`reduce()`/list comprehension in a `LIMIT` or `SKIP` clause raises internal error `unsupported SubLink` (0A000)

[hkjiang26]

Bug description

Putting a reduce() expression — or a list comprehension — inside a LIMIT or SKIP clause makes AGE 1.8.0 fail with the internal error ERROR: 0A000: unsupported SubLink. The query has no subquery and no outer variable; the trigger is the reduce's own list iteration variable (b IN [0]).

Access method

• Command line via psql, inside the official Docker container apache/age:1.8.0

Data setup

No data is required — the error reproduces on an empty graph. Only the graph itself must exist:

CREATE EXTENSION IF NOT EXISTS age;
LOAD 'age';
SET search_path = ag_catalog, "$user", public;
SELECT create_graph('graph_test');

Configuration

• None beyond the stock AGE extension. No additional modules (no PostGIS, etc.), default search_path handling as shown above.

Command that triggers the error

SELECT * FROM cypher('graph_test', $$ RETURN 1 LIMIT reduce(a = 1, b IN [0] | a + b) $$) AS (c0 agtype);

ERROR:  unsupported SubLink

(SQLSTATE 0A000, internal error.) Run the statement on its own (e.g. psql -c "..."): when several statements are piped to psql at once, stdout/stderr buffering can push the ERROR line to a different position in the output and make it look like the query succeeded.

The failure is specific to LIMIT/SKIP: the same reduce returns a row without one, and LIMIT accepts other data-free expressions:

-- works: reduce without LIMIT
SELECT * FROM cypher('graph_test', $$ RETURN reduce(a = 1, b IN [0] | a + b) $$) AS (c0 agtype);
-- works: arithmetic / function in LIMIT
SELECT * FROM cypher('graph_test', $$ RETURN 1 LIMIT 1 + 1 $$) AS (c0 agtype);
SELECT * FROM cypher('graph_test', $$ RETURN 1 LIMIT size([0, 0]) $$) AS (c0 agtype);

Environment

• Version: 1.8.0 (official apache/age:1.8.0 Docker image)
• PostgreSQL: 18.1 (Debian 18.1-1.pgdg13+2), x86_64