Integer modulo (%) by a zero divisor errors with `floating-point exception` (22P01) instead of `division by zero`

Start in src/backend/utils/adt/agtype_ops.c, inspect agtype_mod alongside agtype_div and reproduce the issue with the provided psql cypher command. Add the missing zero-divisor handling for integer modulo, then verify that RETURN 5 % 0 reports division by zero (22012) while RETURN 5 % 2 still returns 1.

Bug description

Computing an integer modulo % whose divisor is zero makes AGE 1.8.0 fail with a misclassified error: ERROR: 22P01: floating-point exception, whose detail text only guesses that division by zero is involved. The same zero divisor through the sibling division operator / correctly raises division by zero (22012), and so does native PostgreSQL SELECT 5 % 0. The % path is the only one that leaks a low-level hardware signal (SIGFPE from integer division by zero) instead of reporting a proper arithmetic error.

Root cause: in src/backend/utils/adt/agtype_ops.c, agtype_mod computes lhs % rhs for integer operands with no zero-divisor guard, whereas the sibling agtype_div explicitly checks rhs == 0 and raises ERRCODE_DIVISION_BY_ZERO. An unprotected int % 0 traps as SIGFPE, which PostgreSQL's signal handler surfaces as ERRCODE_FLOATING_POINT_EXCEPTION.

No graph data is required — a bare RETURN 5 % 0 (no MATCH) is enough to trigger it.

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');

Command that triggers the error

SELECT * FROM cypher('graph_test', $$ RETURN 5 % 0 $$) AS (c0 agtype);

ERROR:  22P01: floating-point exception
DETAIL:  An invalid floating-point operation was signaled. This probably means an out-of-range result or an invalid operation, such as division by zero.

The zero divisor can be a literal (0), a property value (CREATE (n {q: 0}) then MATCH (n) WHERE (n.q) % 0 = 0), or a bound variable — all raise the same error.

The same division by zero behaves correctly in every other path, all run in the same session:

• RETURN 5 / 0 → ERROR: division by zero (the / operator guards rhs == 0)
• Native PostgreSQL SELECT 5 % 0; → ERROR: division by zero
• Non-zero divisor RETURN 5 % 2 → returns 1

Expected behavior

Modulo by zero is division by zero. RETURN 5 % 0 should raise the same clean division by zero (22012) that the / operator and native PostgreSQL raise, not an unrelated floating-point exception. The error should come from a deliberate zero-divisor check, not from an unhandled hardware signal.

Environment

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