/* $NetBSD: bt_seq.c,v 1.20 2016/09/24 21:31:25 christos Exp $ */
/*-
* 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. 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 HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif
#include <sys/cdefs.h>
__RCSID("$NetBSD: bt_seq.c,v 1.20 2016/09/24 21:31:25 christos Exp $");
#include "namespace.h"
#include <sys/types.h>
#include <assert.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <db.h>
#include "btree.h"
static int __bt_first(BTREE *, const DBT *, EPG *, int *);
static int __bt_seqadv(BTREE *, EPG *, int);
static int __bt_seqset(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, R_RNEXT, R_RPREV.
*
* 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 uninitialized 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, (int)flags);
break;
}
/* FALLTHROUGH */
case R_FIRST:
case R_LAST:
case R_CURSOR:
status = __bt_seqset(t, &e, key, (int)flags);
break;
default:
errno = EINVAL;
return (RET_ERROR);
}
if (status == RET_SUCCESS) {
__bt_setcur(t, e.page->pgno, (u_int)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, R_RNEXT, R_RPREV.
*
* 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;
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, R_RNEXT, R_RPREV
*
* 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; /* pacify gcc */
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;
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;
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;
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
* idx: page index
*/
void
__bt_setcur(BTREE *t, 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);
}