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bt_delete.c

/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998, 1999, 2000
 *    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. 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 "db_config.h"

#ifndef lint
static const char revid[] = "$Id: bt_delete.c,v 11.31 2001/01/17 18:48:46 bostic Exp $";
#endif /* not lint */

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

#include <string.h>
#endif

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

/*
 * __bam_delete --
 *    Delete the items referenced by a key.
 *
 * PUBLIC: int __bam_delete __P((DB *, DB_TXN *, DBT *, u_int32_t));
 */
int
__bam_delete(dbp, txn, key, flags)
      DB *dbp;
      DB_TXN *txn;
      DBT *key;
      u_int32_t flags;
{
      DBC *dbc;
      DBT lkey;
      DBT data;
      u_int32_t f_init, f_next;
      int ret, t_ret;

      PANIC_CHECK(dbp->dbenv);
      DB_ILLEGAL_BEFORE_OPEN(dbp, "DB->del");
      DB_CHECK_TXN(dbp, txn);

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

      /* Allocate a cursor. */
      if ((ret = dbp->cursor(dbp, txn, &dbc, DB_WRITELOCK)) != 0)
            return (ret);

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

      /*
       * Walk a cursor through the key/data pairs, deleting as we go.  Set
       * the DB_DBT_USERMEM flag, as this might be a threaded application
       * and the flags checking will catch us.  We don't actually want the
       * keys or data, so request a partial of length 0.
       */
      memset(&lkey, 0, sizeof(lkey));
      F_SET(&lkey, DB_DBT_USERMEM | DB_DBT_PARTIAL);
      memset(&data, 0, sizeof(data));
      F_SET(&data, DB_DBT_USERMEM | DB_DBT_PARTIAL);

      /*
       * If locking (and we haven't already acquired CDB locks), set the
       * read-modify-write flag.
       */
      f_init = DB_SET;
      f_next = DB_NEXT_DUP;
      if (STD_LOCKING(dbc)) {
            f_init |= DB_RMW;
            f_next |= DB_RMW;
      }

      /* Walk through the set of key/data pairs, deleting as we go. */
      if ((ret = dbc->c_get(dbc, key, &data, f_init)) != 0)
            goto err;
      for (;;) {
            if ((ret = dbc->c_del(dbc, 0)) != 0)
                  goto err;
            if ((ret = dbc->c_get(dbc, &lkey, &data, f_next)) != 0) {
                  if (ret == DB_NOTFOUND) {
                        ret = 0;
                        break;
                  }
                  goto err;
            }
      }

err:  /* Discard the cursor. */
      if ((t_ret = dbc->c_close(dbc)) != 0 && ret == 0)
            ret = t_ret;

      return (ret);
}

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

      dbp = dbc->dbp;

      switch (TYPE(h)) {
      case P_IBTREE:
            bi = GET_BINTERNAL(h, indx);
            switch (B_TYPE(bi->type)) {
            case B_DUPLICATE:
            case B_KEYDATA:
                  nbytes = BINTERNAL_SIZE(bi->len);
                  break;
            case B_OVERFLOW:
                  nbytes = BINTERNAL_SIZE(bi->len);
                  if ((ret =
                      __db_doff(dbc, ((BOVERFLOW *)bi->data)->pgno)) != 0)
                        return (ret);
                  break;
            default:
                  return (__db_pgfmt(dbp, PGNO(h)));
            }
            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.
             *
             * !!!
             * 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(dbc,
                            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(dbc,
                            h, indx, indx - P_INDX, 0));
            }
            /* FALLTHROUGH */
      case P_LDUP:
      case P_LRECNO:
            bk = GET_BKEYDATA(h, indx);
            switch (B_TYPE(bk->type)) {
            case B_DUPLICATE:
                  nbytes = BOVERFLOW_SIZE;
                  break;
            case B_OVERFLOW:
                  nbytes = BOVERFLOW_SIZE;
                  if ((ret = __db_doff(
                      dbc, (GET_BOVERFLOW(h, indx))->pgno)) != 0)
                        return (ret);
                  break;
            case B_KEYDATA:
                  nbytes = BKEYDATA_SIZE(bk->len);
                  break;
            default:
                  return (__db_pgfmt(dbp, PGNO(h)));
            }
            break;
      default:
            return (__db_pgfmt(dbp, PGNO(h)));
      }

      /* Delete the item and mark the page dirty. */
      if ((ret = __db_ditem(dbc, h, indx, nbytes)) != 0)
            return (ret);
      if ((ret = memp_fset(dbp->mpf, h, DB_MPOOL_DIRTY)) != 0)
            return (ret);

      return (0);
}

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

      dbp = dbc->dbp;

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

      /* Shuffle the indices and mark the page dirty. */
      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));
      }
      if ((ret = memp_fset(dbp->mpf, h, DB_MPOOL_DIRTY)) != 0)
            return (ret);

      return (0);
}

/*
 * __bam_dpages --
 *    Delete a set of locked pages.
 *
 * PUBLIC: int __bam_dpages __P((DBC *, EPG *));
 */
int
__bam_dpages(dbc, stack_epg)
      DBC *dbc;
      EPG *stack_epg;
{
      BTREE_CURSOR *cp;
      BINTERNAL *bi;
      DB *dbp;
      DBT a, b;
      DB_LOCK c_lock, p_lock;
      EPG *epg;
      PAGE *child, *parent;
      db_indx_t nitems;
      db_pgno_t pgno, root_pgno;
      db_recno_t rcnt;
      int done, ret, t_ret;

      dbp = dbc->dbp;
      cp = (BTREE_CURSOR *)dbc->internal;

      /*
       * We have the entire stack of deletable pages locked.
       *
       * Btree calls us with a pointer to the beginning of a stack, where
       * the first page in the stack is to have a single item deleted, and
       * the rest of the pages are to be removed.
       *
       * Recno calls us with a pointer into the middle of the stack, where
       * the referenced page is to have a single item deleted, and pages
       * after the stack reference are to be removed.
       *
       * First, discard any pages that we don't care about.
       */
      ret = 0;
      for (epg = cp->sp; epg < stack_epg; ++epg) {
            if ((t_ret =
                memp_fput(dbp->mpf, epg->page, 0)) != 0 && ret == 0)
                  ret = t_ret;
            (void)__TLPUT(dbc, epg->lock);
      }
      if (ret != 0)
            goto err;

      /*
       * !!!
       * 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.  Before we unlink the subtree, we relink the
       * leaf page chain.
       */
      if ((ret = __db_relink(dbc, DB_REM_PAGE, cp->csp->page, NULL, 1)) != 0)
            goto err;

      /*
       * Delete the last item that references the underlying pages that are
       * to be deleted, and adjust cursors that reference that page.  Then,
       * save that page's page number and item count and release it.  If
       * the application isn't retaining locks because it's running without
       * transactions, this lets the rest of the tree get back to business
       * immediately.
       */
      if ((ret = __bam_ditem(dbc, epg->page, epg->indx)) != 0)
            goto err;
      if ((ret = __bam_ca_di(dbc, PGNO(epg->page), epg->indx, -1)) != 0)
            goto err;

      pgno = PGNO(epg->page);
      nitems = NUM_ENT(epg->page);

      if ((ret = memp_fput(dbp->mpf, epg->page, 0)) != 0)
            goto err_inc;
      (void)__TLPUT(dbc, epg->lock);

      /* Free the rest of the pages in the stack. */
      while (++epg <= cp->csp) {
            /*
             * Delete page entries so they will be restored as part of
             * recovery.  We don't need to do cursor adjustment here as
             * the pages are being emptied by definition and so cannot
             * be referenced by a cursor.
             */
            if (NUM_ENT(epg->page) != 0) {
                  DB_ASSERT(NUM_ENT(epg->page) == 1);

                  if ((ret = __bam_ditem(dbc, epg->page, epg->indx)) != 0)
                        goto err;
            }

            if ((ret = __db_free(dbc, epg->page)) != 0) {
                  epg->page = NULL;
                  goto err_inc;
            }
            (void)__TLPUT(dbc, epg->lock);
      }

      if (0) {
err_inc:    ++epg;
err:        for (; epg <= cp->csp; ++epg) {
                  if (epg->page != NULL)
                        (void)memp_fput(dbp->mpf, epg->page, 0);
                  (void)__TLPUT(dbc, epg->lock);
            }
            BT_STK_CLR(cp);
            return (ret);
      }
      BT_STK_CLR(cp);

      /*
       * If we just deleted the next-to-last item from the root page, the
       * tree can collapse one or more levels.  While there remains only a
       * single item on the root page, write lock the last page referenced
       * by the root page and copy it over the root page.
       */
      root_pgno = cp->root;
      if (pgno != root_pgno || nitems != 1)
            return (0);

      for (done = 0; !done;) {
            /* Initialize. */
            parent = child = NULL;
            p_lock.off = c_lock.off = LOCK_INVALID;

            /* Lock the root. */
            pgno = root_pgno;
            if ((ret =
                __db_lget(dbc, 0, pgno, DB_LOCK_WRITE, 0, &p_lock)) != 0)
                  goto stop;
            if ((ret = memp_fget(dbp->mpf, &pgno, 0, &parent)) != 0)
                  goto stop;

            if (NUM_ENT(parent) != 1)
                  goto stop;

            switch (TYPE(parent)) {
            case P_IBTREE:
                  /*
                   * If this is overflow, then try to delete it.
                   * The child may or may not still point at it.
                   */
                  bi = GET_BINTERNAL(parent, 0);
                  if (B_TYPE(bi->type) == B_OVERFLOW)
                        if ((ret = __db_doff(dbc,
                            ((BOVERFLOW *)bi->data)->pgno)) != 0)
                              goto stop;
                  pgno = bi->pgno;
                  break;
            case P_IRECNO:
                  pgno = GET_RINTERNAL(parent, 0)->pgno;
                  break;
            default:
                  goto stop;
            }

            /* Lock the child page. */
            if ((ret =
                __db_lget(dbc, 0, pgno, DB_LOCK_WRITE, 0, &c_lock)) != 0)
                  goto stop;
            if ((ret = memp_fget(dbp->mpf, &pgno, 0, &child)) != 0)
                  goto stop;

            /* Log the change. */
            if (DB_LOGGING(dbc)) {
                  memset(&a, 0, sizeof(a));
                  a.data = child;
                  a.size = dbp->pgsize;
                  memset(&b, 0, sizeof(b));
                  b.data = P_ENTRY(parent, 0);
                  b.size = TYPE(parent) == P_IRECNO ? RINTERNAL_SIZE :
                      BINTERNAL_SIZE(((BINTERNAL *)b.data)->len);
                  if ((ret =
                     __bam_rsplit_log(dbp->dbenv, dbc->txn, &child->lsn,
                     0, dbp->log_fileid, PGNO(child), &a, PGNO(parent),
                     RE_NREC(parent), &b, &parent->lsn)) != 0)
                        goto stop;
            }

            /*
             * Make the switch.
             *
             * One fixup -- internal pages below the top level do not store
             * a record count, so we have to preserve it if we're not
             * converting to a leaf page.  Note also that we are about to
             * overwrite the parent page, including its LSN.  This is OK
             * because the log message we wrote describing this update
             * stores its LSN on the child page.  When the child is copied
             * onto the parent, the correct LSN is copied into place.
             */
            COMPQUIET(rcnt, 0);
            if (F_ISSET(cp, C_RECNUM) && LEVEL(child) > LEAFLEVEL)
                  rcnt = RE_NREC(parent);
            memcpy(parent, child, dbp->pgsize);
            PGNO(parent) = root_pgno;
            if (F_ISSET(cp, C_RECNUM) && LEVEL(child) > LEAFLEVEL)
                  RE_NREC_SET(parent, rcnt);

            /* Mark the pages dirty. */
            if ((ret = memp_fset(dbp->mpf, parent, DB_MPOOL_DIRTY)) != 0)
                  goto stop;
            if ((ret = memp_fset(dbp->mpf, child, DB_MPOOL_DIRTY)) != 0)
                  goto stop;

            /* Adjust the cursors. */
            if ((ret = __bam_ca_rsplit(dbc, PGNO(child), root_pgno)) != 0)
                  goto stop;

            /*
             * Free the page copied onto the root page and discard its
             * lock.  (The call to __db_free() discards our reference
             * to the page.)
             */
            if ((ret = __db_free(dbc, child)) != 0) {
                  child = NULL;
                  goto stop;
            }
            child = NULL;

            if (0) {
stop:             done = 1;
            }
            if (p_lock.off != LOCK_INVALID)
                  (void)__TLPUT(dbc, p_lock);
            if (parent != NULL &&
                (t_ret = memp_fput(dbp->mpf, parent, 0)) != 0 && ret == 0)
                  ret = t_ret;
            if (c_lock.off != LOCK_INVALID)
                  (void)__TLPUT(dbc, c_lock);
            if (child != NULL &&
                (t_ret = memp_fput(dbp->mpf, child, 0)) != 0 && ret == 0)
                  ret = t_ret;
      }

      return (ret);
}

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