Fix the incorrect assertion introduced in commit 7f13ac8123.

It has been incorrectly assumed in commit 7f13ac8123 that we can either
purge all or none in the catalog modifying xids list retrieved from a
serialized snapshot. It is quite possible that some of the xids in that
array are old enough to be pruned but not others.

As per buildfarm

Author: Amit Kapila and Masahiko Sawada
Reviwed-by: Masahiko Sawada
Discussion: https://postgr.es/m/CAA4eK1LBtv6ayE+TvCcPmC-xse=DVg=SmbyQD1nv_AaqcpUJEg@mail.gmail.com

1 files changed, 20 insertions, 0 deletions

diff --git a/contrib/test_decoding/specs/catalog_change_snapshot.spec b/contrib/test_decoding/specs/catalog_change_snapshot.spec
index 2971ddc69cb..ff8f68489bb 100644
--- a/contrib/test_decoding/specs/catalog_change_snapshot.spec
+++ b/contrib/test_decoding/specs/catalog_change_snapshot.spec
@@ -3,12 +3,15 @@
 setup
 {
     DROP TABLE IF EXISTS tbl1;
+    DROP TABLE IF EXISTS tbl2;
     CREATE TABLE tbl1 (val1 integer, val2 integer);
+    CREATE TABLE tbl2 (val1 integer, val2 integer);
 }
 
 teardown
 {
     DROP TABLE tbl1;
+    DROP TABLE tbl2;
     SELECT 'stop' FROM pg_drop_replication_slot('isolation_slot');
 }
 
@@ -26,6 +29,12 @@ setup { SET synchronous_commit=on; }
 step "s1_checkpoint" { CHECKPOINT; }
 step "s1_get_changes" { SELECT data FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'skip-empty-xacts', '1', 'include-xids', '0'); }
 
+session "s2"
+setup { SET synchronous_commit=on; }
+step "s2_begin" { BEGIN; }
+step "s2_truncate" { TRUNCATE tbl2; }
+step "s2_commit" { COMMIT; }
+
 # For the transaction that TRUNCATEd the table tbl1, the last decoding decodes
 # only its COMMIT record, because it starts from the RUNNING_XACTS record emitted
 # during the first checkpoint execution.  This transaction must be marked as
@@ -37,3 +46,14 @@ step "s1_get_changes" { SELECT data FROM pg_logical_slot_get_changes('isolation_
 # record written by bgwriter.  One might think we can either stop the bgwriter or
 # increase LOG_SNAPSHOT_INTERVAL_MS but it's not practical via tests.
 permutation "s0_init" "s0_begin" "s0_savepoint" "s0_truncate" "s1_checkpoint" "s1_get_changes" "s0_commit" "s0_begin" "s0_insert" "s1_checkpoint" "s1_get_changes" "s0_commit" "s1_get_changes"
+
+# Test that we can purge the old catalog modifying transactions after restoring
+# them from the serialized snapshot. The first checkpoint will serialize the list
+# of two catalog modifying xacts. The purpose of the second checkpoint is to allow
+# partial pruning of the list of catalog modifying xact. The third checkpoint
+# followed by get_changes establishes a restart_point at the first checkpoint LSN.
+# The last get_changes will start decoding from the first checkpoint which
+# restores the list of catalog modifying xacts and then while decoding the second
+# checkpoint record it prunes one of the xacts in that list and when decoding the
+# next checkpoint, it will completely prune that list.
+permutation "s0_init" "s0_begin" "s0_truncate" "s2_begin" "s2_truncate" "s1_checkpoint" "s1_get_changes" "s0_commit" "s0_begin" "s0_insert" "s1_checkpoint" "s1_get_changes" "s2_commit" "s1_checkpoint" "s1_get_changes" "s0_commit" "s1_get_changes"