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Make pg_replication_origin_drop safe against concurrent drops.

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Currently, we get the origin id from the name and then drop the origin by
taking ExclusiveLock on ReplicationOriginRelationId. So, two concurrent
sessions can get the id from the name at the same time and then when they
try to drop the origin, one of the sessions will get the either
"tuple concurrently deleted" or "cache lookup failed for replication
origin ..".

To prevent this race condition we do the entire operation under lock. This
obviates the need for replorigin_drop() API and we have removed it so if
any extension authors are using it they need to instead use
replorigin_drop_by_name. See it's usage in pg_replication_origin_drop().

Author: Peter Smith
Reviewed-by: Amit Kapila, Euler Taveira, Petr Jelinek, and Alvaro
Herrera
Discussion: https://www.postgresql.org/message-id/CAHut%2BPuW8DWV5fskkMWWMqzt-x7RPcNQOtJQBp6SdwyRghCk7A%40mail.gmail.com
This commit is contained in:
Amit Kapila
2021-02-10 07:17:09 +05:30
parent 31c7fb41e2
commit cd142e032e
3 changed files with 38 additions and 28 deletions
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5
src/backend/commands/subscriptioncmds.c
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@ -926,7 +926,6 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
ListCell *lc;
char originname[NAMEDATALEN];
char *err = NULL;
RepOriginId originid;
WalReceiverConn *wrconn = NULL;
StringInfoData cmd;
Form_pg_subscription form;
@ -1050,9 +1049,7 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
/* Remove the origin tracking if exists. */
snprintf(originname, sizeof(originname), "pg_%u", subid);
originid = replorigin_by_name(originname, true);
if (originid != InvalidRepOriginId)
replorigin_drop(originid, false);
replorigin_drop_by_name(originname, true, false);
/*
* If there is no slot associated with the subscription, we can finish