pgsql: Handle non-chain tuples outside of heap_prune_chain()

Handle non-chain tuples outside of heap_prune_chain()

Handle dead branches of aborted HOT chains outside heap_prune_chain()
as a separate phase. This simplifies the logic in heap_prune_chain(),
as well as allowing us to clean up more RECENTLY_DEAD -> DEAD chains.

To accomplish this efficiently, partition tuples into HOT and non-HOT
while first collecting visibility information for each tuple in
heap_page_prune(). Then call heap_prune_chain() only on potential
chain members. Then mop up the leftover HOT tuples afterwards.

As part of this, keep track of which items on page have already been
processed, in 'processed' array. This replaces the 'marked' array
which was only set for tuples marked for removal or redirection. The
'processed' array is updated also for items that are left unchanged,
when we conclude that an item can be left unchanged. At the end of
pruning, every item on the page should be marked as processed in the
array; an assertion is added for that.

Author: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Author: Heikki Linnakangas <heikki(dot)linnakangas(at)iki(dot)fi>
Discussion: https://www.postgresql.org/message-id/20240330055710.kqg6ii2cdojsxgje@liskov

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/6f47f6883151366c031cd6fd4011e66d2c702a90

Modified Files
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src/backend/access/heap/pruneheap.c | 289 +++++++++++++++++++++++-------------
1 file changed, 187 insertions(+), 102 deletions(-)