1996-07-09 08:22:35 +02:00
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/*-------------------------------------------------------------------------
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*
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* btsearch.c--
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* search code for postgres btrees.
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*
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* Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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1996-11-05 11:35:38 +01:00
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* $Header: /cvsroot/pgsql/src/backend/access/nbtree/nbtsearch.c,v 1.8 1996/11/05 10:35:34 scrappy Exp $
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1996-07-09 08:22:35 +02:00
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*
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*-------------------------------------------------------------------------
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*/
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1996-11-05 11:35:38 +01:00
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#include <postgres.h>
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1996-07-09 08:22:35 +02:00
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1996-11-05 11:35:38 +01:00
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#include <access/genam.h>
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#include <fmgr.h>
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#include <storage/bufpage.h>
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#include <storage/bufmgr.h>
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#include <access/nbtree.h>
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1996-10-23 09:42:13 +02:00
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1996-11-03 13:35:27 +01:00
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#ifndef HAVE_MEMMOVE
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1996-11-05 11:35:38 +01:00
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# include <regex/utils.h>
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1996-11-03 13:35:27 +01:00
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#else
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# include <string.h>
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#endif
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1996-07-09 08:22:35 +02:00
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static BTStack _bt_searchr(Relation rel, int keysz, ScanKey scankey, Buffer *bufP, BTStack stack_in);
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static OffsetNumber _bt_firsteq(Relation rel, TupleDesc itupdesc, Page page, Size keysz, ScanKey scankey, OffsetNumber offnum);
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static int _bt_compare(Relation rel, TupleDesc itupdesc, Page page, int keysz, ScanKey scankey, OffsetNumber offnum);
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static bool _bt_twostep(IndexScanDesc scan, Buffer *bufP, ScanDirection dir);
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static RetrieveIndexResult _bt_endpoint(IndexScanDesc scan, ScanDirection dir);
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/*
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* _bt_search() -- Search for a scan key in the index.
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*
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* This routine is actually just a helper that sets things up and
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* calls a recursive-descent search routine on the tree.
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*/
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BTStack
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_bt_search(Relation rel, int keysz, ScanKey scankey, Buffer *bufP)
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{
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*bufP = _bt_getroot(rel, BT_READ);
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return (_bt_searchr(rel, keysz, scankey, bufP, (BTStack) NULL));
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}
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/*
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* _bt_searchr() -- Search the tree recursively for a particular scankey.
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*/
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static BTStack
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_bt_searchr(Relation rel,
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int keysz,
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ScanKey scankey,
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Buffer *bufP,
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BTStack stack_in)
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{
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BTStack stack;
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OffsetNumber offnum;
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Page page;
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BTPageOpaque opaque;
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BlockNumber par_blkno;
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BlockNumber blkno;
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ItemId itemid;
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BTItem btitem;
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BTItem item_save;
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int item_nbytes;
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IndexTuple itup;
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/* if this is a leaf page, we're done */
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page = BufferGetPage(*bufP);
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opaque = (BTPageOpaque) PageGetSpecialPointer(page);
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if (opaque->btpo_flags & BTP_LEAF)
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return (stack_in);
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/*
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* Find the appropriate item on the internal page, and get the child
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* page that it points to.
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*/
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par_blkno = BufferGetBlockNumber(*bufP);
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offnum = _bt_binsrch(rel, *bufP, keysz, scankey, BT_DESCENT);
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itemid = PageGetItemId(page, offnum);
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btitem = (BTItem) PageGetItem(page, itemid);
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itup = &(btitem->bti_itup);
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blkno = ItemPointerGetBlockNumber(&(itup->t_tid));
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/*
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* We need to save the bit image of the index entry we chose in the
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* parent page on a stack. In case we split the tree, we'll use this
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* bit image to figure out what our real parent page is, in case the
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* parent splits while we're working lower in the tree. See the paper
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* by Lehman and Yao for how this is detected and handled. (We use
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* unique OIDs to disambiguate duplicate keys in the index -- Lehman
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* and Yao disallow duplicate keys).
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*/
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item_nbytes = ItemIdGetLength(itemid);
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item_save = (BTItem) palloc(item_nbytes);
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memmove((char *) item_save, (char *) btitem, item_nbytes);
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stack = (BTStack) palloc(sizeof(BTStackData));
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stack->bts_blkno = par_blkno;
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stack->bts_offset = offnum;
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stack->bts_btitem = item_save;
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stack->bts_parent = stack_in;
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/* drop the read lock on the parent page and acquire one on the child */
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_bt_relbuf(rel, *bufP, BT_READ);
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*bufP = _bt_getbuf(rel, blkno, BT_READ);
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/*
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* Race -- the page we just grabbed may have split since we read its
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* pointer in the parent. If it has, we may need to move right to its
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* new sibling. Do that.
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*/
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*bufP = _bt_moveright(rel, *bufP, keysz, scankey, BT_READ);
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/* okay, all set to move down a level */
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return (_bt_searchr(rel, keysz, scankey, bufP, stack));
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}
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/*
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* _bt_moveright() -- move right in the btree if necessary.
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*
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* When we drop and reacquire a pointer to a page, it is possible that
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* the page has changed in the meanwhile. If this happens, we're
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* guaranteed that the page has "split right" -- that is, that any
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* data that appeared on the page originally is either on the page
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* or strictly to the right of it.
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*
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* This routine decides whether or not we need to move right in the
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* tree by examining the high key entry on the page. If that entry
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* is strictly less than one we expect to be on the page, then our
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* picture of the page is incorrect and we need to move right.
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*
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* On entry, we have the buffer pinned and a lock of the proper type.
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* If we move right, we release the buffer and lock and acquire the
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* same on the right sibling.
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*/
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Buffer
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_bt_moveright(Relation rel,
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Buffer buf,
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int keysz,
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ScanKey scankey,
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int access)
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{
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Page page;
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BTPageOpaque opaque;
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ItemId hikey;
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ItemId itemid;
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BlockNumber rblkno;
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page = BufferGetPage(buf);
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opaque = (BTPageOpaque) PageGetSpecialPointer(page);
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/* if we're on a rightmost page, we don't need to move right */
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if (P_RIGHTMOST(opaque))
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return (buf);
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/* by convention, item 0 on non-rightmost pages is the high key */
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hikey = PageGetItemId(page, P_HIKEY);
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/*
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* If the scan key that brought us to this page is >= the high key
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* stored on the page, then the page has split and we need to move
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* right.
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*/
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if (_bt_skeycmp(rel, keysz, scankey, page, hikey,
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BTGreaterEqualStrategyNumber)) {
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/* move right as long as we need to */
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do {
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/*
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* If this page consists of all duplicate keys (hikey and first
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* key on the page have the same value), then we don't need to
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* step right.
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*/
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if (PageGetMaxOffsetNumber(page) > P_HIKEY) {
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itemid = PageGetItemId(page, P_FIRSTKEY);
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if (_bt_skeycmp(rel, keysz, scankey, page, itemid,
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BTEqualStrategyNumber)) {
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/* break is for the "move right" while loop */
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break;
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}
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}
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/* step right one page */
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rblkno = opaque->btpo_next;
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_bt_relbuf(rel, buf, access);
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buf = _bt_getbuf(rel, rblkno, access);
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page = BufferGetPage(buf);
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opaque = (BTPageOpaque) PageGetSpecialPointer(page);
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hikey = PageGetItemId(page, P_HIKEY);
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} while (! P_RIGHTMOST(opaque)
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&& _bt_skeycmp(rel, keysz, scankey, page, hikey,
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BTGreaterEqualStrategyNumber));
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}
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return (buf);
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}
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/*
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* _bt_skeycmp() -- compare a scan key to a particular item on a page using
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* a requested strategy (<, <=, =, >=, >).
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*
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* We ignore the unique OIDs stored in the btree item here. Those
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* numbers are intended for use internally only, in repositioning a
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* scan after a page split. They do not impose any meaningful ordering.
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*
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* The comparison is A <op> B, where A is the scan key and B is the
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* tuple pointed at by itemid on page.
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*/
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bool
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_bt_skeycmp(Relation rel,
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Size keysz,
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ScanKey scankey,
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Page page,
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ItemId itemid,
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StrategyNumber strat)
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{
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BTItem item;
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IndexTuple indexTuple;
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TupleDesc tupDes;
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ScanKey entry;
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int i;
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Datum attrDatum;
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Datum keyDatum;
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bool compare;
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bool isNull;
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item = (BTItem) PageGetItem(page, itemid);
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indexTuple = &(item->bti_itup);
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tupDes = RelationGetTupleDescriptor(rel);
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/* see if the comparison is true for all of the key attributes */
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for (i=1; i <= keysz; i++) {
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entry = &scankey[i-1];
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attrDatum = index_getattr(indexTuple,
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entry->sk_attno,
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tupDes,
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&isNull);
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keyDatum = entry->sk_argument;
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1996-10-30 07:08:10 +01:00
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/*
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* This may happen in a nested loop if an attribute used
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* as scan key is null. DZ 29-10-1996
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*/
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if ((entry->sk_flags & SK_ISNULL) || (isNull)) {
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if ((entry->sk_flags & SK_ISNULL) && (isNull)) {
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return (true);
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} else {
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return (false);
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}
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}
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1996-07-09 08:22:35 +02:00
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compare = _bt_invokestrat(rel, i, strat, keyDatum, attrDatum);
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if (!compare)
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return (false);
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}
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return (true);
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}
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/*
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* _bt_binsrch() -- Do a binary search for a key on a particular page.
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*
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* The scankey we get has the compare function stored in the procedure
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* entry of each data struct. We invoke this regproc to do the
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* comparison for every key in the scankey. _bt_binsrch() returns
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* the OffsetNumber of the first matching key on the page, or the
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* OffsetNumber at which the matching key would appear if it were
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* on this page.
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*
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* By the time this procedure is called, we're sure we're looking
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* at the right page -- don't need to walk right. _bt_binsrch() has
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* no lock or refcount side effects on the buffer.
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*/
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OffsetNumber
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_bt_binsrch(Relation rel,
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Buffer buf,
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int keysz,
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ScanKey scankey,
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int srchtype)
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{
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TupleDesc itupdesc;
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Page page;
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BTPageOpaque opaque;
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OffsetNumber low, mid, high;
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int result;
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page = BufferGetPage(buf);
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opaque = (BTPageOpaque) PageGetSpecialPointer(page);
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/* by convention, item 0 on any non-rightmost page is the high key */
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1996-10-23 09:42:13 +02:00
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low = mid = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
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1996-07-09 08:22:35 +02:00
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high = PageGetMaxOffsetNumber(page);
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/*
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* Since for non-rightmost pages, the zeroeth item on the page is the
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* high key, there are two notions of emptiness. One is if nothing
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* appears on the page. The other is if nothing but the high key does.
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* The reason we test high <= low, rather than high == low, is that
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* after vacuuming there may be nothing *but* the high key on a page.
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* In that case, given the scheme above, low = 1 and high = 0.
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*/
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if (PageIsEmpty(page) || (! P_RIGHTMOST(opaque) && high <= low))
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return (low);
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itupdesc = RelationGetTupleDescriptor(rel);
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while ((high - low) > 1) {
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mid = low + ((high - low) / 2);
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result = _bt_compare(rel, itupdesc, page, keysz, scankey, mid);
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if (result > 0)
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low = mid;
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else if (result < 0)
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high = mid - 1;
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1996-10-23 09:42:13 +02:00
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else
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1996-07-09 08:22:35 +02:00
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return (_bt_firsteq(rel, itupdesc, page, keysz, scankey, mid));
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1996-10-23 09:42:13 +02:00
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}
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1996-07-09 08:22:35 +02:00
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/*
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* We terminated because the endpoints got too close together. There
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* are two cases to take care of.
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*
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* For non-insertion searches on internal pages, we want to point at
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* the last key <, or first key =, the scankey on the page. This
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* guarantees that we'll descend the tree correctly.
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*
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* For all other cases, we want to point at the first key >=
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* the scankey on the page. This guarantees that scans and
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* insertions will happen correctly.
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*/
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opaque = (BTPageOpaque) PageGetSpecialPointer(page);
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if (!(opaque->btpo_flags & BTP_LEAF) && srchtype == BT_DESCENT) {
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/*
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* We want the last key <, or first key ==, the scan key.
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*/
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result = _bt_compare(rel, itupdesc, page, keysz, scankey, high);
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if (result == 0) {
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return (_bt_firsteq(rel, itupdesc, page, keysz, scankey, high));
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} else if (result > 0) {
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return (high);
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} else {
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return (low);
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}
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|
} else {
|
|
|
|
|
|
|
|
/* we want the first key >= the scan key */
|
|
|
|
result = _bt_compare(rel, itupdesc, page, keysz, scankey, low);
|
|
|
|
if (result <= 0) {
|
|
|
|
return (low);
|
|
|
|
} else {
|
|
|
|
if (low == high)
|
|
|
|
return (OffsetNumberNext(low));
|
|
|
|
|
|
|
|
result = _bt_compare(rel, itupdesc, page, keysz, scankey, high);
|
|
|
|
if (result <= 0)
|
|
|
|
return (high);
|
|
|
|
else
|
|
|
|
return (OffsetNumberNext(high));
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
static OffsetNumber
|
|
|
|
_bt_firsteq(Relation rel,
|
|
|
|
TupleDesc itupdesc,
|
|
|
|
Page page,
|
|
|
|
Size keysz,
|
|
|
|
ScanKey scankey,
|
|
|
|
OffsetNumber offnum)
|
|
|
|
{
|
|
|
|
BTPageOpaque opaque;
|
|
|
|
OffsetNumber limit;
|
|
|
|
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
|
|
|
|
/* skip the high key, if any */
|
|
|
|
limit = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
|
|
|
|
|
|
|
|
/* walk backwards looking for the first key in the chain of duplicates */
|
|
|
|
while (offnum > limit
|
|
|
|
&& _bt_compare(rel, itupdesc, page,
|
|
|
|
keysz, scankey, OffsetNumberPrev(offnum)) == 0) {
|
|
|
|
offnum = OffsetNumberPrev(offnum);
|
|
|
|
}
|
|
|
|
|
|
|
|
return (offnum);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* _bt_compare() -- Compare scankey to a particular tuple on the page.
|
|
|
|
*
|
|
|
|
* This routine returns:
|
|
|
|
* -1 if scankey < tuple at offnum;
|
|
|
|
* 0 if scankey == tuple at offnum;
|
|
|
|
* +1 if scankey > tuple at offnum.
|
|
|
|
*
|
|
|
|
* In order to avoid having to propagate changes up the tree any time
|
|
|
|
* a new minimal key is inserted, the leftmost entry on the leftmost
|
|
|
|
* page is less than all possible keys, by definition.
|
|
|
|
*/
|
|
|
|
static int
|
|
|
|
_bt_compare(Relation rel,
|
|
|
|
TupleDesc itupdesc,
|
|
|
|
Page page,
|
|
|
|
int keysz,
|
|
|
|
ScanKey scankey,
|
|
|
|
OffsetNumber offnum)
|
|
|
|
{
|
|
|
|
Datum datum;
|
|
|
|
BTItem btitem;
|
|
|
|
ItemId itemid;
|
|
|
|
IndexTuple itup;
|
|
|
|
BTPageOpaque opaque;
|
|
|
|
ScanKey entry;
|
|
|
|
AttrNumber attno;
|
|
|
|
int result;
|
|
|
|
int i;
|
|
|
|
bool null;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* If this is a leftmost internal page, and if our comparison is
|
|
|
|
* with the first key on the page, then the item at that position is
|
|
|
|
* by definition less than the scan key.
|
|
|
|
*/
|
|
|
|
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
if (!(opaque->btpo_flags & BTP_LEAF)
|
|
|
|
&& P_LEFTMOST(opaque)
|
|
|
|
&& offnum == P_HIKEY) {
|
|
|
|
itemid = PageGetItemId(page, offnum);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* we just have to believe that this will only be called with
|
|
|
|
* offnum == P_HIKEY when P_HIKEY is the OffsetNumber of the
|
|
|
|
* first actual data key (i.e., this is also a rightmost
|
|
|
|
* page). there doesn't seem to be any code that implies
|
|
|
|
* that the leftmost page is normally missing a high key as
|
|
|
|
* well as the rightmost page. but that implies that this
|
|
|
|
* code path only applies to the root -- which seems
|
|
|
|
* unlikely..
|
|
|
|
*/
|
|
|
|
if (! P_RIGHTMOST(opaque)) {
|
|
|
|
elog(WARN, "_bt_compare: invalid comparison to high key");
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* If the item on the page is equal to the scankey, that's
|
|
|
|
* okay to admit. We just can't claim that the first key on
|
|
|
|
* the page is greater than anything.
|
|
|
|
*/
|
|
|
|
|
|
|
|
if (_bt_skeycmp(rel, keysz, scankey, page, itemid,
|
|
|
|
BTEqualStrategyNumber)) {
|
|
|
|
return (0);
|
|
|
|
}
|
|
|
|
return (1);
|
|
|
|
}
|
|
|
|
|
|
|
|
btitem = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
|
|
|
|
itup = &(btitem->bti_itup);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* The scan key is set up with the attribute number associated with each
|
|
|
|
* term in the key. It is important that, if the index is multi-key,
|
|
|
|
* the scan contain the first k key attributes, and that they be in
|
|
|
|
* order. If you think about how multi-key ordering works, you'll
|
|
|
|
* understand why this is.
|
|
|
|
*
|
|
|
|
* We don't test for violation of this condition here.
|
|
|
|
*/
|
|
|
|
|
|
|
|
for (i = 1; i <= keysz; i++) {
|
|
|
|
long tmpres;
|
|
|
|
|
|
|
|
entry = &scankey[i - 1];
|
|
|
|
attno = entry->sk_attno;
|
|
|
|
datum = index_getattr(itup, attno, itupdesc, &null);
|
1996-10-30 07:08:10 +01:00
|
|
|
|
|
|
|
/*
|
|
|
|
* This may happen in a nested loop if an attribute used
|
|
|
|
* as scan key is null. DZ 29-10-1996
|
|
|
|
*/
|
|
|
|
if ((entry->sk_flags & SK_ISNULL) || (null)) {
|
|
|
|
if ((entry->sk_flags & SK_ISNULL) && (null)) {
|
|
|
|
return (0);
|
|
|
|
} else {
|
|
|
|
return (null ? +1 : -1);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
1996-07-09 08:22:35 +02:00
|
|
|
tmpres = (long) FMGR_PTR2(entry->sk_func, entry->sk_procedure,
|
|
|
|
entry->sk_argument, datum);
|
|
|
|
result = tmpres;
|
|
|
|
|
|
|
|
/* if the keys are unequal, return the difference */
|
|
|
|
if (result != 0)
|
|
|
|
return (result);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* by here, the keys are equal */
|
|
|
|
return (0);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* _bt_next() -- Get the next item in a scan.
|
|
|
|
*
|
|
|
|
* On entry, we have a valid currentItemData in the scan, and a
|
|
|
|
* read lock on the page that contains that item. We do not have
|
|
|
|
* the page pinned. We return the next item in the scan. On
|
|
|
|
* exit, we have the page containing the next item locked but not
|
|
|
|
* pinned.
|
|
|
|
*/
|
|
|
|
RetrieveIndexResult
|
|
|
|
_bt_next(IndexScanDesc scan, ScanDirection dir)
|
|
|
|
{
|
|
|
|
Relation rel;
|
|
|
|
Buffer buf;
|
|
|
|
Page page;
|
|
|
|
OffsetNumber offnum;
|
|
|
|
RetrieveIndexResult res;
|
|
|
|
BlockNumber blkno;
|
|
|
|
ItemPointer current;
|
|
|
|
ItemPointer iptr;
|
|
|
|
BTItem btitem;
|
|
|
|
IndexTuple itup;
|
|
|
|
BTScanOpaque so;
|
|
|
|
|
|
|
|
rel = scan->relation;
|
|
|
|
so = (BTScanOpaque) scan->opaque;
|
|
|
|
current = &(scan->currentItemData);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* XXX 10 may 91: somewhere there's a bug in our management of the
|
|
|
|
* cached buffer for this scan. wei discovered it. the following
|
|
|
|
* is a workaround so he can work until i figure out what's going on.
|
|
|
|
*/
|
|
|
|
|
|
|
|
if (!BufferIsValid(so->btso_curbuf))
|
|
|
|
so->btso_curbuf = _bt_getbuf(rel, ItemPointerGetBlockNumber(current),
|
|
|
|
BT_READ);
|
|
|
|
|
|
|
|
/* we still have the buffer pinned and locked */
|
|
|
|
buf = so->btso_curbuf;
|
|
|
|
blkno = BufferGetBlockNumber(buf);
|
|
|
|
|
|
|
|
/* step one tuple in the appropriate direction */
|
|
|
|
if (!_bt_step(scan, &buf, dir))
|
|
|
|
return ((RetrieveIndexResult) NULL);
|
|
|
|
|
|
|
|
/* by here, current is the tuple we want to return */
|
|
|
|
offnum = ItemPointerGetOffsetNumber(current);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
btitem = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
|
|
|
|
itup = &btitem->bti_itup;
|
|
|
|
|
|
|
|
if (_bt_checkqual(scan, itup)) {
|
|
|
|
iptr = (ItemPointer) palloc(sizeof(ItemPointerData));
|
|
|
|
memmove((char *) iptr, (char *) &(itup->t_tid),
|
|
|
|
sizeof(ItemPointerData));
|
|
|
|
res = FormRetrieveIndexResult(current, iptr);
|
|
|
|
|
|
|
|
/* remember which buffer we have pinned and locked */
|
|
|
|
so->btso_curbuf = buf;
|
|
|
|
} else {
|
|
|
|
ItemPointerSetInvalid(current);
|
|
|
|
so->btso_curbuf = InvalidBuffer;
|
|
|
|
_bt_relbuf(rel, buf, BT_READ);
|
|
|
|
res = (RetrieveIndexResult) NULL;
|
|
|
|
}
|
|
|
|
|
|
|
|
return (res);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* _bt_first() -- Find the first item in a scan.
|
|
|
|
*
|
|
|
|
* We need to be clever about the type of scan, the operation it's
|
|
|
|
* performing, and the tree ordering. We return the RetrieveIndexResult
|
|
|
|
* of the first item in the tree that satisfies the qualification
|
|
|
|
* associated with the scan descriptor. On exit, the page containing
|
|
|
|
* the current index tuple is read locked and pinned, and the scan's
|
|
|
|
* opaque data entry is updated to include the buffer.
|
|
|
|
*/
|
|
|
|
RetrieveIndexResult
|
|
|
|
_bt_first(IndexScanDesc scan, ScanDirection dir)
|
|
|
|
{
|
|
|
|
Relation rel;
|
|
|
|
TupleDesc itupdesc;
|
|
|
|
Buffer buf;
|
|
|
|
Page page;
|
|
|
|
BTStack stack;
|
|
|
|
OffsetNumber offnum, maxoff;
|
|
|
|
BTItem btitem;
|
|
|
|
IndexTuple itup;
|
|
|
|
ItemPointer current;
|
|
|
|
ItemPointer iptr;
|
|
|
|
BlockNumber blkno;
|
|
|
|
StrategyNumber strat;
|
|
|
|
RetrieveIndexResult res;
|
|
|
|
RegProcedure proc;
|
|
|
|
int result;
|
|
|
|
BTScanOpaque so;
|
|
|
|
ScanKeyData skdata;
|
|
|
|
|
1996-07-30 09:56:04 +02:00
|
|
|
so = (BTScanOpaque) scan->opaque;
|
|
|
|
if ( so->qual_ok == 0 ) /* may be set by _bt_orderkeys */
|
|
|
|
return ((RetrieveIndexResult) NULL);
|
|
|
|
|
1996-07-09 08:22:35 +02:00
|
|
|
/* if we just need to walk down one edge of the tree, do that */
|
|
|
|
if (scan->scanFromEnd)
|
|
|
|
return (_bt_endpoint(scan, dir));
|
|
|
|
|
|
|
|
rel = scan->relation;
|
|
|
|
itupdesc = RelationGetTupleDescriptor(scan->relation);
|
|
|
|
current = &(scan->currentItemData);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Okay, we want something more complicated. What we'll do is use
|
|
|
|
* the first item in the scan key passed in (which has been correctly
|
|
|
|
* ordered to take advantage of index ordering) to position ourselves
|
|
|
|
* at the right place in the scan.
|
|
|
|
*/
|
|
|
|
|
|
|
|
/*
|
|
|
|
* XXX -- The attribute number stored in the scan key is the attno
|
|
|
|
* in the heap relation. We need to transmogrify this into
|
|
|
|
* the index relation attno here. For the moment, we have
|
|
|
|
* hardwired attno == 1.
|
|
|
|
*/
|
|
|
|
proc = index_getprocid(rel, 1, BTORDER_PROC);
|
1996-10-30 07:08:10 +01:00
|
|
|
ScanKeyEntryInitialize(&skdata, so->keyData[0].sk_flags, 1, proc,
|
1996-07-30 09:56:04 +02:00
|
|
|
so->keyData[0].sk_argument);
|
1996-07-09 08:22:35 +02:00
|
|
|
|
|
|
|
stack = _bt_search(rel, 1, &skdata, &buf);
|
|
|
|
_bt_freestack(stack);
|
|
|
|
|
|
|
|
/* find the nearest match to the manufactured scan key on the page */
|
|
|
|
offnum = _bt_binsrch(rel, buf, 1, &skdata, BT_DESCENT);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* This will happen if the tree we're searching is entirely empty,
|
|
|
|
* or if we're doing a search for a key that would appear on an
|
|
|
|
* entirely empty internal page. In either case, there are no
|
|
|
|
* matching tuples in the index.
|
|
|
|
*/
|
|
|
|
|
|
|
|
if (PageIsEmpty(page)) {
|
|
|
|
ItemPointerSetInvalid(current);
|
|
|
|
so->btso_curbuf = InvalidBuffer;
|
|
|
|
_bt_relbuf(rel, buf, BT_READ);
|
|
|
|
return ((RetrieveIndexResult) NULL);
|
|
|
|
}
|
|
|
|
|
|
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
|
|
|
|
if (offnum > maxoff)
|
|
|
|
offnum = maxoff;
|
|
|
|
|
|
|
|
blkno = BufferGetBlockNumber(buf);
|
|
|
|
ItemPointerSet(current, blkno, offnum);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Now find the right place to start the scan. Result is the
|
|
|
|
* value we're looking for minus the value we're looking at
|
|
|
|
* in the index.
|
|
|
|
*/
|
|
|
|
|
|
|
|
result = _bt_compare(rel, itupdesc, page, 1, &skdata, offnum);
|
1996-07-30 09:56:04 +02:00
|
|
|
strat = _bt_getstrat(rel, 1, so->keyData[0].sk_procedure);
|
1996-07-09 08:22:35 +02:00
|
|
|
|
|
|
|
switch (strat) {
|
|
|
|
case BTLessStrategyNumber:
|
|
|
|
if (result <= 0) {
|
|
|
|
do {
|
|
|
|
if (!_bt_twostep(scan, &buf, BackwardScanDirection))
|
|
|
|
break;
|
|
|
|
|
|
|
|
offnum = ItemPointerGetOffsetNumber(current);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
result = _bt_compare(rel, itupdesc, page, 1, &skdata, offnum);
|
|
|
|
} while (result <= 0);
|
|
|
|
|
|
|
|
/* if this is true, the key we just looked at is gone */
|
|
|
|
if (result > 0)
|
|
|
|
(void) _bt_twostep(scan, &buf, ForwardScanDirection);
|
|
|
|
}
|
|
|
|
break;
|
|
|
|
|
|
|
|
case BTLessEqualStrategyNumber:
|
|
|
|
if (result >= 0) {
|
|
|
|
do {
|
|
|
|
if (!_bt_twostep(scan, &buf, ForwardScanDirection))
|
|
|
|
break;
|
|
|
|
|
|
|
|
offnum = ItemPointerGetOffsetNumber(current);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
result = _bt_compare(rel, itupdesc, page, 1, &skdata, offnum);
|
|
|
|
} while (result >= 0);
|
|
|
|
|
|
|
|
if (result < 0)
|
|
|
|
(void) _bt_twostep(scan, &buf, BackwardScanDirection);
|
|
|
|
}
|
|
|
|
break;
|
|
|
|
|
|
|
|
case BTEqualStrategyNumber:
|
|
|
|
if (result != 0) {
|
|
|
|
_bt_relbuf(scan->relation, buf, BT_READ);
|
|
|
|
so->btso_curbuf = InvalidBuffer;
|
|
|
|
ItemPointerSetInvalid(&(scan->currentItemData));
|
|
|
|
return ((RetrieveIndexResult) NULL);
|
|
|
|
}
|
|
|
|
break;
|
|
|
|
|
|
|
|
case BTGreaterEqualStrategyNumber:
|
|
|
|
if (result < 0) {
|
|
|
|
do {
|
|
|
|
if (!_bt_twostep(scan, &buf, BackwardScanDirection))
|
|
|
|
break;
|
|
|
|
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
offnum = ItemPointerGetOffsetNumber(current);
|
|
|
|
result = _bt_compare(rel, itupdesc, page, 1, &skdata, offnum);
|
|
|
|
} while (result < 0);
|
|
|
|
|
|
|
|
if (result > 0)
|
|
|
|
(void) _bt_twostep(scan, &buf, ForwardScanDirection);
|
|
|
|
}
|
|
|
|
break;
|
|
|
|
|
|
|
|
case BTGreaterStrategyNumber:
|
|
|
|
if (result >= 0) {
|
|
|
|
do {
|
|
|
|
if (!_bt_twostep(scan, &buf, ForwardScanDirection))
|
|
|
|
break;
|
|
|
|
|
|
|
|
offnum = ItemPointerGetOffsetNumber(current);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
result = _bt_compare(rel, itupdesc, page, 1, &skdata, offnum);
|
|
|
|
} while (result >= 0);
|
|
|
|
}
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* okay, current item pointer for the scan is right */
|
|
|
|
offnum = ItemPointerGetOffsetNumber(current);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
btitem = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
|
|
|
|
itup = &btitem->bti_itup;
|
|
|
|
|
|
|
|
if (_bt_checkqual(scan, itup)) {
|
|
|
|
iptr = (ItemPointer) palloc(sizeof(ItemPointerData));
|
|
|
|
memmove((char *) iptr, (char *) &(itup->t_tid),
|
|
|
|
sizeof(ItemPointerData));
|
|
|
|
res = FormRetrieveIndexResult(current, iptr);
|
|
|
|
pfree(iptr);
|
|
|
|
|
|
|
|
/* remember which buffer we have pinned */
|
|
|
|
so->btso_curbuf = buf;
|
|
|
|
} else {
|
|
|
|
ItemPointerSetInvalid(current);
|
|
|
|
so->btso_curbuf = InvalidBuffer;
|
|
|
|
_bt_relbuf(rel, buf, BT_READ);
|
|
|
|
res = (RetrieveIndexResult) NULL;
|
|
|
|
}
|
|
|
|
|
|
|
|
return (res);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* _bt_step() -- Step one item in the requested direction in a scan on
|
|
|
|
* the tree.
|
|
|
|
*
|
|
|
|
* If no adjacent record exists in the requested direction, return
|
|
|
|
* false. Else, return true and set the currentItemData for the
|
|
|
|
* scan to the right thing.
|
|
|
|
*/
|
|
|
|
bool
|
|
|
|
_bt_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir)
|
|
|
|
{
|
|
|
|
Page page;
|
|
|
|
BTPageOpaque opaque;
|
|
|
|
OffsetNumber offnum, maxoff;
|
|
|
|
OffsetNumber start;
|
|
|
|
BlockNumber blkno;
|
|
|
|
BlockNumber obknum;
|
|
|
|
BTScanOpaque so;
|
|
|
|
ItemPointer current;
|
|
|
|
Relation rel;
|
|
|
|
|
|
|
|
rel = scan->relation;
|
|
|
|
current = &(scan->currentItemData);
|
|
|
|
offnum = ItemPointerGetOffsetNumber(current);
|
|
|
|
page = BufferGetPage(*bufP);
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
so = (BTScanOpaque) scan->opaque;
|
|
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
|
|
|
|
/* get the next tuple */
|
|
|
|
if (ScanDirectionIsForward(dir)) {
|
|
|
|
if (!PageIsEmpty(page) && offnum < maxoff) {
|
|
|
|
offnum = OffsetNumberNext(offnum);
|
|
|
|
} else {
|
|
|
|
|
|
|
|
/* if we're at end of scan, release the buffer and return */
|
|
|
|
blkno = opaque->btpo_next;
|
|
|
|
if (P_RIGHTMOST(opaque)) {
|
|
|
|
_bt_relbuf(rel, *bufP, BT_READ);
|
|
|
|
ItemPointerSetInvalid(current);
|
|
|
|
*bufP = so->btso_curbuf = InvalidBuffer;
|
|
|
|
return (false);
|
|
|
|
} else {
|
|
|
|
|
|
|
|
/* walk right to the next page with data */
|
|
|
|
_bt_relbuf(rel, *bufP, BT_READ);
|
|
|
|
for (;;) {
|
|
|
|
*bufP = _bt_getbuf(rel, blkno, BT_READ);
|
|
|
|
page = BufferGetPage(*bufP);
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
start = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
|
|
|
|
|
|
|
|
if (!PageIsEmpty(page) && start <= maxoff) {
|
|
|
|
break;
|
|
|
|
} else {
|
|
|
|
blkno = opaque->btpo_next;
|
|
|
|
_bt_relbuf(rel, *bufP, BT_READ);
|
|
|
|
if (blkno == P_NONE) {
|
|
|
|
*bufP = so->btso_curbuf = InvalidBuffer;
|
|
|
|
ItemPointerSetInvalid(current);
|
|
|
|
return (false);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
offnum = start;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
} else if (ScanDirectionIsBackward(dir)) {
|
|
|
|
|
|
|
|
/* remember that high key is item zero on non-rightmost pages */
|
|
|
|
start = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
|
|
|
|
|
|
|
|
if (offnum > start) {
|
|
|
|
offnum = OffsetNumberPrev(offnum);
|
|
|
|
} else {
|
|
|
|
|
|
|
|
/* if we're at end of scan, release the buffer and return */
|
|
|
|
blkno = opaque->btpo_prev;
|
|
|
|
if (P_LEFTMOST(opaque)) {
|
|
|
|
_bt_relbuf(rel, *bufP, BT_READ);
|
|
|
|
*bufP = so->btso_curbuf = InvalidBuffer;
|
|
|
|
ItemPointerSetInvalid(current);
|
|
|
|
return (false);
|
|
|
|
} else {
|
|
|
|
|
|
|
|
obknum = BufferGetBlockNumber(*bufP);
|
|
|
|
|
|
|
|
/* walk right to the next page with data */
|
|
|
|
_bt_relbuf(rel, *bufP, BT_READ);
|
|
|
|
for (;;) {
|
|
|
|
*bufP = _bt_getbuf(rel, blkno, BT_READ);
|
|
|
|
page = BufferGetPage(*bufP);
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* If the adjacent page just split, then we may have the
|
|
|
|
* wrong block. Handle this case. Because pages only
|
|
|
|
* split right, we don't have to worry about this failing
|
|
|
|
* to terminate.
|
|
|
|
*/
|
|
|
|
|
|
|
|
while (opaque->btpo_next != obknum) {
|
|
|
|
blkno = opaque->btpo_next;
|
|
|
|
_bt_relbuf(rel, *bufP, BT_READ);
|
|
|
|
*bufP = _bt_getbuf(rel, blkno, BT_READ);
|
|
|
|
page = BufferGetPage(*bufP);
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* don't consider the high key */
|
|
|
|
start = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
|
|
|
|
|
|
|
|
/* anything to look at here? */
|
|
|
|
if (!PageIsEmpty(page) && maxoff >= start) {
|
|
|
|
break;
|
|
|
|
} else {
|
|
|
|
blkno = opaque->btpo_prev;
|
|
|
|
obknum = BufferGetBlockNumber(*bufP);
|
|
|
|
_bt_relbuf(rel, *bufP, BT_READ);
|
|
|
|
if (blkno == P_NONE) {
|
|
|
|
*bufP = so->btso_curbuf = InvalidBuffer;
|
|
|
|
ItemPointerSetInvalid(current);
|
|
|
|
return (false);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
offnum = maxoff; /* XXX PageIsEmpty? */
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
blkno = BufferGetBlockNumber(*bufP);
|
|
|
|
so->btso_curbuf = *bufP;
|
|
|
|
ItemPointerSet(current, blkno, offnum);
|
|
|
|
|
|
|
|
return (true);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* _bt_twostep() -- Move to an adjacent record in a scan on the tree,
|
|
|
|
* if an adjacent record exists.
|
|
|
|
*
|
|
|
|
* This is like _bt_step, except that if no adjacent record exists
|
|
|
|
* it restores us to where we were before trying the step. This is
|
|
|
|
* only hairy when you cross page boundaries, since the page you cross
|
|
|
|
* from could have records inserted or deleted, or could even split.
|
|
|
|
* This is unlikely, but we try to handle it correctly here anyway.
|
|
|
|
*
|
|
|
|
* This routine contains the only case in which our changes to Lehman
|
|
|
|
* and Yao's algorithm.
|
|
|
|
*
|
|
|
|
* Like step, this routine leaves the scan's currentItemData in the
|
|
|
|
* proper state and acquires a lock and pin on *bufP. If the twostep
|
|
|
|
* succeeded, we return true; otherwise, we return false.
|
|
|
|
*/
|
|
|
|
static bool
|
|
|
|
_bt_twostep(IndexScanDesc scan, Buffer *bufP, ScanDirection dir)
|
|
|
|
{
|
|
|
|
Page page;
|
|
|
|
BTPageOpaque opaque;
|
|
|
|
OffsetNumber offnum, maxoff;
|
|
|
|
OffsetNumber start;
|
|
|
|
ItemPointer current;
|
|
|
|
ItemId itemid;
|
|
|
|
int itemsz;
|
|
|
|
BTItem btitem;
|
|
|
|
BTItem svitem;
|
|
|
|
BlockNumber blkno;
|
|
|
|
|
|
|
|
blkno = BufferGetBlockNumber(*bufP);
|
|
|
|
page = BufferGetPage(*bufP);
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
current = &(scan->currentItemData);
|
|
|
|
offnum = ItemPointerGetOffsetNumber(current);
|
|
|
|
|
|
|
|
start = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
|
|
|
|
|
|
|
|
/* if we're safe, just do it */
|
|
|
|
if (ScanDirectionIsForward(dir) && offnum < maxoff) { /* XXX PageIsEmpty? */
|
|
|
|
ItemPointerSet(current, blkno, OffsetNumberNext(offnum));
|
|
|
|
return (true);
|
|
|
|
} else if (ScanDirectionIsBackward(dir) && offnum > start) {
|
|
|
|
ItemPointerSet(current, blkno, OffsetNumberPrev(offnum));
|
|
|
|
return (true);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* if we've hit end of scan we don't have to do any work */
|
|
|
|
if (ScanDirectionIsForward(dir) && P_RIGHTMOST(opaque)) {
|
|
|
|
return (false);
|
|
|
|
} else if (ScanDirectionIsBackward(dir) && P_LEFTMOST(opaque)) {
|
|
|
|
return (false);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Okay, it's off the page; let _bt_step() do the hard work, and we'll
|
|
|
|
* try to remember where we were. This is not guaranteed to work; this
|
|
|
|
* is the only place in the code where concurrency can screw us up,
|
|
|
|
* and it's because we want to be able to move in two directions in
|
|
|
|
* the scan.
|
|
|
|
*/
|
|
|
|
|
|
|
|
itemid = PageGetItemId(page, offnum);
|
|
|
|
itemsz = ItemIdGetLength(itemid);
|
|
|
|
btitem = (BTItem) PageGetItem(page, itemid);
|
|
|
|
svitem = (BTItem) palloc(itemsz);
|
|
|
|
memmove((char *) svitem, (char *) btitem, itemsz);
|
|
|
|
|
|
|
|
if (_bt_step(scan, bufP, dir)) {
|
|
|
|
pfree(svitem);
|
|
|
|
return (true);
|
|
|
|
}
|
|
|
|
|
|
|
|
/* try to find our place again */
|
|
|
|
*bufP = _bt_getbuf(scan->relation, blkno, BT_READ);
|
|
|
|
page = BufferGetPage(*bufP);
|
|
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
|
|
|
|
while (offnum <= maxoff) {
|
|
|
|
itemid = PageGetItemId(page, offnum);
|
|
|
|
btitem = (BTItem) PageGetItem(page, itemid);
|
|
|
|
if (btitem->bti_oid == svitem->bti_oid) {
|
|
|
|
pfree(svitem);
|
|
|
|
ItemPointerSet(current, blkno, offnum);
|
|
|
|
return (false);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* XXX crash and burn -- can't find our place. We can be a little
|
|
|
|
* smarter -- walk to the next page to the right, for example, since
|
|
|
|
* that's the only direction that splits happen in. Deletions screw
|
|
|
|
* us up less often since they're only done by the vacuum daemon.
|
|
|
|
*/
|
|
|
|
|
|
|
|
elog(WARN, "btree synchronization error: concurrent update botched scan");
|
|
|
|
|
|
|
|
return (false);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* _bt_endpoint() -- Find the first or last key in the index.
|
|
|
|
*/
|
|
|
|
static RetrieveIndexResult
|
|
|
|
_bt_endpoint(IndexScanDesc scan, ScanDirection dir)
|
|
|
|
{
|
|
|
|
Relation rel;
|
|
|
|
Buffer buf;
|
|
|
|
Page page;
|
|
|
|
BTPageOpaque opaque;
|
|
|
|
ItemPointer current;
|
|
|
|
ItemPointer iptr;
|
|
|
|
OffsetNumber offnum, maxoff;
|
1996-10-23 09:42:13 +02:00
|
|
|
OffsetNumber start = 0;
|
1996-07-09 08:22:35 +02:00
|
|
|
BlockNumber blkno;
|
|
|
|
BTItem btitem;
|
|
|
|
IndexTuple itup;
|
|
|
|
BTScanOpaque so;
|
|
|
|
RetrieveIndexResult res;
|
|
|
|
|
|
|
|
rel = scan->relation;
|
|
|
|
current = &(scan->currentItemData);
|
|
|
|
|
|
|
|
buf = _bt_getroot(rel, BT_READ);
|
|
|
|
blkno = BufferGetBlockNumber(buf);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
|
|
|
|
for (;;) {
|
|
|
|
if (opaque->btpo_flags & BTP_LEAF)
|
|
|
|
break;
|
|
|
|
|
|
|
|
if (ScanDirectionIsForward(dir)) {
|
|
|
|
offnum = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
|
|
|
|
} else {
|
|
|
|
offnum = PageGetMaxOffsetNumber(page);
|
|
|
|
}
|
|
|
|
|
|
|
|
btitem = (BTItem) PageGetItem(page, PageGetItemId(page, offnum));
|
|
|
|
itup = &(btitem->bti_itup);
|
|
|
|
|
|
|
|
blkno = ItemPointerGetBlockNumber(&(itup->t_tid));
|
|
|
|
|
|
|
|
_bt_relbuf(rel, buf, BT_READ);
|
|
|
|
buf = _bt_getbuf(rel, blkno, BT_READ);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Race condition: If the child page we just stepped onto is
|
|
|
|
* in the process of being split, we need to make sure we're
|
|
|
|
* all the way at the right edge of the tree. See the paper
|
|
|
|
* by Lehman and Yao.
|
|
|
|
*/
|
|
|
|
|
|
|
|
if (ScanDirectionIsBackward(dir) && ! P_RIGHTMOST(opaque)) {
|
|
|
|
do {
|
|
|
|
blkno = opaque->btpo_next;
|
|
|
|
_bt_relbuf(rel, buf, BT_READ);
|
|
|
|
buf = _bt_getbuf(rel, blkno, BT_READ);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
} while (! P_RIGHTMOST(opaque));
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/* okay, we've got the {left,right}-most page in the tree */
|
|
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
|
|
|
|
if (ScanDirectionIsForward(dir)) {
|
|
|
|
if (PageIsEmpty(page)) {
|
|
|
|
maxoff = FirstOffsetNumber;
|
|
|
|
} else {
|
|
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
}
|
|
|
|
start = P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY;
|
|
|
|
|
|
|
|
if (PageIsEmpty(page) || start > maxoff) {
|
|
|
|
ItemPointerSet(current, blkno, maxoff);
|
|
|
|
if (!_bt_step(scan, &buf, BackwardScanDirection))
|
|
|
|
return ((RetrieveIndexResult) NULL);
|
|
|
|
|
|
|
|
start = ItemPointerGetOffsetNumber(current);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
} else {
|
|
|
|
ItemPointerSet(current, blkno, start);
|
|
|
|
}
|
|
|
|
} else if (ScanDirectionIsBackward(dir)) {
|
|
|
|
if (PageIsEmpty(page)) {
|
|
|
|
ItemPointerSet(current, blkno, FirstOffsetNumber);
|
|
|
|
if (!_bt_step(scan, &buf, ForwardScanDirection))
|
|
|
|
return ((RetrieveIndexResult) NULL);
|
|
|
|
|
|
|
|
start = ItemPointerGetOffsetNumber(current);
|
|
|
|
page = BufferGetPage(buf);
|
|
|
|
} else {
|
|
|
|
start = PageGetMaxOffsetNumber(page);
|
|
|
|
ItemPointerSet(current, blkno, start);
|
|
|
|
}
|
|
|
|
} else {
|
|
|
|
elog(WARN, "Illegal scan direction %d", dir);
|
|
|
|
}
|
|
|
|
|
|
|
|
btitem = (BTItem) PageGetItem(page, PageGetItemId(page, start));
|
|
|
|
itup = &(btitem->bti_itup);
|
|
|
|
|
|
|
|
/* see if we picked a winner */
|
|
|
|
if (_bt_checkqual(scan, itup)) {
|
|
|
|
iptr = (ItemPointer) palloc(sizeof(ItemPointerData));
|
|
|
|
memmove((char *) iptr, (char *) &(itup->t_tid),
|
|
|
|
sizeof(ItemPointerData));
|
|
|
|
res = FormRetrieveIndexResult(current, iptr);
|
|
|
|
|
|
|
|
/* remember which buffer we have pinned */
|
|
|
|
so = (BTScanOpaque) scan->opaque;
|
|
|
|
so->btso_curbuf = buf;
|
|
|
|
} else {
|
|
|
|
_bt_relbuf(rel, buf, BT_READ);
|
|
|
|
res = (RetrieveIndexResult) NULL;
|
|
|
|
}
|
|
|
|
|
|
|
|
return (res);
|
|
|
|
}
|