pgsql: Avoid unnecessary catalog updates in ALTER SEQUENCE

Avoid unnecessary catalog updates in ALTER SEQUENCE

ALTER SEQUENCE can do nontransactional changes to the sequence (RESTART
clause) and transactional updates to the pg_sequence catalog (most other
clauses). When just calling RESTART, the code would still needlessly do
a catalog update without any changes. This would entangle that
operation in the concurrency issues of a catalog update (causing either
locking or concurrency errors, depending on how that issue is to be
resolved).

Fix by keeping track during options parsing whether a catalog update is
needed, and skip it if not.

Reported-by: Jason Petersen <jason(at)citusdata(dot)com>

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3d092fe5409b98272ddd6e623b657308a3c5f004

Modified Files
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src/backend/commands/sequence.c | 51 ++++++++++++++++++++++++++++++++++-------
1 file changed, 43 insertions(+), 8 deletions(-)