I spent some time thinking about a special case of evaluation of the row filter and wrote a comment that might be useful (see the attachment). However now I think that it's not perfect if the code really relies on the fact that value of an indexed column cannot be TOASTed due to size restrictions.
I could hit two different error messages when trying activate TOAST on an index column (in this case PG was build with 16kB pages), but still I think the code is unnecessarily fragile if it relies on such errors: ERROR: index row requires 8224 bytes, maximum size is 8191 ERROR: index row size 8048 exceeds btree version 4 maximum 5432 for index "b_pkey" DETAIL: Index row references tuple (0,3) in relation "b". HINT: Values larger than 1/3 of a buffer page cannot be indexed. Note that at least in ExtractReplicaIdentity() we do expect that an indexed column value can be TOASTed. /* * If the tuple, which by here only contains indexed columns, still has * toasted columns, force them to be inlined. This is somewhat unlikely * since there's limits on the size of indexed columns, so we don't * duplicate toast_flatten_tuple()s functionality in the above loop over * the indexed columns, even if it would be more efficient. */ if (HeapTupleHasExternal(key_tuple)) { HeapTuple oldtup = key_tuple; key_tuple = toast_flatten_tuple(oldtup, desc); heap_freetuple(oldtup); } Do I miss anything? -- Antonin Houska Web: https://www.cybertec-postgresql.com
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c index 20d0b1e1253..2be5aaa18c4 100644 --- a/src/backend/replication/pgoutput/pgoutput.c +++ b/src/backend/replication/pgoutput/pgoutput.c @@ -1246,6 +1246,15 @@ pgoutput_row_filter(Relation relation, TupleTableSlot *old_slot, */ if (!new_slot || !old_slot) { + /* + * For UPDATE, we should only get here if the replica identity is != + * FULL and thus all the identity columns are index columns, i.e. + * never TOASTed. Therefore, we don't need to care of the unchanged + * toasted replica identity columns like we do below. + */ + Assert(relation->rd_rel->relreplident != REPLICA_IDENTITY_FULL || + map_changetype_pubaction[*action] != PUBACTION_UPDATE); + ecxt->ecxt_scantuple = new_slot ? new_slot : old_slot; result = pgoutput_row_filter_exec_expr(filter_exprstate, ecxt);