org.apache.drill.exec.physical.impl.scan.project

Class ExplicitSchemaProjection

java.lang.Object

org.apache.drill.exec.physical.impl.scan.project.ReaderLevelProjection

org.apache.drill.exec.physical.impl.scan.project.ExplicitSchemaProjection

public class ExplicitSchemaProjection
extends ReaderLevelProjection

Perform a schema projection for the case of an explicit list of projected columns. Example: SELECT a, b, c.

An explicit projection starts with the requested set of columns, then looks in the table schema to find matches. That is, it is driven by the query itself.

An explicit projection may include columns that do not exist in the source schema. In this case, we fill in null columns for unmatched projections.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.drill.exec.physical.impl.scan.project.ReaderLevelProjection

ReaderLevelProjection.ReaderProjectionResolver

Field Summary

Fields inherited from class org.apache.drill.exec.physical.impl.scan.project.ReaderLevelProjection

resolvers

Constructor Summary

Constructors

Constructor and Description
ExplicitSchemaProjection(ScanLevelProjection scanProj, TupleMetadata readerSchema, ResolvedTuple rootTuple, List<ReaderLevelProjection.ReaderProjectionResolver> resolvers)

Method Summary

Methods inherited from class org.apache.drill.exec.physical.impl.scan.project.ReaderLevelProjection

resolveSpecial

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ExplicitSchemaProjection

public ExplicitSchemaProjection(ScanLevelProjection scanProj,
                                TupleMetadata readerSchema,
                                ResolvedTuple rootTuple,
                                List<ReaderLevelProjection.ReaderProjectionResolver> resolvers)