PostgreSQL raises invalid_regular_expression (SQLSTATE 2201B) when a supplied regular expression has incorrect syntax or unsupported features.
invalid_regular_expression occurs in PostgreSQL when a regex used in ~, ~*, SIMILAR TO, or regexp_* functions contains bad syntax or unsupported features. Correct the pattern or escape special characters to resolve the error.
PostgreSQL Error 2201B invalid_regular_expression
The error appears when PostgreSQL encounters a malformed or unsupported regular expression in operators like ~, ~*, !~, SIMILAR TO, or in regexp_* functions.
PostgreSQL validates each pattern against its regex engine before execution.
If the pattern breaks syntax rules or uses options the engine cannot handle, it returns SQLSTATE 2201B and aborts the query.
ERROR: invalid regular expression (SQLSTATE 2201B)
Incorrect escape sequences, unbalanced brackets, or misplaced quantifiers quickly trigger the error.
Using PCRE-specific syntax, backreferences, or look-behinds that PostgreSQL does not support will also fail validation.
First, isolate the pattern and test it with the regexp_matches function.
Then correct escapes, close brackets, or replace unsupported syntax with an equivalent PostgreSQL-compatible construct.
Galaxy’s editor highlights regex syntax and shows SQLSTATE codes inline, letting you spot issues before you run the query.
A dot (.) that you meant to treat literally must be escaped as \.
If you need non-greedy matching, swap PCRE’s .*? with a POSIX-compatible workaround such as [^ ]* or a quantifier range.
Validate any new regex with the regexp_matches function inside a SELECT before embedding it in production DML.
Store complex patterns in one source-controlled view or constant so they are tested once and reused safely.
Errors like invalid_escape_sequence (SQLSTATE 22P05) or unterminated_string_literal often surface together when the pattern is inline text.
Fix them in the same review.
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Python uses PCRE-style features that PostgreSQL’s POSIX engine lacks. Rewrite patterns using POSIX-compatible constructs.
Use standard_conforming_strings=on and double every backslash (\\) in string literals to form a single backslash in the regex.
Not natively. You can install pg_pcre or write a PL/Perl function, but core PostgreSQL only supports POSIX.
Galaxy flags regex syntax issues during editing, links SQLSTATE codes to docs, and lets teams endorse fixed queries for reuse.
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