Logo Search packages:      
Sourcecode: db2 version File versions  Download package

bt_delete.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998
 *    Sleepycat Software.  All rights reserved.
 */
/*
 * Copyright (c) 1990, 1993, 1994, 1995, 1996
 *    Keith Bostic.  All rights reserved.
 */
/*
 * Copyright (c) 1990, 1993, 1994, 1995
 *    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.
 */

#include "config.h"

#ifndef lint
static const char sccsid[] = "@(#)bt_delete.c   10.31 (Sleepycat) 5/6/98";
#endif /* not lint */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <string.h>
#endif

#include "db_int.h"
#include "db_page.h"
#include "btree.h"

static int __bam_dpages __P((DB *, BTREE *));

/*
 * __bam_delete --
 *    Delete the items referenced by a key.
 *
 * PUBLIC: int __bam_delete __P((DB *, DB_TXN *, DBT *, u_int32_t));
 */
int
__bam_delete(argdbp, txn, key, flags)
      DB *argdbp;
      DB_TXN *txn;
      DBT *key;
      u_int32_t flags;
{
      BTREE *t;
      DB *dbp;
      PAGE *h;
      db_indx_t cnt, i, indx;
      int dpage, exact, ret, stack;

      DEBUG_LWRITE(argdbp, txn, "bam_delete", key, NULL, flags);

      stack = 0;

      /* Check for invalid flags. */
      if ((ret = __db_delchk(argdbp,
          key, flags, F_ISSET(argdbp, DB_AM_RDONLY))) != 0)
            return (ret);

      GETHANDLE(argdbp, txn, &dbp, ret);
      t = dbp->internal;

      /* Search the tree for the key; delete only deletes exact matches. */
      if ((ret = __bam_search(dbp, key, S_DELETE, 1, NULL, &exact)) != 0)
            goto err;
      stack = 1;
      h = t->bt_csp->page;
      indx = t->bt_csp->indx;

      /* Delete the key/data pair, including any on-or-off page duplicates. */
      for (cnt = 1, i = indx;; ++cnt)
            if ((i += P_INDX) >= NUM_ENT(h) || h->inp[i] != h->inp[indx])
                  break;
      for (; cnt > 0; --cnt, ++t->lstat.bt_deleted)
            if (__bam_ca_delete(dbp, h->pgno, indx, NULL, 1) == 0) {
                  /*
                   * XXX
                   * Delete the key item first, otherwise the duplicate
                   * checks in __bam_ditem() won't work!
                   */
                  if ((ret = __bam_ditem(dbp, h, indx)) != 0)
                        goto err;
                  if ((ret = __bam_ditem(dbp, h, indx)) != 0)
                        goto err;
            } else {
                  B_DSET(GET_BKEYDATA(h, indx + O_INDX)->type);
                  indx += P_INDX;
            }

      /* If we're using record numbers, update internal page record counts. */
      if (F_ISSET(dbp, DB_BT_RECNUM) && (ret = __bam_adjust(dbp, t, -1)) != 0)
            goto err;

      /* If the page is now empty, delete it. */
      dpage = NUM_ENT(h) == 0 && h->pgno != PGNO_ROOT;

      __bam_stkrel(dbp);
      stack = 0;

      ret = dpage ? __bam_dpage(dbp, key) : 0;

err:  if (stack)
            __bam_stkrel(dbp);
      PUTHANDLE(dbp);
      return (ret);
}

/*
 * __ram_delete --
 *    Delete the items referenced by a key.
 *
 * PUBLIC: int __ram_delete __P((DB *, DB_TXN *, DBT *, u_int32_t));
 */
int
__ram_delete(argdbp, txn, key, flags)
      DB *argdbp;
      DB_TXN *txn;
      DBT *key;
      u_int32_t flags;
{
      BKEYDATA bk;
      BTREE *t;
      DB *dbp;
      DBT hdr, data;
      PAGE *h;
      db_indx_t indx;
      db_recno_t recno;
      int exact, ret, stack;

      stack = 0;

      /* Check for invalid flags. */
      if ((ret = __db_delchk(argdbp,
          key, flags, F_ISSET(argdbp, DB_AM_RDONLY))) != 0)
            return (ret);

      GETHANDLE(argdbp, txn, &dbp, ret);
      t = dbp->internal;

      /* Check the user's record number and fill in as necessary. */
      if ((ret = __ram_getno(argdbp, key, &recno, 0)) != 0)
            goto err;

      /* Search the tree for the key; delete only deletes exact matches. */
      if ((ret = __bam_rsearch(dbp, &recno, S_DELETE, 1, &exact)) != 0)
            goto err;
      if (!exact) {
            ret = DB_NOTFOUND;
            goto err;
      }

      h = t->bt_csp->page;
      indx = t->bt_csp->indx;
      stack = 1;

      /* If the record has already been deleted, we couldn't have found it. */
      if (B_DISSET(GET_BKEYDATA(h, indx)->type)) {
            ret = DB_KEYEMPTY;
            goto done;
      }

      /*
       * If we're not renumbering records, replace the record with a marker
       * and return.
       */
      if (!F_ISSET(dbp, DB_RE_RENUMBER)) {
            if ((ret = __bam_ditem(dbp, h, indx)) != 0)
                  goto err;

            B_TSET(bk.type, B_KEYDATA, 1);
            bk.len = 0;
            memset(&hdr, 0, sizeof(hdr));
            hdr.data = &bk;
            hdr.size = SSZA(BKEYDATA, data);
            memset(&data, 0, sizeof(data));
            data.data = (char *)"";
            data.size = 0;
            if ((ret = __db_pitem(dbp,
                h, indx, BKEYDATA_SIZE(0), &hdr, &data)) != 0)
                  goto err;

            ++t->lstat.bt_deleted;
            goto done;
      }

      /* Delete the item. */
      if ((ret = __bam_ditem(dbp, h, indx)) != 0)
            goto err;

      ++t->lstat.bt_deleted;
      if (t->bt_recno != NULL)
            F_SET(t->bt_recno, RECNO_MODIFIED);

      /* Adjust the counts. */
      __bam_adjust(dbp, t, -1);

      /* Adjust the cursors. */
      __ram_ca(dbp, recno, CA_DELETE);

      /*
       * If the page is now empty, delete it -- we have the whole tree
       * locked, so there are no preparations to make.  Else, release
       * the pages.
       */
      if (NUM_ENT(h) == 0 && h->pgno != PGNO_ROOT) {
            stack = 0;
            ret = __bam_dpages(dbp, t);
      }

done:
err:  if (stack)
            __bam_stkrel(dbp);

      PUTHANDLE(dbp);
      return (ret);
}

/*
 * __bam_ditem --
 *    Delete one or more entries from a page.
 *
 * PUBLIC: int __bam_ditem __P((DB *, PAGE *, u_int32_t));
 */
int
__bam_ditem(dbp, h, indx)
      DB *dbp;
      PAGE *h;
      u_int32_t indx;
{
      BINTERNAL *bi;
      BKEYDATA *bk;
      BOVERFLOW *bo;
      u_int32_t nbytes;
      int ret;

      switch (TYPE(h)) {
      case P_IBTREE:
            bi = GET_BINTERNAL(h, indx);
            switch (B_TYPE(bi->type)) {
            case B_DUPLICATE:
            case B_OVERFLOW:
                  nbytes = BINTERNAL_SIZE(bi->len);
                  bo = (BOVERFLOW *)bi->data;
                  goto offpage;
            case B_KEYDATA:
                  nbytes = BINTERNAL_SIZE(bi->len);
                  break;
            default:
                  return (__db_pgfmt(dbp, h->pgno));
            }
            break;
      case P_IRECNO:
            nbytes = RINTERNAL_SIZE;
            break;
      case P_LBTREE:
            /*
             * If it's a duplicate key, discard the index and don't touch
             * the actual page item.
             *
             * XXX
             * This works because no data item can have an index matching
             * any other index so even if the data item is in a key "slot",
             * it won't match any other index.
             */
            if ((indx % 2) == 0) {
                  /*
                   * Check for a duplicate after us on the page.  NOTE:
                   * we have to delete the key item before deleting the
                   * data item, otherwise the "indx + P_INDX" calculation
                   * won't work!
                   */
                  if (indx + P_INDX < (u_int32_t)NUM_ENT(h) &&
                      h->inp[indx] == h->inp[indx + P_INDX])
                        return (__bam_adjindx(dbp,
                            h, indx, indx + O_INDX, 0));
                  /*
                   * Check for a duplicate before us on the page.  It
                   * doesn't matter if we delete the key item before or
                   * after the data item for the purposes of this one.
                   */
                  if (indx > 0 && h->inp[indx] == h->inp[indx - P_INDX])
                        return (__bam_adjindx(dbp,
                            h, indx, indx - P_INDX, 0));
            }
            /* FALLTHROUGH */
      case P_LRECNO:
            bk = GET_BKEYDATA(h, indx);
            switch (B_TYPE(bk->type)) {
            case B_DUPLICATE:
            case B_OVERFLOW:
                  nbytes = BOVERFLOW_SIZE;
                  bo = GET_BOVERFLOW(h, indx);

offpage:          /* Delete duplicate/offpage chains. */
                  if (B_TYPE(bo->type) == B_DUPLICATE) {
                        if ((ret =
                            __db_ddup(dbp, bo->pgno, __bam_free)) != 0)
                              return (ret);
                  } else
                        if ((ret =
                            __db_doff(dbp, bo->pgno, __bam_free)) != 0)
                              return (ret);
                  break;
            case B_KEYDATA:
                  nbytes = BKEYDATA_SIZE(bk->len);
                  break;
            default:
                  return (__db_pgfmt(dbp, h->pgno));
            }
            break;
      default:
            return (__db_pgfmt(dbp, h->pgno));
      }

      /* Delete the item. */
      if ((ret = __db_ditem(dbp, h, indx, nbytes)) != 0)
            return (ret);

      /* Mark the page dirty. */
      return (memp_fset(dbp->mpf, h, DB_MPOOL_DIRTY));
}

/*
 * __bam_adjindx --
 *    Adjust an index on the page.
 *
 * PUBLIC: int __bam_adjindx __P((DB *, PAGE *, u_int32_t, u_int32_t, int));
 */
int
__bam_adjindx(dbp, h, indx, indx_copy, is_insert)
      DB *dbp;
      PAGE *h;
      u_int32_t indx, indx_copy;
      int is_insert;
{
      db_indx_t copy;
      int ret;

      /* Log the change. */
      if (DB_LOGGING(dbp) &&
          (ret = __bam_adj_log(dbp->dbenv->lg_info, dbp->txn, &LSN(h),
          0, dbp->log_fileid, PGNO(h), &LSN(h), indx, indx_copy,
          (u_int32_t)is_insert)) != 0)
            return (ret);

      if (is_insert) {
            copy = h->inp[indx_copy];
            if (indx != NUM_ENT(h))
                  memmove(&h->inp[indx + O_INDX], &h->inp[indx],
                      sizeof(db_indx_t) * (NUM_ENT(h) - indx));
            h->inp[indx] = copy;
            ++NUM_ENT(h);
      } else {
            --NUM_ENT(h);
            if (indx != NUM_ENT(h))
                  memmove(&h->inp[indx], &h->inp[indx + O_INDX],
                      sizeof(db_indx_t) * (NUM_ENT(h) - indx));
      }

      /* Mark the page dirty. */
      ret = memp_fset(dbp->mpf, h, DB_MPOOL_DIRTY);

      /* Adjust the cursors. */
      __bam_ca_di(dbp, h->pgno, indx, is_insert ? 1 : -1);
      return (0);
}

/*
 * __bam_dpage --
 *    Delete a page from the tree.
 *
 * PUBLIC: int __bam_dpage __P((DB *, const DBT *));
 */
int
__bam_dpage(dbp, key)
      DB *dbp;
      const DBT *key;
{
      BTREE *t;
      DB_LOCK lock;
      PAGE *h;
      db_pgno_t pgno;
      int level;        /* !!!: has to hold number of tree levels. */
      int exact, ret;

      ret = 0;
      t = dbp->internal;

      /*
       * The locking protocol is that we acquire locks by walking down the
       * tree, to avoid the obvious deadlocks.
       *
       * Call __bam_search to reacquire the empty leaf page, but this time
       * get both the leaf page and it's parent, locked.  Walk back up the
       * tree, until we have the top pair of pages that we want to delete.
       * Once we have the top page that we want to delete locked, lock the
       * underlying pages and check to make sure they're still empty.  If
       * they are, delete them.
       */
      for (level = LEAFLEVEL;; ++level) {
            /* Acquire a page and its parent, locked. */
            if ((ret =
                __bam_search(dbp, key, S_WRPAIR, level, NULL, &exact)) != 0)
                  return (ret);

            /*
             * If we reach the root or the page isn't going to be empty
             * when we delete one record, quit.
             */
            h = t->bt_csp[-1].page;
            if (h->pgno == PGNO_ROOT || NUM_ENT(h) != 1)
                  break;

            /* Release the two locked pages. */
            (void)memp_fput(dbp->mpf, t->bt_csp[-1].page, 0);
            (void)__BT_TLPUT(dbp, t->bt_csp[-1].lock);
            (void)memp_fput(dbp->mpf, t->bt_csp[0].page, 0);
            (void)__BT_TLPUT(dbp, t->bt_csp[0].lock);
      }

      /*
       * Leave the stack pointer one after the last entry, we may be about
       * to push more items on the stack.
       */
      ++t->bt_csp;

      /*
       * t->bt_csp[-2].page is the top page, which we're not going to delete,
       * and t->bt_csp[-1].page is the first page we are going to delete.
       *
       * Walk down the chain, acquiring the rest of the pages until we've
       * retrieved the leaf page.  If we find any pages that aren't going
       * to be emptied by the delete, someone else added something while we
       * were walking the tree, and we discontinue the delete.
       */
      for (h = t->bt_csp[-1].page;;) {
            if (ISLEAF(h)) {
                  if (NUM_ENT(h) != 0)
                        goto release;
                  break;
            } else
                  if (NUM_ENT(h) != 1)
                        goto release;

            /*
             * Get the next page, write lock it and push it onto the stack.
             * We know it's index 0, because it can only have one element.
             */
            pgno = TYPE(h) == P_IBTREE ?
                GET_BINTERNAL(h, 0)->pgno : GET_RINTERNAL(h, 0)->pgno;

            if ((ret = __bam_lget(dbp, 0, pgno, DB_LOCK_WRITE, &lock)) != 0)
                  goto release;
            if ((ret = __bam_pget(dbp, &h, &pgno, 0)) != 0)
                  goto release;
            BT_STK_PUSH(t, h, 0, lock, ret);
            if (ret != 0)
                  goto release;
      }

      BT_STK_POP(t);
      return (__bam_dpages(dbp, t));

release:
      /* Discard any locked pages and return. */
      BT_STK_POP(t);
      __bam_stkrel(dbp);
      return (ret);
}

/*
 * __bam_dpages --
 *    Delete a set of locked pages.
 */
static int
__bam_dpages(dbp, t)
      DB *dbp;
      BTREE *t;
{
      DBT a, b;
      DB_LOCK lock;
      EPG *epg;
      PAGE *h;
      db_pgno_t pgno;
      db_recno_t rcnt;
      int ret;

      COMPQUIET(rcnt, 0);

      epg = t->bt_sp;

      /*
       * !!!
       * There is an interesting deadlock situation here.  We have to relink
       * the leaf page chain around the leaf page being deleted.  Consider
       * a cursor walking through the leaf pages, that has the previous page
       * read-locked and is waiting on a lock for the page we're deleting.
       * It will deadlock here.  This is a problem, because if our process is
       * selected to resolve the deadlock, we'll leave an empty leaf page
       * that we can never again access by walking down the tree.  So, before
       * we unlink the subtree, we relink the leaf page chain.
       */
      if ((ret = __db_relink(dbp, t->bt_csp->page, NULL, 1)) != 0)
            goto release;

      /*
       * We have the entire stack of deletable pages locked.  Start from the
       * top of the tree and move to the bottom, as it's better to release
       * the inner pages as soon as possible.
       */
      if ((ret = __bam_ditem(dbp, epg->page, epg->indx)) != 0)
            goto release;

      /*
       * If we just deleted the last or next-to-last item from the root page,
       * the tree can collapse a level.  Write lock the last page referenced
       * by the root page and copy it over the root page.  If we can't get a
       * write lock, that's okay, the tree just remains a level deeper than
       * we'd like.
       */
      h = epg->page;
      if (h->pgno == PGNO_ROOT && NUM_ENT(h) <= 1) {
            pgno = TYPE(epg->page) == P_IBTREE ?
                GET_BINTERNAL(epg->page, 0)->pgno :
                GET_RINTERNAL(epg->page, 0)->pgno;
            if ((ret = __bam_lget(dbp, 0, pgno, DB_LOCK_WRITE, &lock)) != 0)
                  goto release;
            if ((ret = __bam_pget(dbp, &h, &pgno, 0)) != 0)
                  goto release;

            /* Log the change. */
            if (DB_LOGGING(dbp)) {
                  memset(&a, 0, sizeof(a));
                  a.data = h;
                  a.size = dbp->pgsize;
                  memset(&b, 0, sizeof(b));
                  b.data = P_ENTRY(epg->page, 0);
                  b.size = BINTERNAL_SIZE(((BINTERNAL *)b.data)->len);
                  __bam_rsplit_log(dbp->dbenv->lg_info, dbp->txn,
                     &h->lsn, 0, dbp->log_fileid, h->pgno, &a,
                     RE_NREC(epg->page), &b, &epg->page->lsn);
            }

            /*
             * Make the switch.
             *
             * One fixup -- if the tree has record numbers and we're not
             * converting to a leaf page, we have to preserve the total
             * record count.
             */
            if (TYPE(h) == P_IRECNO ||
                (TYPE(h) == P_IBTREE && F_ISSET(dbp, DB_BT_RECNUM)))
                  rcnt = RE_NREC(epg->page);
            memcpy(epg->page, h, dbp->pgsize);
            epg->page->pgno = PGNO_ROOT;
            if (TYPE(h) == P_IRECNO ||
                (TYPE(h) == P_IBTREE && F_ISSET(dbp, DB_BT_RECNUM)))
                  RE_NREC_SET(epg->page, rcnt);
            (void)memp_fset(dbp->mpf, epg->page, DB_MPOOL_DIRTY);

            /*
             * Free the page copied onto the root page and discard its
             * lock.  (The call to __bam_free() discards our reference
             * to the page.)
             *
             * It's possible that the reverse split we're doing involves
             * pages from the stack of pages we're deleting.  Don't free
             * the page twice.
             */
             if (h->pgno == (epg + 1)->page->pgno)
                  (void)memp_fput(dbp->mpf, h, 0);
            else {
                  (void)__bam_free(dbp, h);
                  ++t->lstat.bt_freed;
            }
            (void)__BT_TLPUT(dbp, lock);

            /* Adjust the cursors. */
            __bam_ca_move(dbp, h->pgno, PGNO_ROOT);
      }

      /* Release the top page in the subtree. */
      (void)memp_fput(dbp->mpf, epg->page, 0);
      (void)__BT_TLPUT(dbp, epg->lock);

      /*
       * Free the rest of the pages.
       *
       * XXX
       * Don't bother checking for errors.  We've unlinked the subtree from
       * the tree, and there's no possibility of recovery.
       */
      while (++epg <= t->bt_csp) {
            /*
             * XXX
             * Why do we need to do this?  Isn't the page already empty?
             */
            if (NUM_ENT(epg->page) != 0)
                  (void)__bam_ditem(dbp, epg->page, epg->indx);

            (void)__bam_free(dbp, epg->page);
            (void)__BT_TLPUT(dbp, epg->lock);
            ++t->lstat.bt_freed;
      }
      return (0);

release:
      /* Discard any remaining pages and return. */
      for (; epg <= t->bt_csp; ++epg) {
            (void)memp_fput(dbp->mpf, epg->page, 0);
            (void)__BT_TLPUT(dbp, epg->lock);
      }
      return (ret);
}

Generated by  Doxygen 1.6.0   Back to index