[PATCH] Add isolation test for session variables.

---
 .../isolation/expected/session-variable.out   | 87 +++++++++++++++++++
 src/test/isolation/isolation_schedule         |  1 +
 .../isolation/specs/session-variable.spec     | 34 ++++++++
 3 files changed, 122 insertions(+)
 create mode 100644 src/test/isolation/expected/session-variable.out
 create mode 100644 src/test/isolation/specs/session-variable.spec

diff --git a/src/test/isolation/expected/session-variable.out b/src/test/isolation/expected/session-variable.out
new file mode 100644
index 0000000000..d8c817f05a
--- /dev/null
+++ b/src/test/isolation/expected/session-variable.out
@@ -0,0 +1,87 @@
+Parsed test spec with 2 sessions
+
+starting permutation: let val drop val
+step let: LET myvar = 'test';
+step val: SELECT myvar;
+myvar
+-----
+test 
+(1 row)
+
+step drop: DROP VARIABLE myvar;
+step val: SELECT myvar;
+ERROR:  column or variable "myvar" does not exist
+
+starting permutation: let val s1 drop val sr1
+step let: LET myvar = 'test';
+step val: SELECT myvar;
+myvar
+-----
+test 
+(1 row)
+
+step s1: BEGIN;
+step drop: DROP VARIABLE myvar;
+step val: SELECT myvar;
+ERROR:  column or variable "myvar" does not exist
+step sr1: ROLLBACK;
+
+starting permutation: let val dbg drop create dbg val
+step let: LET myvar = 'test';
+step val: SELECT myvar;
+myvar
+-----
+test 
+(1 row)
+
+step dbg: SELECT schema, name, removed FROM pg_debug_show_used_session_variables();
+schema|name |removed
+------+-----+-------
+public|myvar|f      
+(1 row)
+
+step drop: DROP VARIABLE myvar;
+step create: CREATE VARIABLE myvar AS text
+step dbg: SELECT schema, name, removed FROM pg_debug_show_used_session_variables();
+schema|name |removed
+------+-----+-------
+public|myvar|t      
+(1 row)
+
+step val: SELECT myvar;
+myvar
+-----
+     
+(1 row)
+
+
+starting permutation: let val s1 dbg drop create dbg val sr1
+step let: LET myvar = 'test';
+step val: SELECT myvar;
+myvar
+-----
+test 
+(1 row)
+
+step s1: BEGIN;
+step dbg: SELECT schema, name, removed FROM pg_debug_show_used_session_variables();
+schema|name |removed
+------+-----+-------
+public|myvar|f      
+(1 row)
+
+step drop: DROP VARIABLE myvar;
+step create: CREATE VARIABLE myvar AS text
+step dbg: SELECT schema, name, removed FROM pg_debug_show_used_session_variables();
+schema|name |removed
+------+-----+-------
+public|myvar|t      
+(1 row)
+
+step val: SELECT myvar;
+myvar
+-----
+     
+(1 row)
+
+step sr1: ROLLBACK;
diff --git a/src/test/isolation/isolation_schedule b/src/test/isolation/isolation_schedule
index 529a4cbd4d..96ecf93e32 100644
--- a/src/test/isolation/isolation_schedule
+++ b/src/test/isolation/isolation_schedule
@@ -107,3 +107,4 @@ test: cluster-conflict-partition
 test: truncate-conflict
 test: serializable-parallel
 test: serializable-parallel-2
+test: session-variable
diff --git a/src/test/isolation/specs/session-variable.spec b/src/test/isolation/specs/session-variable.spec
new file mode 100644
index 0000000000..a138f0449e
--- /dev/null
+++ b/src/test/isolation/specs/session-variable.spec
@@ -0,0 +1,34 @@
+#
+
+setup
+{
+    CREATE VARIABLE myvar AS text;
+}
+
+teardown
+{
+    DROP VARIABLE IF EXISTS myvar;
+}
+
+session s1
+step s1		{ BEGIN; }
+step let	{ LET myvar = 'test'; }
+step val	{ SELECT myvar; }
+step dbg	{ SELECT schema, name, removed FROM pg_debug_show_used_session_variables(); }
+step sr1	{ ROLLBACK; }
+
+
+session s2
+step drop		{ DROP VARIABLE myvar; }
+step create		{ CREATE VARIABLE myvar AS text }
+
+# Concurrent drop of a known variable should lead to an error
+permutation let val drop val
+# Same, but with an explicit transaction
+permutation let val s1 drop val sr1
+# Concurrent drop/create of a known variable should lead to empty variable
+permutation let val dbg drop create dbg val
+# Concurrent drop/create of a known variable should lead to empty variable
+# We need a transaction to make sure that we won't accept invalidation when
+# calling the dbg step after the concurrent drop
+permutation let val s1 dbg drop create dbg val sr1
-- 
2.37.0


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