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Fix logic error in tbm_intersect: the intersection of a normal page and

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a lossy page has to be lossy, because we don't know exactly which tuples
on the page should remain part of the bitmap.  Per Jie Zhang.
This commit is contained in:
Tom Lane 2005-07-24 02:25:26 +00:00
parent eaa5d52bfe
commit c17abc1c54
1 changed files with 23 additions and 6 deletions
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29
src/backend/nodes/tidbitmap.c
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@ -23,7 +23,7 @@
* Copyright (c) 2003-2005, PostgreSQL Global Development Group
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/nodes/tidbitmap.c,v 1.4 2005/05/29 04:23:03 tgl Exp $
* $PostgreSQL: pgsql/src/backend/nodes/tidbitmap.c,v 1.5 2005/07/24 02:25:26 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -135,7 +135,8 @@ struct TIDBitmap
/* Local function prototypes */
static void tbm_union_page(TIDBitmap *a, const PagetableEntry *bpage);
static bool tbm_intersect_page(PagetableEntry *apage, const TIDBitmap *b);
static bool tbm_intersect_page(TIDBitmap *a, PagetableEntry *apage,
const TIDBitmap *b);
static const PagetableEntry *tbm_find_pageentry(const TIDBitmap *tbm,
BlockNumber pageno);
static PagetableEntry *tbm_get_pageentry(TIDBitmap *tbm, BlockNumber pageno);
@ -382,7 +383,7 @@ tbm_intersect(TIDBitmap *a, const TIDBitmap *b)
/* Scan through chunks and pages in a, try to match to b */
if (a->status == TBM_ONE_PAGE)
{
if (tbm_intersect_page(&a->entry1, b))
if (tbm_intersect_page(a, &a->entry1, b))
{
/* Page is now empty, remove it from a */
Assert(!a->entry1.ischunk);
@ -401,7 +402,7 @@ tbm_intersect(TIDBitmap *a, const TIDBitmap *b)
hash_seq_init(&status, a->pagetable);
while ((apage = (PagetableEntry *) hash_seq_search(&status)) != NULL)
{
if (tbm_intersect_page(apage, b))
if (tbm_intersect_page(a, apage, b))
{
/* Page or chunk is now empty, remove it from a */
if (apage->ischunk)
@ -424,7 +425,7 @@ tbm_intersect(TIDBitmap *a, const TIDBitmap *b)
* Returns TRUE if apage is now empty and should be deleted from a
*/
static bool
tbm_intersect_page(PagetableEntry *apage, const TIDBitmap *b)
tbm_intersect_page(TIDBitmap *a, PagetableEntry *apage, const TIDBitmap *b)
{
const PagetableEntry *bpage;
int wordnum;
@ -470,7 +471,23 @@ tbm_intersect_page(PagetableEntry *apage, const TIDBitmap *b)
}
else if (tbm_page_is_lossy(b, apage->blockno))
{
/* page is lossy in b, cannot clear any bits */
/*
* When the page is lossy in b, we have to mark it lossy in a too.
* We know that no bits need be set in bitmap a, but we do not know
* which ones should be cleared, and we have no API for "at most
* these tuples need be checked". (Perhaps it's worth adding that?)
*/
tbm_mark_page_lossy(a, apage->blockno);
/*
* Note: tbm_mark_page_lossy will have removed apage from a, and
* may have inserted a new lossy chunk instead. We can continue the
* same seq_search scan at the caller level, because it does not
* matter whether we visit such a new chunk or not: it will have
* only the bit for apage->blockno set, which is correct.
*
* We must return false here since apage was already deleted.
*/
return false;
}
else