Move SQL escape functions to the Postgres package

These are specific to Postgres. Add tests and remove unused functions.

internal/pgbouncer/postgres.go

@@ -41,14 +41,14 @@ func sqlAuthenticationQuery(sqlFunctionName string) string {
 		// No replicators.
 		`NOT pg_authid.rolreplication`,
 		// Not the PgBouncer role itself.
-		`pg_authid.rolname <> ` + util.SQLQuoteLiteral(postgresqlUser),
+		`pg_authid.rolname <> ` + postgres.QuoteLiteral(postgresqlUser),
 		// Those without a password expiration or an expiration in the future.
 		`(pg_authid.rolvaliduntil IS NULL OR pg_authid.rolvaliduntil >= CURRENT_TIMESTAMP)`,
 	}, "\n    AND ")
 
 	return strings.TrimSpace(`
 CREATE OR REPLACE FUNCTION ` + sqlFunctionName + `(username TEXT)
-RETURNS TABLE(username TEXT, password TEXT) AS ` + util.SQLQuoteLiteral(`
+RETURNS TABLE(username TEXT, password TEXT) AS ` + postgres.QuoteLiteral(`
   SELECT rolname::TEXT, rolpassword::TEXT
   FROM pg_catalog.pg_authid
   WHERE pg_authid.rolname = $1

internal/pgbouncer/postgres_test.go

@@ -19,14 +19,14 @@ import (
 func TestSQLAuthenticationQuery(t *testing.T) {
 	assert.Equal(t, sqlAuthenticationQuery("some.fn_name"),
 		`CREATE OR REPLACE FUNCTION some.fn_name(username TEXT)
-RETURNS TABLE(username TEXT, password TEXT) AS '
+RETURNS TABLE(username TEXT, password TEXT) AS  E'
   SELECT rolname::TEXT, rolpassword::TEXT
   FROM pg_catalog.pg_authid
   WHERE pg_authid.rolname = $1
     AND pg_authid.rolcanlogin
     AND NOT pg_authid.rolsuper
     AND NOT pg_authid.rolreplication
-    AND pg_authid.rolname <> ''_crunchypgbouncer''
+    AND pg_authid.rolname <>  E''_crunchypgbouncer''
     AND (pg_authid.rolvaliduntil IS NULL OR pg_authid.rolvaliduntil >= CURRENT_TIMESTAMP)'
 LANGUAGE SQL STABLE SECURITY DEFINER;`)
 }
@@ -150,14 +150,14 @@ REVOKE ALL PRIVILEGES
  GRANT USAGE
     ON SCHEMA :"namespace" TO :"username";
 CREATE OR REPLACE FUNCTION :"namespace".get_auth(username TEXT)
-RETURNS TABLE(username TEXT, password TEXT) AS '
+RETURNS TABLE(username TEXT, password TEXT) AS  E'
   SELECT rolname::TEXT, rolpassword::TEXT
   FROM pg_catalog.pg_authid
   WHERE pg_authid.rolname = $1
     AND pg_authid.rolcanlogin
     AND NOT pg_authid.rolsuper
     AND NOT pg_authid.rolreplication
-    AND pg_authid.rolname <> ''_crunchypgbouncer''
+    AND pg_authid.rolname <>  E''_crunchypgbouncer''
     AND (pg_authid.rolvaliduntil IS NULL OR pg_authid.rolvaliduntil >= CURRENT_TIMESTAMP)'
 LANGUAGE SQL STABLE SECURITY DEFINER;
 REVOKE ALL PRIVILEGES

internal/postgres/sql.go

@@ -0,0 +1,22 @@
+// Copyright 2021 - 2024 Crunchy Data Solutions, Inc.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package postgres
+
+import "strings"
+
+// escapeLiteral is called by QuoteLiteral to add backslashes before special
+// characters of the "escape" string syntax. Double quote marks to escape them
+// regardless of the "backslash_quote" parameter.
+var escapeLiteral = strings.NewReplacer(`'`, `''`, `\`, `\\`).Replace
+
+// QuoteLiteral escapes v so it can be safely used as a literal (or constant)
+// in an SQL statement.
+func QuoteLiteral(v string) string {
+	// Use the "escape" syntax to ensure that backslashes behave consistently regardless
+	// of the "standard_conforming_strings" parameter. Include a space before so
+	// the "E" cannot change the meaning of an adjacent SQL keyword or identifier.
+	// - https://www.postgresql.org/docs/current/sql-syntax-lexical.html
+	return ` E'` + escapeLiteral(v) + `'`
+}

internal/postgres/sql_test.go

@@ -0,0 +1,16 @@
+// Copyright 2021 - 2024 Crunchy Data Solutions, Inc.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package postgres
+
+import (
+	"testing"
+
+	"gotest.tools/v3/assert"
+)
+
+func TestQuoteLiteral(t *testing.T) {
+	assert.Equal(t, QuoteLiteral(``), ` E''`)
+	assert.Equal(t, QuoteLiteral(`ab"cd\ef'gh`), ` E'ab"cd\\ef''gh'`)
+}