hkjiang26 opened a new issue, #2511:
URL: https://github.com/apache/age/issues/2511
**Bug description**
Writing a Cypher query that passes a boolean expression together with a
constant literal to `coalesce()` — e.g. `coalesce(1 = 1, false)` — makes AGE
generate a PostgreSQL COALESCE whose argument types do not match: the boolean
comparison is compiled to a native `boolean`, while the constant branch remains
`agtype`. PostgreSQL rejects the whole query at parse time with error 42804
`COALESCE types boolean and agtype cannot be matched`. The statement is valid
Cypher (it returns a boolean in Neo4j) and is rejected before producing any
result.
**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:
```pgsql
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**
```pgsql
SELECT * FROM cypher('graph_test', $$ RETURN coalesce(1 = 1, false) AS c $$)
AS (a agtype);
```
```
ERROR: COALESCE types boolean and agtype cannot be matched
LINE 1: ...OM cypher('graph_test', $$ RETURN coalesce(1 = 1, false) AS ...
^
```
The same error also occurs:
- when the boolean branch is a node-property comparison, e.g. `MATCH (n)
RETURN coalesce(n.id = 42, false)`;
- when the constant branch is `true` or `null` instead of `false`;
- with aggregates, e.g. `RETURN coalesce(avg(x), 0)` (message: `COALESCE
types double precision and agtype cannot be matched`).
Only coalesce calls whose arguments are all `agtype` already work, e.g.
`RETURN coalesce(42, 0)` or `MATCH (n) RETURN coalesce(n.id, 0)`.
**Expected behavior**
The statement is valid Cypher: both arguments of `coalesce()` are booleans
(or coercible to a common type), so it should run successfully and return
`true` (the first non-null argument). A query mixing a comparison with a
constant is routine and must not be rejected with a PostgreSQL type-coercion
error. The bug is in AGE's SQL generation: the constant branch should be
coerced to `agtype` so the generated COALESCE type-checks.
**Environment**
- Version: 1.8.0 (official `apache/age:1.8.0` Docker image)
- PostgreSQL: 18.1 (Debian 18.1-1.pgdg13+2), x86_64
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