Fix oversight in previous error-reporting patch; mustn't pfree path string

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

/*-------------------------------------------------------------------------
 *
 * catalog.c
 *              routines concerned with catalog naming conventions and other
 *              bits of hard-wired knowledge
 *
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *        $PostgreSQL$
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <fcntl.h>
#include <unistd.h>

#include "access/genam.h"
#include "access/sysattr.h"
#include "access/transam.h"
#include "catalog/catalog.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_auth_members.h"
#include "catalog/pg_authid.h"
#include "catalog/pg_database.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_pltemplate.h"
#include "catalog/pg_shdepend.h"
#include "catalog/pg_shdescription.h"
#include "catalog/pg_tablespace.h"
#include "catalog/toasting.h"
#include "miscadmin.h"
#include "storage/fd.h"
#include "utils/fmgroids.h"
#include "utils/rel.h"
#include "utils/tqual.h"


#define OIDCHARS                10                      /* max chars printed by %u */
#define FORKNAMECHARS   4                       /* max chars for a fork name */

/*
 * Lookup table of fork name by fork number.
 *
 * If you add a new entry, remember to update the errhint below, and the
 * documentation for pg_relation_size(). Also keep FORKNAMECHARS above
 * up-to-date.
 */
const char *forkNames[] = {
        "main", /* MAIN_FORKNUM */
        "fsm"   /* FSM_FORKNUM */
};

/*
 * forkname_to_number - look up fork number by name
 */
ForkNumber
forkname_to_number(char *forkName)
{
        ForkNumber forkNum;

        for (forkNum = 0; forkNum <= MAX_FORKNUM; forkNum++)
                if (strcmp(forkNames[forkNum], forkName) == 0)
                        return forkNum;

        ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("invalid fork name"),
                         errhint("Valid fork names are 'main' and 'fsm'")));
        return InvalidForkNumber; /* keep compiler quiet */
}

/*
 * relpath                      - construct path to a relation's file
 *
 * Result is a palloc'd string.
 */
char *
relpath(RelFileNode rnode, ForkNumber forknum)
{
        int                     pathlen;
        char       *path;

        if (rnode.spcNode == GLOBALTABLESPACE_OID)
        {
                /* Shared system relations live in {datadir}/global */
                Assert(rnode.dbNode == 0);
                pathlen = 7 + OIDCHARS + 1 + FORKNAMECHARS + 1;
                path = (char *) palloc(pathlen);
                if (forknum != MAIN_FORKNUM)
                        snprintf(path, pathlen, "global/%u_%s",
                                         rnode.relNode, forkNames[forknum]);
                else
                        snprintf(path, pathlen, "global/%u", rnode.relNode);
        }
        else if (rnode.spcNode == DEFAULTTABLESPACE_OID)
        {
                /* The default tablespace is {datadir}/base */
                pathlen = 5 + OIDCHARS + 1 + OIDCHARS + 1 + FORKNAMECHARS + 1;
                path = (char *) palloc(pathlen);
                if (forknum != MAIN_FORKNUM)
                        snprintf(path, pathlen, "base/%u/%u_%s",
                                         rnode.dbNode, rnode.relNode, forkNames[forknum]);
                else
                        snprintf(path, pathlen, "base/%u/%u",
                                         rnode.dbNode, rnode.relNode);
        }
        else
        {
                /* All other tablespaces are accessed via symlinks */
                pathlen = 10 + OIDCHARS + 1 + OIDCHARS + 1 + OIDCHARS + 1
                        + FORKNAMECHARS + 1;
                path = (char *) palloc(pathlen);
                if (forknum != MAIN_FORKNUM)
                        snprintf(path, pathlen, "pg_tblspc/%u/%u/%u_%s",
                                         rnode.spcNode, rnode.dbNode, rnode.relNode,
                                         forkNames[forknum]);
                else
                        snprintf(path, pathlen, "pg_tblspc/%u/%u/%u",
                                         rnode.spcNode, rnode.dbNode, rnode.relNode);
        }
        return path;
}

/*
 * GetDatabasePath                      - construct path to a database dir
 *
 * Result is a palloc'd string.
 *
 * XXX this must agree with relpath()!
 */
char *
GetDatabasePath(Oid dbNode, Oid spcNode)
{
        int                     pathlen;
        char       *path;

        if (spcNode == GLOBALTABLESPACE_OID)
        {
                /* Shared system relations live in {datadir}/global */
                Assert(dbNode == 0);
                pathlen = 6 + 1;
                path = (char *) palloc(pathlen);
                snprintf(path, pathlen, "global");
        }
        else if (spcNode == DEFAULTTABLESPACE_OID)
        {
                /* The default tablespace is {datadir}/base */
                pathlen = 5 + OIDCHARS + 1;
                path = (char *) palloc(pathlen);
                snprintf(path, pathlen, "base/%u",
                                 dbNode);
        }
        else
        {
                /* All other tablespaces are accessed via symlinks */
                pathlen = 10 + OIDCHARS + 1 + OIDCHARS + 1;
                path = (char *) palloc(pathlen);
                snprintf(path, pathlen, "pg_tblspc/%u/%u",
                                 spcNode, dbNode);
        }
        return path;
}


/*
 * IsSystemRelation
 *              True iff the relation is a system catalog relation.
 *
 *              NB: TOAST relations are considered system relations by this test
 *              for compatibility with the old IsSystemRelationName function.
 *              This is appropriate in many places but not all.  Where it's not,
 *              also check IsToastRelation.
 *
 *              We now just test if the relation is in the system catalog namespace;
 *              so it's no longer necessary to forbid user relations from having
 *              names starting with pg_.
 */
bool
IsSystemRelation(Relation relation)
{
        return IsSystemNamespace(RelationGetNamespace(relation)) ||
                IsToastNamespace(RelationGetNamespace(relation));
}

/*
 * IsSystemClass
 *              Like the above, but takes a Form_pg_class as argument.
 *              Used when we do not want to open the relation and have to
 *              search pg_class directly.
 */
bool
IsSystemClass(Form_pg_class reltuple)
{
        Oid                     relnamespace = reltuple->relnamespace;

        return IsSystemNamespace(relnamespace) ||
                IsToastNamespace(relnamespace);
}

/*
 * IsToastRelation
 *              True iff relation is a TOAST support relation (or index).
 */
bool
IsToastRelation(Relation relation)
{
        return IsToastNamespace(RelationGetNamespace(relation));
}

/*
 * IsToastClass
 *              Like the above, but takes a Form_pg_class as argument.
 *              Used when we do not want to open the relation and have to
 *              search pg_class directly.
 */
bool
IsToastClass(Form_pg_class reltuple)
{
        Oid                     relnamespace = reltuple->relnamespace;

        return IsToastNamespace(relnamespace);
}

/*
 * IsSystemNamespace
 *              True iff namespace is pg_catalog.
 *
 * NOTE: the reason this isn't a macro is to avoid having to include
 * catalog/pg_namespace.h in a lot of places.
 */
bool
IsSystemNamespace(Oid namespaceId)
{
        return namespaceId == PG_CATALOG_NAMESPACE;
}

/*
 * IsToastNamespace
 *              True iff namespace is pg_toast or my temporary-toast-table namespace.
 *
 * Note: this will return false for temporary-toast-table namespaces belonging
 * to other backends.  Those are treated the same as other backends' regular
 * temp table namespaces, and access is prevented where appropriate.
 */
bool
IsToastNamespace(Oid namespaceId)
{
        return (namespaceId == PG_TOAST_NAMESPACE) ||
                isTempToastNamespace(namespaceId);
}


/*
 * IsReservedName
 *              True iff name starts with the pg_ prefix.
 *
 *              For some classes of objects, the prefix pg_ is reserved for
 *              system objects only.  As of 8.0, this is only true for
 *              schema and tablespace names.
 */
bool
IsReservedName(const char *name)
{
        /* ugly coding for speed */
        return (name[0] == 'p' &&
                        name[1] == 'g' &&
                        name[2] == '_');
}


/*
 * IsSharedRelation
 *              Given the OID of a relation, determine whether it's supposed to be
 *              shared across an entire database cluster.
 *
 * Hard-wiring this list is pretty grotty, but we really need it so that
 * we can compute the locktag for a relation (and then lock it) without
 * having already read its pg_class entry.      If we try to retrieve relisshared
 * from pg_class with no pre-existing lock, there is a race condition against
 * anyone who is concurrently committing a change to the pg_class entry:
 * since we read system catalog entries under SnapshotNow, it's possible
 * that both the old and new versions of the row are invalid at the instants
 * we scan them.  We fix this by insisting that updaters of a pg_class
 * row must hold exclusive lock on the corresponding rel, and that users
 * of a relation must hold at least AccessShareLock on the rel *before*
 * trying to open its relcache entry.  But to lock a rel, you have to
 * know if it's shared.  Fortunately, the set of shared relations is
 * fairly static, so a hand-maintained list of their OIDs isn't completely
 * impractical.
 */
bool
IsSharedRelation(Oid relationId)
{
        /* These are the shared catalogs (look for BKI_SHARED_RELATION) */
        if (relationId == AuthIdRelationId ||
                relationId == AuthMemRelationId ||
                relationId == DatabaseRelationId ||
                relationId == PLTemplateRelationId ||
                relationId == SharedDescriptionRelationId ||
                relationId == SharedDependRelationId ||
                relationId == TableSpaceRelationId)
                return true;
        /* These are their indexes (see indexing.h) */
        if (relationId == AuthIdRolnameIndexId ||
                relationId == AuthIdOidIndexId ||
                relationId == AuthMemRoleMemIndexId ||
                relationId == AuthMemMemRoleIndexId ||
                relationId == DatabaseNameIndexId ||
                relationId == DatabaseOidIndexId ||
                relationId == PLTemplateNameIndexId ||
                relationId == SharedDescriptionObjIndexId ||
                relationId == SharedDependDependerIndexId ||
                relationId == SharedDependReferenceIndexId ||
                relationId == TablespaceOidIndexId ||
                relationId == TablespaceNameIndexId)
                return true;
        /* These are their toast tables and toast indexes (see toasting.h) */
        if (relationId == PgAuthidToastTable ||
                relationId == PgAuthidToastIndex ||
                relationId == PgDatabaseToastTable ||
                relationId == PgDatabaseToastIndex ||
                relationId == PgShdescriptionToastTable ||
                relationId == PgShdescriptionToastIndex)
                return true;
        return false;
}


/*
 * GetNewOid
 *              Generate a new OID that is unique within the given relation.
 *
 * Caller must have a suitable lock on the relation.
 *
 * Uniqueness is promised only if the relation has a unique index on OID.
 * This is true for all system catalogs that have OIDs, but might not be
 * true for user tables.  Note that we are effectively assuming that the
 * table has a relatively small number of entries (much less than 2^32)
 * and there aren't very long runs of consecutive existing OIDs.  Again,
 * this is reasonable for system catalogs but less so for user tables.
 *
 * Since the OID is not immediately inserted into the table, there is a
 * race condition here; but a problem could occur only if someone else
 * managed to cycle through 2^32 OIDs and generate the same OID before we
 * finish inserting our row.  This seems unlikely to be a problem.      Note
 * that if we had to *commit* the row to end the race condition, the risk
 * would be rather higher; therefore we use SnapshotDirty in the test,
 * so that we will see uncommitted rows.
 */
Oid
GetNewOid(Relation relation)
{
        Oid                     oidIndex;

        /* If relation doesn't have OIDs at all, caller is confused */
        Assert(relation->rd_rel->relhasoids);

        /* In bootstrap mode, we don't have any indexes to use */
        if (IsBootstrapProcessingMode())
                return GetNewObjectId();

        /* The relcache will cache the identity of the OID index for us */
        oidIndex = RelationGetOidIndex(relation);

        /* If no OID index, just hand back the next OID counter value */
        if (!OidIsValid(oidIndex))
        {
                /*
                 * System catalogs that have OIDs should *always* have a unique OID
                 * index; we should only take this path for user tables. Give a
                 * warning if it looks like somebody forgot an index.
                 */
                if (IsSystemRelation(relation))
                        elog(WARNING, "generating possibly-non-unique OID for \"%s\"",
                                 RelationGetRelationName(relation));

                return GetNewObjectId();
        }

        /* Otherwise, use the index to find a nonconflicting OID */
        return GetNewOidWithIndex(relation, oidIndex, ObjectIdAttributeNumber);
}

/*
 * GetNewOidWithIndex
 *              Guts of GetNewOid: use the supplied index
 *
 * This is exported separately because there are cases where we want to use
 * an index that will not be recognized by RelationGetOidIndex: TOAST tables
 * and pg_largeobject have indexes that are usable, but have multiple columns
 * and are on ordinary columns rather than a true OID column.  This code
 * will work anyway, so long as the OID is the index's first column.  The
 * caller must pass in the actual heap attnum of the OID column, however.
 *
 * Caller must have a suitable lock on the relation.
 */
Oid
GetNewOidWithIndex(Relation relation, Oid indexId, AttrNumber oidcolumn)
{
        Oid                     newOid;
        SnapshotData SnapshotDirty;
        SysScanDesc     scan;
        ScanKeyData key;
        bool            collides;

        InitDirtySnapshot(SnapshotDirty);

        /* Generate new OIDs until we find one not in the table */
        do
        {
                CHECK_FOR_INTERRUPTS();

                newOid = GetNewObjectId();

                ScanKeyInit(&key,
                                        oidcolumn,
                                        BTEqualStrategyNumber, F_OIDEQ,
                                        ObjectIdGetDatum(newOid));

                /* see notes above about using SnapshotDirty */
                scan = systable_beginscan(relation, indexId, true,
                                                                  &SnapshotDirty, 1, &key);

                collides = HeapTupleIsValid(systable_getnext(scan));

                systable_endscan(scan);
        } while (collides);

        return newOid;
}

/*
 * GetNewRelFileNode
 *              Generate a new relfilenode number that is unique within the given
 *              tablespace.
 *
 * If the relfilenode will also be used as the relation's OID, pass the
 * opened pg_class catalog, and this routine will guarantee that the result
 * is also an unused OID within pg_class.  If the result is to be used only
 * as a relfilenode for an existing relation, pass NULL for pg_class.
 *
 * As with GetNewOid, there is some theoretical risk of a race condition,
 * but it doesn't seem worth worrying about.
 *
 * Note: we don't support using this in bootstrap mode.  All relations
 * created by bootstrap have preassigned OIDs, so there's no need.
 */
Oid
GetNewRelFileNode(Oid reltablespace, bool relisshared, Relation pg_class)
{
        RelFileNode rnode;
        char       *rpath;
        int                     fd;
        bool            collides;

        /* This should match RelationInitPhysicalAddr */
        rnode.spcNode = reltablespace ? reltablespace : MyDatabaseTableSpace;
        rnode.dbNode = relisshared ? InvalidOid : MyDatabaseId;

        do
        {
                CHECK_FOR_INTERRUPTS();

                /* Generate the OID */
                if (pg_class)
                        rnode.relNode = GetNewOid(pg_class);
                else
                        rnode.relNode = GetNewObjectId();

                /* Check for existing file of same name */
                rpath = relpath(rnode, MAIN_FORKNUM);
                fd = BasicOpenFile(rpath, O_RDONLY | PG_BINARY, 0);

                if (fd >= 0)
                {
                        /* definite collision */
                        close(fd);
                        collides = true;
                }
                else
                {
                        /*
                         * Here we have a little bit of a dilemma: if errno is something
                         * other than ENOENT, should we declare a collision and loop? In
                         * particular one might think this advisable for, say, EPERM.
                         * However there really shouldn't be any unreadable files in a
                         * tablespace directory, and if the EPERM is actually complaining
                         * that we can't read the directory itself, we'd be in an infinite
                         * loop.  In practice it seems best to go ahead regardless of the
                         * errno.  If there is a colliding file we will get an smgr
                         * failure when we attempt to create the new relation file.
                         */
                        collides = false;
                }

                pfree(rpath);
        } while (collides);

        return rnode.relNode;
}