239 lines
6.4 KiB
C
239 lines
6.4 KiB
C
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/*-
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Mike Olson.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)bt_get.c 8.2 (Berkeley) 9/7/93";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/types.h>
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#include <errno.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <db.h>
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#include "btree.h"
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/*
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* __BT_GET -- Get a record from the btree.
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*
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* Parameters:
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* dbp: pointer to access method
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* key: key to find
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* data: data to return
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* flag: currently unused
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*
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* Returns:
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* RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
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*/
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int
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__bt_get(dbp, key, data, flags)
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const DB *dbp;
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const DBT *key;
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DBT *data;
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u_int flags;
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{
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BTREE *t;
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EPG *e;
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int exact, status;
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t = dbp->internal;
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/* Toss any page pinned across calls. */
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if (t->bt_pinned != NULL) {
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mpool_put(t->bt_mp, t->bt_pinned, 0);
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t->bt_pinned = NULL;
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}
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/* Get currently doesn't take any flags. */
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if (flags) {
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errno = EINVAL;
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return (RET_ERROR);
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}
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if ((e = __bt_search(t, key, &exact)) == NULL)
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return (RET_ERROR);
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if (!exact) {
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mpool_put(t->bt_mp, e->page, 0);
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return (RET_SPECIAL);
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}
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/*
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* A special case is if we found the record but it's flagged for
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* deletion. In this case, we want to find another record with the
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* same key, if it exists. Rather than look around the tree we call
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* __bt_first and have it redo the search, as __bt_first will not
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* return keys marked for deletion. Slow, but should never happen.
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*/
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if (ISSET(t, B_DELCRSR) && e->page->pgno == t->bt_bcursor.pgno &&
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e->index == t->bt_bcursor.index) {
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mpool_put(t->bt_mp, e->page, 0);
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if ((e = __bt_first(t, key, &exact)) == NULL)
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return (RET_ERROR);
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if (!exact)
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return (RET_SPECIAL);
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}
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status = __bt_ret(t, e, NULL, data);
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/*
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* If the user is doing concurrent access, we copied the
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* key/data, toss the page.
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*/
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if (ISSET(t, B_DB_LOCK))
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mpool_put(t->bt_mp, e->page, 0);
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else
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t->bt_pinned = e->page;
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return (status);
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}
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/*
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* __BT_FIRST -- Find the first entry.
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*
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* Parameters:
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* t: the tree
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* key: the key
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*
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* Returns:
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* The first entry in the tree greater than or equal to key.
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*/
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EPG *
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__bt_first(t, key, exactp)
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BTREE *t;
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const DBT *key;
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int *exactp;
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{
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register PAGE *h;
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register EPG *e;
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EPG save;
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pgno_t cpgno, pg;
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indx_t cindex;
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int found;
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/*
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* Find any matching record; __bt_search pins the page. Only exact
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* matches are tricky, otherwise just return the location of the key
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* if it were to be inserted into the tree.
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*/
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if ((e = __bt_search(t, key, exactp)) == NULL)
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return (NULL);
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if (!*exactp)
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return (e);
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if (ISSET(t, B_DELCRSR)) {
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cpgno = t->bt_bcursor.pgno;
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cindex = t->bt_bcursor.index;
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} else {
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cpgno = P_INVALID;
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cindex = 0; /* GCC thinks it's uninitialized. */
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}
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/*
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* Walk backwards, skipping empty pages, as long as the entry matches
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* and there are keys left in the tree. Save a copy of each match in
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* case we go too far. A special case is that we don't return a match
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* on records that the cursor references that have already been flagged
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* for deletion.
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*/
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save = *e;
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h = e->page;
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found = 0;
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do {
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if (cpgno != h->pgno || cindex != e->index) {
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if (save.page->pgno != e->page->pgno) {
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mpool_put(t->bt_mp, save.page, 0);
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save = *e;
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} else
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save.index = e->index;
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found = 1;
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}
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/*
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* Make a special effort not to unpin the page the last (or
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* original) match was on, but also make sure it's unpinned
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* if an error occurs.
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*/
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while (e->index == 0) {
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if (h->prevpg == P_INVALID)
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goto done1;
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if (h->pgno != save.page->pgno)
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mpool_put(t->bt_mp, h, 0);
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if ((h = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL) {
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if (h->pgno == save.page->pgno)
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mpool_put(t->bt_mp, save.page, 0);
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return (NULL);
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}
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e->page = h;
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e->index = NEXTINDEX(h);
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}
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--e->index;
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} while (__bt_cmp(t, key, e) == 0);
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/*
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* Reach here with the last page that was looked at pinned, which may
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* or may not be the same as the last (or original) match page. If
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* it's not useful, release it.
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*/
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done1: if (h->pgno != save.page->pgno)
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mpool_put(t->bt_mp, h, 0);
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/*
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* If still haven't found a record, the only possibility left is the
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* next one. Move forward one slot, skipping empty pages and check.
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*/
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if (!found) {
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h = save.page;
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if (++save.index == NEXTINDEX(h)) {
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do {
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pg = h->nextpg;
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mpool_put(t->bt_mp, h, 0);
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if (pg == P_INVALID) {
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*exactp = 0;
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return (e);
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}
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if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
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return (NULL);
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} while ((save.index = NEXTINDEX(h)) == 0);
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save.page = h;
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}
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if (__bt_cmp(t, key, &save) != 0) {
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*exactp = 0;
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return (e);
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}
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}
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*e = save;
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*exactp = 1;
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return (e);
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}
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