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2fc3e1b44a
Commitf9b7fc65fixed a race when predicate-locking completely empty btrees: without a buffer lock held, a matching key could be inserted between _bt_search and the PredicateLockRelation call, so the scan would miss concurrently inserted tuples while the writer wouldn't see the reader's predicate lock. That commit only fixed _bt_first's _bt_search path, though. Scans without useful insertion scan keys return early from _bt_first via _bt_endpoint, which still didn't recheck if the relation was empty. To fix, add handling to _bt_endpoint that is analogous to the handling added to _bt_search by commitf9b7fc65. Author: Peter Geoghegan <pg@bowt.ie> Discussion: https://postgr.es/m/CAH2-WzkNoTn3yXY0iGkSuavJ+sL8EROf+kitW+_2v2tJVWuKmA@mail.gmail.com Backpatch-through: 14