db/btree/FreeBSD/bt_seq.c

   1 /*-
   2  * Copyright (c) 1990, 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Mike Olson.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 static char sccsid[] = "@(#)bt_seq.c    8.7 (Berkeley) 7/20/94";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/db/btree/bt_seq.c,v 1.7 2009/03/04 00:58:04 delphij Exp $");
  38
  39 #include <sys/types.h>
  40
  41 #include <errno.h>
  42 #include <stddef.h>
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45
  46 #include <db.h>
  47 #include "btree.h"
  48
  49 static int __bt_first(BTREE *, const DBT *, EPG *, int *);
  50 static int __bt_seqadv(BTREE *, EPG *, int);
  51 static int __bt_seqset(BTREE *, EPG *, DBT *, int);
  52
  53 /*
  54  * Sequential scan support.
  55  *
  56  * The tree can be scanned sequentially, starting from either end of the
  57  * tree or from any specific key.  A scan request before any scanning is
  58  * done is initialized as starting from the least node.
  59  */
  60
  61 /*
  62  * __bt_seq --
  63  *      Btree sequential scan interface.
  64  *
  65  * Parameters:
  66  *      dbp:    pointer to access method
  67  *      key:    key for positioning and return value
  68  *      data:   data return value
  69  *      flags:  R_CURSOR, R_FIRST, R_LAST, R_NEXT, R_PREV.
  70  *
  71  * Returns:
  72  *      RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key.
  73  */
  74 int
  75 __bt_seq(const DB *dbp, DBT *key, DBT *data, u_int flags)
  76 {
  77         BTREE *t;
  78         EPG e;
  79         int status;
  80
  81         t = dbp->internal;
  82
  83         /* Toss any page pinned across calls. */
  84         if (t->bt_pinned != NULL) {
  85                 mpool_put(t->bt_mp, t->bt_pinned, 0);
  86                 t->bt_pinned = NULL;
  87         }
  88
  89         /*
  90          * If scan unitialized as yet, or starting at a specific record, set
  91          * the scan to a specific key.  Both __bt_seqset and __bt_seqadv pin
  92          * the page the cursor references if they're successful.
  93          */
  94         switch (flags) {
  95         case R_NEXT:
  96         case R_PREV:
  97                 if (F_ISSET(&t->bt_cursor, CURS_INIT)) {
  98                         status = __bt_seqadv(t, &e, flags);
  99                         break;
 100                 }
 101                 /* FALLTHROUGH */
 102         case R_FIRST:
 103         case R_LAST:
 104         case R_CURSOR:
 105                 status = __bt_seqset(t, &e, key, flags);
 106                 break;
 107         default:
 108                 errno = EINVAL;
 109                 return (RET_ERROR);
 110         }
 111
 112         if (status == RET_SUCCESS) {
 113                 __bt_setcur(t, e.page->pgno, e.index);
 114
 115                 status =
 116                     __bt_ret(t, &e, key, &t->bt_rkey, data, &t->bt_rdata, 0);
 117
 118                 /*
 119                  * If the user is doing concurrent access, we copied the
 120                  * key/data, toss the page.
 121                  */
 122                 if (F_ISSET(t, B_DB_LOCK))
 123                         mpool_put(t->bt_mp, e.page, 0);
 124                 else
 125                         t->bt_pinned = e.page;
 126         }
 127         return (status);
 128 }
 129
 130 /*
 131  * __bt_seqset --
 132  *      Set the sequential scan to a specific key.
 133  *
 134  * Parameters:
 135  *      t:      tree
 136  *      ep:     storage for returned key
 137  *      key:    key for initial scan position
 138  *      flags:  R_CURSOR, R_FIRST, R_LAST, R_NEXT, R_PREV
 139  *
 140  * Side effects:
 141  *      Pins the page the cursor references.
 142  *
 143  * Returns:
 144  *      RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key.
 145  */
 146 static int
 147 __bt_seqset(BTREE *t, EPG *ep, DBT *key, int flags)
 148 {
 149         PAGE *h;
 150         pgno_t pg;
 151         int exact;
 152
 153         /*
 154          * Find the first, last or specific key in the tree and point the
 155          * cursor at it.  The cursor may not be moved until a new key has
 156          * been found.
 157          */
 158         switch (flags) {
 159         case R_CURSOR:                          /* Keyed scan. */
 160                 /*
 161                  * Find the first instance of the key or the smallest key
 162                  * which is greater than or equal to the specified key.
 163                  */
 164                 if (key->data == NULL || key->size == 0) {
 165                         errno = EINVAL;
 166                         return (RET_ERROR);
 167                 }
 168                 return (__bt_first(t, key, ep, &exact));
 169         case R_FIRST:                           /* First record. */
 170         case R_NEXT:
 171                 /* Walk down the left-hand side of the tree. */
 172                 for (pg = P_ROOT;;) {
 173                         if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 174                                 return (RET_ERROR);
 175
 176                         /* Check for an empty tree. */
 177                         if (NEXTINDEX(h) == 0) {
 178                                 mpool_put(t->bt_mp, h, 0);
 179                                 return (RET_SPECIAL);
 180                         }
 181
 182                         if (h->flags & (P_BLEAF | P_RLEAF))
 183                                 break;
 184                         pg = GETBINTERNAL(h, 0)->pgno;
 185                         mpool_put(t->bt_mp, h, 0);
 186                 }
 187                 ep->page = h;
 188                 ep->index = 0;
 189                 break;
 190         case R_LAST:                            /* Last record. */
 191         case R_PREV:
 192                 /* Walk down the right-hand side of the tree. */
 193                 for (pg = P_ROOT;;) {
 194                         if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 195                                 return (RET_ERROR);
 196
 197                         /* Check for an empty tree. */
 198                         if (NEXTINDEX(h) == 0) {
 199                                 mpool_put(t->bt_mp, h, 0);
 200                                 return (RET_SPECIAL);
 201                         }
 202
 203                         if (h->flags & (P_BLEAF | P_RLEAF))
 204                                 break;
 205                         pg = GETBINTERNAL(h, NEXTINDEX(h) - 1)->pgno;
 206                         mpool_put(t->bt_mp, h, 0);
 207                 }
 208
 209                 ep->page = h;
 210                 ep->index = NEXTINDEX(h) - 1;
 211                 break;
 212         }
 213         return (RET_SUCCESS);
 214 }
 215
 216 /*
 217  * __bt_seqadvance --
 218  *      Advance the sequential scan.
 219  *
 220  * Parameters:
 221  *      t:      tree
 222  *      flags:  R_NEXT, R_PREV
 223  *
 224  * Side effects:
 225  *      Pins the page the new key/data record is on.
 226  *
 227  * Returns:
 228  *      RET_ERROR, RET_SUCCESS or RET_SPECIAL if there's no next key.
 229  */
 230 static int
 231 __bt_seqadv(BTREE *t, EPG *ep, int flags)
 232 {
 233         CURSOR *c;
 234         PAGE *h;
 235         indx_t idx;
 236         pgno_t pg;
 237         int exact;
 238
 239         /*
 240          * There are a couple of states that we can be in.  The cursor has
 241          * been initialized by the time we get here, but that's all we know.
 242          */
 243         c = &t->bt_cursor;
 244
 245         /*
 246          * The cursor was deleted where there weren't any duplicate records,
 247          * so the key was saved.  Find out where that key would go in the
 248          * current tree.  It doesn't matter if the returned key is an exact
 249          * match or not -- if it's an exact match, the record was added after
 250          * the delete so we can just return it.  If not, as long as there's
 251          * a record there, return it.
 252          */
 253         if (F_ISSET(c, CURS_ACQUIRE))
 254                 return (__bt_first(t, &c->key, ep, &exact));
 255
 256         /* Get the page referenced by the cursor. */
 257         if ((h = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL)
 258                 return (RET_ERROR);
 259
 260         /*
 261          * Find the next/previous record in the tree and point the cursor at
 262          * it.  The cursor may not be moved until a new key has been found.
 263          */
 264         switch (flags) {
 265         case R_NEXT:                    /* Next record. */
 266                 /*
 267                  * The cursor was deleted in duplicate records, and moved
 268                  * forward to a record that has yet to be returned.  Clear
 269                  * that flag, and return the record.
 270                  */
 271                 if (F_ISSET(c, CURS_AFTER))
 272                         goto usecurrent;
 273                 idx = c->pg.index;
 274                 if (++idx == NEXTINDEX(h)) {
 275                         pg = h->nextpg;
 276                         mpool_put(t->bt_mp, h, 0);
 277                         if (pg == P_INVALID)
 278                                 return (RET_SPECIAL);
 279                         if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 280                                 return (RET_ERROR);
 281                         idx = 0;
 282                 }
 283                 break;
 284         case R_PREV:                    /* Previous record. */
 285                 /*
 286                  * The cursor was deleted in duplicate records, and moved
 287                  * backward to a record that has yet to be returned.  Clear
 288                  * that flag, and return the record.
 289                  */
 290                 if (F_ISSET(c, CURS_BEFORE)) {
 291 usecurrent:             F_CLR(c, CURS_AFTER | CURS_BEFORE);
 292                         ep->page = h;
 293                         ep->index = c->pg.index;
 294                         return (RET_SUCCESS);
 295                 }
 296                 idx = c->pg.index;
 297                 if (idx == 0) {
 298                         pg = h->prevpg;
 299                         mpool_put(t->bt_mp, h, 0);
 300                         if (pg == P_INVALID)
 301                                 return (RET_SPECIAL);
 302                         if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 303                                 return (RET_ERROR);
 304                         idx = NEXTINDEX(h) - 1;
 305                 } else
 306                         --idx;
 307                 break;
 308         }
 309
 310         ep->page = h;
 311         ep->index = idx;
 312         return (RET_SUCCESS);
 313 }
 314
 315 /*
 316  * __bt_first --
 317  *      Find the first entry.
 318  *
 319  * Parameters:
 320  *      t:      the tree
 321  *    key:      the key
 322  *  erval:      return EPG
 323  * exactp:      pointer to exact match flag
 324  *
 325  * Returns:
 326  *      The first entry in the tree greater than or equal to key,
 327  *      or RET_SPECIAL if no such key exists.
 328  */
 329 static int
 330 __bt_first(BTREE *t, const DBT *key, EPG *erval, int *exactp)
 331 {
 332         PAGE *h;
 333         EPG *ep, save;
 334         pgno_t pg;
 335
 336         /*
 337          * Find any matching record; __bt_search pins the page.
 338          *
 339          * If it's an exact match and duplicates are possible, walk backwards
 340          * in the tree until we find the first one.  Otherwise, make sure it's
 341          * a valid key (__bt_search may return an index just past the end of a
 342          * page) and return it.
 343          */
 344         if ((ep = __bt_search(t, key, exactp)) == NULL)
 345                 return (0);
 346         if (*exactp) {
 347                 if (F_ISSET(t, B_NODUPS)) {
 348                         *erval = *ep;
 349                         return (RET_SUCCESS);
 350                 }
 351
 352                 /*
 353                  * Walk backwards, as long as the entry matches and there are
 354                  * keys left in the tree.  Save a copy of each match in case
 355                  * we go too far.
 356                  */
 357                 save = *ep;
 358                 h = ep->page;
 359                 do {
 360                         if (save.page->pgno != ep->page->pgno) {
 361                                 mpool_put(t->bt_mp, save.page, 0);
 362                                 save = *ep;
 363                         } else
 364                                 save.index = ep->index;
 365
 366                         /*
 367                          * Don't unpin the page the last (or original) match
 368                          * was on, but make sure it's unpinned if an error
 369                          * occurs.
 370                          */
 371                         if (ep->index == 0) {
 372                                 PAGE *hprev;
 373                                 if (h->prevpg == P_INVALID)
 374                                         break;
 375                                 if (h->pgno != save.page->pgno)
 376                                         mpool_put(t->bt_mp, h, 0);
 377                                 if ((hprev = mpool_get(t->bt_mp,
 378                                     h->prevpg, 0)) == NULL) {
 379                                         if (h->pgno == save.page->pgno)
 380                                                 mpool_put(t->bt_mp,
 381                                                     save.page, 0);
 382                                         return (RET_ERROR);
 383                                 }
 384                                 ep->page = h = hprev;
 385                                 ep->index = NEXTINDEX(h);
 386                         }
 387                         --ep->index;
 388                 } while (__bt_cmp(t, key, ep) == 0);
 389
 390                 /*
 391                  * Reach here with the last page that was looked at pinned,
 392                  * which may or may not be the same as the last (or original)
 393                  * match page.  If it's not useful, release it.
 394                  */
 395                 if (h->pgno != save.page->pgno)
 396                         mpool_put(t->bt_mp, h, 0);
 397
 398                 *erval = save;
 399                 return (RET_SUCCESS);
 400         }
 401
 402         /* If at the end of a page, find the next entry. */
 403         if (ep->index == NEXTINDEX(ep->page)) {
 404                 h = ep->page;
 405                 pg = h->nextpg;
 406                 mpool_put(t->bt_mp, h, 0);
 407                 if (pg == P_INVALID)
 408                         return (RET_SPECIAL);
 409                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
 410                         return (RET_ERROR);
 411                 ep->index = 0;
 412                 ep->page = h;
 413         }
 414         *erval = *ep;
 415         return (RET_SUCCESS);
 416 }
 417
 418 /*
 419  * __bt_setcur --
 420  *      Set the cursor to an entry in the tree.
 421  *
 422  * Parameters:
 423  *      t:      the tree
 424  *   pgno:      page number
 425  *    idx:      page index
 426  */
 427 void
 428 __bt_setcur(BTREE *t, pgno_t pgno, u_int idx)
 429 {
 430         /* Lose any already deleted key. */
 431         if (t->bt_cursor.key.data != NULL) {
 432                 free(t->bt_cursor.key.data);
 433                 t->bt_cursor.key.size = 0;
 434                 t->bt_cursor.key.data = NULL;
 435         }
 436         F_CLR(&t->bt_cursor, CURS_ACQUIRE | CURS_AFTER | CURS_BEFORE);
 437
 438         /* Update the cursor. */
 439         t->bt_cursor.pg.pgno = pgno;
 440         t->bt_cursor.pg.index = idx;
 441         F_SET(&t->bt_cursor, CURS_INIT);
 442 }