[GitHub] [spark] MaxGekk commented on a change in pull request #31475: [SPARK-34360][SQL] Support truncation of v2 tables

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MaxGekk commented on a change in pull request #31475:
URL: https://github.com/apache/spark/pull/31475#discussion_r573518309



##########
File path: sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/TruncatableTable.java
##########
@@ -0,0 +1,36 @@
+/*
+ * 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 org.apache.spark.annotation.Evolving;
+
+/**
+ * Represents a table which can be atomically truncated.
+ */
+@Evolving
+public interface TruncatableTable extends Table {
+  /**
+   * Truncate a table by removing all rows from the table atomically.
+   * If the table supports partitions, the method removes all existing partitions.

Review comment:
       > Is there a compelling reason to force this behavior?
   
   Yes, I wanted to highlight that it can remove not only all rows but also partitions to align to Spark's v1 (and Hive) `TRUNCATE TABLE` but the command doesn't drop partitions in fact:
   ```sql
   spark-sql> CREATE TABLE tbl (col0 INT) PARTITIONED BY (part INT);
   spark-sql> INSERT INTO tbl PARTITION (part=0) SELECT 0;
   spark-sql> ALTER TABLE tbl ADD PARTITION (part=1);
   spark-sql> SHOW PARTITIONS tbl;
   part=0
   part=1
   spark-sql> SELECT * FROM tbl;
   0	0
   spark-sql> TRUNCATE TABLE tbl;
   spark-sql> SHOW PARTITIONS tbl;
   part=0
   part=1
   spark-sql> SELECT * FROM tbl;
   spark-sql>
   ```
   Let me remove the sentence.




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