gecko-dev/db/btree/bt_search.c

352 строки
9.8 KiB
C

/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 1996, 1997, 1998
* Sleepycat Software. All rights reserved.
*/
/*
* Copyright (c) 1990, 1993, 1994, 1995, 1996
* Keith Bostic. All rights reserved.
*/
/*
* Copyright (c) 1990, 1993, 1994, 1995
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Mike Olson.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "config.h"
#ifndef lint
static const char sccsid[] = "@(#)bt_search.c 10.15 (Sleepycat) 5/6/98";
#endif /* not lint */
#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>
#include <errno.h>
#include <string.h>
#endif
#include "db_int.h"
#include "db_page.h"
#include "btree.h"
/*
* __bam_search --
* Search a btree for a key.
*
* PUBLIC: int __bam_search __P((DB *,
* PUBLIC: const DBT *, u_int32_t, int, db_recno_t *, int *));
*/
int
__bam_search(dbp, key, flags, stop, recnop, exactp)
DB *dbp;
const DBT *key;
u_int32_t flags;
int stop, *exactp;
db_recno_t *recnop;
{
BTREE *t;
DB_LOCK lock;
EPG cur;
PAGE *h;
db_indx_t base, i, indx, lim;
db_pgno_t pg;
db_recno_t recno;
int cmp, jump, ret, stack;
t = dbp->internal;
recno = 0;
BT_STK_CLR(t);
/*
* There are several ways we search a btree tree. The flags argument
* specifies if we're acquiring read or write locks, if we position
* to the first or last item in a set of duplicates, if we return
* deleted items, and if we are locking pairs of pages. See btree.h
* for more details. In addition, if we're doing record numbers, we
* have to lock the entire tree regardless.
*
* If write-locking pages, we need to know whether or not to acquire a
* write lock on a page before getting it. This depends on how deep it
* is in tree, which we don't know until we acquire the root page. So,
* if we need to lock the root page we may have to upgrade it later,
* because we won't get the correct lock initially.
*
* Retrieve the root page.
*/
pg = PGNO_ROOT;
stack = F_ISSET(dbp, DB_BT_RECNUM) && LF_ISSET(S_STACK);
if ((ret = __bam_lget(dbp,
0, pg, stack ? DB_LOCK_WRITE : DB_LOCK_READ, &lock)) != 0)
return (ret);
if ((ret = __bam_pget(dbp, &h, &pg, 0)) != 0) {
(void)__BT_LPUT(dbp, lock);
return (ret);
}
/*
* Decide if we need to save this page; if we do, write lock it.
* We deliberately don't lock-couple on this call. If the tree
* is tiny, i.e., one page, and two threads are busily updating
* the root page, we're almost guaranteed deadlocks galore, as
* each one gets a read lock and then blocks the other's attempt
* for a write lock.
*/
if (!stack &&
((LF_ISSET(S_PARENT) && (u_int8_t)(stop + 1) >= h->level) ||
(LF_ISSET(S_WRITE) && h->level == LEAFLEVEL))) {
(void)memp_fput(dbp->mpf, h, 0);
(void)__BT_LPUT(dbp, lock);
if ((ret = __bam_lget(dbp, 0, pg, DB_LOCK_WRITE, &lock)) != 0)
return (ret);
if ((ret = __bam_pget(dbp, &h, &pg, 0)) != 0) {
(void)__BT_LPUT(dbp, lock);
return (ret);
}
stack = 1;
}
for (;;) {
/*
* Do a binary search on the current page. If we're searching
* a leaf page, we have to manipulate the indices in groups of
* two. If we're searching an internal page, they're an index
* per page item. If we find an exact match on a leaf page,
* we're done.
*/
cur.page = h;
jump = TYPE(h) == P_LBTREE ? P_INDX : O_INDX;
for (base = 0,
lim = NUM_ENT(h) / (db_indx_t)jump; lim != 0; lim >>= 1) {
cur.indx = indx = base + ((lim >> 1) * jump);
if ((cmp = __bam_cmp(dbp, key, &cur)) == 0) {
if (TYPE(h) == P_LBTREE)
goto match;
goto next;
}
if (cmp > 0) {
base = indx + jump;
--lim;
}
}
/*
* No match found. Base is the smallest index greater than
* key and may be zero or a last + O_INDX index.
*
* If it's a leaf page, return base as the "found" value.
* Delete only deletes exact matches.
*/
if (TYPE(h) == P_LBTREE) {
*exactp = 0;
if (LF_ISSET(S_EXACT))
goto notfound;
/*
* !!!
* Possibly returning a deleted record -- DB_SET_RANGE,
* DB_KEYFIRST and DB_KEYLAST don't require an exact
* match, and we don't want to walk multiple pages here
* to find an undeleted record. This is handled in the
* __bam_c_search() routine.
*/
BT_STK_ENTER(t, h, base, lock, ret);
return (ret);
}
/*
* If it's not a leaf page, record the internal page (which is
* a parent page for the key). Decrement the base by 1 if it's
* non-zero so that if a split later occurs, the inserted page
* will be to the right of the saved page.
*/
indx = base > 0 ? base - O_INDX : base;
/*
* If we're trying to calculate the record number, sum up
* all the record numbers on this page up to the indx point.
*/
if (recnop != NULL)
for (i = 0; i < indx; ++i)
recno += GET_BINTERNAL(h, i)->nrecs;
next: pg = GET_BINTERNAL(h, indx)->pgno;
if (stack) {
/* Return if this is the lowest page wanted. */
if (LF_ISSET(S_PARENT) && stop == h->level) {
BT_STK_ENTER(t, h, indx, lock, ret);
return (ret);
}
BT_STK_PUSH(t, h, indx, lock, ret);
if (ret != 0)
goto err;
if ((ret =
__bam_lget(dbp, 0, pg, DB_LOCK_WRITE, &lock)) != 0)
goto err;
} else {
(void)memp_fput(dbp->mpf, h, 0);
/*
* Decide if we want to return a pointer to the next
* page in the stack. If we do, write lock it and
* never unlock it.
*/
if ((LF_ISSET(S_PARENT) &&
(u_int8_t)(stop + 1) >= (u_int8_t)(h->level - 1)) ||
(h->level - 1) == LEAFLEVEL)
stack = 1;
if ((ret =
__bam_lget(dbp, 1, pg, stack && LF_ISSET(S_WRITE) ?
DB_LOCK_WRITE : DB_LOCK_READ, &lock)) != 0)
goto err;
}
if ((ret = __bam_pget(dbp, &h, &pg, 0)) != 0)
goto err;
}
/* NOTREACHED */
match: *exactp = 1;
/*
* If we're trying to calculate the record number, add in the
* offset on this page and correct for the fact that records
* in the tree are 0-based.
*/
if (recnop != NULL)
*recnop = recno + (indx / P_INDX) + 1;
/*
* If we got here, we know that we have a btree leaf page.
*
* If there are duplicates, go to the first/last one. This is
* safe because we know that we're not going to leave the page,
* all duplicate sets that are not on overflow pages exist on a
* single leaf page.
*/
if (LF_ISSET(S_DUPLAST))
while (indx < (db_indx_t)(NUM_ENT(h) - P_INDX) &&
h->inp[indx] == h->inp[indx + P_INDX])
indx += P_INDX;
else
while (indx > 0 &&
h->inp[indx] == h->inp[indx - P_INDX])
indx -= P_INDX;
/*
* Now check if we are allowed to return deleted items; if not
* find the next (or previous) non-deleted item.
*/
if (LF_ISSET(S_DELNO)) {
if (LF_ISSET(S_DUPLAST))
while (B_DISSET(GET_BKEYDATA(h, indx + O_INDX)->type) &&
indx > 0 &&
h->inp[indx] == h->inp[indx - P_INDX])
indx -= P_INDX;
else
while (B_DISSET(GET_BKEYDATA(h, indx + O_INDX)->type) &&
indx < (db_indx_t)(NUM_ENT(h) - P_INDX) &&
h->inp[indx] == h->inp[indx + P_INDX])
indx += P_INDX;
if (B_DISSET(GET_BKEYDATA(h, indx + O_INDX)->type))
goto notfound;
}
BT_STK_ENTER(t, h, indx, lock, ret);
return (ret);
notfound:
(void)memp_fput(dbp->mpf, h, 0);
(void)__BT_LPUT(dbp, lock);
ret = DB_NOTFOUND;
err: if (t->bt_csp > t->bt_sp) {
BT_STK_POP(t);
__bam_stkrel(dbp);
}
return (ret);
}
/*
* __bam_stkrel --
* Release all pages currently held in the stack.
*
* PUBLIC: int __bam_stkrel __P((DB *));
*/
int
__bam_stkrel(dbp)
DB *dbp;
{
BTREE *t;
EPG *epg;
t = dbp->internal;
for (epg = t->bt_sp; epg <= t->bt_csp; ++epg) {
(void)memp_fput(dbp->mpf, epg->page, 0);
(void)__BT_TLPUT(dbp, epg->lock);
}
return (0);
}
/*
* __bam_stkgrow --
* Grow the stack.
*
* PUBLIC: int __bam_stkgrow __P((BTREE *));
*/
int
__bam_stkgrow(t)
BTREE *t;
{
EPG *p;
size_t entries;
entries = t->bt_esp - t->bt_sp;
if ((p = (EPG *)__db_calloc(entries * 2, sizeof(EPG))) == NULL)
return (ENOMEM);
memcpy(p, t->bt_sp, entries * sizeof(EPG));
if (t->bt_sp != t->bt_stack)
FREE(t->bt_sp, entries * sizeof(EPG));
t->bt_sp = p;
t->bt_csp = p + entries;
t->bt_esp = p + entries * 2;
return (0);
}