4.4BSD/usr/src/contrib/nvi/nvi/PORT/db/btree/bt_delete.c
/*-
* Copyright (c) 1990, 1993
* 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.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)bt_delete.c 8.1 (Berkeley) 6/4/93";
#endif /* LIBC_SCCS and not lint */
#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <db.h>
#include "btree.h"
static int bt_bdelete __P((BTREE *, const DBT *));
/*
* __BT_DELETE -- Delete the item(s) referenced by a key.
*
* Parameters:
* dbp: pointer to access method
* key: key to delete
* flags: R_CURSOR if deleting what the cursor references
*
* Returns:
* RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
*/
int
__bt_delete(dbp, key, flags)
const DB *dbp;
const DBT *key;
u_int flags;
{
BTREE *t;
int status;
t = dbp->internal;
if (ISSET(t, B_RDONLY)) {
errno = EPERM;
return (RET_ERROR);
}
switch(flags) {
case 0:
status = bt_bdelete(t, key);
break;
case R_CURSOR:
/*
* If flags is R_CURSOR, delete the cursor; must already have
* started a scan and not have already deleted the record. For
* the delete cursor bit to have been set requires that the
* scan be initialized, so no reason to check.
*/
if (!ISSET(t, B_SEQINIT))
goto einval;
status = ISSET(t, B_DELCRSR) ?
RET_SPECIAL : __bt_crsrdel(t, &t->bt_bcursor);
break;
default:
einval: errno = EINVAL;
return (RET_ERROR);
}
if (status == RET_SUCCESS)
SET(t, B_MODIFIED);
return (status);
}
/*
* BT_BDELETE -- Delete all key/data pairs matching the specified key.
*
* Parameters:
* tree: tree
* key: key to delete
*
* Returns:
* RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
*/
static int
bt_bdelete(t, key)
BTREE *t;
const DBT *key;
{
EPG *e, save;
PAGE *h;
pgno_t cpgno, pg;
indx_t cindex;
int deleted, dirty1, dirty2, exact;
/* Find any matching record; __bt_search pins the page. */
if ((e = __bt_search(t, key, &exact)) == NULL)
return (RET_ERROR);
if (!exact) {
mpool_put(t->bt_mp, e->page, 0);
return (RET_SPECIAL);
}
/*
* Delete forward, then delete backward, from the found key. The
* ordering is so that the deletions don't mess up the page refs.
* The first loop deletes the key from the original page, the second
* unpins the original page. In the first loop, dirty1 is set if
* the original page is modified, and dirty2 is set if any subsequent
* pages are modified. In the second loop, dirty1 starts off set if
* the original page has been modified, and is set if any subsequent
* pages are modified.
*
* If find the key referenced by the cursor, don't delete it, just
* flag it for future deletion. The cursor page number is P_INVALID
* unless the sequential scan is initialized, so no reason to check.
* A special case is when the already deleted cursor record was the
* only record found. If so, then the delete opertion fails as no
* records were deleted.
*
* Cycle in place in the current page until the current record doesn't
* match the key or the page is empty. If the latter, walk forward,
* skipping empty pages and repeating until a record doesn't match
* the key or the end of the tree is reached.
*/
cpgno = t->bt_bcursor.pgno;
cindex = t->bt_bcursor.index;
save = *e;
dirty1 = 0;
for (h = e->page, deleted = 0;;) {
dirty2 = 0;
do {
if (h->pgno == cpgno && e->index == cindex) {
if (!ISSET(t, B_DELCRSR)) {
SET(t, B_DELCRSR);
deleted = 1;
}
++e->index;
} else {
if (__bt_dleaf(t, h, e->index)) {
if (h->pgno != save.page->pgno)
mpool_put(t->bt_mp, h, dirty2);
mpool_put(t->bt_mp, save.page, dirty1);
return (RET_ERROR);
}
if (h->pgno == save.page->pgno)
dirty1 = MPOOL_DIRTY;
else
dirty2 = MPOOL_DIRTY;
deleted = 1;
}
} while (e->index < NEXTINDEX(h) && __bt_cmp(t, key, e) == 0);
/*
* Quit if didn't find a match, no next page, or first key on
* the next page doesn't match. Don't unpin the original page
* unless an error occurs.
*/
if (e->index < NEXTINDEX(h))
break;
for (;;) {
if ((pg = h->nextpg) == P_INVALID)
goto done1;
if (h->pgno != save.page->pgno)
mpool_put(t->bt_mp, h, dirty2);
if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) {
mpool_put(t->bt_mp, save.page, dirty1);
return (RET_ERROR);
}
if (NEXTINDEX(h) != 0) {
e->page = h;
e->index = 0;
break;
}
}
if (__bt_cmp(t, key, e) != 0)
break;
}
/*
* Reach here with the original page and the last page referenced
* pinned (they may be the same). Release it if not the original.
*/
done1: if (h->pgno != save.page->pgno)
mpool_put(t->bt_mp, h, dirty2);
/*
* Walk backwards from the record previous to the record returned by
* __bt_search, skipping empty pages, until a record doesn't match
* the key or reach the beginning of the tree.
*/
*e = save;
for (;;) {
if (e->index)
--e->index;
for (h = e->page; e->index; --e->index) {
if (__bt_cmp(t, key, e) != 0)
goto done2;
if (h->pgno == cpgno && e->index == cindex) {
if (!ISSET(t, B_DELCRSR)) {
SET(t, B_DELCRSR);
deleted = 1;
}
} else {
if (__bt_dleaf(t, h, e->index) == RET_ERROR) {
mpool_put(t->bt_mp, h, dirty1);
return (RET_ERROR);
}
if (h->pgno == save.page->pgno)
dirty1 = MPOOL_DIRTY;
deleted = 1;
}
}
if ((pg = h->prevpg) == P_INVALID)
goto done2;
mpool_put(t->bt_mp, h, dirty1);
dirty1 = 0;
if ((e->page = mpool_get(t->bt_mp, pg, 0)) == NULL)
return (RET_ERROR);
e->index = NEXTINDEX(e->page);
}
/*
* Reach here with the last page that was looked at pinned. Release
* it.
*/
done2: mpool_put(t->bt_mp, h, dirty1);
return (deleted ? RET_SUCCESS : RET_SPECIAL);
}
/*
* __BT_DLEAF -- Delete a single record from a leaf page.
*
* Parameters:
* t: tree
* index: index on current page to delete
*
* Returns:
* RET_SUCCESS, RET_ERROR.
*/
int
__bt_dleaf(t, h, index)
BTREE *t;
PAGE *h;
int index;
{
register BLEAF *bl;
register indx_t *ip, offset;
register size_t nbytes;
register int cnt;
char *from;
void *to;
/*
* Delete a record from a btree leaf page. Internal records are never
* deleted from internal pages, regardless of the records that caused
* them to be added being deleted. Pages made empty by deletion are
* not reclaimed. They are, however, made available for reuse.
*
* Pack the remaining entries at the end of the page, shift the indices
* down, overwriting the deleted record and its index. If the record
* uses overflow pages, make them available for reuse.
*/
to = bl = GETBLEAF(h, index);
if (bl->flags & P_BIGKEY && __ovfl_delete(t, bl->bytes) == RET_ERROR)
return (RET_ERROR);
if (bl->flags & P_BIGDATA &&
__ovfl_delete(t, bl->bytes + bl->ksize) == RET_ERROR)
return (RET_ERROR);
nbytes = NBLEAF(bl);
/*
* Compress the key/data pairs. Compress and adjust the [BR]LEAF
* offsets. Reset the headers.
*/
from = (char *)h + h->upper;
memmove(from + nbytes, from, (char *)to - from);
h->upper += nbytes;
offset = h->linp[index];
for (cnt = index, ip = &h->linp[0]; cnt--; ++ip)
if (ip[0] < offset)
ip[0] += nbytes;
for (cnt = NEXTINDEX(h) - index; --cnt; ++ip)
ip[0] = ip[1] < offset ? ip[1] + nbytes : ip[1];
h->lower -= sizeof(indx_t);
return (RET_SUCCESS);
}