Consistently use "superuser" instead of "super user"

[pgsql.git] / src / include / access / nbtree.h

/*-------------------------------------------------------------------------
 *
 * nbtree.h
 *        header file for postgres btree access method implementation.
 *
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/access/nbtree.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef NBTREE_H
#define NBTREE_H

#include "access/amapi.h"
#include "access/itup.h"
#include "access/sdir.h"
#include "access/tableam.h"
#include "access/xlogreader.h"
#include "catalog/pg_am_d.h"
#include "catalog/pg_index.h"
#include "lib/stringinfo.h"
#include "storage/bufmgr.h"
#include "storage/shm_toc.h"

/* There's room for a 16-bit vacuum cycle ID in BTPageOpaqueData */
typedef uint16 BTCycleId;

/*
 *      BTPageOpaqueData -- At the end of every page, we store a pointer
 *      to both siblings in the tree.  This is used to do forward/backward
 *      index scans.  The next-page link is also critical for recovery when
 *      a search has navigated to the wrong page due to concurrent page splits
 *      or deletions; see src/backend/access/nbtree/README for more info.
 *
 *      In addition, we store the page's btree level (counting upwards from
 *      zero at a leaf page) as well as some flag bits indicating the page type
 *      and status.  If the page is deleted, a BTDeletedPageData struct is stored
 *      in the page's tuple area, while a standard BTPageOpaqueData struct is
 *      stored in the page special area.
 *
 *      We also store a "vacuum cycle ID".  When a page is split while VACUUM is
 *      processing the index, a nonzero value associated with the VACUUM run is
 *      stored into both halves of the split page.  (If VACUUM is not running,
 *      both pages receive zero cycleids.)      This allows VACUUM to detect whether
 *      a page was split since it started, with a small probability of false match
 *      if the page was last split some exact multiple of MAX_BT_CYCLE_ID VACUUMs
 *      ago.  Also, during a split, the BTP_SPLIT_END flag is cleared in the left
 *      (original) page, and set in the right page, but only if the next page
 *      to its right has a different cycleid.
 *
 *      NOTE: the BTP_LEAF flag bit is redundant since level==0 could be tested
 *      instead.
 *
 *      NOTE: the btpo_level field used to be a union type in order to allow
 *      deleted pages to store a 32-bit safexid in the same field.  We now store
 *      64-bit/full safexid values using BTDeletedPageData instead.
 */

typedef struct BTPageOpaqueData
{
        BlockNumber btpo_prev;          /* left sibling, or P_NONE if leftmost */
        BlockNumber btpo_next;          /* right sibling, or P_NONE if rightmost */
        uint32          btpo_level;             /* tree level --- zero for leaf pages */
        uint16          btpo_flags;             /* flag bits, see below */
        BTCycleId       btpo_cycleid;   /* vacuum cycle ID of latest split */
} BTPageOpaqueData;

typedef BTPageOpaqueData *BTPageOpaque;

/* Bits defined in btpo_flags */
#define BTP_LEAF                (1 << 0)        /* leaf page, i.e. not internal page */
#define BTP_ROOT                (1 << 1)        /* root page (has no parent) */
#define BTP_DELETED             (1 << 2)        /* page has been deleted from tree */
#define BTP_META                (1 << 3)        /* meta-page */
#define BTP_HALF_DEAD   (1 << 4)        /* empty, but still in tree */
#define BTP_SPLIT_END   (1 << 5)        /* rightmost page of split group */
#define BTP_HAS_GARBAGE (1 << 6)        /* page has LP_DEAD tuples (deprecated) */
#define BTP_INCOMPLETE_SPLIT (1 << 7)   /* right sibling's downlink is missing */
#define BTP_HAS_FULLXID (1 << 8)        /* contains BTDeletedPageData */

/*
 * The max allowed value of a cycle ID is a bit less than 64K.  This is
 * for convenience of pg_filedump and similar utilities: we want to use
 * the last 2 bytes of special space as an index type indicator, and
 * restricting cycle ID lets btree use that space for vacuum cycle IDs
 * while still allowing index type to be identified.
 */
#define MAX_BT_CYCLE_ID         0xFF7F


/*
 * The Meta page is always the first page in the btree index.
 * Its primary purpose is to point to the location of the btree root page.
 * We also point to the "fast" root, which is the current effective root;
 * see README for discussion.
 */

typedef struct BTMetaPageData
{
        uint32          btm_magic;              /* should contain BTREE_MAGIC */
        uint32          btm_version;    /* nbtree version (always <= BTREE_VERSION) */
        BlockNumber btm_root;           /* current root location */
        uint32          btm_level;              /* tree level of the root page */
        BlockNumber btm_fastroot;       /* current "fast" root location */
        uint32          btm_fastlevel;  /* tree level of the "fast" root page */
        /* remaining fields only valid when btm_version >= BTREE_NOVAC_VERSION */

        /* number of deleted, non-recyclable pages during last cleanup */
        uint32          btm_last_cleanup_num_delpages;
        /* number of heap tuples during last cleanup (deprecated) */
        float8          btm_last_cleanup_num_heap_tuples;

        bool            btm_allequalimage;      /* are all columns "equalimage"? */
} BTMetaPageData;

#define BTPageGetMeta(p) \
        ((BTMetaPageData *) PageGetContents(p))

/*
 * The current Btree version is 4.  That's what you'll get when you create
 * a new index.
 *
 * Btree version 3 was used in PostgreSQL v11.  It is mostly the same as
 * version 4, but heap TIDs were not part of the keyspace.  Index tuples
 * with duplicate keys could be stored in any order.  We continue to
 * support reading and writing Btree versions 2 and 3, so that they don't
 * need to be immediately re-indexed at pg_upgrade.  In order to get the
 * new heapkeyspace semantics, however, a REINDEX is needed.
 *
 * Deduplication is safe to use when the btm_allequalimage field is set to
 * true.  It's safe to read the btm_allequalimage field on version 3, but
 * only version 4 indexes make use of deduplication.  Even version 4
 * indexes created on PostgreSQL v12 will need a REINDEX to make use of
 * deduplication, though, since there is no other way to set
 * btm_allequalimage to true (pg_upgrade hasn't been taught to set the
 * metapage field).
 *
 * Btree version 2 is mostly the same as version 3.  There are two new
 * fields in the metapage that were introduced in version 3.  A version 2
 * metapage will be automatically upgraded to version 3 on the first
 * insert to it.  INCLUDE indexes cannot use version 2.
 */
#define BTREE_METAPAGE  0               /* first page is meta */
#define BTREE_MAGIC             0x053162        /* magic number in metapage */
#define BTREE_VERSION   4               /* current version number */
#define BTREE_MIN_VERSION       2       /* minimum supported version */
#define BTREE_NOVAC_VERSION     3       /* version with all meta fields set */

/*
 * Maximum size of a btree index entry, including its tuple header.
 *
 * We actually need to be able to fit three items on every page,
 * so restrict any one item to 1/3 the per-page available space.
 *
 * There are rare cases where _bt_truncate() will need to enlarge
 * a heap index tuple to make space for a tiebreaker heap TID
 * attribute, which we account for here.
 */
#define BTMaxItemSize(page) \
        MAXALIGN_DOWN((PageGetPageSize(page) - \
                                   MAXALIGN(SizeOfPageHeaderData + \
                                                        3*sizeof(ItemIdData)  + \
                                                        3*sizeof(ItemPointerData)) - \
                                   MAXALIGN(sizeof(BTPageOpaqueData))) / 3)
#define BTMaxItemSizeNoHeapTid(page) \
        MAXALIGN_DOWN((PageGetPageSize(page) - \
                                   MAXALIGN(SizeOfPageHeaderData + 3*sizeof(ItemIdData)) - \
                                   MAXALIGN(sizeof(BTPageOpaqueData))) / 3)

/*
 * MaxTIDsPerBTreePage is an upper bound on the number of heap TIDs tuples
 * that may be stored on a btree leaf page.  It is used to size the
 * per-page temporary buffers.
 *
 * Note: we don't bother considering per-tuple overheads here to keep
 * things simple (value is based on how many elements a single array of
 * heap TIDs must have to fill the space between the page header and
 * special area).  The value is slightly higher (i.e. more conservative)
 * than necessary as a result, which is considered acceptable.
 */
#define MaxTIDsPerBTreePage \
        (int) ((BLCKSZ - SizeOfPageHeaderData - sizeof(BTPageOpaqueData)) / \
                   sizeof(ItemPointerData))

/*
 * The leaf-page fillfactor defaults to 90% but is user-adjustable.
 * For pages above the leaf level, we use a fixed 70% fillfactor.
 * The fillfactor is applied during index build and when splitting
 * a rightmost page; when splitting non-rightmost pages we try to
 * divide the data equally.  When splitting a page that's entirely
 * filled with a single value (duplicates), the effective leaf-page
 * fillfactor is 96%, regardless of whether the page is a rightmost
 * page.
 */
#define BTREE_MIN_FILLFACTOR            10
#define BTREE_DEFAULT_FILLFACTOR        90
#define BTREE_NONLEAF_FILLFACTOR        70
#define BTREE_SINGLEVAL_FILLFACTOR      96

/*
 *      In general, the btree code tries to localize its knowledge about
 *      page layout to a couple of routines.  However, we need a special
 *      value to indicate "no page number" in those places where we expect
 *      page numbers.  We can use zero for this because we never need to
 *      make a pointer to the metadata page.
 */

#define P_NONE                  0

/*
 * Macros to test whether a page is leftmost or rightmost on its tree level,
 * as well as other state info kept in the opaque data.
 */
#define P_LEFTMOST(opaque)              ((opaque)->btpo_prev == P_NONE)
#define P_RIGHTMOST(opaque)             ((opaque)->btpo_next == P_NONE)
#define P_ISLEAF(opaque)                (((opaque)->btpo_flags & BTP_LEAF) != 0)
#define P_ISROOT(opaque)                (((opaque)->btpo_flags & BTP_ROOT) != 0)
#define P_ISDELETED(opaque)             (((opaque)->btpo_flags & BTP_DELETED) != 0)
#define P_ISMETA(opaque)                (((opaque)->btpo_flags & BTP_META) != 0)
#define P_ISHALFDEAD(opaque)    (((opaque)->btpo_flags & BTP_HALF_DEAD) != 0)
#define P_IGNORE(opaque)                (((opaque)->btpo_flags & (BTP_DELETED|BTP_HALF_DEAD)) != 0)
#define P_HAS_GARBAGE(opaque)   (((opaque)->btpo_flags & BTP_HAS_GARBAGE) != 0)
#define P_INCOMPLETE_SPLIT(opaque)      (((opaque)->btpo_flags & BTP_INCOMPLETE_SPLIT) != 0)
#define P_HAS_FULLXID(opaque)   (((opaque)->btpo_flags & BTP_HAS_FULLXID) != 0)

/*
 * BTDeletedPageData is the page contents of a deleted page
 */
typedef struct BTDeletedPageData
{
        FullTransactionId safexid;      /* See BTPageIsRecyclable() */
} BTDeletedPageData;

static inline void
BTPageSetDeleted(Page page, FullTransactionId safexid)
{
        BTPageOpaque opaque;
        PageHeader      header;
        BTDeletedPageData *contents;

        opaque = (BTPageOpaque) PageGetSpecialPointer(page);
        header = ((PageHeader) page);

        opaque->btpo_flags &= ~BTP_HALF_DEAD;
        opaque->btpo_flags |= BTP_DELETED | BTP_HAS_FULLXID;
        header->pd_lower = MAXALIGN(SizeOfPageHeaderData) +
                sizeof(BTDeletedPageData);
        header->pd_upper = header->pd_special;

        /* Set safexid in deleted page */
        contents = ((BTDeletedPageData *) PageGetContents(page));
        contents->safexid = safexid;
}

static inline FullTransactionId
BTPageGetDeleteXid(Page page)
{
        BTPageOpaque opaque;
        BTDeletedPageData *contents;

        /* We only expect to be called with a deleted page */
        Assert(!PageIsNew(page));
        opaque = (BTPageOpaque) PageGetSpecialPointer(page);
        Assert(P_ISDELETED(opaque));

        /* pg_upgrade'd deleted page -- must be safe to delete now */
        if (!P_HAS_FULLXID(opaque))
                return FirstNormalFullTransactionId;

        /* Get safexid from deleted page */
        contents = ((BTDeletedPageData *) PageGetContents(page));
        return contents->safexid;
}

/*
 * Is an existing page recyclable?
 *
 * This exists to centralize the policy on which deleted pages are now safe to
 * re-use.  However, _bt_pendingfsm_finalize() duplicates some of the same
 * logic because it doesn't work directly with pages -- keep the two in sync.
 *
 * Note: PageIsNew() pages are always safe to recycle, but we can't deal with
 * them here (caller is responsible for that case themselves).  Caller might
 * well need special handling for new pages anyway.
 */
static inline bool
BTPageIsRecyclable(Page page)
{
        BTPageOpaque opaque;

        Assert(!PageIsNew(page));

        /* Recycling okay iff page is deleted and safexid is old enough */
        opaque = (BTPageOpaque) PageGetSpecialPointer(page);
        if (P_ISDELETED(opaque))
        {
                /*
                 * The page was deleted, but when? If it was just deleted, a scan
                 * might have seen the downlink to it, and will read the page later.
                 * As long as that can happen, we must keep the deleted page around as
                 * a tombstone.
                 *
                 * For that check if the deletion XID could still be visible to
                 * anyone. If not, then no scan that's still in progress could have
                 * seen its downlink, and we can recycle it.
                 *
                 * XXX: If we had the heap relation we could be more aggressive about
                 * recycling deleted pages in non-catalog relations.  For now we just
                 * pass NULL.  That is at least simple and consistent.
                 */
                return GlobalVisCheckRemovableFullXid(NULL, BTPageGetDeleteXid(page));
        }

        return false;
}

/*
 * BTVacState and BTPendingFSM are private nbtree.c state used during VACUUM.
 * They are exported for use by page deletion related code in nbtpage.c.
 */
typedef struct BTPendingFSM
{
        BlockNumber target;                     /* Page deleted by current VACUUM */
        FullTransactionId safexid;      /* Page's BTDeletedPageData.safexid */
} BTPendingFSM;

typedef struct BTVacState
{
        IndexVacuumInfo *info;
        IndexBulkDeleteResult *stats;
        IndexBulkDeleteCallback callback;
        void       *callback_state;
        BTCycleId       cycleid;
        MemoryContext pagedelcontext;

        /*
         * _bt_pendingfsm_finalize() state
         */
        int                     bufsize;                /* pendingpages space (in # elements) */
        int                     maxbufsize;             /* max bufsize that respects work_mem */
        BTPendingFSM *pendingpages; /* One entry per newly deleted page */
        int                     npendingpages;  /* current # valid pendingpages */
} BTVacState;

/*
 *      Lehman and Yao's algorithm requires a ``high key'' on every non-rightmost
 *      page.  The high key is not a tuple that is used to visit the heap.  It is
 *      a pivot tuple (see "Notes on B-Tree tuple format" below for definition).
 *      The high key on a page is required to be greater than or equal to any
 *      other key that appears on the page.  If we find ourselves trying to
 *      insert a key that is strictly > high key, we know we need to move right
 *      (this should only happen if the page was split since we examined the
 *      parent page).
 *
 *      Our insertion algorithm guarantees that we can use the initial least key
 *      on our right sibling as the high key.  Once a page is created, its high
 *      key changes only if the page is split.
 *
 *      On a non-rightmost page, the high key lives in item 1 and data items
 *      start in item 2.  Rightmost pages have no high key, so we store data
 *      items beginning in item 1.
 */

#define P_HIKEY                         ((OffsetNumber) 1)
#define P_FIRSTKEY                      ((OffsetNumber) 2)
#define P_FIRSTDATAKEY(opaque)  (P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY)

/*
 * Notes on B-Tree tuple format, and key and non-key attributes:
 *
 * INCLUDE B-Tree indexes have non-key attributes.  These are extra
 * attributes that may be returned by index-only scans, but do not influence
 * the order of items in the index (formally, non-key attributes are not
 * considered to be part of the key space).  Non-key attributes are only
 * present in leaf index tuples whose item pointers actually point to heap
 * tuples (non-pivot tuples).  _bt_check_natts() enforces the rules
 * described here.
 *
 * Non-pivot tuple format (plain/non-posting variant):
 *
 *  t_tid | t_info | key values | INCLUDE columns, if any
 *
 * t_tid points to the heap TID, which is a tiebreaker key column as of
 * BTREE_VERSION 4.
 *
 * Non-pivot tuples complement pivot tuples, which only have key columns.
 * The sole purpose of pivot tuples is to represent how the key space is
 * separated.  In general, any B-Tree index that has more than one level
 * (i.e. any index that does not just consist of a metapage and a single
 * leaf root page) must have some number of pivot tuples, since pivot
 * tuples are used for traversing the tree.  Suffix truncation can omit
 * trailing key columns when a new pivot is formed, which makes minus
 * infinity their logical value.  Since BTREE_VERSION 4 indexes treat heap
 * TID as a trailing key column that ensures that all index tuples are
 * physically unique, it is necessary to represent heap TID as a trailing
 * key column in pivot tuples, though very often this can be truncated
 * away, just like any other key column. (Actually, the heap TID is
 * omitted rather than truncated, since its representation is different to
 * the non-pivot representation.)
 *
 * Pivot tuple format:
 *
 *  t_tid | t_info | key values | [heap TID]
 *
 * We store the number of columns present inside pivot tuples by abusing
 * their t_tid offset field, since pivot tuples never need to store a real
 * offset (pivot tuples generally store a downlink in t_tid, though).  The
 * offset field only stores the number of columns/attributes when the
 * INDEX_ALT_TID_MASK bit is set, which doesn't count the trailing heap
 * TID column sometimes stored in pivot tuples -- that's represented by
 * the presence of BT_PIVOT_HEAP_TID_ATTR.  The INDEX_ALT_TID_MASK bit in
 * t_info is always set on BTREE_VERSION 4 pivot tuples, since
 * BTreeTupleIsPivot() must work reliably on heapkeyspace versions.
 *
 * In version 2 or version 3 (!heapkeyspace) indexes, INDEX_ALT_TID_MASK
 * might not be set in pivot tuples.  BTreeTupleIsPivot() won't work
 * reliably as a result.  The number of columns stored is implicitly the
 * same as the number of columns in the index, just like any non-pivot
 * tuple. (The number of columns stored should not vary, since suffix
 * truncation of key columns is unsafe within any !heapkeyspace index.)
 *
 * The 12 least significant bits from t_tid's offset number are used to
 * represent the number of key columns within a pivot tuple.  This leaves 4
 * status bits (BT_STATUS_OFFSET_MASK bits), which are shared by all tuples
 * that have the INDEX_ALT_TID_MASK bit set (set in t_info) to store basic
 * tuple metadata.  BTreeTupleIsPivot() and BTreeTupleIsPosting() use the
 * BT_STATUS_OFFSET_MASK bits.
 *
 * Sometimes non-pivot tuples also use a representation that repurposes
 * t_tid to store metadata rather than a TID.  PostgreSQL v13 introduced a
 * new non-pivot tuple format to support deduplication: posting list
 * tuples.  Deduplication merges together multiple equal non-pivot tuples
 * into a logically equivalent, space efficient representation.  A posting
 * list is an array of ItemPointerData elements.  Non-pivot tuples are
 * merged together to form posting list tuples lazily, at the point where
 * we'd otherwise have to split a leaf page.
 *
 * Posting tuple format (alternative non-pivot tuple representation):
 *
 *  t_tid | t_info | key values | posting list (TID array)
 *
 * Posting list tuples are recognized as such by having the
 * INDEX_ALT_TID_MASK status bit set in t_info and the BT_IS_POSTING status
 * bit set in t_tid's offset number.  These flags redefine the content of
 * the posting tuple's t_tid to store the location of the posting list
 * (instead of a block number), as well as the total number of heap TIDs
 * present in the tuple (instead of a real offset number).
 *
 * The 12 least significant bits from t_tid's offset number are used to
 * represent the number of heap TIDs present in the tuple, leaving 4 status
 * bits (the BT_STATUS_OFFSET_MASK bits).  Like any non-pivot tuple, the
 * number of columns stored is always implicitly the total number in the
 * index (in practice there can never be non-key columns stored, since
 * deduplication is not supported with INCLUDE indexes).
 */
#define INDEX_ALT_TID_MASK                      INDEX_AM_RESERVED_BIT

/* Item pointer offset bit masks */
#define BT_OFFSET_MASK                          0x0FFF
#define BT_STATUS_OFFSET_MASK           0xF000
/* BT_STATUS_OFFSET_MASK status bits */
#define BT_PIVOT_HEAP_TID_ATTR          0x1000
#define BT_IS_POSTING                           0x2000

/*
 * Note: BTreeTupleIsPivot() can have false negatives (but not false
 * positives) when used with !heapkeyspace indexes
 */
static inline bool
BTreeTupleIsPivot(IndexTuple itup)
{
        if ((itup->t_info & INDEX_ALT_TID_MASK) == 0)
                return false;
        /* absence of BT_IS_POSTING in offset number indicates pivot tuple */
        if ((ItemPointerGetOffsetNumberNoCheck(&itup->t_tid) & BT_IS_POSTING) != 0)
                return false;

        return true;
}

static inline bool
BTreeTupleIsPosting(IndexTuple itup)
{
        if ((itup->t_info & INDEX_ALT_TID_MASK) == 0)
                return false;
        /* presence of BT_IS_POSTING in offset number indicates posting tuple */
        if ((ItemPointerGetOffsetNumberNoCheck(&itup->t_tid) & BT_IS_POSTING) == 0)
                return false;

        return true;
}

static inline void
BTreeTupleSetPosting(IndexTuple itup, uint16 nhtids, int postingoffset)
{
        Assert(nhtids > 1);
        Assert((nhtids & BT_STATUS_OFFSET_MASK) == 0);
        Assert((size_t) postingoffset == MAXALIGN(postingoffset));
        Assert(postingoffset < INDEX_SIZE_MASK);
        Assert(!BTreeTupleIsPivot(itup));

        itup->t_info |= INDEX_ALT_TID_MASK;
        ItemPointerSetOffsetNumber(&itup->t_tid, (nhtids | BT_IS_POSTING));
        ItemPointerSetBlockNumber(&itup->t_tid, postingoffset);
}

static inline uint16
BTreeTupleGetNPosting(IndexTuple posting)
{
        OffsetNumber existing;

        Assert(BTreeTupleIsPosting(posting));

        existing = ItemPointerGetOffsetNumberNoCheck(&posting->t_tid);
        return (existing & BT_OFFSET_MASK);
}

static inline uint32
BTreeTupleGetPostingOffset(IndexTuple posting)
{
        Assert(BTreeTupleIsPosting(posting));

        return ItemPointerGetBlockNumberNoCheck(&posting->t_tid);
}

static inline ItemPointer
BTreeTupleGetPosting(IndexTuple posting)
{
        return (ItemPointer) ((char *) posting +
                                                  BTreeTupleGetPostingOffset(posting));
}

static inline ItemPointer
BTreeTupleGetPostingN(IndexTuple posting, int n)
{
        return BTreeTupleGetPosting(posting) + n;
}

/*
 * Get/set downlink block number in pivot tuple.
 *
 * Note: Cannot assert that tuple is a pivot tuple.  If we did so then
 * !heapkeyspace indexes would exhibit false positive assertion failures.
 */
static inline BlockNumber
BTreeTupleGetDownLink(IndexTuple pivot)
{
        return ItemPointerGetBlockNumberNoCheck(&pivot->t_tid);
}

static inline void
BTreeTupleSetDownLink(IndexTuple pivot, BlockNumber blkno)
{
        ItemPointerSetBlockNumber(&pivot->t_tid, blkno);
}

/*
 * Get number of attributes within tuple.
 *
 * Note that this does not include an implicit tiebreaker heap TID
 * attribute, if any.  Note also that the number of key attributes must be
 * explicitly represented in all heapkeyspace pivot tuples.
 *
 * Note: This is defined as a macro rather than an inline function to
 * avoid including rel.h.
 */
#define BTreeTupleGetNAtts(itup, rel)   \
        ( \
                (BTreeTupleIsPivot(itup)) ? \
                ( \
                        ItemPointerGetOffsetNumberNoCheck(&(itup)->t_tid) & BT_OFFSET_MASK \
                ) \
                : \
                IndexRelationGetNumberOfAttributes(rel) \
        )

/*
 * Set number of key attributes in tuple.
 *
 * The heap TID tiebreaker attribute bit may also be set here, indicating that
 * a heap TID value will be stored at the end of the tuple (i.e. using the
 * special pivot tuple representation).
 */
static inline void
BTreeTupleSetNAtts(IndexTuple itup, uint16 nkeyatts, bool heaptid)
{
        Assert(nkeyatts <= INDEX_MAX_KEYS);
        Assert((nkeyatts & BT_STATUS_OFFSET_MASK) == 0);
        Assert(!heaptid || nkeyatts > 0);
        Assert(!BTreeTupleIsPivot(itup) || nkeyatts == 0);

        itup->t_info |= INDEX_ALT_TID_MASK;

        if (heaptid)
                nkeyatts |= BT_PIVOT_HEAP_TID_ATTR;

        /* BT_IS_POSTING bit is deliberately unset here */
        ItemPointerSetOffsetNumber(&itup->t_tid, nkeyatts);
        Assert(BTreeTupleIsPivot(itup));
}

/*
 * Get/set leaf page's "top parent" link from its high key.  Used during page
 * deletion.
 *
 * Note: Cannot assert that tuple is a pivot tuple.  If we did so then
 * !heapkeyspace indexes would exhibit false positive assertion failures.
 */
static inline BlockNumber
BTreeTupleGetTopParent(IndexTuple leafhikey)
{
        return ItemPointerGetBlockNumberNoCheck(&leafhikey->t_tid);
}

static inline void
BTreeTupleSetTopParent(IndexTuple leafhikey, BlockNumber blkno)
{
        ItemPointerSetBlockNumber(&leafhikey->t_tid, blkno);
        BTreeTupleSetNAtts(leafhikey, 0, false);
}

/*
 * Get tiebreaker heap TID attribute, if any.
 *
 * This returns the first/lowest heap TID in the case of a posting list tuple.
 */
static inline ItemPointer
BTreeTupleGetHeapTID(IndexTuple itup)
{
        if (BTreeTupleIsPivot(itup))
        {
                /* Pivot tuple heap TID representation? */
                if ((ItemPointerGetOffsetNumberNoCheck(&itup->t_tid) &
                         BT_PIVOT_HEAP_TID_ATTR) != 0)
                        return (ItemPointer) ((char *) itup + IndexTupleSize(itup) -
                                                                  sizeof(ItemPointerData));

                /* Heap TID attribute was truncated */
                return NULL;
        }
        else if (BTreeTupleIsPosting(itup))
                return BTreeTupleGetPosting(itup);

        return &itup->t_tid;
}

/*
 * Get maximum heap TID attribute, which could be the only TID in the case of
 * a non-pivot tuple that does not have a posting list tuple.
 *
 * Works with non-pivot tuples only.
 */
static inline ItemPointer
BTreeTupleGetMaxHeapTID(IndexTuple itup)
{
        Assert(!BTreeTupleIsPivot(itup));

        if (BTreeTupleIsPosting(itup))
        {
                uint16          nposting = BTreeTupleGetNPosting(itup);

                return BTreeTupleGetPostingN(itup, nposting - 1);
        }

        return &itup->t_tid;
}

/*
 *      Operator strategy numbers for B-tree have been moved to access/stratnum.h,
 *      because many places need to use them in ScanKeyInit() calls.
 *
 *      The strategy numbers are chosen so that we can commute them by
 *      subtraction, thus:
 */
#define BTCommuteStrategyNumber(strat)  (BTMaxStrategyNumber + 1 - (strat))

/*
 *      When a new operator class is declared, we require that the user
 *      supply us with an amproc procedure (BTORDER_PROC) for determining
 *      whether, for two keys a and b, a < b, a = b, or a > b.  This routine
 *      must return < 0, 0, > 0, respectively, in these three cases.
 *
 *      To facilitate accelerated sorting, an operator class may choose to
 *      offer a second procedure (BTSORTSUPPORT_PROC).  For full details, see
 *      src/include/utils/sortsupport.h.
 *
 *      To support window frames defined by "RANGE offset PRECEDING/FOLLOWING",
 *      an operator class may choose to offer a third amproc procedure
 *      (BTINRANGE_PROC), independently of whether it offers sortsupport.
 *      For full details, see doc/src/sgml/btree.sgml.
 *
 *      To facilitate B-Tree deduplication, an operator class may choose to
 *      offer a forth amproc procedure (BTEQUALIMAGE_PROC).  For full details,
 *      see doc/src/sgml/btree.sgml.
 */

#define BTORDER_PROC            1
#define BTSORTSUPPORT_PROC      2
#define BTINRANGE_PROC          3
#define BTEQUALIMAGE_PROC       4
#define BTOPTIONS_PROC          5
#define BTNProcs                        5

/*
 *      We need to be able to tell the difference between read and write
 *      requests for pages, in order to do locking correctly.
 */

#define BT_READ                 BUFFER_LOCK_SHARE
#define BT_WRITE                BUFFER_LOCK_EXCLUSIVE

/*
 * BTStackData -- As we descend a tree, we push the location of pivot
 * tuples whose downlink we are about to follow onto a private stack.  If
 * we split a leaf, we use this stack to walk back up the tree and insert
 * data into its parent page at the correct location.  We also have to
 * recursively insert into the grandparent page if and when the parent page
 * splits.  Our private stack can become stale due to concurrent page
 * splits and page deletions, but it should never give us an irredeemably
 * bad picture.
 */
typedef struct BTStackData
{
        BlockNumber bts_blkno;
        OffsetNumber bts_offset;
        struct BTStackData *bts_parent;
} BTStackData;

typedef BTStackData *BTStack;

/*
 * BTScanInsertData is the btree-private state needed to find an initial
 * position for an indexscan, or to insert new tuples -- an "insertion
 * scankey" (not to be confused with a search scankey).  It's used to descend
 * a B-Tree using _bt_search.
 *
 * heapkeyspace indicates if we expect all keys in the index to be physically
 * unique because heap TID is used as a tiebreaker attribute, and if index may
 * have truncated key attributes in pivot tuples.  This is actually a property
 * of the index relation itself (not an indexscan).  heapkeyspace indexes are
 * indexes whose version is >= version 4.  It's convenient to keep this close
 * by, rather than accessing the metapage repeatedly.
 *
 * allequalimage is set to indicate that deduplication is safe for the index.
 * This is also a property of the index relation rather than an indexscan.
 *
 * anynullkeys indicates if any of the keys had NULL value when scankey was
 * built from index tuple (note that already-truncated tuple key attributes
 * set NULL as a placeholder key value, which also affects value of
 * anynullkeys).  This is a convenience for unique index non-pivot tuple
 * insertion, which usually temporarily unsets scantid, but shouldn't iff
 * anynullkeys is true.  Value generally matches non-pivot tuple's HasNulls
 * bit, but may not when inserting into an INCLUDE index (tuple header value
 * is affected by the NULL-ness of both key and non-key attributes).
 *
 * When nextkey is false (the usual case), _bt_search and _bt_binsrch will
 * locate the first item >= scankey.  When nextkey is true, they will locate
 * the first item > scan key.
 *
 * pivotsearch is set to true by callers that want to re-find a leaf page
 * using a scankey built from a leaf page's high key.  Most callers set this
 * to false.
 *
 * scantid is the heap TID that is used as a final tiebreaker attribute.  It
 * is set to NULL when index scan doesn't need to find a position for a
 * specific physical tuple.  Must be set when inserting new tuples into
 * heapkeyspace indexes, since every tuple in the tree unambiguously belongs
 * in one exact position (it's never set with !heapkeyspace indexes, though).
 * Despite the representational difference, nbtree search code considers
 * scantid to be just another insertion scankey attribute.
 *
 * scankeys is an array of scan key entries for attributes that are compared
 * before scantid (user-visible attributes).  keysz is the size of the array.
 * During insertion, there must be a scan key for every attribute, but when
 * starting a regular index scan some can be omitted.  The array is used as a
 * flexible array member, though it's sized in a way that makes it possible to
 * use stack allocations.  See nbtree/README for full details.
 */
typedef struct BTScanInsertData
{
        bool            heapkeyspace;
        bool            allequalimage;
        bool            anynullkeys;
        bool            nextkey;
        bool            pivotsearch;
        ItemPointer scantid;            /* tiebreaker for scankeys */
        int                     keysz;                  /* Size of scankeys array */
        ScanKeyData scankeys[INDEX_MAX_KEYS];   /* Must appear last */
} BTScanInsertData;

typedef BTScanInsertData *BTScanInsert;

/*
 * BTInsertStateData is a working area used during insertion.
 *
 * This is filled in after descending the tree to the first leaf page the new
 * tuple might belong on.  Tracks the current position while performing
 * uniqueness check, before we have determined which exact page to insert
 * to.
 *
 * (This should be private to nbtinsert.c, but it's also used by
 * _bt_binsrch_insert)
 */
typedef struct BTInsertStateData
{
        IndexTuple      itup;                   /* Item we're inserting */
        Size            itemsz;                 /* Size of itup -- should be MAXALIGN()'d */
        BTScanInsert itup_key;          /* Insertion scankey */

        /* Buffer containing leaf page we're likely to insert itup on */
        Buffer          buf;

        /*
         * Cache of bounds within the current buffer.  Only used for insertions
         * where _bt_check_unique is called.  See _bt_binsrch_insert and
         * _bt_findinsertloc for details.
         */
        bool            bounds_valid;
        OffsetNumber low;
        OffsetNumber stricthigh;

        /*
         * if _bt_binsrch_insert found the location inside existing posting list,
         * save the position inside the list.  -1 sentinel value indicates overlap
         * with an existing posting list tuple that has its LP_DEAD bit set.
         */
        int                     postingoff;
} BTInsertStateData;

typedef BTInsertStateData *BTInsertState;

/*
 * State used to representing an individual pending tuple during
 * deduplication.
 */
typedef struct BTDedupInterval
{
        OffsetNumber baseoff;
        uint16          nitems;
} BTDedupInterval;

/*
 * BTDedupStateData is a working area used during deduplication.
 *
 * The status info fields track the state of a whole-page deduplication pass.
 * State about the current pending posting list is also tracked.
 *
 * A pending posting list is comprised of a contiguous group of equal items
 * from the page, starting from page offset number 'baseoff'.  This is the
 * offset number of the "base" tuple for new posting list.  'nitems' is the
 * current total number of existing items from the page that will be merged to
 * make a new posting list tuple, including the base tuple item.  (Existing
 * items may themselves be posting list tuples, or regular non-pivot tuples.)
 *
 * The total size of the existing tuples to be freed when pending posting list
 * is processed gets tracked by 'phystupsize'.  This information allows
 * deduplication to calculate the space saving for each new posting list
 * tuple, and for the entire pass over the page as a whole.
 */
typedef struct BTDedupStateData
{
        /* Deduplication status info for entire pass over page */
        bool            deduplicate;    /* Still deduplicating page? */
        int                     nmaxitems;              /* Number of max-sized tuples so far */
        Size            maxpostingsize; /* Limit on size of final tuple */

        /* Metadata about base tuple of current pending posting list */
        IndexTuple      base;                   /* Use to form new posting list */
        OffsetNumber baseoff;           /* page offset of base */
        Size            basetupsize;    /* base size without original posting list */

        /* Other metadata about pending posting list */
        ItemPointer htids;                      /* Heap TIDs in pending posting list */
        int                     nhtids;                 /* Number of heap TIDs in htids array */
        int                     nitems;                 /* Number of existing tuples/line pointers */
        Size            phystupsize;    /* Includes line pointer overhead */

        /*
         * Array of tuples to go on new version of the page.  Contains one entry
         * for each group of consecutive items.  Note that existing tuples that
         * will not become posting list tuples do not appear in the array (they
         * are implicitly unchanged by deduplication pass).
         */
        int                     nintervals;             /* current number of intervals in array */
        BTDedupInterval intervals[MaxIndexTuplesPerPage];
} BTDedupStateData;

typedef BTDedupStateData *BTDedupState;

/*
 * BTVacuumPostingData is state that represents how to VACUUM (or delete) a
 * posting list tuple when some (though not all) of its TIDs are to be
 * deleted.
 *
 * Convention is that itup field is the original posting list tuple on input,
 * and palloc()'d final tuple used to overwrite existing tuple on output.
 */
typedef struct BTVacuumPostingData
{
        /* Tuple that will be/was updated */
        IndexTuple      itup;
        OffsetNumber updatedoffset;

        /* State needed to describe final itup in WAL */
        uint16          ndeletedtids;
        uint16          deletetids[FLEXIBLE_ARRAY_MEMBER];
} BTVacuumPostingData;

typedef BTVacuumPostingData *BTVacuumPosting;

/*
 * BTScanOpaqueData is the btree-private state needed for an indexscan.
 * This consists of preprocessed scan keys (see _bt_preprocess_keys() for
 * details of the preprocessing), information about the current location
 * of the scan, and information about the marked location, if any.  (We use
 * BTScanPosData to represent the data needed for each of current and marked
 * locations.)  In addition we can remember some known-killed index entries
 * that must be marked before we can move off the current page.
 *
 * Index scans work a page at a time: we pin and read-lock the page, identify
 * all the matching items on the page and save them in BTScanPosData, then
 * release the read-lock while returning the items to the caller for
 * processing.  This approach minimizes lock/unlock traffic.  Note that we
 * keep the pin on the index page until the caller is done with all the items
 * (this is needed for VACUUM synchronization, see nbtree/README).  When we
 * are ready to step to the next page, if the caller has told us any of the
 * items were killed, we re-lock the page to mark them killed, then unlock.
 * Finally we drop the pin and step to the next page in the appropriate
 * direction.
 *
 * If we are doing an index-only scan, we save the entire IndexTuple for each
 * matched item, otherwise only its heap TID and offset.  The IndexTuples go
 * into a separate workspace array; each BTScanPosItem stores its tuple's
 * offset within that array.  Posting list tuples store a "base" tuple once,
 * allowing the same key to be returned for each TID in the posting list
 * tuple.
 */

typedef struct BTScanPosItem    /* what we remember about each match */
{
        ItemPointerData heapTid;        /* TID of referenced heap item */
        OffsetNumber indexOffset;       /* index item's location within page */
        LocationIndex tupleOffset;      /* IndexTuple's offset in workspace, if any */
} BTScanPosItem;

typedef struct BTScanPosData
{
        Buffer          buf;                    /* if valid, the buffer is pinned */

        XLogRecPtr      lsn;                    /* pos in the WAL stream when page was read */
        BlockNumber currPage;           /* page referenced by items array */
        BlockNumber nextPage;           /* page's right link when we scanned it */

        /*
         * moreLeft and moreRight track whether we think there may be matching
         * index entries to the left and right of the current page, respectively.
         * We can clear the appropriate one of these flags when _bt_checkkeys()
         * returns continuescan = false.
         */
        bool            moreLeft;
        bool            moreRight;

        /*
         * If we are doing an index-only scan, nextTupleOffset is the first free
         * location in the associated tuple storage workspace.
         */
        int                     nextTupleOffset;

        /*
         * The items array is always ordered in index order (ie, increasing
         * indexoffset).  When scanning backwards it is convenient to fill the
         * array back-to-front, so we start at the last slot and fill downwards.
         * Hence we need both a first-valid-entry and a last-valid-entry counter.
         * itemIndex is a cursor showing which entry was last returned to caller.
         */
        int                     firstItem;              /* first valid index in items[] */
        int                     lastItem;               /* last valid index in items[] */
        int                     itemIndex;              /* current index in items[] */

        BTScanPosItem items[MaxTIDsPerBTreePage];       /* MUST BE LAST */
} BTScanPosData;

typedef BTScanPosData *BTScanPos;

#define BTScanPosIsPinned(scanpos) \
( \
        AssertMacro(BlockNumberIsValid((scanpos).currPage) || \
                                !BufferIsValid((scanpos).buf)), \
        BufferIsValid((scanpos).buf) \
)
#define BTScanPosUnpin(scanpos) \
        do { \
                ReleaseBuffer((scanpos).buf); \
                (scanpos).buf = InvalidBuffer; \
        } while (0)
#define BTScanPosUnpinIfPinned(scanpos) \
        do { \
                if (BTScanPosIsPinned(scanpos)) \
                        BTScanPosUnpin(scanpos); \
        } while (0)

#define BTScanPosIsValid(scanpos) \
( \
        AssertMacro(BlockNumberIsValid((scanpos).currPage) || \
                                !BufferIsValid((scanpos).buf)), \
        BlockNumberIsValid((scanpos).currPage) \
)
#define BTScanPosInvalidate(scanpos) \
        do { \
                (scanpos).currPage = InvalidBlockNumber; \
                (scanpos).nextPage = InvalidBlockNumber; \
                (scanpos).buf = InvalidBuffer; \
                (scanpos).lsn = InvalidXLogRecPtr; \
                (scanpos).nextTupleOffset = 0; \
        } while (0)

/* We need one of these for each equality-type SK_SEARCHARRAY scan key */
typedef struct BTArrayKeyInfo
{
        int                     scan_key;               /* index of associated key in arrayKeyData */
        int                     cur_elem;               /* index of current element in elem_values */
        int                     mark_elem;              /* index of marked element in elem_values */
        int                     num_elems;              /* number of elems in current array value */
        Datum      *elem_values;        /* array of num_elems Datums */
} BTArrayKeyInfo;

typedef struct BTScanOpaqueData
{
        /* these fields are set by _bt_preprocess_keys(): */
        bool            qual_ok;                /* false if qual can never be satisfied */
        int                     numberOfKeys;   /* number of preprocessed scan keys */
        ScanKey         keyData;                /* array of preprocessed scan keys */

        /* workspace for SK_SEARCHARRAY support */
        ScanKey         arrayKeyData;   /* modified copy of scan->keyData */
        int                     numArrayKeys;   /* number of equality-type array keys (-1 if
                                                                 * there are any unsatisfiable array keys) */
        int                     arrayKeyCount;  /* count indicating number of array scan keys
                                                                 * processed */
        BTArrayKeyInfo *arrayKeys;      /* info about each equality-type array key */
        MemoryContext arrayContext; /* scan-lifespan context for array data */

        /* info about killed items if any (killedItems is NULL if never used) */
        int                *killedItems;        /* currPos.items indexes of killed items */
        int                     numKilled;              /* number of currently stored items */

        /*
         * If we are doing an index-only scan, these are the tuple storage
         * workspaces for the currPos and markPos respectively.  Each is of size
         * BLCKSZ, so it can hold as much as a full page's worth of tuples.
         */
        char       *currTuples;         /* tuple storage for currPos */
        char       *markTuples;         /* tuple storage for markPos */

        /*
         * If the marked position is on the same page as current position, we
         * don't use markPos, but just keep the marked itemIndex in markItemIndex
         * (all the rest of currPos is valid for the mark position). Hence, to
         * determine if there is a mark, first look at markItemIndex, then at
         * markPos.
         */
        int                     markItemIndex;  /* itemIndex, or -1 if not valid */

        /* keep these last in struct for efficiency */
        BTScanPosData currPos;          /* current position data */
        BTScanPosData markPos;          /* marked position, if any */
} BTScanOpaqueData;

typedef BTScanOpaqueData *BTScanOpaque;

/*
 * We use some private sk_flags bits in preprocessed scan keys.  We're allowed
 * to use bits 16-31 (see skey.h).  The uppermost bits are copied from the
 * index's indoption[] array entry for the index attribute.
 */
#define SK_BT_REQFWD    0x00010000      /* required to continue forward scan */
#define SK_BT_REQBKWD   0x00020000      /* required to continue backward scan */
#define SK_BT_INDOPTION_SHIFT  24       /* must clear the above bits */
#define SK_BT_DESC                      (INDOPTION_DESC << SK_BT_INDOPTION_SHIFT)
#define SK_BT_NULLS_FIRST       (INDOPTION_NULLS_FIRST << SK_BT_INDOPTION_SHIFT)

typedef struct BTOptions
{
        int32           varlena_header_;        /* varlena header (do not touch directly!) */
        int                     fillfactor;             /* page fill factor in percent (0..100) */
        float8          vacuum_cleanup_index_scale_factor;      /* deprecated */
        bool            deduplicate_items;      /* Try to deduplicate items? */
} BTOptions;

#define BTGetFillFactor(relation) \
        (AssertMacro(relation->rd_rel->relkind == RELKIND_INDEX && \
                                 relation->rd_rel->relam == BTREE_AM_OID), \
         (relation)->rd_options ? \
         ((BTOptions *) (relation)->rd_options)->fillfactor : \
         BTREE_DEFAULT_FILLFACTOR)
#define BTGetTargetPageFreeSpace(relation) \
        (BLCKSZ * (100 - BTGetFillFactor(relation)) / 100)
#define BTGetDeduplicateItems(relation) \
        (AssertMacro(relation->rd_rel->relkind == RELKIND_INDEX && \
                                 relation->rd_rel->relam == BTREE_AM_OID), \
        ((relation)->rd_options ? \
         ((BTOptions *) (relation)->rd_options)->deduplicate_items : true))

/*
 * Constant definition for progress reporting.  Phase numbers must match
 * btbuildphasename.
 */
/* PROGRESS_CREATEIDX_SUBPHASE_INITIALIZE is 1 (see progress.h) */
#define PROGRESS_BTREE_PHASE_INDEXBUILD_TABLESCAN               2
#define PROGRESS_BTREE_PHASE_PERFORMSORT_1                              3
#define PROGRESS_BTREE_PHASE_PERFORMSORT_2                              4
#define PROGRESS_BTREE_PHASE_LEAF_LOAD                                  5

/*
 * external entry points for btree, in nbtree.c
 */
extern void btbuildempty(Relation index);
extern bool btinsert(Relation rel, Datum *values, bool *isnull,
                                         ItemPointer ht_ctid, Relation heapRel,
                                         IndexUniqueCheck checkUnique,
                                         bool indexUnchanged,
                                         struct IndexInfo *indexInfo);
extern IndexScanDesc btbeginscan(Relation rel, int nkeys, int norderbys);
extern Size btestimateparallelscan(void);
extern void btinitparallelscan(void *target);
extern bool btgettuple(IndexScanDesc scan, ScanDirection dir);
extern int64 btgetbitmap(IndexScanDesc scan, TIDBitmap *tbm);
extern void btrescan(IndexScanDesc scan, ScanKey scankey, int nscankeys,
                                         ScanKey orderbys, int norderbys);
extern void btparallelrescan(IndexScanDesc scan);
extern void btendscan(IndexScanDesc scan);
extern void btmarkpos(IndexScanDesc scan);
extern void btrestrpos(IndexScanDesc scan);
extern IndexBulkDeleteResult *btbulkdelete(IndexVacuumInfo *info,
                                                                                   IndexBulkDeleteResult *stats,
                                                                                   IndexBulkDeleteCallback callback,
                                                                                   void *callback_state);
extern IndexBulkDeleteResult *btvacuumcleanup(IndexVacuumInfo *info,
                                                                                          IndexBulkDeleteResult *stats);
extern bool btcanreturn(Relation index, int attno);

/*
 * prototypes for internal functions in nbtree.c
 */
extern bool _bt_parallel_seize(IndexScanDesc scan, BlockNumber *pageno);
extern void _bt_parallel_release(IndexScanDesc scan, BlockNumber scan_page);
extern void _bt_parallel_done(IndexScanDesc scan);
extern void _bt_parallel_advance_array_keys(IndexScanDesc scan);

/*
 * prototypes for functions in nbtdedup.c
 */
extern void _bt_dedup_pass(Relation rel, Buffer buf, Relation heapRel,
                                                   IndexTuple newitem, Size newitemsz,
                                                   bool checkingunique);
extern bool _bt_bottomupdel_pass(Relation rel, Buffer buf, Relation heapRel,
                                                                 Size newitemsz);
extern void _bt_dedup_start_pending(BTDedupState state, IndexTuple base,
                                                                        OffsetNumber baseoff);
extern bool _bt_dedup_save_htid(BTDedupState state, IndexTuple itup);
extern Size _bt_dedup_finish_pending(Page newpage, BTDedupState state);
extern IndexTuple _bt_form_posting(IndexTuple base, ItemPointer htids,
                                                                   int nhtids);
extern void _bt_update_posting(BTVacuumPosting vacposting);
extern IndexTuple _bt_swap_posting(IndexTuple newitem, IndexTuple oposting,
                                                                   int postingoff);

/*
 * prototypes for functions in nbtinsert.c
 */
extern bool _bt_doinsert(Relation rel, IndexTuple itup,
                                                 IndexUniqueCheck checkUnique, bool indexUnchanged,
                                                 Relation heapRel);
extern void _bt_finish_split(Relation rel, Buffer lbuf, BTStack stack);
extern Buffer _bt_getstackbuf(Relation rel, BTStack stack, BlockNumber child);

/*
 * prototypes for functions in nbtsplitloc.c
 */
extern OffsetNumber _bt_findsplitloc(Relation rel, Page origpage,
                                                                         OffsetNumber newitemoff, Size newitemsz, IndexTuple newitem,
                                                                         bool *newitemonleft);

/*
 * prototypes for functions in nbtpage.c
 */
extern void _bt_initmetapage(Page page, BlockNumber rootbknum, uint32 level,
                                                         bool allequalimage);
extern bool _bt_vacuum_needs_cleanup(Relation rel);
extern void _bt_set_cleanup_info(Relation rel, BlockNumber num_delpages);
extern void _bt_upgrademetapage(Page page);
extern Buffer _bt_getroot(Relation rel, int access);
extern Buffer _bt_gettrueroot(Relation rel);
extern int      _bt_getrootheight(Relation rel);
extern void _bt_metaversion(Relation rel, bool *heapkeyspace,
                                                        bool *allequalimage);
extern void _bt_checkpage(Relation rel, Buffer buf);
extern Buffer _bt_getbuf(Relation rel, BlockNumber blkno, int access);
extern Buffer _bt_relandgetbuf(Relation rel, Buffer obuf,
                                                           BlockNumber blkno, int access);
extern void _bt_relbuf(Relation rel, Buffer buf);
extern void _bt_lockbuf(Relation rel, Buffer buf, int access);
extern void _bt_unlockbuf(Relation rel, Buffer buf);
extern bool _bt_conditionallockbuf(Relation rel, Buffer buf);
extern void _bt_upgradelockbufcleanup(Relation rel, Buffer buf);
extern void _bt_pageinit(Page page, Size size);
extern void _bt_delitems_vacuum(Relation rel, Buffer buf,
                                                                OffsetNumber *deletable, int ndeletable,
                                                                BTVacuumPosting *updatable, int nupdatable);
extern void _bt_delitems_delete_check(Relation rel, Buffer buf,
                                                                          Relation heapRel,
                                                                          TM_IndexDeleteOp *delstate);
extern void _bt_pagedel(Relation rel, Buffer leafbuf, BTVacState *vstate);
extern void _bt_pendingfsm_init(Relation rel, BTVacState *vstate,
                                                                bool cleanuponly);
extern void _bt_pendingfsm_finalize(Relation rel, BTVacState *vstate);

/*
 * prototypes for functions in nbtsearch.c
 */
extern BTStack _bt_search(Relation rel, BTScanInsert key, Buffer *bufP,
                                                  int access, Snapshot snapshot);
extern Buffer _bt_moveright(Relation rel, BTScanInsert key, Buffer buf,
                                                        bool forupdate, BTStack stack, int access, Snapshot snapshot);
extern OffsetNumber _bt_binsrch_insert(Relation rel, BTInsertState insertstate);
extern int32 _bt_compare(Relation rel, BTScanInsert key, Page page, OffsetNumber offnum);
extern bool _bt_first(IndexScanDesc scan, ScanDirection dir);
extern bool _bt_next(IndexScanDesc scan, ScanDirection dir);
extern Buffer _bt_get_endpoint(Relation rel, uint32 level, bool rightmost,
                                                           Snapshot snapshot);

/*
 * prototypes for functions in nbtutils.c
 */
extern BTScanInsert _bt_mkscankey(Relation rel, IndexTuple itup);
extern void _bt_freestack(BTStack stack);
extern void _bt_preprocess_array_keys(IndexScanDesc scan);
extern void _bt_start_array_keys(IndexScanDesc scan, ScanDirection dir);
extern bool _bt_advance_array_keys(IndexScanDesc scan, ScanDirection dir);
extern void _bt_mark_array_keys(IndexScanDesc scan);
extern void _bt_restore_array_keys(IndexScanDesc scan);
extern void _bt_preprocess_keys(IndexScanDesc scan);
extern bool _bt_checkkeys(IndexScanDesc scan, IndexTuple tuple,
                                                  int tupnatts, ScanDirection dir, bool *continuescan);
extern void _bt_killitems(IndexScanDesc scan);
extern BTCycleId _bt_vacuum_cycleid(Relation rel);
extern BTCycleId _bt_start_vacuum(Relation rel);
extern void _bt_end_vacuum(Relation rel);
extern void _bt_end_vacuum_callback(int code, Datum arg);
extern Size BTreeShmemSize(void);
extern void BTreeShmemInit(void);
extern bytea *btoptions(Datum reloptions, bool validate);
extern bool btproperty(Oid index_oid, int attno,
                                           IndexAMProperty prop, const char *propname,
                                           bool *res, bool *isnull);
extern char *btbuildphasename(int64 phasenum);
extern IndexTuple _bt_truncate(Relation rel, IndexTuple lastleft,
                                                           IndexTuple firstright, BTScanInsert itup_key);
extern int      _bt_keep_natts_fast(Relation rel, IndexTuple lastleft,
                                                                IndexTuple firstright);
extern bool _bt_check_natts(Relation rel, bool heapkeyspace, Page page,
                                                        OffsetNumber offnum);
extern void _bt_check_third_page(Relation rel, Relation heap,
                                                                 bool needheaptidspace, Page page, IndexTuple newtup);
extern bool _bt_allequalimage(Relation rel, bool debugmessage);

/*
 * prototypes for functions in nbtvalidate.c
 */
extern bool btvalidate(Oid opclassoid);
extern void btadjustmembers(Oid opfamilyoid,
                                                        Oid opclassoid,
                                                        List *operators,
                                                        List *functions);

/*
 * prototypes for functions in nbtsort.c
 */
extern IndexBuildResult *btbuild(Relation heap, Relation index,
                                                                 struct IndexInfo *indexInfo);
extern void _bt_parallel_build_main(dsm_segment *seg, shm_toc *toc);

#endif                                                  /* NBTREE_H */