Github user rdblue commented on a diff in the pull request:
https://github.com/apache/spark/pull/23086#discussion_r236820896
--- Diff:
sql/core/src/main/java/org/apache/spark/sql/sources/v2/reader/Batch.java ---
@@ -0,0 +1,47 @@
+/*
+ * 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.reader;
+
+import org.apache.spark.annotation.Evolving;
+
+/**
+ * A physical representation of a data source scan for batch queries. This
interface is used to
+ * provide physical information, like how many partitions the scanned data
has, and how to read
+ * records from the partitions.
+ */
+@Evolving
+public interface Batch {
+
+ /**
+ * Returns a list of {@link InputPartition input partitions}. Each
{@link InputPartition}
+ * represents a data split that can be processed by one Spark task. The
number of input
+ * partitions returned here is the same as the number of RDD partitions
this scan outputs.
+ *
+ * Note that, this may not be a full scan if the data source supports
optimization like filter
+ * push-down. Implementations should check the status of {@link Scan}
that creates this batch,
+ * and adjust the resulting {@link InputPartition input partitions}.
--- End diff --
I think this is a little unclear. Implementations do not necessarily check
the scan. This Batch is likely configured with a filter and is responsible for
creating splits for that filter.
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