Rethink function argument sorting in pg_dump

Enterprise / PostgreSQL - Tom Lane [sss.pgh.pa.us] - 6 March 2015 12:27 UTC

Commit 7b583b20b1c95acb621c71251150beef958bb603 created an unnecessary dump failure hazard by applying pg_get_function_identity_arguments() to every function in the database, even those that won't get dumped. This could result in snapshot-related problems if concurrent sessions are, for example, creating and dropping temporary functions, as noted by Marko Tiikkaja in bug #12832. While this is by no means pg_dump's only such issue with concurrent DDL, it's unfortunate that we added a new failure mode for cases that used to work, and even more so that the failure was created for basically cosmetic reasons (ie, to sort overloaded functions more deterministically).

To fix, revert that patch and instead sort function arguments using information that pg_dump has available anyway, namely the names of the argument types. This will produce a slightly different sort ordering for overloaded functions than the previous coding; but applying strcmp directly to the output of pg_get_function_identity_arguments really was a bit odd anyway. The sorting will still be name-based and hence independent of possibly-installation-specific OID assignments. A small additional benefit is that sorting now works regardless of server version.

Back-patch to 9.3, where the previous commit appeared.

e3bfe6d Rethink function argument sorting in pg_dump.
src/bin/pg_dump/pg_dump.c | 47 ++--------------------------------------
src/bin/pg_dump/pg_dump.h | 1 -
src/bin/pg_dump/pg_dump_sort.c | 23 +++++++++++++++++---
3 files changed, 22 insertions(+), 49 deletions(-)

Upstream: git.postgresql.org

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