[GitHub] [spark] xkrogen commented on a diff in pull request #37556: [SPARK-39799][SQL] DataSourceV2: View catalog interface

[GitBox <gi...@apache.org>]

xkrogen commented on code in PR #37556:
URL: https://github.com/apache/spark/pull/37556#discussion_r1014502881


##########
sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/View.java:
##########
@@ -0,0 +1,69 @@
+/*
+ * 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.connector.catalog;
+
+import java.util.Map;
+
+import org.apache.spark.annotation.DeveloperApi;
+import org.apache.spark.sql.types.StructType;
+
+/**
+ * An interface representing a persisted view.
+ */
+@DeveloperApi
+public interface View {
+  /**
+   * A name to identify this view.
+   */
+  String name();
+
+  /**
+   * The view query SQL text.
+   */
+  String sql();
+
+  /**
+   * The current catalog when the view is created.
+   */
+  String currentCatalog();
+
+  /**
+   * The current namespace when the view is created.
+   */
+  String[] currentNamespace();
+
+  /**
+   * The schema for the SQL text when the view is created.
+   */
+  StructType schema();
+
+  /**
+   * The view column aliases.
+   */
+  String[] columnAliases();
+

Review Comment:
   @jzhuge is the intent that `schema()` contains the _pre-alias_ schema and `columnAliases()` contains the list of aliases, such that you need to combine `schema() + columnAliases()` to get the _post-alias_ schema? This is in contrast to how V1 views work, where `CatalogTable.schema()` contains the _post-alias_ schema and `viewQueryColumnNames` contains the original column names. The plan is constructed by aliasing from the `viewQueryColumnNames` to the names stored in `schema` (see [this code in SessionCatalog](https://github.com/apache/spark/blob/933dc0c42f0caf74aaa077fd4f2c2e7208452b9b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/SessionCatalog.scala#L949-L985)).
   
   I don't have a strong opinion about whether it makes more sense for `schema()` to be pre- or post-aliasing, but we need to make this very clear in the interface description. If we go with pre-aliasing, we can convert it to post-alias inside of [V2ViewDescription](https://github.com/apache/spark/pull/28147/files#diff-d0c6f499b30df039d13bf2740c559251ab63ba4cea312e622e23b74fcbb2fcf0) to make it match V1 in the analyzer, reducing implementation complexity by avoiding having to special-case V1 vs V2.



-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org


---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org
For additional commands, e-mail: reviews-help@spark.apache.org