Github user rdblue commented on a diff in the pull request:
https://github.com/apache/spark/pull/22009#discussion_r208343665
--- Diff:
sql/core/src/main/java/org/apache/spark/sql/sources/v2/reader/ReadSupport.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.reader;
+
+import org.apache.spark.annotation.InterfaceStability;
+import org.apache.spark.sql.types.StructType;
+
+/**
+ * The base interface for all the batch and streaming read supports. Data
sources should implement
+ * concrete read support interfaces like {@link BatchReadSupport}.
+ */
[email protected]
+public interface ReadSupport {
+
+ /**
+ * Returns the full schema of this data source, which is usually the
physical schema of the
+ * underlying storage. This full schema should not be affected by column
pruning or other
+ * optimizations.
+ *
+ * If this method fails (by throwing an exception), the action will fail
and no Spark job will be
+ * submitted.
+ */
+ StructType fullSchema();
+
+ /**
+ * Returns a list of {@link InputPartition}s. 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 input {@link ScanConfig}
and adjust the resulting
+ * {@link InputPartition}s.
+ *
+ * If this method fails (by throwing an exception), the action will fail
and no Spark job will be
+ * submitted.
+ */
+ InputPartition[] planInputPartitions(ScanConfig config);
+
+ /**
+ * Returns a factory to produce {@link PartitionReader}s for {@link
InputPartition}s.
--- End diff --
Minor: Adding 's' after a link isn't good Javadoc style.
For cases like this, it is better to use the singular for both classes to
communicate the expectation that each `InputPartition` produces a single
`PartitionReader`.
For cases where you don't need to communicate a one-to-one relationship,
you can use `{@link InputPartition partitions}` to change the link text.
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