feat: support default schema and catalog for PostgreSQL databases

src/main/java/com/google/cloud/spanner/jdbc/JdbcConnection.java

@@ -47,6 +47,7 @@
 import java.util.Map;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
+import javax.annotation.Nonnull;
 
 /** Jdbc Connection class for Google Cloud Spanner */
 class JdbcConnection extends AbstractJdbcConnection {
@@ -394,31 +395,66 @@ public Array createArrayOf(String typeName, Object[] elements) throws SQLExcepti
   @Override
   public void setCatalog(String catalog) throws SQLException {
     // This method could be changed to allow the user to change to another database.
-    // For now we only support setting an empty string in order to support frameworks
+    // For now, we only support setting the default catalog in order to support frameworks
     // and applications that set this when no catalog has been specified in the connection
     // URL.
     checkClosed();
-    JdbcPreconditions.checkArgument("".equals(catalog), "Only catalog \"\" is supported");
+    checkValidCatalog(catalog);
+  }
+
+  void checkValidCatalog(String catalog) throws SQLException {
+    String defaultCatalog = getDefaultCatalog();
+    JdbcPreconditions.checkArgument(
+        defaultCatalog.equals(catalog),
+        String.format("Only catalog %s is supported", defaultCatalog));
   }
 
   @Override
   public String getCatalog() throws SQLException {
     checkClosed();
-    return "";
+    return getDefaultCatalog();
+  }
+
+  @Nonnull
+  String getDefaultCatalog() {
+    switch (getDialect()) {
+      case POSTGRESQL:
+        String database = getConnectionOptions().getDatabaseName();
+        // It should not be possible that database is null, but it's better to be safe than sorry.
+        return database == null ? "" : database;
+      case GOOGLE_STANDARD_SQL:
+      default:
+        return "";
+    }
   }
 
   @Override
   public void setSchema(String schema) throws SQLException {
     checkClosed();
-    // Cloud Spanner does not support schemas, but does contain a pseudo 'empty string' schema that
-    // might be set by frameworks and applications that read the database metadata.
-    JdbcPreconditions.checkArgument("".equals(schema), "Only schema \"\" is supported");
+    checkValidSchema(schema);
+  }
+
+  void checkValidSchema(String schema) throws SQLException {
+    String defaultSchema = getDefaultSchema();
+    JdbcPreconditions.checkArgument(
+        defaultSchema.equals(schema), String.format("Only schema %s is supported", defaultSchema));
   }
 
   @Override
   public String getSchema() throws SQLException {
     checkClosed();
-    return "";
+    return getDefaultSchema();
+  }
+
+  @Nonnull
+  String getDefaultSchema() {
+    switch (getDialect()) {
+      case POSTGRESQL:
+        return "public";
+      case GOOGLE_STANDARD_SQL:
+      default:
+        return "";
+    }
   }
 
   @Override

src/main/java/com/google/cloud/spanner/jdbc/JdbcDatabaseMetaData.java

@@ -777,11 +777,12 @@ public ResultSet getSchemas() throws SQLException {
   }
 
   @Override
-  public ResultSet getCatalogs() {
+  public ResultSet getCatalogs() throws SQLException {
     return JdbcResultSet.of(
         ResultSets.forRows(
             Type.struct(StructField.of("TABLE_CAT", Type.string())),
-            Collections.singletonList(Struct.newBuilder().set("TABLE_CAT").to("").build())));
+            Collections.singletonList(
+                Struct.newBuilder().set("TABLE_CAT").to(getConnection().getCatalog()).build())));
   }
 
   @Override
@@ -1524,9 +1525,10 @@ public RowIdLifetime getRowIdLifetime() {
   @Override
   public ResultSet getSchemas(String catalog, String schemaPattern) throws SQLException {
     String sql = readSqlFromFile("DatabaseMetaData_GetSchemas.sql", connection.getDialect());
-    JdbcPreparedStatement statement =
-        prepareStatementReplaceNullWithAnyString(sql, catalog, schemaPattern);
-    return statement.executeQueryWithOptions(InternalMetadataQuery.INSTANCE);
+    try (JdbcPreparedStatement statement =
+        prepareStatementReplaceNullWithAnyString(sql, catalog, schemaPattern)) {
+      return statement.executeQueryWithOptions(InternalMetadataQuery.INSTANCE);
+    }
   }
 
   @Override

src/test/java/com/google/cloud/spanner/jdbc/JdbcConnectionTest.java

@@ -20,6 +20,7 @@
 import static com.google.common.truth.Truth.assertWithMessage;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.mockito.Mockito.any;
@@ -700,34 +701,33 @@ public void testCatalog() throws SQLException {
     ConnectionOptions options = mockOptions();
     when(options.getDatabaseName()).thenReturn("test");
     try (JdbcConnection connection = createConnection(options)) {
-      // The connection should always return the empty string as the current catalog, as no other
+      // The connection should always return the default catalog as the current catalog, as no other
       // catalogs exist in the INFORMATION_SCHEMA.
-      assertThat(connection.getCatalog()).isEqualTo("");
+      // The default catalog is the empty string for GoogleSQL databases.
+      // The default catalog is the database name for PostgreSQL databases.
+      assertEquals(connection.getDefaultCatalog(), connection.getCatalog());
       // This should be allowed.
-      connection.setCatalog("");
-      try {
-        // This should cause an exception.
-        connection.setCatalog("other");
-        fail("missing expected exception");
-      } catch (JdbcSqlExceptionImpl e) {
-        assertThat(e.getCode()).isEqualTo(Code.INVALID_ARGUMENT);
-      }
+      connection.setCatalog(connection.getDefaultCatalog());
+      // This should cause an exception.
+      JdbcSqlExceptionImpl exception =
+          assertThrows(JdbcSqlExceptionImpl.class, () -> connection.setCatalog("other"));
+      assertEquals(Code.INVALID_ARGUMENT, exception.getCode());
     }
   }
 
   @Test
   public void testSchema() throws SQLException {
     try (JdbcConnection connection = createConnection(mockOptions())) {
-      assertThat(connection.getSchema()).isEqualTo("");
+      // The connection should always return the default schema as the current schema, as we
+      // currently do not support setting the connection to a different schema.
+      // The default schema is the empty string for GoogleSQL databases.
+      // The default schema is 'public' for PostgreSQL databases.
+      assertEquals(connection.getDefaultSchema(), connection.getSchema());
       // This should be allowed.
-      connection.setSchema("");
-      try {
-        // This should cause an exception.
-        connection.setSchema("other");
-        fail("missing expected exception");
-      } catch (JdbcSqlExceptionImpl e) {
-        assertThat(e.getCode()).isEqualTo(Code.INVALID_ARGUMENT);
-      }
+      connection.setSchema(connection.getDefaultSchema());
+      JdbcSqlExceptionImpl exception =
+          assertThrows(JdbcSqlExceptionImpl.class, () -> connection.setSchema("other"));
+      assertEquals(Code.INVALID_ARGUMENT, exception.getCode());
     }
   }
 

src/test/java/com/google/cloud/spanner/jdbc/JdbcDatabaseMetaDataTest.java

@@ -41,10 +41,19 @@
 import java.util.Objects;
 import org.junit.Test;
 import org.junit.runner.RunWith;
-import org.junit.runners.JUnit4;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameter;
+import org.junit.runners.Parameterized.Parameters;
 
-@RunWith(JUnit4.class)
+@RunWith(Parameterized.class)
 public class JdbcDatabaseMetaDataTest {
+  @Parameter public Dialect dialect;
+
+  @Parameters(name = "dialect = {0}")
+  public static Object[] data() {
+    return Dialect.values();
+  }
+
   private static final String DEFAULT_CATALOG = "";
   private static final String DEFAULT_SCHEMA = "";
   private static final String TEST_TABLE = "FOO";
@@ -314,10 +323,12 @@ public void testGetBestRowIdentifier() throws SQLException {
   @Test
   public void testGetCatalogs() throws SQLException {
     JdbcConnection connection = mock(JdbcConnection.class);
+    when(connection.getDialect()).thenReturn(dialect);
+    when(connection.getCatalog()).thenCallRealMethod();
     DatabaseMetaData meta = new JdbcDatabaseMetaData(connection);
     try (ResultSet rs = meta.getCatalogs()) {
       assertThat(rs.next(), is(true));
-      assertThat(rs.getString("TABLE_CAT"), is(equalTo("")));
+      assertThat(rs.getString("TABLE_CAT"), is(equalTo(connection.getDefaultCatalog())));
       assertThat(rs.next(), is(false));
       ResultSetMetaData rsmd = rs.getMetaData();
       assertThat(rsmd.getColumnCount(), is(equalTo(1)));

src/test/java/com/google/cloud/spanner/jdbc/it/ITJdbcDatabaseMetaDataTest.java

@@ -822,18 +822,30 @@ public void testGetViews() throws SQLException {
   @Test
   public void testGetSchemas() throws SQLException {
     try (Connection connection = createConnection(env, database)) {
+      assertEquals("", connection.getSchema());
       try (ResultSet rs = connection.getMetaData().getSchemas()) {
         assertThat(rs.next(), is(true));
         assertThat(rs.getString("TABLE_SCHEM"), is(equalTo(DEFAULT_SCHEMA)));
         assertThat(rs.getString("TABLE_CATALOG"), is(equalTo(DEFAULT_CATALOG)));
         assertThat(rs.next(), is(true));
         assertThat(rs.getString("TABLE_SCHEM"), is(equalTo("INFORMATION_SCHEMA")));
         assertThat(rs.getString("TABLE_CATALOG"), is(equalTo(DEFAULT_CATALOG)));
-        if (!EmulatorSpannerHelper.isUsingEmulator()) {
-          assertThat(rs.next(), is(true));
-          assertThat(rs.getString("TABLE_SCHEM"), is(equalTo("SPANNER_SYS")));
-          assertThat(rs.getString("TABLE_CATALOG"), is(equalTo(DEFAULT_CATALOG)));
-        }
+        assertThat(rs.next(), is(true));
+        assertThat(rs.getString("TABLE_SCHEM"), is(equalTo("SPANNER_SYS")));
+        assertThat(rs.getString("TABLE_CATALOG"), is(equalTo(DEFAULT_CATALOG)));
+        assertFalse(rs.next());
+      }
+    }
+  }
+
+  @Test
+  public void testGetCatalogs() throws SQLException {
+    try (Connection connection = createConnection(env, database)) {
+      assertEquals("", connection.getCatalog());
+      try (ResultSet rs = connection.getMetaData().getCatalogs()) {
+        assertTrue(rs.next());
+        assertEquals("", rs.getString("TABLE_CAT"));
+
         assertFalse(rs.next());
       }
     }

src/test/java/com/google/cloud/spanner/jdbc/it/ITJdbcPgDatabaseMetaDataTest.java

@@ -752,6 +752,7 @@ public void testGetViews() throws SQLException {
   @Test
   public void testGetSchemas() throws SQLException {
     try (Connection connection = createConnection(env, database)) {
+      assertEquals("public", connection.getSchema());
       try (ResultSet rs = connection.getMetaData().getSchemas()) {
         assertTrue(rs.next());
         assertEquals(getDefaultCatalog(database), rs.getString("TABLE_CATALOG"));
@@ -774,6 +775,19 @@ public void testGetSchemas() throws SQLException {
     }
   }
 
+  @Test
+  public void testGetCatalogs() throws SQLException {
+    try (Connection connection = createConnection(env, database)) {
+      assertEquals(database.getId().getDatabase(), connection.getCatalog());
+      try (ResultSet rs = connection.getMetaData().getCatalogs()) {
+        assertTrue(rs.next());
+        assertEquals(database.getId().getDatabase(), rs.getString("TABLE_CAT"));
+
+        assertFalse(rs.next());
+      }
+    }
+  }
+
   private static final class Table {
     private final String name;
     private final String type;