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Refactor tidstore.c iterator buffering.

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Previously, TidStoreIterateNext() would expand the set of offsets for
each block into an internal buffer that it overwrote each time.  In
order to be able to collect the offsets for multiple blocks before
working with them, change the contract.  Now, the offsets are obtained
by a separate call to TidStoreGetBlockOffsets(), which can be called at
a later time.  TidStoreIteratorResult objects are safe to copy and store
in a queue.

Reviewed-by: Noah Misch <noah@leadboat.com>
Discussion: https://postgr.es/m/CAAKRu_bbkmwAzSBgnezancgJeXrQZXy4G4kBTd+5=cr86H5yew@mail.gmail.com
This commit is contained in:
Thomas Munro
2024-07-24 17:24:59 +12:00
parent 1462aad2e4
commit f6bef362ca
4 changed files with 51 additions and 42 deletions
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9
src/backend/access/heap/vacuumlazy.c
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@@ -2126,12 +2126,17 @@ lazy_vacuum_heap_rel(LVRelState *vacrel)
Buffer buf;
Page page;
Size freespace;
OffsetNumber offsets[MaxOffsetNumber];
int num_offsets;
vacuum_delay_point();
blkno = iter_result->blkno;
vacrel->blkno = blkno;
num_offsets = TidStoreGetBlockOffsets(iter_result, offsets, lengthof(offsets));
Assert(num_offsets <= lengthof(offsets));
/*
* Pin the visibility map page in case we need to mark the page
* all-visible. In most cases this will be very cheap, because we'll
@@ -2143,8 +2148,8 @@ lazy_vacuum_heap_rel(LVRelState *vacrel)
buf = ReadBufferExtended(vacrel->rel, MAIN_FORKNUM, blkno, RBM_NORMAL,
vacrel->bstrategy);
LockBuffer(buf, BUFFER_LOCK_EXCLUSIVE);
lazy_vacuum_heap_page(vacrel, blkno, buf, iter_result->offsets,
iter_result->num_offsets, vmbuffer);
lazy_vacuum_heap_page(vacrel, blkno, buf, offsets,
num_offsets, vmbuffer);
/* Now that we've vacuumed the page, record its available space */
page = BufferGetPage(buf);