Function jsonFuncReturnsNonJSON

transpiler/transform/operators.go:700–711

jsonFuncReturnsNonJSON reports whether a json*-named function returns a non-JSON value (VARCHAR, BIGINT, BOOLEAN, ...), so its result concatenated with || must keep DuckDB string-concat semantics. Covers both the PostgreSQL names and the DuckDB names FunctionTransform rewrites them to (function mapp

(name string)

// names and the DuckDB names FunctionTransform rewrites them to (function
// mapping runs before this transform in the pipeline).
func jsonFuncReturnsNonJSON(name string) bool {
	for _, suffix := range []string{"_string", "_text", "_length", "_keys", "_valid", "_exists", "_contains"} {
		if strings.HasSuffix(name, suffix) {
			return true
		}
	}
	switch name {
	case "json_type", "json_typeof", "jsonb_typeof":
		return true
	}
	return false
}

// createJSONConcatExpr rewrites `a || b` (with a JSON-looking operand) to a
// CASE expression reproducing Postgres jsonb || semantics in DuckDB: