summary refs log tree commit diff
path: root/db/btree/bt_seq.c
blob: eacef2998f9b66304e3138d28081254fc51f7fd9 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
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 (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 ((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);
}