feature_not_supported set-returning functions are not allowed in WHERE — 0A000

Symptoms

A set-returning function (SRF) was used in a WHERE clause, which is not allowed. PostgreSQL raises SQLSTATE 0A000 (feature_not_supported).

• An SRF (e.g. generate_series, unnest) appeared in WHERE.
• SRFs belong in FROM, not in row-filtering predicates.
• Common when filtering against expanded sets.

What the server log shows

ERROR:  set-returning functions are not allowed in WHERE

Why PostgreSQL raises this — what the manual says

As Section 9.25 Set Returning Functions explains:

A set-returning function was placed where only a scalar value is allowed, such as a WHERE or HAVING clause or an aggregate argument; set-returning functions are permitted in the SELECT list or in the FROM clause (as a table function), so rewrite the query using a LATERAL join or a subquery in FROM.

A WHERE predicate must evaluate to a single boolean per candidate row. A set-returning function produces multiple rows, which has no defined meaning as a row filter, so PostgreSQL rejects it with 0A000.

Common causes

• Calling unnest()/generate_series() directly in WHERE.
• Trying to filter membership against an expanded set inline.

How to fix it

1. Move the SRF to the FROM clause (e.g. a LATERAL join) and filter on its output.
2. Use = ANY(array) or IN (subquery) for membership tests.
3. Rewrite to join against the expanded set.

Related & next steps

• SQLSTATE 0A000 — Feature Not Supported (full reference)
• Message: DISTINCT is not implemented for window functions
• Glossary: Set-returning function

Reference: PostgreSQL 18 — Set Returning Functions.