[KYUUBI #1643][FOLLOWUP] Fix Flink GetFunctions result schema

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### _Why are the changes needed?_
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  1. If you add a feature, you can talk about the use case of it.
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Implement GetFunctions operation.

### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible

- [ ] Add screenshots for manual tests if appropriate

- [x] [Run test](https://kyuubi.readthedocs.io/en/latest/develop_tools/testing.html#running-tests) locally before make a pull request

Closes #1773 from SteNicholas/KYUUBI-1643.

Closes #1643

498c7f9 [SteNicholas] [KYUUBI #1643] Implement GetFunctions operation

Authored-by: SteNicholas <programgeek@163.com>
Signed-off-by: Cheng Pan <chengpan@apache.org>

externals/kyuubi-flink-sql-engine/src/main/scala/org/apache/kyuubi/engine/flink/operation/GetFunctions.scala

@@ -17,6 +17,8 @@
 
 package org.apache.kyuubi.engine.flink.operation
 
+import java.sql.DatabaseMetaData
+
 import scala.collection.JavaConverters._
 
 import org.apache.commons.lang3.StringUtils
@@ -45,22 +47,35 @@ class GetFunctions(
       val systemFunctions = filterPattern(
         tableEnv.listFunctions().diff(tableEnv.listUserDefinedFunctions()),
         functionPattern)
-        .map { f => Row.of(null, null, f) }
+        .map { f =>
+          Row.of(null, null, f, null, Integer.valueOf(DatabaseMetaData.functionResultUnknown), null)
+        }
       val catalogFunctions = tableEnv.listCatalogs()
         .filter { c => StringUtils.isEmpty(catalogName) || c == catalogName }
         .flatMap { c =>
           val catalog = tableEnv.getCatalog(c).get()
           filterPattern(catalog.listDatabases().asScala, schemaPattern)
             .flatMap { d =>
               filterPattern(catalog.listFunctions(d).asScala, functionPattern)
-                .map { f => Row.of(c, d, f) }
+                .map { f =>
+                  Row.of(
+                    c,
+                    d,
+                    f,
+                    null,
+                    Integer.valueOf(DatabaseMetaData.functionResultUnknown),
+                    null)
+                }
             }
         }
       resultSet = ResultSet.builder.resultKind(ResultKind.SUCCESS_WITH_CONTENT)
         .columns(
           Column.physical(FUNCTION_CAT, DataTypes.STRING()),
           Column.physical(FUNCTION_SCHEM, DataTypes.STRING()),
-          Column.physical(FUNCTION_NAME, DataTypes.STRING()))
+          Column.physical(FUNCTION_NAME, DataTypes.STRING()),
+          Column.physical(REMARKS, DataTypes.STRING()),
+          Column.physical(FUNCTION_TYPE, DataTypes.INT()),
+          Column.physical(SPECIFIC_NAME, DataTypes.STRING()))
         .data(systemFunctions ++: catalogFunctions)
         .build
     } catch {

externals/kyuubi-flink-sql-engine/src/test/scala/org/apache/kyuubi/engine/flink/operation/FlinkOperationSuite.scala

@@ -17,6 +17,8 @@
 
 package org.apache.kyuubi.engine.flink.operation
 
+import java.sql.DatabaseMetaData
+
 import org.apache.flink.table.api.EnvironmentSettings.DEFAULT_BUILTIN_CATALOG
 import org.apache.flink.table.api.EnvironmentSettings.DEFAULT_BUILTIN_DATABASE
 import org.apache.flink.table.types.logical.LogicalTypeRoot
@@ -330,14 +332,14 @@ class FlinkOperationSuite extends WithFlinkSQLEngine with HiveJDBCTestHelper {
       val metaData = statement.getConnection.getMetaData
       var resultSet = metaData.getSchemas(null, null)
       while (resultSet.next()) {
-        assert(resultSet.getString(TABLE_SCHEM) == DEFAULT_BUILTIN_DATABASE)
+        assert(resultSet.getString(TABLE_SCHEM) === DEFAULT_BUILTIN_DATABASE)
         assert(resultSet.getString(TABLE_CATALOG) === DEFAULT_BUILTIN_CATALOG)
       }
       resultSet = metaData.getSchemas(
         DEFAULT_BUILTIN_CATALOG.split("_").apply(0),
         DEFAULT_BUILTIN_DATABASE.split("_").apply(0))
       while (resultSet.next()) {
-        assert(resultSet.getString(TABLE_SCHEM) == DEFAULT_BUILTIN_DATABASE)
+        assert(resultSet.getString(TABLE_SCHEM) === DEFAULT_BUILTIN_DATABASE)
         assert(resultSet.getString(TABLE_CATALOG) === DEFAULT_BUILTIN_CATALOG)
       }
     }
@@ -412,26 +414,28 @@ class FlinkOperationSuite extends WithFlinkSQLEngine with HiveJDBCTestHelper {
       val metaData = statement.getConnection.getMetaData
       Seq("currentTimestamp", "currentDate", "currentTime", "localTimestamp", "localTime")
         .foreach { func =>
-          Seq(metaData.getFunctions _).foreach { apiFunc =>
-            val resultSet = apiFunc(null, null, func)
-            while (resultSet.next()) {
-              assert(resultSet.getString(FUNCTION_CAT) == null)
-              assert(resultSet.getString(FUNCTION_SCHEM) === null)
-              assert(resultSet.getString(FUNCTION_NAME) === func)
-            }
+          val resultSet = metaData.getFunctions(null, null, func)
+          while (resultSet.next()) {
+            assert(resultSet.getString(FUNCTION_CAT) === null)
+            assert(resultSet.getString(FUNCTION_SCHEM) === null)
+            assert(resultSet.getString(FUNCTION_NAME) === func)
+            assert(resultSet.getString(REMARKS) === null)
+            assert(resultSet.getInt(FUNCTION_TYPE) === DatabaseMetaData.functionResultUnknown)
+            assert(resultSet.getString(SPECIFIC_NAME) === null)
           }
         }
       val expected =
         List("currentTimestamp", "currentDate", "currentTime", "localTimestamp", "localTime")
       Seq("current", "local")
         .foreach { funcPattern =>
-          Seq(metaData.getFunctions _).foreach { apiFunc =>
-            val resultSet = apiFunc(null, null, funcPattern)
-            while (resultSet.next()) {
-              assert(resultSet.getString(FUNCTION_CAT) == null)
-              assert(resultSet.getString(FUNCTION_SCHEM) === null)
-              assert(expected.contains(resultSet.getString(FUNCTION_NAME)))
-            }
+          val resultSet = metaData.getFunctions(null, null, funcPattern)
+          while (resultSet.next()) {
+            assert(resultSet.getString(FUNCTION_CAT) === null)
+            assert(resultSet.getString(FUNCTION_SCHEM) === null)
+            assert(expected.contains(resultSet.getString(FUNCTION_NAME)))
+            assert(resultSet.getString(REMARKS) === null)
+            assert(resultSet.getString(FUNCTION_TYPE) === DatabaseMetaData.functionResultUnknown)
+            assert(resultSet.getString(SPECIFIC_NAME) === null)
           }
         }
     }