Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/19136#discussion_r138623586
--- Diff:
sql/core/src/main/java/org/apache/spark/sql/sources/v2/reader/downward/ColumnPruningSupport.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.sources.v2.reader.downward;
+
+import org.apache.spark.sql.types.StructType;
+
+/**
+ * A mix-in interface for `DataSourceV2Reader`. Users can implement this
interface to only read the
+ * required columns/nested fields during scan.
+ */
+public interface ColumnPruningSupport {
+
+ /**
+ * Apply column pruning w.r.t. the given requiredSchema.
+ *
+ * Implementation should try its best to prune the unnecessary
columns/nested fields, but it's
+ * also OK to do the pruning partially, e.g., a data source may not be
able to prune nested
+ * fields, and only prune top-level columns.
+ */
+ void pruneColumns(StructType requiredSchema);
--- End diff --
link this to readSchema function
---
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
