Github user rdblue commented on a diff in the pull request:
https://github.com/apache/spark/pull/22190#discussion_r212119716
--- Diff:
sql/core/src/main/java/org/apache/spark/sql/sources/v2/writer/BatchOverwriteSupport.java
---
@@ -0,0 +1,61 @@
+/*
+ * 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.writer;
+
+import org.apache.spark.sql.catalyst.plans.logical.Filter;
+import org.apache.spark.sql.sources.v2.DataSourceOptions;
+import org.apache.spark.sql.types.StructType;
+
+/**
+ * An interface that adds support to {@link BatchWriteSupport} for a
replace data operation that
+ * replaces a subset of the output table with the output of a write
operation. The subset removed is
+ * determined by a set of filter expressions.
+ * <p>
+ * Data source implementations can implement this interface in addition to
{@link BatchWriteSupport}
+ * to support idempotent write operations that replace data matched by a
set of delete filters with
+ * the result of the write operation.
+ * <p>
+ * This is used to build idempotent writes. For example, a query that
produces a daily summary
+ * may be run several times as new data arrives. Each run should replace
the output of the last
+ * run for a particular day in the partitioned output table. Such a job
would write using this
+ * WriteSupport and would pass a filter matching the previous job's
output, like
+ * <code>$"day" === '2018-08-22'</code>, to remove that data and commit
the replacement data at
+ * the same time.
+ */
+public interface BatchOverwriteSupport extends BatchWriteSupport {
--- End diff --
This class will be used to create the `WriteConfig` for idempotent
overwrite operations. This would be triggered by an overwrite like this (the
API could be different).
```
df.writeTo("table").overwrite($"day" === "2018-08-22")
```
That would produce a `OverwriteData(source, deleteFilter, query)` logical
plan, which would result in the exec node calling this to create the write
config.
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