While running some tests on v13 patches, I noticed that, in case the published table data already exists on the subscriber database before creating the subscription, at the time of
CREATE subscription/table synchronization, an error as seen as follows
With the patch:
2021-03-29 14:32:56.265 IST [78467] STATEMENT: CREATE_REPLICATION_SLOT "pg_16406_sync_16390_6944995860755251708" LOGICAL pgoutput USE_SNAPSHOT 2021-03-29 14:32:56.279 IST [78467] LOG: could not send data to client: Broken pipe 2021-03-29 14:32:56.279 IST [78467] STATEMENT: COPY (SELECT aid, bid, abalance, filler FROM public.pgbench_accounts WHERE (aid > 0)) TO STDOUT 2021-03-29 14:32:56.279 IST [78467] FATAL: connection to client lost 2021-03-29 14:32:56.279 IST [78467] STATEMENT: COPY (SELECT aid, bid, abalance, filler FROM public.pgbench_accounts WHERE (aid > 0)) TO STDOUT 2021-03-29 14:33:01.302 IST [78470] LOG: logical decoding found consistent point at 0/4E2B8460 2021-03-29 14:33:01.302 IST [78470] DETAIL: There are no running transactions.
Without the patch:
2021-03-29 15:05:01.581 IST [79029] ERROR: duplicate key value violates unique constraint "pgbench_branches_pkey" 2021-03-29 15:05:01.581 IST [79029] DETAIL: Key (bid)=(1) already exists. 2021-03-29 15:05:01.581 IST [79029] CONTEXT: COPY pgbench_branches, line 1 2021-03-29 15:05:01.583 IST [78538] LOG: background worker "logical replication worker" (PID 79029) exited with exit code 1 2021-03-29 15:05:06.593 IST [79031] LOG: logical replication table synchronization worker for subscription "test_sub2", table "pgbench_branches" has started
Without the patch the COPY command throws an ERROR, but with the patch, a similar scenario results in client connection being lost.
I didn't investigate it more, but looks like we should maintain the existing behaviour when table synchronization fails due to duplicate data.
