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

bt_delete.c

/*-
 * 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_delete.c   8.13 (Berkeley) 7/28/94";
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>

#include <errno.h>
#include <stdio.h>
#include <string.h>

#include <db.h>
#include "btree.h"

static int __bt_bdelete __P((BTREE *, const DBT *));
static int __bt_curdel __P((BTREE *, const DBT *, PAGE *, u_int));
static int __bt_pdelete __P((BTREE *, PAGE *));
static int __bt_relink __P((BTREE *, PAGE *));
static int __bt_stkacq __P((BTREE *, PAGE **, CURSOR *));

/*
 * __bt_delete
 *    Delete the item(s) referenced by a key.
 *
 * Return RET_SPECIAL if the key is not found.
 */
int
__bt_delete(dbp, key, flags)
      const DB *dbp;
      const DBT *key;
      u_int flags;
{
      BTREE *t;
      CURSOR *c;
      PAGE *h;
      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;
      }

      /* Check for change to a read-only tree. */
      if (F_ISSET(t, B_RDONLY)) {
            errno = EPERM;
            return (RET_ERROR);
      }

      switch (flags) {
      case 0:
            status = __bt_bdelete(t, key);
            break;
      case R_CURSOR:
            /*
             * If flags is R_CURSOR, delete the cursor.  Must already
             * have started a scan and not have already deleted it.
             */
            c = &t->bt_cursor;
            if (F_ISSET(c, CURS_INIT)) {
                  if (F_ISSET(c, CURS_ACQUIRE | CURS_AFTER | CURS_BEFORE))
                        return (RET_SPECIAL);
                  if ((h = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL)
                        return (RET_ERROR);

                  /*
                   * If the page is about to be emptied, we'll need to
                   * delete it, which means we have to acquire a stack.
                   */
                  if (NEXTINDEX(h) == 1)
                        if (__bt_stkacq(t, &h, &t->bt_cursor))
                              return (RET_ERROR);

                  status = __bt_dleaf(t, NULL, h, c->pg.index);

                  if (NEXTINDEX(h) == 0 && status == RET_SUCCESS) {
                        if (__bt_pdelete(t, h))
                              return (RET_ERROR);
                  } else
                        mpool_put(t->bt_mp,
                            h, status == RET_SUCCESS ? MPOOL_DIRTY : 0);
                  break;
            }
            /* FALLTHROUGH */
      default:
            errno = EINVAL;
            return (RET_ERROR);
      }
      if (status == RET_SUCCESS)
            F_SET(t, B_MODIFIED);
      return (status);
}

/*
 * __bt_stkacq --
 *    Acquire a stack so we can delete a cursor entry.
 *
 * Parameters:
 *      t:  tree
 *     hp:  pointer to current, pinned PAGE pointer
 *      c:  pointer to the cursor
 *
 * Returns:
 *    0 on success, 1 on failure
 */
static int
__bt_stkacq(t, hp, c)
      BTREE *t;
      PAGE **hp;
      CURSOR *c;
{
      BINTERNAL *bi;
      EPG *e;
      EPGNO *parent;
      PAGE *h;
      indx_t index;
      pgno_t pgno;
      recno_t nextpg, prevpg;
      int exact, level;
      
      /*
       * Find the first occurrence of the key in the tree.  Toss the
       * currently locked page so we don't hit an already-locked page.
       */
      h = *hp;
      mpool_put(t->bt_mp, h, 0);
      if ((e = __bt_search(t, &c->key, &exact)) == NULL)
            return (1);
      h = e->page;

      /* See if we got it in one shot. */
      if (h->pgno == c->pg.pgno)
            goto ret;

      /*
       * Move right, looking for the page.  At each move we have to move
       * up the stack until we don't have to move to the next page.  If
       * we have to change pages at an internal level, we have to fix the
       * stack back up.
       */
      while (h->pgno != c->pg.pgno) {
            if ((nextpg = h->nextpg) == P_INVALID)
                  break;
            mpool_put(t->bt_mp, h, 0);

            /* Move up the stack. */
            for (level = 0; (parent = BT_POP(t)) != NULL; ++level) {
                  /* Get the parent page. */
                  if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
                        return (1);

                  /* Move to the next index. */
                  if (parent->index != NEXTINDEX(h) - 1) {
                        index = parent->index + 1;
                        BT_PUSH(t, h->pgno, index);
                        break;
                  }
                  mpool_put(t->bt_mp, h, 0);
            }

            /* Restore the stack. */
            while (level--) {
                  /* Push the next level down onto the stack. */
                  bi = GETBINTERNAL(h, index);
                  pgno = bi->pgno;
                  BT_PUSH(t, pgno, 0);

                  /* Lose the currently pinned page. */
                  mpool_put(t->bt_mp, h, 0);

                  /* Get the next level down. */
                  if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL)
                        return (1);
                  index = 0;
            }
            mpool_put(t->bt_mp, h, 0);
            if ((h = mpool_get(t->bt_mp, nextpg, 0)) == NULL)
                  return (1);
      }

      if (h->pgno == c->pg.pgno)
            goto ret;

      /* Reacquire the original stack. */
      mpool_put(t->bt_mp, h, 0);
      if ((e = __bt_search(t, &c->key, &exact)) == NULL)
            return (1);
      h = e->page;

      /*
       * Move left, looking for the page.  At each move we have to move
       * up the stack until we don't have to change pages to move to the
       * next page.  If we have to change pages at an internal level, we
       * have to fix the stack back up.
       */
      while (h->pgno != c->pg.pgno) {
            if ((prevpg = h->prevpg) == P_INVALID)
                  break;
            mpool_put(t->bt_mp, h, 0);

            /* Move up the stack. */
            for (level = 0; (parent = BT_POP(t)) != NULL; ++level) {
                  /* Get the parent page. */
                  if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
                        return (1);

                  /* Move to the next index. */
                  if (parent->index != 0) {
                        index = parent->index - 1;
                        BT_PUSH(t, h->pgno, index);
                        break;
                  }
                  mpool_put(t->bt_mp, h, 0);
            }

            /* Restore the stack. */
            while (level--) {
                  /* Push the next level down onto the stack. */
                  bi = GETBINTERNAL(h, index);
                  pgno = bi->pgno;

                  /* Lose the currently pinned page. */
                  mpool_put(t->bt_mp, h, 0);

                  /* Get the next level down. */
                  if ((h = mpool_get(t->bt_mp, pgno, 0)) == NULL)
                        return (1);

                  index = NEXTINDEX(h) - 1;
                  BT_PUSH(t, pgno, index);
            }
            mpool_put(t->bt_mp, h, 0);
            if ((h = mpool_get(t->bt_mp, prevpg, 0)) == NULL)
                  return (1);
      }
      

ret:  mpool_put(t->bt_mp, h, 0);
      return ((*hp = mpool_get(t->bt_mp, c->pg.pgno, 0)) == NULL);
}

/*
 * __bt_bdelete --
 *    Delete all key/data pairs matching the specified key.
 *
 * Parameters:
 *      t:  tree
 *    key:  key to delete
 *
 * Returns:
 *    RET_ERROR, RET_SUCCESS and RET_SPECIAL if the key not found.
 */
static int
__bt_bdelete(t, key)
      BTREE *t;
      const DBT *key;
{
      EPG *e;
      PAGE *h;
      int deleted, exact, redo;

      deleted = 0;

      /* Find any matching record; __bt_search pins the page. */
loop: if ((e = __bt_search(t, key, &exact)) == NULL)
            return (deleted ? RET_SUCCESS : RET_ERROR);
      if (!exact) {
            mpool_put(t->bt_mp, e->page, 0);
            return (deleted ? RET_SUCCESS : RET_SPECIAL);
      }

      /*
       * Delete forward, then delete backward, from the found key.  If
       * there are duplicates and we reach either side of the page, do
       * the key search again, so that we get them all.
       */
      redo = 0;
      h = e->page;
      do {
            if (__bt_dleaf(t, key, h, e->index)) {
                  mpool_put(t->bt_mp, h, 0);
                  return (RET_ERROR);
            }
            if (F_ISSET(t, B_NODUPS)) {
                  if (NEXTINDEX(h) == 0) {
                        if (__bt_pdelete(t, h))
                              return (RET_ERROR);
                  } else
                        mpool_put(t->bt_mp, h, MPOOL_DIRTY);
                  return (RET_SUCCESS);
            }
            deleted = 1;
      } while (e->index < NEXTINDEX(h) && __bt_cmp(t, key, e) == 0);

      /* Check for right-hand edge of the page. */
      if (e->index == NEXTINDEX(h))
            redo = 1;

      /* Delete from the key to the beginning of the page. */
      while (e->index-- > 0) {
            if (__bt_cmp(t, key, e) != 0)
                  break;
            if (__bt_dleaf(t, key, h, e->index) == RET_ERROR) {
                  mpool_put(t->bt_mp, h, 0);
                  return (RET_ERROR);
            }
            if (e->index == 0)
                  redo = 1;
      }

      /* Check for an empty page. */
      if (NEXTINDEX(h) == 0) {
            if (__bt_pdelete(t, h))
                  return (RET_ERROR);
            goto loop;
      }

      /* Put the page. */
      mpool_put(t->bt_mp, h, MPOOL_DIRTY);

      if (redo)
            goto loop;
      return (RET_SUCCESS);
}

/*
 * __bt_pdelete --
 *    Delete a single page from the tree.
 *
 * Parameters:
 *    t:    tree
 *    h:    leaf page
 *
 * Returns:
 *    RET_SUCCESS, RET_ERROR.
 *
 * Side-effects:
 *    mpool_put's the page
 */
static int
__bt_pdelete(t, h)
      BTREE *t;
      PAGE *h;
{
      BINTERNAL *bi;
      PAGE *pg;
      EPGNO *parent;
      indx_t cnt, index, *ip, offset;
      u_int32_t nksize;
      char *from;

      /*
       * Walk the parent page stack -- a LIFO stack of the pages that were
       * traversed when we searched for the page where the delete occurred.
       * Each stack entry is a page number and a page index offset.  The
       * offset is for the page traversed on the search.  We've just deleted
       * a page, so we have to delete the key from the parent page.
       *
       * If the delete from the parent page makes it empty, this process may
       * continue all the way up the tree.  We stop if we reach the root page
       * (which is never deleted, it's just not worth the effort) or if the
       * delete does not empty the page.
       */
      while ((parent = BT_POP(t)) != NULL) {
            /* Get the parent page. */
            if ((pg = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
                  return (RET_ERROR);
            
            index = parent->index;
            bi = GETBINTERNAL(pg, index);

            /* Free any overflow pages. */
            if (bi->flags & P_BIGKEY &&
                __ovfl_delete(t, bi->bytes) == RET_ERROR) {
                  mpool_put(t->bt_mp, pg, 0);
                  return (RET_ERROR);
            }

            /*
             * Free the parent if it has only the one key and it's not the
             * root page. If it's the rootpage, turn it back into an empty
             * leaf page.
             */
            if (NEXTINDEX(pg) == 1)
                  if (pg->pgno == P_ROOT) {
                        pg->lower = BTDATAOFF;
                        pg->upper = t->bt_psize;
                        pg->flags = P_BLEAF;
                  } else {
                        if (__bt_relink(t, pg) || __bt_free(t, pg))
                              return (RET_ERROR);
                        continue;
                  }
            else {
                  /* Pack remaining key items at the end of the page. */
                  nksize = NBINTERNAL(bi->ksize);
                  from = (char *)pg + pg->upper;
                  memmove(from + nksize, from, (char *)bi - from);
                  pg->upper += nksize;

                  /* Adjust indices' offsets, shift the indices down. */
                  offset = pg->linp[index];
                  for (cnt = index, ip = &pg->linp[0]; cnt--; ++ip)
                        if (ip[0] < offset)
                              ip[0] += nksize;
                  for (cnt = NEXTINDEX(pg) - index; --cnt; ++ip)
                        ip[0] = ip[1] < offset ? ip[1] + nksize : ip[1];
                  pg->lower -= sizeof(indx_t);
            }

            mpool_put(t->bt_mp, pg, MPOOL_DIRTY);
            break;
      }

      /* Free the leaf page, as long as it wasn't the root. */
      if (h->pgno == P_ROOT) {
            mpool_put(t->bt_mp, h, MPOOL_DIRTY);
            return (RET_SUCCESS);
      }
      return (__bt_relink(t, h) || __bt_free(t, h));
}

/*
 * __bt_dleaf --
 *    Delete a single record from a leaf page.
 *
 * Parameters:
 *    t:    tree
 *    key:  referenced key
 *    h:    page
 *    index:      index on page to delete
 *
 * Returns:
 *    RET_SUCCESS, RET_ERROR.
 */
int
__bt_dleaf(t, key, h, index)
      BTREE *t;
      const DBT *key;
      PAGE *h;
      u_int index;
{
      BLEAF *bl;
      indx_t cnt, *ip, offset;
      u_int32_t nbytes;
      void *to;
      char *from;

      /* If this record is referenced by the cursor, delete the cursor. */
      if (F_ISSET(&t->bt_cursor, CURS_INIT) &&
          !F_ISSET(&t->bt_cursor, CURS_ACQUIRE) &&
          t->bt_cursor.pg.pgno == h->pgno && t->bt_cursor.pg.index == index &&
          __bt_curdel(t, key, h, index))
            return (RET_ERROR);

      /* If the entry uses overflow pages, make them available for reuse. */
      to = bl = GETBLEAF(h, index);
      if (bl->flags & P_BIGKEY && __ovfl_delete(t, bl->bytes) == RET_ERROR)
            return (RET_ERROR);
      if (bl->flags & P_BIGDATA &&
          __ovfl_delete(t, bl->bytes + bl->ksize) == RET_ERROR)
            return (RET_ERROR);

      /* Pack the remaining key/data items at the end of the page. */
      nbytes = NBLEAF(bl);
      from = (char *)h + h->upper;
      memmove(from + nbytes, from, (char *)to - from);
      h->upper += nbytes;

      /* Adjust the indices' offsets, shift the indices down. */
      offset = h->linp[index];
      for (cnt = index, ip = &h->linp[0]; cnt--; ++ip)
            if (ip[0] < offset)
                  ip[0] += nbytes;
      for (cnt = NEXTINDEX(h) - index; --cnt; ++ip)
            ip[0] = ip[1] < offset ? ip[1] + nbytes : ip[1];
      h->lower -= sizeof(indx_t);

      /* If the cursor is on this page, adjust it as necessary. */
      if (F_ISSET(&t->bt_cursor, CURS_INIT) &&
          !F_ISSET(&t->bt_cursor, CURS_ACQUIRE) &&
          t->bt_cursor.pg.pgno == h->pgno && t->bt_cursor.pg.index > index)
            --t->bt_cursor.pg.index;

      return (RET_SUCCESS);
}

/*
 * __bt_curdel --
 *    Delete the cursor.
 *
 * Parameters:
 *    t:    tree
 *    key:  referenced key (or NULL)
 *    h:    page
 *  index:  index on page to delete
 *
 * Returns:
 *    RET_SUCCESS, RET_ERROR.
 */
static int
__bt_curdel(t, key, h, index)
      BTREE *t;
      const DBT *key;
      PAGE *h;
      u_int index;
{
      CURSOR *c;
      EPG e;
      PAGE *pg;
      int curcopy, status;

      /*
       * If there are duplicates, move forward or backward to one.
       * Otherwise, copy the key into the cursor area.
       */
      c = &t->bt_cursor;
      F_CLR(c, CURS_AFTER | CURS_BEFORE | CURS_ACQUIRE);

      curcopy = 0;
      if (!F_ISSET(t, B_NODUPS)) {
            /*
             * We're going to have to do comparisons.  If we weren't
             * provided a copy of the key, i.e. the user is deleting
             * the current cursor position, get one.
             */
            if (key == NULL) {
                  e.page = h;
                  e.index = index;
                  if ((status = __bt_ret(t, &e,
                      &c->key, &c->key, NULL, NULL, 1)) != RET_SUCCESS)
                        return (status);
                  curcopy = 1;
                  key = &c->key;
            }
            /* Check previous key, if not at the beginning of the page. */
            if (index > 0) { 
                  e.page = h;
                  e.index = index - 1;
                  if (__bt_cmp(t, key, &e) == 0) {
                        F_SET(c, CURS_BEFORE);
                        goto dup2;
                  }
            }
            /* Check next key, if not at the end of the page. */
            if (index < NEXTINDEX(h) - 1) {
                  e.page = h;
                  e.index = index + 1;
                  if (__bt_cmp(t, key, &e) == 0) {
                        F_SET(c, CURS_AFTER);
                        goto dup2;
                  }
            }
            /* Check previous key if at the beginning of the page. */
            if (index == 0 && h->prevpg != P_INVALID) {
                  if ((pg = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
                        return (RET_ERROR);
                  e.page = pg;
                  e.index = NEXTINDEX(pg) - 1;
                  if (__bt_cmp(t, key, &e) == 0) {
                        F_SET(c, CURS_BEFORE);
                        goto dup1;
                  }
                  mpool_put(t->bt_mp, pg, 0);
            }
            /* Check next key if at the end of the page. */
            if (index == NEXTINDEX(h) - 1 && h->nextpg != P_INVALID) {
                  if ((pg = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
                        return (RET_ERROR);
                  e.page = pg;
                  e.index = 0;
                  if (__bt_cmp(t, key, &e) == 0) {
                        F_SET(c, CURS_AFTER);
dup1:                   mpool_put(t->bt_mp, pg, 0);
dup2:                   c->pg.pgno = e.page->pgno;
                        c->pg.index = e.index;
                        return (RET_SUCCESS);
                  }
                  mpool_put(t->bt_mp, pg, 0);
            }
      }
      e.page = h;
      e.index = index;
      if (curcopy || (status =
          __bt_ret(t, &e, &c->key, &c->key, NULL, NULL, 1)) == RET_SUCCESS) {
            F_SET(c, CURS_ACQUIRE);
            return (RET_SUCCESS);
      }
      return (status);
}

/*
 * __bt_relink --
 *    Link around a deleted page.
 *
 * Parameters:
 *    t:    tree
 *    h:    page to be deleted
 */
static int
__bt_relink(t, h)
      BTREE *t;
      PAGE *h;
{
      PAGE *pg;

      if (h->nextpg != P_INVALID) {
            if ((pg = mpool_get(t->bt_mp, h->nextpg, 0)) == NULL)
                  return (RET_ERROR);
            pg->prevpg = h->prevpg;
            mpool_put(t->bt_mp, pg, MPOOL_DIRTY);
      }
      if (h->prevpg != P_INVALID) {
            if ((pg = mpool_get(t->bt_mp, h->prevpg, 0)) == NULL)
                  return (RET_ERROR);
            pg->nextpg = h->nextpg;
            mpool_put(t->bt_mp, pg, MPOOL_DIRTY);
      }
      return (0);
}

Generated by  Doxygen 1.6.0   Back to index