fix: allow QueryMessage with empty query string (#113)

PostgreSQL accepts QueryMessages with an empty query string. PGAdapter now also accepts these and sends back a NoDataResponse without sending the statement to Spanner.

Author: olavloite

src/main/java/com/google/cloud/spanner/pgadapter/statements/IntermediateStatement.java

@@ -411,11 +411,14 @@ private void executeSingleStatement(int index) {
  executionStatus = ExecutionStatus.AUTOCOMMIT;
  }
  }
- try {
- StatementResult result = this.connection.execute(Statement.of(statement));
- updateResultCount(index, result);
- } catch (SpannerException e) {
- handleExecutionExceptionAndTransactionStatus(index, e);
+ // Ignore empty statements.
+ if (!"".equals(statement)) {
+ try {
+ StatementResult result = this.connection.execute(Statement.of(statement));
+ updateResultCount(index, result);
+ } catch (SpannerException e) {
+ handleExecutionExceptionAndTransactionStatus(index, e);
+ }
  }
  }
 

src/test/java/com/google/cloud/spanner/pgadapter/JdbcSimpleModeMockServerTest.java

@@ -92,6 +92,18 @@ public void testQuery() throws SQLException {
  assertTrue(request.getTransaction().getSingleUse().hasReadOnly());
  }
 
+ @Test
+ public void testEmptyStatement() throws SQLException {
+ String sql = "";
+
+ try (Connection connection = DriverManager.getConnection(createUrl())) {
+ assertFalse(connection.createStatement().execute(sql));
+ }
+
+ // An empty statement is not sent to Spanner.
+ assertEquals(0, mockSpanner.countRequestsOfType(ExecuteSqlRequest.class));
+ }
+
  @Test
  public void testWrongDialect() {
  // Let the mock server respond with the Google SQL dialect instead of PostgreSQL. The