invalid_regular_expression Invalid Regular Expression — SQLSTATE 2201B

A regular expression pattern is invalid.

• The error is written to the server log and returned to the client carrying SQLSTATE 2201B.
• Any driver (libpq, JDBC, psycopg, npgsql, pgx) surfaces this code in its error object so you can branch on it programmatically.
• PL/pgSQL can trap it by name: EXCEPTION WHEN invalid_regular_expression THEN.

Severity: ERROR  |  PostgreSQL versions: 12, 13, 14, 15, 16, 17

Reproduce with the exact statement and read the full message in the server log (raise log_min_messages / set log_min_error_statement for more context).

The regex passed to ~, the regexp_* functions, or SIMILAR TO is malformed.

Common causes:

• Unescaped metacharacters.
• Unbalanced parentheses or brackets.
• Invalid backreferences or quantifiers.

Steps to resolve 2201B:

1. Escape literals (for example \., \() and balance groups.
2. Test the pattern in isolation: SELECT 'sample' ~ 'pattern';.
3. When building patterns from user input, escape it (for example with regexp_replace).

Reference: PostgreSQL error codes — Class 22 (Data Exception).