Fix segfault after second ANALYZE

Issue occurs in extended query protocol mode only where every
query goes through PREPARE and EXECUTE phase. First time ANALYZE
is executed, a list of relations to be vaccumed is extracted and
saved in a list. This list is referenced in parsetree node. Once
execution of ANALYZE is complete, this list is cleaned up, however
reference to the same is not cleaned up in parsetree node. When
second time ANALYZE is executed, segfault happens as we access an
invalid memory location.

Fixed the issue by restoring the actual value in parsetree node
once ANALYZE completes its execution.

Fixes timescale#4857

CHANGELOG.md

@@ -4,6 +4,12 @@
 `psql` with the `-X` flag to prevent any `.psqlrc` commands from
 accidentally triggering the load of a previous DB version.**
 
+**Thanks**
+* @kyrias for reporting a crash when ANALYZE is executed on extended query protocol mode with extension loaded.
+
+**Bugfixes**
+* #5054 Fix segfault after second ANALYZE
+
 ## 2.9.0
 This release adds major new features since the 2.8.1 release.
 We deem it moderate priority for upgrading.

src/process_utility.c

@@ -906,6 +906,8 @@ process_vacuum(ProcessUtilityArgs *args)
 	Hypertable *ht;
 	List *vacuum_rels = NIL;
 	bool is_vacuumcmd;
+	/* save original VacuumRelation list */
+	List *stmt_rels = list_copy(stmt->rels);
 
 	is_vacuumcmd = stmt->is_vacuumcmd;
 
@@ -975,6 +977,12 @@ process_vacuum(ProcessUtilityArgs *args)
 															  cp->compressed_relid);
 		}
 	}
+	/*
+	Restore original list. stmt->rels which has references to
+	VacuumRelation list is freed up, however VacuumStmt is not
+	cleaned up because of which there is a crash.
+	*/
+	stmt->rels = list_copy(stmt_rels);
 	return DDL_DONE;
 }
 

test/expected/size_utils.out

@@ -744,3 +744,17 @@ SELECT * FROM hypertable_index_size('hypersize_time_idx');
                  24576
 (1 row)
 
+-- github issue #4857
+-- below procedure should not crash
+SET client_min_messages = ERROR;
+do
+$$
+DECLARE
+  o INT;
+BEGIN
+  FOR c IN 1..20 LOOP
+    ANALYZE;
+  END LOOP;
+END;
+$$;
+RESET client_min_messages;

test/sql/size_utils.sql

@@ -273,3 +273,18 @@ SELECT * FROM chunks_detailed_size('hypersize') ORDER BY node_name;
 SELECT * FROM hypertable_compression_stats('hypersize') ORDER BY node_name;
 SELECT * FROM chunk_compression_stats('hypersize') ORDER BY node_name;
 SELECT * FROM hypertable_index_size('hypersize_time_idx');
+
+-- github issue #4857
+-- below procedure should not crash
+SET client_min_messages = ERROR;
+do
+$$
+DECLARE
+  o INT;
+BEGIN
+  FOR c IN 1..20 LOOP
+    ANALYZE;
+  END LOOP;
+END;
+$$;
+RESET client_min_messages;