, which is to
 * say expressions inherited from an existing relation.  Newly parsed
 * expressions can be added later, by direct calls to StoreAttrDefault
 * and StoreRelCheck (see AddRelationNewConstraints()).
 */
static void
StoreConstraints(Relation rel, List *cooked_constraints)
{
        int                     numchecks = 0;
        ListCell   *lc;

        if (!cooked_constraints)
                return;                                 /* nothing to do */

        /*
         * Deparsing of constraint expressions will fail unless the just-created
         * pg_attribute tuples for this relation are made visible.      So, bump the
         * command counter.  CAUTION: this will cause a relcache entry rebuild.
         */
        CommandCounterIncrement();

        foreach(lc, cooked_constraints)
        {
                CookedConstraint *con = (CookedConstraint *) lfirst(lc);

                switch (con->contype)
                {
                        case CONSTR_DEFAULT:
                                StoreAttrDefault(rel, con->attnum, con->expr);
                                break;
                        case CONSTR_CHECK:
                                StoreRelCheck(rel, con->name, con->expr,
                                                          con->is_local, con->inhcount);
                                numchecks++;
                                break;
                        default:
                                elog(ERROR, "unrecognized constraint type: %d",
                                         (int) con->contype);
                }
        }

        if (numchecks > 0)
                SetRelationNumChecks(rel, numchecks);
}

/*
 * AddRelationNewConstraints
 *
 * Add new column default expressions and/or constraint check expressions
 * to an existing relation.  This is defined to do both for efficiency in
 * DefineRelation, but of course you can do just one or the other by passing
 * empty lists.
 *
 * rel: relation to be modified
 * newColDefaults: list of RawColumnDefault structures
 * newConstraints: list of Constraint nodes
 * allow_merge: TRUE if check constraints may be merged with existing ones
 * is_local: TRUE if definition is local, FALSE if it's inherited
 *
 * All entries in newColDefaults will be processed.  Entries in newConstraints
 * will be processed only if they are CONSTR_CHECK type.
 *
 * Returns a list of CookedConstraint nodes that shows the cooked form of
 * the default and constraint expressions added to the relation.
 *
 * NB: caller should have opened rel with AccessExclusiveLock, and should
 * hold that lock till end of transaction.      Also, we assume the caller has
 * done a CommandCounterIncrement if necessary to make the relation's catalog
 * tuples visible.
 */
List *
AddRelationNewConstraints(Relation rel,
                                                  List *newColDefaults,
                                                  List *newConstraints,
                                                  bool allow_merge,
                                                  bool is_local)
{
        List       *cookedConstraints = NIL;
        TupleDesc       tupleDesc;
        TupleConstr *oldconstr;
        int                     numoldchecks;
        ParseState *pstate;
        RangeTblEntry *rte;
        int                     numchecks;
        List       *checknames;
        ListCell   *cell;
        Node       *expr;
        CookedConstraint *cooked;

        /*
         * Get info about existing constraints.
         */
        tupleDesc = RelationGetDescr(rel);
        oldconstr = tupleDesc->constr;
        if (oldconstr)
                numoldchecks = oldconstr->num_check;
        else
                numoldchecks = 0;

        /*
         * Create a dummy ParseState and insert the target relation as its sole
         * rangetable entry.  We need a ParseState for transformExpr.
         */
        pstate = make_parsestate(NULL);
        rte = addRangeTableEntryForRelation(pstate,
                                                                                rel,
                                                                                NULL,
                                                                                false,
                                                                                true);
        addRTEtoQuery(pstate, rte, true, true, true);

        /*
         * Process column default expressions.
         */
        foreach(cell, newColDefaults)
        {
                RawColumnDefault *colDef = (RawColumnDefault *) lfirst(cell);
                Form_pg_attribute atp = rel->rd_att->attrs[colDef->attnum - 1];

                expr = cookDefault(pstate, colDef->raw_default,
                                                   atp->atttypid, atp->atttypmod,
                                                   NameStr(atp->attname));

                /*
                 * If the expression is just a NULL constant, we do not bother to make
                 * an explicit pg_attrdef entry, since the default behavior is
                 * equivalent.
                 *
                 * Note a nonobvious property of this test: if the column is of a
                 * domain type, what we'll get is not a bare null Const but a
                 * CoerceToDomain expr, so we will not discard the default.  This is
                 * critical because the column default needs to be retained to
                 * override any default that the domain might have.
                 */
                if (expr == NULL ||
                        (IsA(expr, Const) &&((Const *) expr)->constisnull))
                        continue;

                StoreAttrDefault(rel, colDef->attnum, expr);

                cooked = (CookedConstraint *) palloc(sizeof(CookedConstraint));
                cooked->contype = CONSTR_DEFAULT;
                cooked->name = NULL;
                cooked->attnum = colDef->attnum;
                cooked->expr = expr;
                cooked->is_local = is_local;
                cooked->inhcount = is_local ? 0 : 1;
                cookedConstraints = lappend(cookedConstraints, cooked);
        }

        /*
         * Process constraint expressions.
         */
        numchecks = numoldchecks;
        checknames = NIL;
        foreach(cell, newConstraints)
        {
                Constraint *cdef = (Constraint *) lfirst(cell);
                char       *ccname;

                if (cdef->contype != CONSTR_CHECK)
                        continue;

                if (cdef->raw_expr != NULL)
                {
                        Assert(cdef->cooked_expr == NULL);

                        /*
                         * Transform raw parsetree to executable expression, and verify
                         * it's valid as a CHECK constraint.
                         */
                        expr = cookConstraint(pstate, cdef->raw_expr,
                                                                  RelationGetRelationName(rel));
                }
                else
                {
                        Assert(cdef->cooked_expr != NULL);

                        /*
                         * Here, we assume the parser will only pass us valid CHECK
                         * expressions, so we do no particular checking.
                         */
                        expr = stringToNode(cdef->cooked_expr);
                }

                /*
                 * Check name uniqueness, or generate a name if none was given.
                 */
                if (cdef->name != NULL)
                {
                        ListCell   *cell2;

                        ccname = cdef->name;
                        /* Check against other new constraints */
                        /* Needed because we don't do CommandCounterIncrement in loop */
                        foreach(cell2, checknames)
                        {
                                if (strcmp((char *) lfirst(cell2), ccname) == 0)
                                        ereport(ERROR,
                                                        (errcode(ERRCODE_DUPLICATE_OBJECT),
                                                         errmsg("check constraint \"%s\" already exists",
                                                                        ccname)));
                        }

                        /* save name for future checks */
                        checknames = lappend(checknames, ccname);

                        /*
                         * Check against pre-existing constraints.  If we are allowed
                         * to merge with an existing constraint, there's no more to
                         * do here.  (We omit the duplicate constraint from the result,
                         * which is what ATAddCheckConstraint wants.)
                         */
                        if (MergeWithExistingConstraint(rel, ccname, expr,
                                                                                        allow_merge, is_local))
                                continue;
                }
                else
                {
                        /*
                         * When generating a name, we want to create "tab_col_check" for a
                         * column constraint and "tab_check" for a table constraint.  We
                         * no longer have any info about the syntactic positioning of the
                         * constraint phrase, so we approximate this by seeing whether the
                         * expression references more than one column.  (If the user
                         * played by the rules, the result is the same...)
                         *
                         * Note: pull_var_clause() doesn't descend into sublinks, but we
                         * eliminated those above; and anyway this only needs to be an
                         * approximate answer.
                         */
                        List       *vars;
                        char       *colname;

                        vars = pull_var_clause(expr, false);

                        /* eliminate duplicates */
                        vars = list_union(NIL, vars);

                        if (list_length(vars) == 1)
                                colname = get_attname(RelationGetRelid(rel),
                                                                          ((Var *) linitial(vars))->varattno);
                        else
                                colname = NULL;

                        ccname = ChooseConstraintName(RelationGetRelationName(rel),
                                                                                  colname,
                                                                                  "check",
                                                                                  RelationGetNamespace(rel),
                                                                                  checknames);

                        /* save name for future checks */
                        checknames = lappend(checknames, ccname);
                }

                /*
                 * OK, store it.
                 */
                StoreRelCheck(rel, ccname, expr, is_local, is_local ? 0 : 1);

                numchecks++;

                cooked = (CookedConstraint *) palloc(sizeof(CookedConstraint));
                cooked->contype = CONSTR_CHECK;
                cooked->name = ccname;
                cooked->attnum = 0;
                cooked->expr = expr;
                cooked->is_local = is_local;
                cooked->inhcount = is_local ? 0 : 1;
                cookedConstraints = lappend(cookedConstraints, cooked);
        }

        /*
         * Update the count of constraints in the relation's pg_class tuple. We do
         * this even if there was no change, in order to ensure that an SI update
         * message is sent out for the pg_class tuple, which will force other
         * backends to rebuild their relcache entries for the rel. (This is
         * critical if we added defaults but not constraints.)
         */
        SetRelationNumChecks(rel, numchecks);

        return cookedConstraints;
}

/*
 * Check for a pre-existing check constraint that conflicts with a proposed
 * new one, and either adjust its conislocal/coninhcount settings or throw
 * error as needed.
 *
 * Returns TRUE if merged (constraint is a duplicate), or FALSE if it's
 * got a so-far-unique name, or throws error if conflict.
 */
static bool
MergeWithExistingConstraint(Relation rel, char *ccname, Node *expr,
                                                        bool allow_merge, bool is_local)
{
        bool            found;
        Relation        conDesc;
        SysScanDesc conscan;
        ScanKeyData skey[2];
        HeapTuple       tup;

        /* Search for a pg_constraint entry with same name and relation */
        conDesc = heap_open(ConstraintRelationId, RowExclusiveLock);

        found = false;

        ScanKeyInit(&skey[0],
                                Anum_pg_constraint_conname,
                                BTEqualStrategyNumber, F_NAMEEQ,
                                CStringGetDatum(ccname));

        ScanKeyInit(&skey[1],
                                Anum_pg_constraint_connamespace,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(RelationGetNamespace(rel)));

        conscan = systable_beginscan(conDesc, ConstraintNameNspIndexId, true,
                                                                 SnapshotNow, 2, skey);

        while (HeapTupleIsValid(tup = systable_getnext(conscan)))
        {
                Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tup);

                if (con->conrelid == RelationGetRelid(rel))
                {
                        /* Found it.  Conflicts if not identical check constraint */
                        if (con->contype == CONSTRAINT_CHECK)
                        {
                                Datum   val;
                                bool    isnull;

                                val = fastgetattr(tup,
                                                                  Anum_pg_constraint_conbin,
                                                                  conDesc->rd_att, &isnull);
                                if (isnull)
                                        elog(ERROR, "null conbin for rel %s",
                                                 RelationGetRelationName(rel));
                                if (equal(expr, stringToNode(TextDatumGetCString(val))))
                                        found = true;
                        }
                        if (!found || !allow_merge)
                                ereport(ERROR,
                                                (errcode(ERRCODE_DUPLICATE_OBJECT),
                                errmsg("constraint \"%s\" for relation \"%s\" already exists",
                                           ccname, RelationGetRelationName(rel))));
                        /* OK to update the tuple */
                        ereport(NOTICE,
                                        (errmsg("merging constraint \"%s\" with inherited definition",
                                                        ccname)));
                        tup = heap_copytuple(tup);
                        con = (Form_pg_constraint) GETSTRUCT(tup);
                        if (is_local)
                                con->conislocal = true;
                        else
                                con->coninhcount++;
                        simple_heap_update(conDesc, &tup->t_self, tup);
                        CatalogUpdateIndexes(conDesc, tup);
                        break;
                }
        }

        systable_endscan(conscan);
        heap_close(conDesc, RowExclusiveLock);

        return found;
}

/*
 * Update the count of constraints in the relation's pg_class tuple.
 *
 * Caller had better hold exclusive lock on the relation.
 *
 * An important side effect is that a SI update message will be sent out for
 * the pg_class tuple, which will force other backends to rebuild their
 * relcache entries for the rel.  Also, this backend will rebuild its
 * own relcache entry at the next CommandCounterIncrement.
 */
static void
SetRelationNumChecks(Relation rel, int numchecks)
{
        Relation        relrel;
        HeapTuple       reltup;
        Form_pg_class relStruct;

        relrel = heap_open(RelationRelationId, RowExclusiveLock);
        reltup = SearchSysCacheCopy(RELOID,
                                                                ObjectIdGetDatum(RelationGetRelid(rel)),
                                                                0, 0, 0);
        if (!HeapTupleIsValid(reltup))
                elog(ERROR, "cache lookup failed for relation %u",
                         RelationGetRelid(rel));
        relStruct = (Form_pg_class) GETSTRUCT(reltup);

        if (relStruct->relchecks != numchecks)
        {
                relStruct->relchecks = numchecks;

                simple_heap_update(relrel, &reltup->t_self, reltup);

                /* keep catalog indexes current */
                CatalogUpdateIndexes(relrel, reltup);
        }
        else
        {
                /* Skip the disk update, but force relcache inval anyway */
                CacheInvalidateRelcache(rel);
        }

        heap_freetuple(reltup);
        heap_close(relrel, RowExclusiveLock);
}

/*
 * Take a raw default and convert it to a cooked format ready for
 * storage.
 *
 * Parse state should be set up to recognize any vars that might appear
 * in the expression.  (Even though we plan to reject vars, it's more
 * user-friendly to give the correct error message than "unknown var".)
 *
 * If atttypid is not InvalidOid, coerce the expression to the specified
 * type (and typmod atttypmod).   attname is only needed in this case:
 * it is used in the error message, if any.
 */
Node *
cookDefault(ParseState *pstate,
                        Node *raw_default,
                        Oid atttypid,
                        int32 atttypmod,
                        char *attname)
{
        Node       *expr;

        Assert(raw_default != NULL);

        /*
         * Transform raw parsetree to executable expression.
         */
        expr = transformExpr(pstate, raw_default);

        /*
         * Make sure default expr does not refer to any vars.
         */
        if (contain_var_clause(expr))
                ereport(ERROR,
                                (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
                          errmsg("cannot use column references in default expression")));

        /*
         * It can't return a set either.
         */
        if (expression_returns_set(expr))
                ereport(ERROR,
                                (errcode(ERRCODE_DATATYPE_MISMATCH),
                                 errmsg("default expression must not return a set")));

        /*
         * No subplans or aggregates, either...
         */
        if (pstate->p_hasSubLinks)
                ereport(ERROR,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("cannot use subquery in default expression")));
        if (pstate->p_hasAggs)
                ereport(ERROR,
                                (errcode(ERRCODE_GROUPING_ERROR),
                         errmsg("cannot use aggregate function in default expression")));

        /*
         * Coerce the expression to the correct type and typmod, if given. This
         * should match the parser's processing of non-defaulted expressions ---
         * see transformAssignedExpr().
         */
        if (OidIsValid(atttypid))
        {
                Oid                     type_id = exprType(expr);

                expr = coerce_to_target_type(pstate, expr, type_id,
                                                                         atttypid, atttypmod,
                                                                         COERCION_ASSIGNMENT,
                                                                         COERCE_IMPLICIT_CAST,
                                                                         -1);
                if (expr == NULL)
                        ereport(ERROR,
                                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                                         errmsg("column \"%s\" is of type %s"
                                                        " but default expression is of type %s",
                                                        attname,
                                                        format_type_be(atttypid),
                                                        format_type_be(type_id)),
                           errhint("You will need to rewrite or cast the expression.")));
        }

        return expr;
}

/*
 * Take a raw CHECK constraint expression and convert it to a cooked format
 * ready for storage.
 *
 * Parse state must be set up to recognize any vars that might appear
 * in the expression.
 */
static Node *
cookConstraint(ParseState *pstate,
                           Node *raw_constraint,
                           char *relname)
{
        Node       *expr;

        /*
         * Transform raw parsetree to executable expression.
         */
        expr = transformExpr(pstate, raw_constraint);

        /*
         * Make sure it yields a boolean result.
         */
        expr = coerce_to_boolean(pstate, expr, "CHECK");

        /*
         * Make sure no outside relations are referred to.
         */
        if (list_length(pstate->p_rtable) != 1)
                ereport(ERROR,
                                (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
                                 errmsg("only table \"%s\" can be referenced in check constraint",
                                                relname)));

        /*
         * No subplans or aggregates, either...
         */
        if (pstate->p_hasSubLinks)
                ereport(ERROR,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("cannot use subquery in check constraint")));
        if (pstate->p_hasAggs)
                ereport(ERROR,
                                (errcode(ERRCODE_GROUPING_ERROR),
                                 errmsg("cannot use aggregate function in check constraint")));

        return expr;
}


/*
 * RemoveStatistics --- remove entries in pg_statistic for a rel or column
 *
 * If attnum is zero, remove all entries for rel; else remove only the one
 * for that column.
 */
void
RemoveStatistics(Oid relid, AttrNumber attnum)
{
        Relation        pgstatistic;
        SysScanDesc scan;
        ScanKeyData key[2];
        int                     nkeys;
        HeapTuple       tuple;

        pgstatistic = heap_open(StatisticRelationId, RowExclusiveLock);

        ScanKeyInit(&key[0],
                                Anum_pg_statistic_starelid,
                                BTEqualStrategyNumber, F_OIDEQ,
                                ObjectIdGetDatum(relid));

        if (attnum == 0)
                nkeys = 1;
        else
        {
                ScanKeyInit(&key[1],
                                        Anum_pg_statistic_staattnum,
                                        BTEqualStrategyNumber, F_INT2EQ,
                                        Int16GetDatum(attnum));
                nkeys = 2;
        }

        scan = systable_beginscan(pgstatistic, StatisticRelidAttnumIndexId, true,
                                                          SnapshotNow, nkeys, key);

        while (HeapTupleIsValid(tuple = systable_getnext(scan)))
                simple_heap_delete(pgstatistic, &tuple->t_self);

        systable_endscan(scan);

        heap_close(pgstatistic, RowExclusiveLock);
}


/*
 * RelationTruncateIndexes - truncate all indexes associated
 * with the heap relation to zero tuples.
 *
 * The routine will truncate and then reconstruct the indexes on
 * the specified relation.      Caller must hold exclusive lock on rel.
 */
static void
RelationTruncateIndexes(Relation heapRelation)
{
        ListCell   *indlist;

        /* Ask the relcache to produce a list of the indexes of the rel */
        foreach(indlist, RelationGetIndexList(heapRelation))
        {
                Oid                     indexId = lfirst_oid(indlist);
                Relation        currentIndex;
                IndexInfo  *indexInfo;

                /* Open the index relation; use exclusive lock, just to be sure */
                currentIndex = index_open(indexId, AccessExclusiveLock);

                /* Fetch info needed for index_build */
                indexInfo = BuildIndexInfo(currentIndex);

                /*
                 * Now truncate the actual file (and discard buffers).
                 */
                RelationTruncate(currentIndex, 0);

                /* Initialize the index and rebuild */
                /* Note: we do not need to re-establish pkey setting */
                index_build(heapRelation, currentIndex, indexInfo, false);

                /* We're done with this index */
                index_close(currentIndex, NoLock);
        }
}

/*
 *       heap_truncate
 *
 *       This routine deletes all data within all the specified relations.
 *
 * This is not transaction-safe!  There is another, transaction-safe
 * implementation in commands/tablecmds.c.      We now use this only for
 * ON COMMIT truncation of temporary tables, where it doesn't matter.
 */
void
heap_truncate(List *relids)
{
        List       *relations = NIL;
        ListCell   *cell;

        /* Open relations for processing, and grab exclusive access on each */
        foreach(cell, relids)
        {
                Oid                     rid = lfirst_oid(cell);
                Relation        rel;
                Oid                     toastrelid;

                rel = heap_open(rid, AccessExclusiveLock);
                relations = lappend(relations, rel);

                /* If there is a toast table, add it to the list too */
                toastrelid = rel->rd_rel->reltoastrelid;
                if (OidIsValid(toastrelid))
                {
                        rel = heap_open(toastrelid, AccessExclusiveLock);
                        relations = lappend(relations, rel);
                }
        }

        /* Don't allow truncate on tables that are referenced by foreign keys */
        heap_truncate_check_FKs(relations, true);

        /* OK to do it */
        foreach(cell, relations)
        {
                Relation        rel = lfirst(cell);

                /* Truncate the actual file (and discard buffers) */
                RelationTruncate(rel, 0);

                /* If this relation has indexes, truncate the indexes too */
                RelationTruncateIndexes(rel);

                /*
                 * Close the relation, but keep exclusive lock on it until commit.
                 */
                heap_close(rel, NoLock);
        }
}

/*
 * heap_truncate_check_FKs
 *              Check for foreign keys referencing a list of relations that
 *              are to be truncated, and raise error if there are any
 *
 * We disallow such FKs (except self-referential ones) since the whole point
 * of TRUNCATE is to not scan the individual rows to be thrown away.
 *
 * This is split out so it can be shared by both implementations of truncate.
 * Caller should already hold a suitable lock on the relations.
 *
 * tempTables is only used to select an appropriate error message.
 */
void
heap_truncate_check_FKs(List *relations, bool tempTables)
{
        List       *oids = NIL;
        List       *dependents;
        ListCell   *cell;

        /*
         * Build a list of OIDs of the interesting relations.
         *
         * If a relation has no triggers, then it can neither have FKs nor be
         * referenced by a FK from another table, so we can ignore it.
         */
        foreach(cell, relations)
        {
                Relation        rel = lfirst(cell);

                if (rel->rd_rel->relhastriggers)
                        oids = lappend_oid(oids, RelationGetRelid(rel));
        }

        /*
         * Fast path: if no relation has triggers, none has FKs either.
         */
        if (oids == NIL)
                return;

        /*
         * Otherwise, must scan pg_constraint.  We make one pass with all the
         * relations considered; if this finds nothing, then all is well.
         */
        dependents = heap_truncate_find_FKs(oids);
        if (dependents == NIL)
                return;

        /*
         * Otherwise we repeat the scan once per relation to identify a particular
         * pair of relations to complain about.  This is pretty slow, but
         * performance shouldn't matter much in a failure path.  The reason for
         * doing things this way is to ensure that the message produced is not
         * dependent on chance row locations within pg_constraint.
         */
        foreach(cell, oids)
        {
                Oid                     relid = lfirst_oid(cell);
                ListCell   *cell2;

                dependents = heap_truncate_find_FKs(list_make1_oid(relid));

                foreach(cell2, dependents)
                {
                        Oid                     relid2 = lfirst_oid(cell2);

                        if (!list_member_oid(oids, relid2))
                        {
                                char       *relname = get_rel_name(relid);
                                char       *relname2 = get_rel_name(relid2);

                                if (tempTables)
                                        ereport(ERROR,
                                                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                                         errmsg("unsupported ON COMMIT and foreign key combination"),
                                                         errdetail("Table \"%s\" references \"%s\", but they do not have the same ON COMMIT setting.",
                                                                           relname2, relname)));
                                else
                                        ereport(ERROR,
                                                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                                         errmsg("cannot truncate a table referenced in a foreign key constraint"),
                                                         errdetail("Table \"%s\" references \"%s\".",
                                                                           relname2, relname),
                                                   errhint("Truncate table \"%s\" at the same time, "
                                                                   "or use TRUNCATE ... CASCADE.",
                                                                   relname2)));
                        }
                }
        }
}

/*
 * heap_truncate_find_FKs
 *              Find relations having foreign keys referencing any of the given rels
 *
 * Input and result are both lists of relation OIDs.  The result contains
 * no duplicates, does *not* include any rels that were already in the input
 * list, and is sorted in OID order.  (The last property is enforced mainly
 * to guarantee consistent behavior in the regression tests; we don't want
 * behavior to change depending on chance locations of rows in pg_constraint.)
 *
 * Note: caller should already have appropriate lock on all rels mentioned
 * in relationIds.      Since adding or dropping an FK requires exclusive lock
 * on both rels, this ensures that the answer will be stable.
 */
List *
heap_truncate_find_FKs(List *relationIds)
{
        List       *result = NIL;
        Relation        fkeyRel;
        SysScanDesc fkeyScan;
        HeapTuple       tuple;

        /*
         * Must scan pg_constraint.  Right now, it is a seqscan because there is
         * no available index on confrelid.
         */
        fkeyRel = heap_open(ConstraintRelationId, AccessShareLock);

        fkeyScan = systable_beginscan(fkeyRel, InvalidOid, false,
                                                                  SnapshotNow, 0, NULL);

        while (HeapTupleIsValid(tuple = systable_getnext(fkeyScan)))
        {
                Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tuple);

                /* Not a foreign key */
                if (con->contype != CONSTRAINT_FOREIGN)
                        continue;

                /* Not referencing one of our list of tables */
                if (!list_member_oid(relationIds, con->confrelid))
                        continue;

                /* Add referencer unless already in input or result list */
                if (!list_member_oid(relationIds, con->conrelid))
                        result = insert_ordered_unique_oid(result, con->conrelid);
        }

        systable_endscan(fkeyScan);
        heap_close(fkeyRel, AccessShareLock);

        return result;
}

/*
 * insert_ordered_unique_oid
 *              Insert a new Oid into a sorted list of Oids, preserving ordering,
 *              and eliminating duplicates
 *
 * Building the ordered list this way is O(N^2), but with a pretty small
 * constant, so for the number of entries we expect it will probably be
 * faster than trying to apply qsort().  It seems unlikely someone would be
 * trying to truncate a table with thousands of dependent tables ...
 */
static List *
insert_ordered_unique_oid(List *list, Oid datum)
{
        ListCell   *prev;

        /* Does the datum belong at the front? */
        if (list == NIL || datum < linitial_oid(list))
                return lcons_oid(datum, list);
        /* Does it match the first entry? */
        if (datum == linitial_oid(list))
                return list;                    /* duplicate, so don't insert */
        /* No, so find the entry it belongs after */
        prev = list_head(list);
        for (;;)
        {
                ListCell   *curr = lnext(prev);

                if (curr == NULL || datum < lfirst_oid(curr))
                        break;                          /* it belongs after 'prev', before 'curr' */

                if (datum == lfirst_oid(curr))
                        return list;            /* duplicate, so don't insert */

                prev = curr;
        }
        /* Insert datum into list after 'prev' */
        lappend_cell_oid(list, prev, datum);
        return list;
}