From e75be9e8a649548918e675abc0b28a190d41ab8d Mon Sep 17 00:00:00 2001 From: Laurenz Albe Date: Tue, 12 May 2020 21:47:40 +0200 Subject: [PATCH] Make COPY TO keep locks until transaction end COPY TO released the ACCESS SHARE lock immediately when it was done rather than holding on to it until the end of the transaction. This violates the two-phase locking protocol and breaks MCVV: For example, a REPEATABLE READ transaction could see an empty table if it repeats a COPY statement and somebody truncated the table in the meantime. Before 4dded12faad the lock was also released after COPY FROM, but the commit failed to notice the irregularity in COPY TO. This is old behavior, but the bug doesn't seem important enough to backpatch. Author: Laurenz Albe Reviewed-by: Robert Haas, Tom Lane Discussion: https://postgr.es/m/7bcfc39d4176faf85ab317d0c26786953646a411.camel@cybertec.at --- src/backend/commands/copy.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c index ac07f75bc3..0cd8820696 100644 --- a/src/backend/commands/copy.c +++ b/src/backend/commands/copy.c @@ -1081,13 +1081,7 @@ DoCopy(ParseState *pstate, const CopyStmt *stmt, EndCopyTo(cstate); } - /* - * Close the relation. If reading, we can release the AccessShareLock we - * got; if writing, we should hold the lock until end of transaction to - * ensure that updates will be committed before lock is released. - */ - if (rel != NULL) - table_close(rel, (is_from ? NoLock : AccessShareLock)); + table_close(rel, NoLock); } /* -- 2.21.3