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Add lossy indicator to TBMIterateResult

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TBMIterateResult->ntuples is -1 when the page in the bitmap is lossy.
Add an explicit lossy indicator so that we can move ntuples out of the
TBMIterateResult in a future commit.

Discussion: https://postgr.es/m/CA%2BhUKGLHbKP3jwJ6_%2BhnGi37Pw3BD5j2amjV3oSk7j-KyCnY7Q%40mail.gmail.com
This commit is contained in:
Melanie Plageman
2025-02-24 16:07:50 -05:00
parent c56e8af75e
commit b8778c4cd8
4 changed files with 20 additions and 12 deletions
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11
src/backend/nodes/tidbitmap.c
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@@ -961,12 +961,13 @@ tbm_advance_schunkbit(PagetableEntry *chunk, int *schunkbitp)
*
* Returns a TBMIterateResult representing one page, or NULL if there are
* no more pages to scan. Pages are guaranteed to be delivered in numerical
* order. If result->ntuples < 0, then the bitmap is "lossy" and failed to
* order. If lossy is true, then the bitmap is "lossy" and failed to
* remember the exact tuples to look at on this page --- the caller must
* examine all tuples on the page and check if they meet the intended
* condition. If result->recheck is true, only the indicated tuples need
* condition. result->ntuples is set to -1 when the bitmap is lossy.
* If result->recheck is true, only the indicated tuples need
* be examined, but the condition must be rechecked anyway. (For ease of
* testing, recheck is always set true when ntuples < 0.)
* testing, recheck is always set true when lossy is true.)
*/
TBMIterateResult *
tbm_private_iterate(TBMPrivateIterator *iterator)
@@ -1012,6 +1013,7 @@ tbm_private_iterate(TBMPrivateIterator *iterator)
/* Return a lossy page indicator from the chunk */
output->blockno = chunk_blockno;
output->ntuples = -1;
output->lossy = true;
output->recheck = true;
iterator->schunkbit++;
return output;
@@ -1033,6 +1035,7 @@ tbm_private_iterate(TBMPrivateIterator *iterator)
ntuples = tbm_extract_page_tuple(page, output);
output->blockno = page->blockno;
output->ntuples = ntuples;
output->lossy = false;
output->recheck = page->recheck;
iterator->spageptr++;
return output;
@@ -1105,6 +1108,7 @@ tbm_shared_iterate(TBMSharedIterator *iterator)
/* Return a lossy page indicator from the chunk */
output->blockno = chunk_blockno;
output->ntuples = -1;
output->lossy = true;
output->recheck = true;
istate->schunkbit++;
@@ -1122,6 +1126,7 @@ tbm_shared_iterate(TBMSharedIterator *iterator)
ntuples = tbm_extract_page_tuple(page, output);
output->blockno = page->blockno;
output->ntuples = ntuples;
output->lossy = false;
output->recheck = page->recheck;
istate->spageptr++;