Github user rdblue commented on a diff in the pull request:
https://github.com/apache/spark/pull/21308#discussion_r189730152
--- Diff:
sql/core/src/main/java/org/apache/spark/sql/sources/v2/DeleteSupport.java ---
@@ -0,0 +1,51 @@
+/*
+ * 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.sources.v2;
+
+import org.apache.spark.sql.catalyst.expressions.Expression;
+
+/**
+ * A mix-in interface for {@link DataSourceV2} delete support. Data
sources can implement this
+ * interface to provide the ability to delete data from tables that
matches filter expressions.
+ * <p>
+ * Data sources must implement this interface to support logical
operations that combine writing
+ * data with deleting data, like overwriting partitions.
+ */
+public interface DeleteSupport extends DataSourceV2 {
+ /**
+ * Delete data from a data source table that matches filter expressions.
+ * <p>
+ * Rows are deleted from the data source iff all of the filter
expressions match. That is, the
+ * expressions must be interpreted as a set of filters that are ANDed
together.
+ * <p>
+ * Implementations may reject a delete operation if the delete isn't
possible without significant
+ * effort. For example, partitioned data sources may reject deletes that
do not filter by
+ * partition columns because the filter may require rewriting files
without deleted records.
+ * To reject a delete implementations should throw {@link
IllegalArgumentException} with a clear
+ * error message that identifies which expression was rejected.
+ * <p>
+ * Implementations may throw {@link UnsupportedOperationException} if
the delete operation is not
+ * supported because one of the filter expressions is not supported.
Implementations should throw
+ * this exception with a clear error message that identifies the
unsupported expression.
+ *
+ * @param filters filter expressions, used to select rows to delete when
all expressions match
+ * @throws UnsupportedOperationException If one or more filter
expressions is not supported
+ * @throws IllegalArgumentException If the delete is rejected due to
required effort
+ */
+ void deleteWhere(Expression[] filters);
--- End diff --
Yes, this is a driver-side operation. That's why the source can reject the
delete. Anything that requires a parallel operation should really be
implemented as read, filter, and replace data.
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