4 files changed, 63 insertions, 0 deletions
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index a05f0759643..768a2d492f6 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -779,11 +779,14 @@ DefineIndex(Oid relationId,
 	 * doing CREATE INDEX CONCURRENTLY, which would see our snapshot as one
 	 * they must wait for.  But first, save the snapshot's xmin to use as
 	 * limitXmin for GetCurrentVirtualXIDs().
+	 *
+	 * Our catalog snapshot could have the same effect, so drop that one too.
 	 */
 	limitXmin = snapshot->xmin;
 
 	PopActiveSnapshot();
 	UnregisterSnapshot(snapshot);
+	InvalidateCatalogSnapshot();
 
 	/*
 	 * The index is now valid in the sense that it contains all currently
diff --git a/src/test/isolation/expected/multiple-cic.out b/src/test/isolation/expected/multiple-cic.out
new file mode 100644
index 00000000000..cc579403925
--- /dev/null
+++ b/src/test/isolation/expected/multiple-cic.out
@@ -0,0 +1,19 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s2l s1i s2i
+step s2l: SELECT pg_advisory_lock(281457);
+pg_advisory_lock
+
+               
+step s1i: 
+		CREATE INDEX CONCURRENTLY mcic_one_pkey ON mcic_one (id)
+		WHERE lck_shr(281457);
+ <waiting ...>
+step s2i: 
+		CREATE INDEX CONCURRENTLY mcic_two_pkey ON mcic_two (id)
+		WHERE unlck();
+
+step s1i: <... completed>
+s1             
+
+               
diff --git a/src/test/isolation/isolation_schedule b/src/test/isolation/isolation_schedule
index 27e189f812c..94db2bf07f3 100644
--- a/src/test/isolation/isolation_schedule
+++ b/src/test/isolation/isolation_schedule
@@ -46,6 +46,7 @@ test: skip-locked-2
 test: skip-locked-3
 test: skip-locked-4
 test: drop-index-concurrently-1
+test: multiple-cic
 test: alter-table-1
 test: alter-table-2
 test: alter-table-3
diff --git a/src/test/isolation/specs/multiple-cic.spec b/src/test/isolation/specs/multiple-cic.spec
new file mode 100644
index 00000000000..a7ba4eb4fd1
--- /dev/null
+++ b/src/test/isolation/specs/multiple-cic.spec
@@ -0,0 +1,40 @@
+# Test multiple CREATE INDEX CONCURRENTLY working simultaneously
+
+setup
+{
+  CREATE TABLE mcic_one (
+	id int
+  );
+  CREATE TABLE mcic_two (
+	id int
+  );
+  CREATE FUNCTION lck_shr(bigint) RETURNS bool IMMUTABLE LANGUAGE plpgsql AS $$
+     BEGIN PERFORM pg_advisory_lock_shared($1); RETURN true; END;
+  $$;
+  CREATE FUNCTION unlck() RETURNS bool IMMUTABLE LANGUAGE plpgsql AS $$
+     BEGIN PERFORM pg_advisory_unlock_all(); RETURN true; END;
+  $$;
+}
+teardown
+{
+  DROP TABLE mcic_one, mcic_two;
+  DROP FUNCTION lck_shr(bigint);
+  DROP FUNCTION unlck();
+}
+
+session "s1"
+step "s1i"	{
+		CREATE INDEX CONCURRENTLY mcic_one_pkey ON mcic_one (id)
+		WHERE lck_shr(281457);
+	}
+teardown	{ SELECT pg_advisory_unlock_all() AS "s1"; }
+
+
+session "s2"
+step "s2l"  { SELECT pg_advisory_lock(281457); }
+step "s2i"	{
+		CREATE INDEX CONCURRENTLY mcic_two_pkey ON mcic_two (id)
+		WHERE unlck();
+	}
+
+permutation "s2l" "s1i" "s2i"