/* * Copyright (C) 2002, 2016 by the Massachusetts Institute of Technology. * All rights reserved. * * Export of this software from the United States of America may * require a specific license from the United States Government. * It is the responsibility of any person or organization contemplating * export to obtain such a license before exporting. * * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and * distribute this software and its documentation for any purpose and * without fee is hereby granted, provided that the above copyright * notice appear in all copies and that both that copyright notice and * this permission notice appear in supporting documentation, and that * the name of M.I.T. not be used in advertising or publicity pertaining * to distribution of the software without specific, written prior * permission. Furthermore if you modify this software you must label * your software as modified software and not distribute it in such a * fashion that it might be confused with the original M.I.T. software. * M.I.T. makes no representations about the suitability of * this software for any purpose. It is provided "as is" without express * or implied warranty. */ /*- * 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 8.9 (Berkeley) 6/20/95"; #endif /* LIBC_SCCS and not lint */ #include <sys/types.h> #include <errno.h> #include <stddef.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include "db-int.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)); static int bt_rseq_next(BTREE *, EPG *); static int bt_rseq_prev(BTREE *, EPG *); /* * 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(const DB *dbp, DBT *key, DBT *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: case R_RNEXT: case R_RPREV: 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(BTREE *t, EPG *ep, DBT *key, int flags) { PAGE *h; db_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: case R_RNEXT: BT_CLR(t); /* 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; BT_PUSH(t, h->pgno, 0); mpool_put(t->bt_mp, h, 0); } ep->page = h; ep->index = 0; break; case R_LAST: /* Last record. */ case R_PREV: case R_RPREV: BT_CLR(t); /* 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; BT_PUSH(t, h->pgno, NEXTINDEX(h) - 1); 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(BTREE *t, EPG *ep, int flags) { CURSOR *c; PAGE *h; indx_t idx = 0; db_pgno_t pg; int exact, rval; /* * 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 and there weren't any duplicate records, * so the cursor's key was saved. Find out where that key would * be in the current tree. If the returned key is an exact match, * it means that a key/data pair was inserted into the tree after * the delete. We could reasonably return the key, but the problem * is that this is the access pattern we'll see if the user is * doing seq(..., R_NEXT)/put(..., 0) pairs, i.e. the put deletes * the cursor record and then replaces it, so the cursor was saved, * and we'll simply return the same "new" record until the user * notices and doesn't do a put() of it. Since the key is an exact * match, we could as easily put the new record before the cursor, * and we've made no guarantee to return it. So, move forward or * back a record if it's an exact match. * * XXX * In the current implementation, put's to the cursor are done with * delete/add pairs. This has two consequences. First, it means * that seq(..., R_NEXT)/put(..., R_CURSOR) pairs are going to exhibit * the same behavior as above. Second, you can return the same key * twice if you have duplicate records. The scenario is that the * cursor record is deleted, moving the cursor forward or backward * to a duplicate. The add then inserts the new record at a location * ahead of the cursor because duplicates aren't sorted in any way, * and the new record is later returned. This has to be fixed at some * point. */ if (F_ISSET(c, CURS_ACQUIRE)) { if ((rval = __bt_first(t, &c->key, ep, &exact)) == RET_ERROR) return (RET_ERROR); if (!exact) return (rval); /* * XXX * Kluge -- get, release, get the page. */ c->pg.pgno = ep->page->pgno; c->pg.index = ep->index; mpool_put(t->bt_mp, ep->page, 0); } /* 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. */ case R_RNEXT: /* * 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; idx = c->pg.index; if (++idx == NEXTINDEX(h)) { if (flags == R_RNEXT) { ep->page = h; ep->index = idx; return (bt_rseq_next(t, ep)); } 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); idx = 0; } break; case R_PREV: /* Previous record. */ case R_RPREV: /* * 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); } idx = c->pg.index; if (idx == 0) { if (flags == R_RPREV) { ep->page = h; ep->index = idx; return (bt_rseq_prev(t, ep)); } 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); idx = NEXTINDEX(h) - 1; } else --idx; break; } ep->page = h; ep->index = idx; return (RET_SUCCESS); } /* * Get the first item on the next page, but by going up and down the tree. */ static int bt_rseq_next(BTREE *t, EPG *ep) { PAGE *h; indx_t idx; EPGNO *up; db_pgno_t pg; h = ep->page; idx = ep->index; do { /* Move up the tree. */ up = BT_POP(t); mpool_put(t->bt_mp, h, 0); /* Did we hit the right edge of the root? */ if (up == NULL) return (RET_SPECIAL); if ((h = mpool_get(t->bt_mp, up->pgno, 0)) == NULL) return (RET_ERROR); idx = up->index; } while (++idx == NEXTINDEX(h)); while (!(h->flags & (P_BLEAF | P_RLEAF))) { /* Move back down the tree. */ BT_PUSH(t, h->pgno, idx); pg = GETBINTERNAL(h, idx)->pgno; mpool_put(t->bt_mp, h, 0); if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) return (RET_ERROR); idx = 0; } ep->page = h; ep->index = idx; return (RET_SUCCESS); } /* * Get the last item on the previous page, but by going up and down the tree. */ static int bt_rseq_prev(BTREE *t, EPG *ep) { PAGE *h; indx_t idx; EPGNO *up; db_pgno_t pg; h = ep->page; idx = ep->index; do { /* Move up the tree. */ up = BT_POP(t); mpool_put(t->bt_mp, h, 0); /* Did we hit the left edge of the root? */ if (up == NULL) return (RET_SPECIAL); if ((h = mpool_get(t->bt_mp, up->pgno, 0)) == NULL) return (RET_ERROR); idx = up->index; } while (idx == 0); --idx; while (!(h->flags & (P_BLEAF | P_RLEAF))) { /* Move back down the tree. */ BT_PUSH(t, h->pgno, idx); pg = GETBINTERNAL(h, idx)->pgno; mpool_put(t->bt_mp, h, 0); if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL) return (RET_ERROR); idx = NEXTINDEX(h) - 1; } ep->page = h; ep->index = idx; 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(BTREE *t, const DBT *key, EPG *erval, int *exactp) { PAGE *h, *hprev; EPG *ep, save; db_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 (RET_SPECIAL); 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 ((hprev = 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 = hprev; 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(BTREE *t, db_pgno_t pgno, u_int idx) { /* 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 = idx; F_SET(&t->bt_cursor, CURS_INIT); }
