diff options
Diffstat (limited to 'db/btree/bt_seq.c')
| -rw-r--r-- | db/btree/bt_seq.c | 460 |
1 files changed, 460 insertions, 0 deletions
diff --git a/db/btree/bt_seq.c b/db/btree/bt_seq.c new file mode 100644 index 0000000000..303b481903 --- /dev/null +++ b/db/btree/bt_seq.c @@ -0,0 +1,460 @@ +/*- + * Copyright (c) 1990, 1993, 1994 + * 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_seq.c 8.7 (Berkeley) 7/20/94"; +#endif /* LIBC_SCCS and not lint */ + +#include <sys/types.h> + +#include <errno.h> +#include <stddef.h> +#include <stdio.h> +#include <stdlib.h> + +#include <db.h> +#include "btree.h" + +static int __bt_first __P((BTREE *, const DBT *, EPG *, int *)); +static int __bt_seqadv __P((BTREE *, EPG *, int)); +static int __bt_seqset __P((BTREE *, EPG *, DBT *, int)); + +/* + * Sequential scan support. + * + * The tree can be scanned sequentially, starting from either end of the + * tree or from any specific key. A scan request before any scanning is + * done is initialized as starting from the least node. + */ + +/* + * __bt_seq -- + * Btree sequential scan interface. + * + * Parameters: + * dbp: pointer to access method + * key: key for positioning and return value + * data: data return value + * flags: R_CURSOR, R_FIRST, R_LAST, R_NEXT, R_PREV. + * + * Returns: + * RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key. + */ +int +__bt_seq(dbp, key, data, flags) + const DB *dbp; + DBT *key, *data; + u_int flags; +{ + BTREE *t; + EPG e; + int status; + + t = dbp->internal; + + /* Toss any page pinned across calls. */ + if (t->bt_pinned != NULL) { + mpool_put(t->bt_mp, t->bt_pinned, 0); + t->bt_pinned = NULL; + } + + /* + * If scan unitialized as yet, or starting at a specific record, set + * the scan to a specific key. Both __bt_seqset and __bt_seqadv pin + * the page the cursor references if they're successful. + */ + switch (flags) { + case R_NEXT: + case R_PREV: + if (F_ISSET(&t->bt_cursor, CURS_INIT)) { + status = __bt_seqadv(t, &e, flags); + break; + } + /* FALLTHROUGH */ + case R_FIRST: + case R_LAST: + case R_CURSOR: + status = __bt_seqset(t, &e, key, flags); + break; + default: + errno = EINVAL; + return (RET_ERROR); + } + + if (status == RET_SUCCESS) { + __bt_setcur(t, e.page->pgno, e.index); + + status = + __bt_ret(t, &e, key, &t->bt_rkey, data, &t->bt_rdata, 0); + + /* + * If the user is doing concurrent access, we copied the + * key/data, toss the page. + */ + if (F_ISSET(t, B_DB_LOCK)) + mpool_put(t->bt_mp, e.page, 0); + else + t->bt_pinned = e.page; + } + return (status); +} + +/* + * __bt_seqset -- + * Set the sequential scan to a specific key. + * + * Parameters: + * t: tree + * ep: storage for returned key + * key: key for initial scan position + * flags: R_CURSOR, R_FIRST, R_LAST, R_NEXT, R_PREV + * + * Side effects: + * Pins the page the cursor references. + * + * Returns: + * RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key. + */ +static int +__bt_seqset(t, ep, key, flags) + BTREE *t; + EPG *ep; + DBT *key; + int flags; +{ + PAGE *h; + pgno_t pg; + int exact; + + /* + * Find the first, last or specific key in the tree and point the + * cursor at it. The cursor may not be moved until a new key has + * been found. + */ + switch (flags) { + case R_CURSOR: /* Keyed scan. */ + /* + * Find the first instance of the key or the smallest key + * which is greater than or equal to the specified key. + */ + if (key->data == NULL || key->size == 0) { + errno = EINVAL; + return (RET_ERROR); + } + return (__bt_first(t, key, ep, &exact)); + case R_FIRST: /* First record. */ + case R_NEXT: + /* Walk down the left-hand side of the tree. */ + for (pg = P_ROOT;;) { + if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) + return (RET_ERROR); + + /* Check for an empty tree. */ + if (NEXTINDEX(h) == 0) { + mpool_put(t->bt_mp, h, 0); + return (RET_SPECIAL); + } + + if (h->flags & (P_BLEAF | P_RLEAF)) + break; + pg = GETBINTERNAL(h, 0)->pgno; + mpool_put(t->bt_mp, h, 0); + } + ep->page = h; + ep->index = 0; + break; + case R_LAST: /* Last record. */ + case R_PREV: + /* Walk down the right-hand side of the tree. */ + for (pg = P_ROOT;;) { + if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) + return (RET_ERROR); + + /* Check for an empty tree. */ + if (NEXTINDEX(h) == 0) { + mpool_put(t->bt_mp, h, 0); + return (RET_SPECIAL); + } + + if (h->flags & (P_BLEAF | P_RLEAF)) + break; + pg = GETBINTERNAL(h, NEXTINDEX(h) - 1)->pgno; + mpool_put(t->bt_mp, h, 0); + } + + ep->page = h; + ep->index = NEXTINDEX(h) - 1; + break; + } + return (RET_SUCCESS); +} + +/* + * __bt_seqadvance -- + * Advance the sequential scan. + * + * Parameters: + * t: tree + * flags: R_NEXT, R_PREV + * + * Side effects: + * Pins the page the new key/data record is on. + * + * Returns: + * RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key. + */ +static int +__bt_seqadv(t, ep, flags) + BTREE *t; + EPG *ep; + int flags; +{ + CURSOR *c; + PAGE *h; + indx_t index; + pgno_t pg; + int exact; + + /* + * There are a couple of states that we can be in. The cursor has + * been initialized by the time we get here, but that's all we know. + */ + c = &t->bt_cursor; + + /* + * The cursor was deleted where there weren't any duplicate records, + * so the key was saved. Find out where that key would go in the + * current tree. It doesn't matter if the returned key is an exact + * match or not -- if it's an exact match, the record was added after + * the delete so we can just return it. If not, as long as there's + * a record there, return it. + */ + if (F_ISSET(c, CURS_ACQUIRE)) + return (__bt_first(t, &c->key, ep, &exact)); + + /* Get the page referenced by the cursor. */ + if ((h = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL) + return (RET_ERROR); + + /* + * Find the next/previous record in the tree and point the cursor at + * it. The cursor may not be moved until a new key has been found. + */ + switch (flags) { + case R_NEXT: /* Next record. */ + /* + * The cursor was deleted in duplicate records, and moved + * forward to a record that has yet to be returned. Clear + * that flag, and return the record. + */ + if (F_ISSET(c, CURS_AFTER)) + goto usecurrent; + index = c->pg.index; + if (++index == NEXTINDEX(h)) { + pg = h->nextpg; + mpool_put(t->bt_mp, h, 0); + if (pg == P_INVALID) + return (RET_SPECIAL); + if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) + return (RET_ERROR); + index = 0; + } + break; + case R_PREV: /* Previous record. */ + /* + * The cursor was deleted in duplicate records, and moved + * backward to a record that has yet to be returned. Clear + * that flag, and return the record. + */ + if (F_ISSET(c, CURS_BEFORE)) { +usecurrent: F_CLR(c, CURS_AFTER | CURS_BEFORE); + ep->page = h; + ep->index = c->pg.index; + return (RET_SUCCESS); + } + index = c->pg.index; + if (index == 0) { + pg = h->prevpg; + mpool_put(t->bt_mp, h, 0); + if (pg == P_INVALID) + return (RET_SPECIAL); + if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) + return (RET_ERROR); + index = NEXTINDEX(h) - 1; + } else + --index; + break; + } + + ep->page = h; + ep->index = index; + return (RET_SUCCESS); +} + +/* + * __bt_first -- + * Find the first entry. + * + * Parameters: + * t: the tree + * key: the key + * erval: return EPG + * exactp: pointer to exact match flag + * + * Returns: + * The first entry in the tree greater than or equal to key, + * or RET_SPECIAL if no such key exists. + */ +static int +__bt_first(t, key, erval, exactp) + BTREE *t; + const DBT *key; + EPG *erval; + int *exactp; +{ + PAGE *h; + EPG *ep, save; + pgno_t pg; + + /* + * Find any matching record; __bt_search pins the page. + * + * If it's an exact match and duplicates are possible, walk backwards + * in the tree until we find the first one. Otherwise, make sure it's + * a valid key (__bt_search may return an index just past the end of a + * page) and return it. + */ + if ((ep = __bt_search(t, key, exactp)) == NULL) + return (NULL); + if (*exactp) { + if (F_ISSET(t, B_NODUPS)) { + *erval = *ep; + return (RET_SUCCESS); + } + + /* + * Walk backwards, as long as the entry matches and there are + * keys left in the tree. Save a copy of each match in case + * we go too far. + */ + save = *ep; + h = ep->page; + do { + if (save.page->pgno != ep->page->pgno) { + mpool_put(t->bt_mp, save.page, 0); + save = *ep; + } else + save.index = ep->index; + + /* + * Don't unpin the page the last (or original) match + * was on, but make sure it's unpinned if an error + * occurs. + */ + if (ep->index == 0) { + if (h->prevpg == P_INVALID) + break; + if (h->pgno != save.page->pgno) + mpool_put(t->bt_mp, h, 0); + if ((h = mpool_get(t->bt_mp, + h->prevpg, 0)) == NULL) { + if (h->pgno == save.page->pgno) + mpool_put(t->bt_mp, + save.page, 0); + return (RET_ERROR); + } + ep->page = h; + ep->index = NEXTINDEX(h); + } + --ep->index; + } while (__bt_cmp(t, key, ep) == 0); + + /* + * Reach here with the last page that was looked at pinned, + * which may or may not be the same as the last (or original) + * match page. If it's not useful, release it. + */ + if (h->pgno != save.page->pgno) + mpool_put(t->bt_mp, h, 0); + + *erval = save; + return (RET_SUCCESS); + } + + /* If at the end of a page, find the next entry. */ + if (ep->index == NEXTINDEX(ep->page)) { + h = ep->page; + pg = h->nextpg; + mpool_put(t->bt_mp, h, 0); + if (pg == P_INVALID) + return (RET_SPECIAL); + if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) + return (RET_ERROR); + ep->index = 0; + ep->page = h; + } + *erval = *ep; + return (RET_SUCCESS); +} + +/* + * __bt_setcur -- + * Set the cursor to an entry in the tree. + * + * Parameters: + * t: the tree + * pgno: page number + * index: page index + */ +void +__bt_setcur(t, pgno, index) + BTREE *t; + pgno_t pgno; + u_int index; +{ + /* Lose any already deleted key. */ + if (t->bt_cursor.key.data != NULL) { + free(t->bt_cursor.key.data); + t->bt_cursor.key.size = 0; + t->bt_cursor.key.data = NULL; + } + F_CLR(&t->bt_cursor, CURS_ACQUIRE | CURS_AFTER | CURS_BEFORE); + + /* Update the cursor. */ + t->bt_cursor.pg.pgno = pgno; + t->bt_cursor.pg.index = index; + F_SET(&t->bt_cursor, CURS_INIT); +} |