461 lines
11 KiB
C
461 lines
11 KiB
C
/*-
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* Copyright (c) 1990, 1993, 1994
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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_seq.c 8.7 (Berkeley) 7/20/94";
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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 <stdlib.h>
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#include <db.h>
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#include "btree.h"
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static int __bt_first __P((BTREE *, const DBT *, EPG *, int *));
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static int __bt_seqadv __P((BTREE *, EPG *, int));
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static int __bt_seqset __P((BTREE *, EPG *, DBT *, int));
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/*
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* Sequential scan support.
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*
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* The tree can be scanned sequentially, starting from either end of the
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* tree or from any specific key. A scan request before any scanning is
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* done is initialized as starting from the least node.
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*/
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/*
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* __bt_seq --
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* Btree sequential scan interface.
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*
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* Parameters:
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* dbp: pointer to access method
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* key: key for positioning and return value
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* data: data return value
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* flags: R_CURSOR, R_FIRST, R_LAST, R_NEXT, R_PREV.
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*
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* Returns:
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* RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key.
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*/
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int
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__bt_seq(dbp, key, data, flags)
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const DB *dbp;
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DBT *key, *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 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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/*
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* If scan unitialized as yet, or starting at a specific record, set
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* the scan to a specific key. Both __bt_seqset and __bt_seqadv pin
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* the page the cursor references if they're successful.
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*/
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switch (flags) {
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case R_NEXT:
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case R_PREV:
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if (F_ISSET(&t->bt_cursor, CURS_INIT)) {
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status = __bt_seqadv(t, &e, flags);
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break;
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}
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/* FALLTHROUGH */
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case R_FIRST:
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case R_LAST:
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case R_CURSOR:
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status = __bt_seqset(t, &e, key, flags);
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break;
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default:
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errno = EINVAL;
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return (RET_ERROR);
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}
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if (status == RET_SUCCESS) {
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__bt_setcur(t, e.page->pgno, e.index);
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status =
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__bt_ret(t, &e, key, &t->bt_rkey, data, &t->bt_rdata, 0);
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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 (F_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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}
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return (status);
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}
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/*
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* __bt_seqset --
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* Set the sequential scan to a specific key.
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*
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* Parameters:
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* t: tree
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* ep: storage for returned key
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* key: key for initial scan position
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* flags: R_CURSOR, R_FIRST, R_LAST, R_NEXT, R_PREV
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*
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* Side effects:
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* Pins the page the cursor references.
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*
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* Returns:
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* RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key.
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*/
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static int
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__bt_seqset(t, ep, key, flags)
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BTREE *t;
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EPG *ep;
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DBT *key;
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int flags;
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{
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PAGE *h;
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pgno_t pg;
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int exact;
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/*
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* Find the first, last or specific key in the tree and point the
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* cursor at it. The cursor may not be moved until a new key has
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* been found.
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*/
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switch (flags) {
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case R_CURSOR: /* Keyed scan. */
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/*
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* Find the first instance of the key or the smallest key
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* which is greater than or equal to the specified key.
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*/
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if (key->data == NULL || key->size == 0) {
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errno = EINVAL;
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return (RET_ERROR);
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}
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return (__bt_first(t, key, ep, &exact));
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case R_FIRST: /* First record. */
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case R_NEXT:
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/* Walk down the left-hand side of the tree. */
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for (pg = P_ROOT;;) {
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if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
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return (RET_ERROR);
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/* Check for an empty tree. */
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if (NEXTINDEX(h) == 0) {
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mpool_put(t->bt_mp, h, 0);
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return (RET_SPECIAL);
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}
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if (h->flags & (P_BLEAF | P_RLEAF))
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break;
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pg = GETBINTERNAL(h, 0)->pgno;
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mpool_put(t->bt_mp, h, 0);
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}
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ep->page = h;
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ep->index = 0;
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break;
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case R_LAST: /* Last record. */
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case R_PREV:
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/* Walk down the right-hand side of the tree. */
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for (pg = P_ROOT;;) {
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if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
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return (RET_ERROR);
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/* Check for an empty tree. */
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if (NEXTINDEX(h) == 0) {
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mpool_put(t->bt_mp, h, 0);
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return (RET_SPECIAL);
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}
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if (h->flags & (P_BLEAF | P_RLEAF))
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break;
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pg = GETBINTERNAL(h, NEXTINDEX(h) - 1)->pgno;
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mpool_put(t->bt_mp, h, 0);
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}
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ep->page = h;
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ep->index = NEXTINDEX(h) - 1;
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break;
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}
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return (RET_SUCCESS);
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}
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/*
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* __bt_seqadvance --
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* Advance the sequential scan.
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*
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* Parameters:
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* t: tree
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* flags: R_NEXT, R_PREV
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*
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* Side effects:
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* Pins the page the new key/data record is on.
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*
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* Returns:
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* RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key.
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*/
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static int
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__bt_seqadv(t, ep, flags)
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BTREE *t;
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EPG *ep;
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int flags;
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{
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CURSOR *c;
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PAGE *h;
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indx_t index;
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pgno_t pg;
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int exact;
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/*
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* There are a couple of states that we can be in. The cursor has
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* been initialized by the time we get here, but that's all we know.
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*/
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c = &t->bt_cursor;
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/*
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* The cursor was deleted where there weren't any duplicate records,
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* so the key was saved. Find out where that key would go in the
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* current tree. It doesn't matter if the returned key is an exact
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* match or not -- if it's an exact match, the record was added after
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* the delete so we can just return it. If not, as long as there's
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* a record there, return it.
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*/
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if (F_ISSET(c, CURS_ACQUIRE))
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return (__bt_first(t, &c->key, ep, &exact));
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/* Get the page referenced by the cursor. */
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if ((h = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL)
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return (RET_ERROR);
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/*
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* Find the next/previous record in the tree and point the cursor at
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* it. The cursor may not be moved until a new key has been found.
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*/
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switch (flags) {
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case R_NEXT: /* Next record. */
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/*
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* The cursor was deleted in duplicate records, and moved
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* forward to a record that has yet to be returned. Clear
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* that flag, and return the record.
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*/
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if (F_ISSET(c, CURS_AFTER))
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goto usecurrent;
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index = c->pg.index;
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if (++index == NEXTINDEX(h)) {
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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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return (RET_SPECIAL);
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if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
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return (RET_ERROR);
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index = 0;
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}
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break;
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case R_PREV: /* Previous record. */
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/*
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* The cursor was deleted in duplicate records, and moved
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* backward to a record that has yet to be returned. Clear
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* that flag, and return the record.
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*/
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if (F_ISSET(c, CURS_BEFORE)) {
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usecurrent: F_CLR(c, CURS_AFTER | CURS_BEFORE);
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ep->page = h;
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ep->index = c->pg.index;
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return (RET_SUCCESS);
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}
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index = c->pg.index;
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if (index == 0) {
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pg = h->prevpg;
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mpool_put(t->bt_mp, h, 0);
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if (pg == P_INVALID)
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return (RET_SPECIAL);
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if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
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return (RET_ERROR);
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index = NEXTINDEX(h) - 1;
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} else
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--index;
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break;
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}
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ep->page = h;
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ep->index = index;
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return (RET_SUCCESS);
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}
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/*
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* __bt_first --
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* 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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* erval: return EPG
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* exactp: pointer to exact match flag
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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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* or RET_SPECIAL if no such key exists.
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*/
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static int
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__bt_first(t, key, erval, exactp)
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BTREE *t;
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const DBT *key;
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EPG *erval;
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int *exactp;
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{
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PAGE *h;
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EPG *ep, save;
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pgno_t pg;
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/*
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* Find any matching record; __bt_search pins the page.
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*
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* If it's an exact match and duplicates are possible, walk backwards
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* in the tree until we find the first one. Otherwise, make sure it's
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* a valid key (__bt_search may return an index just past the end of a
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* page) and return it.
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*/
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if ((ep = __bt_search(t, key, exactp)) == NULL)
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return (NULL);
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if (*exactp) {
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if (F_ISSET(t, B_NODUPS)) {
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*erval = *ep;
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return (RET_SUCCESS);
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}
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/*
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* Walk backwards, as long as the entry matches and there are
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* keys left in the tree. Save a copy of each match in case
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* we go too far.
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*/
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save = *ep;
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h = ep->page;
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do {
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if (save.page->pgno != ep->page->pgno) {
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mpool_put(t->bt_mp, save.page, 0);
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save = *ep;
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} else
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save.index = ep->index;
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/*
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* Don't unpin the page the last (or original) match
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* was on, but make sure it's unpinned if an error
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* occurs.
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*/
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if (ep->index == 0) {
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if (h->prevpg == P_INVALID)
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break;
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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,
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h->prevpg, 0)) == NULL) {
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if (h->pgno == save.page->pgno)
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mpool_put(t->bt_mp,
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save.page, 0);
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return (RET_ERROR);
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}
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ep->page = h;
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ep->index = NEXTINDEX(h);
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}
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--ep->index;
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} while (__bt_cmp(t, key, ep) == 0);
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/*
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* Reach here with the last page that was looked at pinned,
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* which may or may not be the same as the last (or original)
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* match page. If it's not useful, release it.
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*/
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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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*erval = save;
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return (RET_SUCCESS);
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}
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/* If at the end of a page, find the next entry. */
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if (ep->index == NEXTINDEX(ep->page)) {
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h = ep->page;
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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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return (RET_SPECIAL);
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if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
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return (RET_ERROR);
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ep->index = 0;
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ep->page = h;
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}
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*erval = *ep;
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return (RET_SUCCESS);
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}
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/*
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* __bt_setcur --
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* Set the cursor to an entry in the tree.
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*
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* Parameters:
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* t: the tree
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* pgno: page number
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* index: page index
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*/
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void
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__bt_setcur(t, pgno, index)
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BTREE *t;
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pgno_t pgno;
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u_int index;
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{
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/* Lose any already deleted key. */
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if (t->bt_cursor.key.data != NULL) {
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free(t->bt_cursor.key.data);
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t->bt_cursor.key.size = 0;
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t->bt_cursor.key.data = NULL;
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}
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F_CLR(&t->bt_cursor, CURS_ACQUIRE | CURS_AFTER | CURS_BEFORE);
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/* Update the cursor. */
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t->bt_cursor.pg.pgno = pgno;
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t->bt_cursor.pg.index = index;
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F_SET(&t->bt_cursor, CURS_INIT);
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}
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