Hi Hackers,
Two recursive functions, generate_setop_from_pathqueries() and
generate_queries_for_path_pattern_recurse() in GRAPH_TABLE rewriter are missing check_stack_depth() calls. Consider a property graph with 400 edge tables with a 2-hop pattern produce 160,000 path queries and therefore 160,000 recursion frames in
generate_setop_from_pathqueries(). This can easily exceed the OS stack limit for some systems and crashes the backend.
I am proposing a stop gap fix of checking stack depth by calling check_stack_depth for now but in future we may want to reduce the recursion depth (for example use a balanced tree to reduce depth from O(N) to O(log N).
Attached a patch for adding the check_stack_depth() check.
Repro:
CREATE TABLE sv (id int PRIMARY KEY);
INSERT INTO sv VALUES (1);
DO $$
BEGIN
FOR i IN 1..400 LOOP
EXECUTE format(
'CREATE TABLE se_%s (id int PRIMARY KEY, src int, dst int)', i);
END LOOP;
END$$;
DO $$
DECLARE
sql text;
edges text := '';
BEGIN
FOR i IN 1..400 LOOP
IF i > 1 THEN edges := edges || ', '; END IF;
edges := edges || format(
'se_%s KEY (id) SOURCE KEY (src) REFERENCES sv (id) '
'DESTINATION KEY (dst) REFERENCES sv (id)', i);
END LOOP;
EXECUTE 'CREATE PROPERTY GRAPH g VERTEX TABLES (sv KEY (id)) '
|| 'EDGE TABLES (' || edges || ')';
END$$;
SELECT * FROM GRAPH_TABLE(g
MATCH (a)-[e1]->(b)-[e2]->(c)
COLUMNS(
a.id AS a_id))
LIMIT 1;
Thanks,
Satya
