[GitHub] [spark] LuciferYang commented on a diff in pull request #40438: [SPARK-42806][CONNECT] Add `Catalog` support

["LuciferYang (via GitHub)" <gi...@apache.org>]

LuciferYang commented on code in PR #40438:
URL: https://github.com/apache/spark/pull/40438#discussion_r1138499467


##########
connector/connect/client/jvm/src/main/scala/org/apache/spark/sql/SparkSession.scala:
##########
@@ -272,6 +274,14 @@ class SparkSession private[sql] (
    */
   def read: DataFrameReader = new DataFrameReader(this)
 
+  /**
+   * Interface through which the user may create, drop, alter or query underlying databases,
+   * tables, functions etc.
+   *
+   * @since 3.4.0

Review Comment:
   ok



##########
connector/connect/client/jvm/src/main/scala/org/apache/spark/sql/internal/CatalogImpl.scala:
##########
@@ -0,0 +1,679 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.internal
+
+import org.apache.spark.sql.{AnalysisException, DataFrame, Dataset, SparkSession}
+import org.apache.spark.sql.catalog.{Catalog, CatalogMetadata, Column, Database, Function, Table}
+import org.apache.spark.sql.catalyst.ScalaReflection
+import org.apache.spark.sql.catalyst.encoders.AgnosticEncoder
+import org.apache.spark.sql.catalyst.encoders.AgnosticEncoders.{PrimitiveBooleanEncoder, StringEncoder}
+import org.apache.spark.sql.connect.common.DataTypeProtoConverter
+import org.apache.spark.sql.types.StructType
+
+class CatalogImpl(sparkSession: SparkSession) extends Catalog {
+
+  /**
+   * Returns the current default database in this session.
+   *
+   * @since 3.4.0
+   */
+  override def currentDatabase: String =
+    sparkSession
+      .newDataset(StringEncoder) { builder =>
+        builder.getCatalogBuilder.getCurrentDatabaseBuilder
+      }
+      .head()
+
+  /**
+   * Sets the current database (namespace) in this session.
+   *
+   * @since 3.4.0
+   */
+  @throws[AnalysisException]("database does not exist")
+  override def setCurrentDatabase(dbName: String): Unit = {

Review Comment:
   2. There are many `Unit` return type function, Is there a better way to trigger compute except `.count()` or `.collect()`
   
   



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