pgindent run for 8.2.

[pg-rex/syncrep.git] / src / include / access / nbtree.h

/*-------------------------------------------------------------------------
 *
 * nbtree.h
 *        header file for postgres btree access method implementation.
 *
 *
 * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $PostgreSQL: pgsql/src/include/access/nbtree.h,v 1.105 2006/10/04 00:30:07 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef NBTREE_H
#define NBTREE_H

#include "access/itup.h"
#include "access/relscan.h"
#include "access/sdir.h"
#include "access/xlogutils.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 65536 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_DELETEd tuples */


/*
 * 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 */

/*
 * 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) \
        ((PageGetPageSize(page) - \
          sizeof(PageHeaderData) - \
          MAXALIGN(sizeof(BTPageOpaqueData))) / 3 - sizeof(ItemIdData))

/*
 * 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_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 tuple */
#define XLOG_BTREE_DELETE_PAGE  0x80    /* delete an entire page */
#define XLOG_BTREE_DELETE_PAGE_META 0x90                /* same, plus update metapage */
#define XLOG_BTREE_NEWROOT              0xA0    /* new root page */

/*
 * 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 items of both left and right siblings
 * and restore content of both pages from 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.
 *
 * 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 otherblk is the right or left
 * page of the split pair).  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
{
        xl_btreetid target;                     /* inserted tuple id */
        BlockNumber otherblk;           /* second block participated in split: */
        /* first one is stored in target' tid */
        BlockNumber leftblk;            /* prev/left block */
        BlockNumber rightblk;           /* next/right block */
        uint32          level;                  /* tree level of page being split */
        uint16          leftlen;                /* len of left page items below */
        /* LEFT AND RIGHT PAGES TUPLES FOLLOW AT THE END */
} xl_btree_split;

#define SizeOfBtreeSplit        (offsetof(xl_btree_split, leftlen) + sizeof(uint16))

/*
 * 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.
 */
typedef struct xl_btree_delete
{
        RelFileNode node;
        BlockNumber block;
        /* TARGET OFFSET NUMBERS FOLLOW AT THE END */
} xl_btree_delete;

#define SizeOfBtreeDelete       (offsetof(xl_btree_delete, block) + 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.
 */
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 */
        /* xl_btree_metadata FOLLOWS IF XLOG_BTREE_DELETE_PAGE_META */
} xl_btree_delete_page;

#define SizeOfBtreeDeletePage   (offsetof(xl_btree_delete_page, rightblk) + sizeof(BlockNumber))

/*
 * 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.
 */

/*
 *      When a new operator class is declared, we require that the user
 *      supply us with an amproc procedure 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.  Since we
 *      only have one such proc in amproc, it's number 1.
 */

#define BTORDER_PROC    1

/*
 *      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.
 *
 * NOTE: in this implementation, btree does not use or set the
 * currentItemData and currentMarkData fields of IndexScanDesc at all.
 */

typedef struct BTScanPosItem    /* what we remember about each match */
{
        ItemPointerData heapTid;        /* TID of referenced heap item */
        OffsetNumber indexOffset;       /* index item's location within page */
} 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;

        /*
         * 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)

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 */

        /* 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 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 these private sk_flags bits in preprocessed scan keys
 */
#define SK_BT_REQFWD    0x00010000              /* required to continue forward scan */
#define SK_BT_REQBKWD   0x00020000              /* required to continue backward scan */


/*
 * prototypes for functions in nbtree.c (external entry points for btree)
 */
extern Datum btbuild(PG_FUNCTION_ARGS);
extern Datum btinsert(PG_FUNCTION_ARGS);
extern Datum btbeginscan(PG_FUNCTION_ARGS);
extern Datum btgettuple(PG_FUNCTION_ARGS);
extern Datum btgetmulti(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 btoptions(PG_FUNCTION_ARGS);

/*
 * prototypes for functions in nbtinsert.c
 */
extern void _bt_doinsert(Relation rel, IndexTuple itup,
                         bool index_is_unique, 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 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(Relation rel, Buffer buf,
                         OffsetNumber *itemnos, int nitems);
extern int      _bt_pagedel(Relation rel, Buffer buf, bool vacuum_full);

/*
 * 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_keys(IndexScanDesc scan);
extern bool _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 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 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 */