[christiangda]

What was wrong

PostgreSQL writes string LIKE pattern [ESCAPE escape-character], and the same after SIMILAR TO. The clause was not part of this grammar, so name LIKE 'x!%' ESCAPE '!' was refused: a pattern could escape only with the backslash.

What changes

• The clause follows LIKE, ILIKE, their negations and SIMILAR TO, written with the keyword, in any case.
• The escape character is a string of one character, counted in characters, not bytes ('é' is one). An empty string turns escaping off.
• What PostgreSQL refuses is refused, each with its own message:
  • two characters (invalid escape string);
  • a number, a boolean or a column as the escape;
  • the clause after ~~, ~~*, !~~ and !~~*, which take none.
• BinaryOperatorNode and SimilarToNode carry it as Escape. It is nil without a clause, which is every filter v1.0.5 accepted, and String() writes it.
• A new field and nothing else changed, so this is a minor version: v1.1.0.

How it was checked

• Every row of TestFilterParser_TheEscapeClause was run against PostgreSQL 18.6 as SELECT … WHERE (<input>), the version and table shape the existing pattern tests use. What it answered is in each row's comment:
  • 10 accepted inputs, including ESCAPE '' and ESCAPE 'é', plus one in an expression;
  • 11 refused, each checked for its message.
• Mutants: 7 of 7 caught, each compiling.
  • The ~~ operators taking the clause.
  • Two characters allowed.
  • Bytes counted instead of characters.
  • A non-string escape allowed.
  • The clause not read after SIMILAR TO.
  • The clause left out of String().
  • The NOT LIKE keyword treated as the !~~ operator.
• go test -race passes, coverage is 97.6%, and golangci-lint reports 0 issues.

Docs: filtering.md (the patterns section, the AST class diagram and table), migration.md (a v1.0.5 → v1.1.0 section).

After this merges and v1.1.0 is tagged, the service and the template each take the bump in a PR of their own.

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