Modified getFunctions to return functions from the current catalog in case of null catalog (#1147)

## Description
<!-- Provide a brief summary of the changes made and the issue they aim
to address.-->
Modified getFunctions to return functions from the current catalog in
case of null catalog . This will allow the users to see system functions
## Testing
<!-- Describe how the changes have been tested-->
Tested locally.
## Additional Notes to the Reviewer
<!-- Share any additional context or insights that may help the reviewer
understand the changes better. This could include challenges faced,
limitations, or compromises made during the development process.
Also, mention any areas of the code that you would like the reviewer to
focus on specifically. -->

---------

Signed-off-by: Madhavendra Rathore <madhavendra.rathore@databricks.com>
Co-authored-by: Claude <noreply@anthropic.com>

Author: msrathore-db

NEXT_CHANGELOG.md

@@ -7,12 +7,12 @@
 ### Updated
 - Log timestamps now explicitly display timezone.
 - **[Breaking Change]** `PreparedStatement.setTimestamp(int, Timestamp, Calendar)` now properly applies Calendar timezone conversion using LocalDateTime pattern (inline with `getTimestamp`). Previously Calendar parameter was ineffective.
-- `DatabaseMetaData.getColumns()` with null catalog parameter now retrieves columns from all catalogs when using SQL Execution API.
+- `DatabaseMetaData.getColumns()` with null catalog parameter now retrieves columns from all catalogs when using SQL Execution API, aligning the behaviour with thrift.
+- `DatabaseMetaData.getFunctions()` with null catalog parameter now retrieves columns from the current catalog when using SQL Execution API, aligning the behaviour with thrift.
 
 ### Fixed
 - Fix timeout exception handling to throw `SQLTimeoutException` instead of `DatabricksSQLException` when queries timeout.
 - Removes dangerous global timezone modification that caused race conditions.
-<<<<<<< HEAD
 - Fixed `Statement.getLargeUpdateCount()` to return -1 instead of throwing Exception when there were no more results or result is not an update count.
 - CVE-2025-66566. Updated lz4-java dependency to 1.10.1.
 - Fix `INVALID_IDENTIFIER` error when using catalog/schema/table names for SQL Exec API with hyphens or special characters in metadata operations (`getSchemas()`, `getTables()`, `getColumns()`, etc.) and connection methods (`setCatalog()`, `setSchema()`). Per Databricks identifier rules, special characters are now properly enclosed in backticks. 

src/main/java/com/databricks/jdbc/dbclient/impl/sqlexec/DatabricksMetadataSdkClient.java

@@ -185,14 +185,19 @@ public DatabricksResultSet listFunctions(
       throws SQLException {
     catalog = autoFillCatalog(catalog, session);
 
-    // Return empty result set if catalog is null
+    // Fetch current catalog if catalog is null
     if (catalog == null) {
-      LOGGER.debug("Catalog is null, returning empty result set for listFunctions");
-      return metadataResultSetBuilder.getResultSetWithGivenRowsAndColumns(
-          MetadataResultConstants.FUNCTION_COLUMNS,
-          new ArrayList<>(),
-          METADATA_STATEMENT_ID,
-          com.databricks.jdbc.common.CommandName.LIST_FUNCTIONS);
+      // #TODO: Make server side changes
+      LOGGER.debug("Catalog is null, fetching current catalog for listFunctions");
+      catalog = session.getCurrentCatalog();
+
+      // Use hive_metastore as fallback if current catalog is null
+      if (catalog == null) {
+        LOGGER.debug("Current catalog is null, using hive_metastore as fallback");
+        catalog = "hive_metastore";
+      } else {
+        LOGGER.debug("Using current catalog: {}", catalog);
+      }
     }
 
     CommandBuilder commandBuilder =

src/test/java/com/databricks/jdbc/dbclient/impl/sqlexec/DatabricksMetadataSdkClientTest.java

@@ -788,18 +788,51 @@ void testGetFunctions(
   }
 
   @Test
-  void testReturnsEmptyResultSetInCaseOfNullCatalog() throws SQLException {
+  void testListFunctionsWithNullCatalog() throws SQLException {
+    when(session.getComputeResource()).thenReturn(WAREHOUSE_COMPUTE);
+    when(session.getCurrentCatalog()).thenReturn("current_catalog");
     IDatabricksConnectionContext mockContext = mock(IDatabricksConnectionContext.class);
     when(mockContext.getEnableMultipleCatalogSupport()).thenReturn(true);
     when(mockClient.getConnectionContext()).thenReturn(mockContext);
+
     DatabricksMetadataSdkClient metadataClient = new DatabricksMetadataSdkClient(mockClient);
 
-    // listFunctions with null catalog should return empty ResultSet
-    DatabricksResultSet functionsResult =
-        metadataClient.listFunctions(session, null, TEST_SCHEMA, TEST_TABLE);
-    assertNotNull(functionsResult);
-    assertFalse(
-        functionsResult.next(), "Expected empty result set for listFunctions with null catalog");
+    String expectedSQL =
+        "SHOW FUNCTIONS IN CATALOG `current_catalog` SCHEMA LIKE 'testSchema' LIKE 'functionPattern'";
+    when(mockClient.executeStatement(
+            expectedSQL,
+            WAREHOUSE_COMPUTE,
+            new HashMap<Integer, ImmutableSqlParameter>(),
+            StatementType.METADATA,
+            session,
+            null))
+        .thenReturn(mockedResultSet);
+    when(mockedResultSet.next()).thenReturn(true, false);
+    doReturn(6).when(mockedMetaData).getColumnCount();
+    doReturn(FUNCTION_NAME_COLUMN.getResultSetColumnName()).when(mockedMetaData).getColumnName(1);
+    doReturn(FUNCTION_SCHEMA_COLUMN.getResultSetColumnName()).when(mockedMetaData).getColumnName(2);
+    doReturn(FUNCTION_CATALOG_COLUMN.getResultSetColumnName())
+        .when(mockedMetaData)
+        .getColumnName(3);
+    doReturn(REMARKS_COLUMN.getResultSetColumnName()).when(mockedMetaData).getColumnName(4);
+    doReturn(FUNCTION_TYPE_COLUMN.getResultSetColumnName()).when(mockedMetaData).getColumnName(5);
+    doReturn(SPECIFIC_NAME_COLUMN.getResultSetColumnName()).when(mockedMetaData).getColumnName(6);
+    when(mockedResultSet.getMetaData()).thenReturn(mockedMetaData);
+
+    DatabricksResultSet actualResult =
+        metadataClient.listFunctions(session, null, TEST_SCHEMA, TEST_FUNCTION_PATTERN);
+
+    assertEquals(StatementState.SUCCEEDED, actualResult.getStatementStatus().getState());
+    assertEquals(GET_FUNCTIONS_STATEMENT_ID, actualResult.getStatementId());
+    assertEquals(1, ((DatabricksResultSetMetaData) actualResult.getMetaData()).getTotalRows());
+  }
+
+  @Test
+  void testReturnsEmptyResultSetInCaseOfNullCatalog() throws SQLException {
+    IDatabricksConnectionContext mockContext = mock(IDatabricksConnectionContext.class);
+    when(mockContext.getEnableMultipleCatalogSupport()).thenReturn(true);
+    when(mockClient.getConnectionContext()).thenReturn(mockContext);
+    DatabricksMetadataSdkClient metadataClient = new DatabricksMetadataSdkClient(mockClient);
 
     // listPrimaryKeys with null catalog should return empty ResultSet
     DatabricksResultSet primaryKeysResult =