Re: row filtering for logical replication

Hi Euler,

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.

Thank you,
Rahila Syed