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authorTom Lane <tgl@sss.pgh.pa.us>2018-12-30 15:40:04 -0500
committerTom Lane <tgl@sss.pgh.pa.us>2018-12-30 15:40:04 -0500
commit0a6ea4001a9dff64e9ba66f68855a59a1bf69bc9 (patch)
tree7ab069dcd37ad075745f99b3e9d56b191c4cd19a /src/backend/executor
parentb5415e3c2187ab304390524f5ae66b4bd2c58279 (diff)
downloadpostgresql-0a6ea4001a9dff64e9ba66f68855a59a1bf69bc9.tar.gz
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Add a hash opclass for type "tid".
Up to now we've not worried much about joins where the join key is a relation's CTID column, reasoning that storing a table's CTIDs in some other table would be pretty useless. However, there are use-cases for this sort of query involving self-joins, so that argument doesn't really hold water. With larger relations, a merge or hash join is desirable. We had a btree opclass for type "tid", allowing merge joins on CTID, but no hash opclass so that hash joins weren't possible. Add the missing infrastructure. This also potentially enables hash aggregation on "tid", though the use-cases for that aren't too clear. Discussion: https://postgr.es/m/1853.1545453106@sss.pgh.pa.us
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