nbtree.h

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/*-------------------------------------------------------------------------
 *
 * nbtree.h
 *    header file for postgres btree access method implementation.
 *
 *
 * Portions Copyright (c) 1996-2013, 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/genam.h"
#include "access/itup.h"
#include "access/sdir.h"
#include "access/xlog.h"
#include "access/xlogutils.h"
#include "catalog/pg_index.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, we replace the level with the
 *  next-transaction-ID value indicating when it is safe to reclaim the page.
 *
 *  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.
 */

typedef struct BTPageOpaqueData
{
    BlockNumber btpo_prev;      /* left sibling, or P_NONE if leftmost */
    BlockNumber btpo_next;      /* right sibling, or P_NONE if rightmost */
    union
    {
        uint32      level;      /* tree level --- zero for leaf pages */
        TransactionId xact;     /* next transaction ID, if deleted */
    }           btpo;
    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 */

/*
 * 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;    /* should contain 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 */
} BTMetaPageData;

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

#define BTREE_METAPAGE  0       /* first page is meta */
#define BTREE_MAGIC     0x053162    /* magic number of btree pages */
#define BTREE_VERSION   2       /* current version number */

/*
 * 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.
 */
#define BTMaxItemSize(page) \
    MAXALIGN_DOWN((PageGetPageSize(page) - \
                   MAXALIGN(SizeOfPageHeaderData + 3*sizeof(ItemIdData)) - \
                   MAXALIGN(sizeof(BTPageOpaqueData))) / 3)

/*
 * 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.
 */
#define BTREE_MIN_FILLFACTOR        10
#define BTREE_DEFAULT_FILLFACTOR    90
#define BTREE_NONLEAF_FILLFACTOR    70

/*
 *  Test whether two btree entries are "the same".
 *
 *  Old comments:
 *  In addition, we must guarantee that all tuples in the index are unique,
 *  in order to satisfy some assumptions in Lehman and Yao.  The way that we
 *  do this is by generating a new OID for every insertion that we do in the
 *  tree.  This adds eight bytes to the size of btree index tuples.  Note
 *  that we do not use the OID as part of a composite key; the OID only
 *  serves as a unique identifier for a given index tuple (logical position
 *  within a page).
 *
 *  New comments:
 *  actually, we must guarantee that all tuples in A LEVEL
 *  are unique, not in ALL INDEX. So, we can use the t_tid
 *  as unique identifier for a given index tuple (logical position
 *  within a level). - vadim 04/09/97
 */
#define BTTidSame(i1, i2)   \
    ( (i1).ip_blkid.bi_hi == (i2).ip_blkid.bi_hi && \
      (i1).ip_blkid.bi_lo == (i2).ip_blkid.bi_lo && \
      (i1).ip_posid == (i2).ip_posid )
#define BTEntrySame(i1, i2) \
    BTTidSame((i1)->t_tid, (i2)->t_tid)


/*
 *  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)
#define P_ISROOT(opaque)        ((opaque)->btpo_flags & BTP_ROOT)
#define P_ISDELETED(opaque)     ((opaque)->btpo_flags & BTP_DELETED)
#define P_ISHALFDEAD(opaque)    ((opaque)->btpo_flags & BTP_HALF_DEAD)
#define P_IGNORE(opaque)        ((opaque)->btpo_flags & (BTP_DELETED|BTP_HALF_DEAD))
#define P_HAS_GARBAGE(opaque)   ((opaque)->btpo_flags & BTP_HAS_GARBAGE)

/*
 *  Lehman and Yao's algorithm requires a ``high key'' on every non-rightmost
 *  page.  The high key is not a data key, but gives info about what range of
 *  keys is supposed to be on this page.  The high key on a page is required
 *  to be greater than or equal to any data key that appears on the page.
 *  If we find ourselves trying to insert a key > 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)

/*
 * XLOG records for btree operations
 *
 * XLOG allows to store some information in high 4 bits of log
 * record xl_info field
 */
#define XLOG_BTREE_INSERT_LEAF  0x00    /* add index tuple without split */
#define XLOG_BTREE_INSERT_UPPER 0x10    /* same, on a non-leaf page */
#define XLOG_BTREE_INSERT_META  0x20    /* same, plus update metapage */
#define XLOG_BTREE_SPLIT_L      0x30    /* add index tuple with split */
#define XLOG_BTREE_SPLIT_R      0x40    /* as above, new item on right */
#define XLOG_BTREE_SPLIT_L_ROOT 0x50    /* add tuple with split of root */
#define XLOG_BTREE_SPLIT_R_ROOT 0x60    /* as above, new item on right */
#define XLOG_BTREE_DELETE       0x70    /* delete leaf index tuples for a page */
#define XLOG_BTREE_DELETE_PAGE  0x80    /* delete an entire page */
#define XLOG_BTREE_DELETE_PAGE_META 0x90        /* same, and update metapage */
#define XLOG_BTREE_NEWROOT      0xA0    /* new root page */
#define XLOG_BTREE_DELETE_PAGE_HALF 0xB0        /* page deletion that makes
                                                 * parent half-dead */
#define XLOG_BTREE_VACUUM       0xC0    /* delete entries on a page during
                                         * vacuum */
#define XLOG_BTREE_REUSE_PAGE   0xD0    /* old page is about to be reused from
                                         * FSM */

/*
 * All that we need to find changed index tuple
 */
typedef struct xl_btreetid
{
    RelFileNode node;
    ItemPointerData tid;        /* changed tuple id */
} xl_btreetid;

/*
 * All that we need to regenerate the meta-data page
 */
typedef struct xl_btree_metadata
{
    BlockNumber root;
    uint32      level;
    BlockNumber fastroot;
    uint32      fastlevel;
} xl_btree_metadata;

/*
 * This is what we need to know about simple (without split) insert.
 *
 * This data record is used for INSERT_LEAF, INSERT_UPPER, INSERT_META.
 * Note that INSERT_META implies it's not a leaf page.
 */
typedef struct xl_btree_insert
{
    xl_btreetid target;         /* inserted tuple id */
    /* BlockNumber downlink field FOLLOWS IF NOT XLOG_BTREE_INSERT_LEAF */
    /* xl_btree_metadata FOLLOWS IF XLOG_BTREE_INSERT_META */
    /* INDEX TUPLE FOLLOWS AT END OF STRUCT */
} xl_btree_insert;

#define SizeOfBtreeInsert   (offsetof(xl_btreetid, tid) + SizeOfIptrData)

/*
 * On insert with split, we save all the items going into the right sibling
 * so that we can restore it completely from the log record.  This way takes
 * less xlog space than the normal approach, because if we did it standardly,
 * XLogInsert would almost always think the right page is new and store its
 * whole page image.  The left page, however, is handled in the normal
 * incremental-update fashion.
 *
 * Note: the four XLOG_BTREE_SPLIT xl_info codes all use this data record.
 * The _L and _R variants indicate whether the inserted tuple went into the
 * left or right split page (and thus, whether newitemoff and the new item
 * are stored or not).  The _ROOT variants indicate that we are splitting
 * the root page, and thus that a newroot record rather than an insert or
 * split record should follow.  Note that a split record never carries a
 * metapage update --- we'll do that in the parent-level update.
 */
typedef struct xl_btree_split
{
    RelFileNode node;
    BlockNumber leftsib;        /* orig page / new left page */
    BlockNumber rightsib;       /* new right page */
    BlockNumber rnext;          /* next block (orig page's rightlink) */
    uint32      level;          /* tree level of page being split */
    OffsetNumber firstright;    /* first item moved to right page */

    /*
     * If level > 0, BlockIdData downlink follows.  (We use BlockIdData rather
     * than BlockNumber for alignment reasons: SizeOfBtreeSplit is only 16-bit
     * aligned.)
     *
     * If level > 0, an IndexTuple representing the HIKEY of the left page
     * follows.  We don't need this on leaf pages, because it's the same as
     * the leftmost key in the new right page.  Also, it's suppressed if
     * XLogInsert chooses to store the left page's whole page image.
     *
     * In the _L variants, next are OffsetNumber newitemoff and the new item.
     * (In the _R variants, the new item is one of the right page's tuples.)
     * The new item, but not newitemoff, is suppressed if XLogInsert chooses
     * to store the left page's whole page image.
     *
     * Last are the right page's tuples in the form used by _bt_restore_page.
     */
} xl_btree_split;

#define SizeOfBtreeSplit    (offsetof(xl_btree_split, firstright) + sizeof(OffsetNumber))

/*
 * This is what we need to know about delete of individual leaf index tuples.
 * The WAL record can represent deletion of any number of index tuples on a
 * single index page when *not* executed by VACUUM.
 */
typedef struct xl_btree_delete
{
    RelFileNode node;           /* RelFileNode of the index */
    BlockNumber block;
    RelFileNode hnode;          /* RelFileNode of the heap the index currently
                                 * points at */
    int         nitems;

    /* TARGET OFFSET NUMBERS FOLLOW AT THE END */
} xl_btree_delete;

#define SizeOfBtreeDelete   (offsetof(xl_btree_delete, nitems) + sizeof(int))

/*
 * This is what we need to know about page reuse within btree.
 */
typedef struct xl_btree_reuse_page
{
    RelFileNode node;
    BlockNumber block;
    TransactionId latestRemovedXid;
} xl_btree_reuse_page;

#define SizeOfBtreeReusePage    (sizeof(xl_btree_reuse_page))

/*
 * This is what we need to know about vacuum of individual leaf index tuples.
 * The WAL record can represent deletion of any number of index tuples on a
 * single index page when executed by VACUUM.
 *
 * The correctness requirement for applying these changes during recovery is
 * that we must do one of these two things for every block in the index:
 *      * lock the block for cleanup and apply any required changes
 *      * EnsureBlockUnpinned()
 * The purpose of this is to ensure that no index scans started before we
 * finish scanning the index are still running by the time we begin to remove
 * heap tuples.
 *
 * Any changes to any one block are registered on just one WAL record. All
 * blocks that we need to run EnsureBlockUnpinned() are listed as a block range
 * starting from the last block vacuumed through until this one. Individual
 * block numbers aren't given.
 *
 * Note that the *last* WAL record in any vacuum of an index is allowed to
 * have a zero length array of offsets. Earlier records must have at least one.
 */
typedef struct xl_btree_vacuum
{
    RelFileNode node;
    BlockNumber block;
    BlockNumber lastBlockVacuumed;

    /* TARGET OFFSET NUMBERS FOLLOW */
} xl_btree_vacuum;

#define SizeOfBtreeVacuum   (offsetof(xl_btree_vacuum, lastBlockVacuumed) + sizeof(BlockNumber))

/*
 * This is what we need to know about deletion of a btree page.  The target
 * identifies the tuple removed from the parent page (note that we remove
 * this tuple's downlink and the *following* tuple's key).  Note we do not
 * store any content for the deleted page --- it is just rewritten as empty
 * during recovery, apart from resetting the btpo.xact.
 */
typedef struct xl_btree_delete_page
{
    xl_btreetid target;         /* deleted tuple id in parent page */
    BlockNumber deadblk;        /* child block being deleted */
    BlockNumber leftblk;        /* child block's left sibling, if any */
    BlockNumber rightblk;       /* child block's right sibling */
    TransactionId btpo_xact;    /* value of btpo.xact for use in recovery */
    /* xl_btree_metadata FOLLOWS IF XLOG_BTREE_DELETE_PAGE_META */
} xl_btree_delete_page;

#define SizeOfBtreeDeletePage   (offsetof(xl_btree_delete_page, btpo_xact) + sizeof(TransactionId))

/*
 * New root log record.  There are zero tuples if this is to establish an
 * empty root, or two if it is the result of splitting an old root.
 *
 * Note that although this implies rewriting the metadata page, we don't need
 * an xl_btree_metadata record --- the rootblk and level are sufficient.
 */
typedef struct xl_btree_newroot
{
    RelFileNode node;
    BlockNumber rootblk;        /* location of new root */
    uint32      level;          /* its tree level */
    /* 0 or 2 INDEX TUPLES FOLLOW AT END OF STRUCT */
} xl_btree_newroot;

#define SizeOfBtreeNewroot  (offsetof(xl_btree_newroot, level) + sizeof(uint32))


/*
 *  Operator strategy numbers for B-tree have been moved to access/skey.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.  (It must
 *  not return INT_MIN, since we may negate the result before using it.)
 *
 *  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.
 */

#define BTORDER_PROC        1
#define BTSORTSUPPORT_PROC  2

/*
 *  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, downlink)
 *  pairs from internal pages onto a private stack.  If we split a
 *  leaf, we use this stack to walk back up the tree and insert data
 *  into parent pages (and possibly to split them, too).  Lehman and
 *  Yao's update algorithm guarantees that under no circumstances can
 *  our private stack give us an irredeemably bad picture up the tree.
 *  Again, see the paper for details.
 */

typedef struct BTStackData
{
    BlockNumber bts_blkno;
    OffsetNumber bts_offset;
    IndexTupleData bts_btentry;
    struct BTStackData *bts_parent;
} BTStackData;

typedef BTStackData *BTStack;

/*
 * 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.
 */

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 */

    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[MaxIndexTuplesPerPage]; /* MUST BE LAST */
} BTScanPosData;

typedef BTScanPosData *BTScanPos;

#define BTScanPosIsValid(scanpos) BufferIsValid((scanpos).buf)

/* 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) */
    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)

/*
 * prototypes for functions in nbtree.c (external entry points for btree)
 */
extern Datum btbuild(PG_FUNCTION_ARGS);
extern Datum btbuildempty(PG_FUNCTION_ARGS);
extern Datum btinsert(PG_FUNCTION_ARGS);
extern Datum btbeginscan(PG_FUNCTION_ARGS);
extern Datum btgettuple(PG_FUNCTION_ARGS);
extern Datum btgetbitmap(PG_FUNCTION_ARGS);
extern Datum btrescan(PG_FUNCTION_ARGS);
extern Datum btendscan(PG_FUNCTION_ARGS);
extern Datum btmarkpos(PG_FUNCTION_ARGS);
extern Datum btrestrpos(PG_FUNCTION_ARGS);
extern Datum btbulkdelete(PG_FUNCTION_ARGS);
extern Datum btvacuumcleanup(PG_FUNCTION_ARGS);
extern Datum btcanreturn(PG_FUNCTION_ARGS);
extern Datum btoptions(PG_FUNCTION_ARGS);

/*
 * prototypes for functions in nbtinsert.c
 */
extern bool _bt_doinsert(Relation rel, IndexTuple itup,
             IndexUniqueCheck checkUnique, Relation heapRel);
extern Buffer _bt_getstackbuf(Relation rel, BTStack stack, int access);
extern void _bt_insert_parent(Relation rel, Buffer buf, Buffer rbuf,
                  BTStack stack, bool is_root, bool is_only);

/*
 * prototypes for functions in nbtpage.c
 */
extern void _bt_initmetapage(Page page, BlockNumber rootbknum, uint32 level);
extern Buffer _bt_getroot(Relation rel, int access);
extern Buffer _bt_gettrueroot(Relation rel);
extern int  _bt_getrootheight(Relation rel);
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_pageinit(Page page, Size size);
extern bool _bt_page_recyclable(Page page);
extern void _bt_delitems_delete(Relation rel, Buffer buf,
                    OffsetNumber *itemnos, int nitems, Relation heapRel);
extern void _bt_delitems_vacuum(Relation rel, Buffer buf,
                    OffsetNumber *itemnos, int nitems,
                    BlockNumber lastBlockVacuumed);
extern int  _bt_pagedel(Relation rel, Buffer buf, BTStack stack);

/*
 * prototypes for functions in nbtsearch.c
 */
extern BTStack _bt_search(Relation rel,
           int keysz, ScanKey scankey, bool nextkey,
           Buffer *bufP, int access);
extern Buffer _bt_moveright(Relation rel, Buffer buf, int keysz,
              ScanKey scankey, bool nextkey, int access);
extern OffsetNumber _bt_binsrch(Relation rel, Buffer buf, int keysz,
            ScanKey scankey, bool nextkey);
extern int32 _bt_compare(Relation rel, int keysz, ScanKey scankey,
            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);

/*
 * prototypes for functions in nbtutils.c
 */
extern ScanKey _bt_mkscankey(Relation rel, IndexTuple itup);
extern ScanKey _bt_mkscankey_nodata(Relation rel);
extern void _bt_freeskey(ScanKey skey);
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 IndexTuple _bt_checkkeys(IndexScanDesc scan,
              Page page, OffsetNumber offnum,
              ScanDirection dir, bool *continuescan);
extern void _bt_killitems(IndexScanDesc scan, bool haveLock);
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);

/*
 * prototypes for functions in nbtsort.c
 */
typedef struct BTSpool BTSpool; /* opaque type known only within nbtsort.c */

extern BTSpool *_bt_spoolinit(Relation heap, Relation index,
              bool isunique, bool isdead);
extern void _bt_spooldestroy(BTSpool *btspool);
extern void _bt_spool(IndexTuple itup, BTSpool *btspool);
extern void _bt_leafbuild(BTSpool *btspool, BTSpool *spool2);

/*
 * prototypes for functions in nbtxlog.c
 */
extern void btree_redo(XLogRecPtr lsn, XLogRecord *record);
extern void btree_desc(StringInfo buf, uint8 xl_info, char *rec);
extern void btree_xlog_startup(void);
extern void btree_xlog_cleanup(void);
extern bool btree_safe_restartpoint(void);

#endif   /* NBTREE_H */