Re: [PATCH] Add NESTED_STATEMENTS option to EXPLAIN

Hello!

With some initial testing I was able to find 2 server crashes with the patch.

1: error during explain

CREATE OR REPLACE FUNCTION divz_plpgsql(x int) RETURNS int LANGUAGE
plpgsql AS $$
DECLARE r int;
BEGIN
SELECT 1/x INTO r;
RETURN r;
END;
$$;
-- error during explain
EXPLAIN (ANALYZE, NESTED_STATEMENTS) SELECT divz_plpgsql(0);
-- run another explain
EXPLAIN (ANALYZE, NESTED_STATEMENTS) SELECT 1;
-- any next query crashes the server
SELECT 1;

2: any nested explain

CREATE FUNCTION f() RETURNS void LANGUAGE plpgsql AS $$
DECLARE r record;
BEGIN
FOR r IN EXECUTE 'EXPLAIN (ANALYZE, NESTED_STATEMENTS) SELECT 1'
LOOP NULL; END LOOP;
END;
$$;

EXPLAIN (ANALYZE, NESTED_STATEMENTS) SELECT f();

+ /*
+ * Switch to TopMemoryContext so the captured plan text survives
+ * until we print it.
+ */
+ oldcxt = MemoryContextSwitchTo(TopMemoryContext);
...
+ ExplainBeginOutput(nes);
+ ExplainPrintPlan(nes, queryDesc);
+ ExplainEndOutput(nes);
...
+ plan_info->query_text = queryDesc->sourceText ?
+ pstrdup(queryDesc->sourceText) : pstrdup("<unknown>");

When is queryDesc freed? This seems like a memory leak.