org.apache.spark.sql.sources.v2.reader.SupportsPushDownRequiredColumns Maven / Gradle / Ivy
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* 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,
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package org.apache.spark.sql.sources.v2.reader;
import org.apache.spark.annotation.InterfaceStability;
import org.apache.spark.sql.types.StructType;
/**
* A mix-in interface for {@link DataSourceReader}. Data source readers can implement this
* interface to push down required columns to the data source and only read these columns during
* scan to reduce the size of the data to be read.
*/
@InterfaceStability.Evolving
public interface SupportsPushDownRequiredColumns extends DataSourceReader {
/**
* Applies column pruning w.r.t. the given requiredSchema.
*
* Implementation should try its best to prune the unnecessary columns or 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.
*
* Note that, data source readers should update {@link DataSourceReader#readSchema()} after
* applying column pruning.
*/
void pruneColumns(StructType requiredSchema);
}