Fix toast rewrites in logical decoding.

Commit 325f2ec555 introduced pg_class.relwrite to skip operations on
tables created as part of a heap rewrite during DDL. It links such
transient heaps to the original relation OID via this new field in
pg_class but forgot to do anything about toast tables. So, logical
decoding was not able to skip operations on internally created toast
tables. This leads to an error when we tried to decode the WAL for the
next operation for which it appeared that there is a toast data where
actually it didn't have any toast data.

To fix this, we set pg_class.relwrite for internally created toast tables
as well which allowed skipping operations on them during logical decoding.

Author: Bertrand Drouvot
Reviewed-by: David Zhang, Amit Kapila
Backpatch-through: 11, where it was introduced
Discussion: https://postgr.es/m/b5146fb1-ad9e-7d6e-f980-98ed68744a7c@amazon.com

1 files changed, 16 insertions, 0 deletions

diff --git a/contrib/test_decoding/sql/toast.sql b/contrib/test_decoding/sql/toast.sql
index 016c3ab7842..d1c560a174d 100644
--- a/contrib/test_decoding/sql/toast.sql
+++ b/contrib/test_decoding/sql/toast.sql
@@ -308,4 +308,20 @@ DROP TABLE toasted_several;
 
 SELECT regexp_replace(data, '^(.{100}).*(.{100})$', '\1..\2') FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1')
 WHERE data NOT LIKE '%INSERT: %';
+
+/*
+ * Test decoding relation rewrite with toast. The insert into tbl2 within the
+ * same transaction is there to check that there is no remaining toast_hash not
+ * being reset.
+ */
+CREATE TABLE tbl1 (a INT, b TEXT);
+CREATE TABLE tbl2 (a INT);
+ALTER TABLE tbl1 ALTER COLUMN b SET STORAGE EXTERNAL;
+BEGIN;
+INSERT INTO tbl1 VALUES(1, repeat('a', 4000)) ;
+ALTER TABLE tbl1 ADD COLUMN id serial primary key;
+INSERT INTO tbl2 VALUES(1);
+commit;
+SELECT substr(data, 1, 200) FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
+
 SELECT pg_drop_replication_slot('regression_slot');