Return to bt_delete.c CVS log

Up to [cvs.NetBSD.org] / src / lib / libc / db / btree

If port provides __weak_alias(), provide an Standard C and POSIX pure
identifier namespace by renaming non standard functions and variables
such that they have a leading underscore.  The library will use those
names internally.  Weak aliases are used to provide the original names
to the API.

This is only the first part of this change.  It is most of the functions
which are implemented in C for all NetBSD ports.  Subsequent changes are
to add the same support to the remaining C files, to assembly files, and
to the automagically generated assembly source used for system calls.
When all of the above is done, ports with weak alias support should add
a definition for __weak_alias to <sys/cdefs.h>.

/*	$NetBSD: bt_delete.c,v 1.9 1997/07/21 14:06:31 jtc Exp $	*/

/*-
 * 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.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)bt_delete.c	8.13 (Berkeley) 7/28/94";
#else
__RCSID("$NetBSD: bt_delete.c,v 1.9 1997/07/21 14:06:31 jtc Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include "namespace.h"
#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 = 0;	/* Pacify gcc */
	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);
}