Package org.apache.drill.exec.physical.impl.scan.framework

Class SchemaNegotiatorImpl

java.lang.Object

org.apache.drill.exec.physical.impl.scan.framework.SchemaNegotiatorImpl

All Implemented Interfaces:

SchemaNegotiator

Direct Known Subclasses:

FileScanFramework.FileSchemaNegotiatorImpl

public class SchemaNegotiatorImpl
extends Object
implements SchemaNegotiator

Implementation of the schema negotiation between scan operator and batch reader. Anticipates that the select list (and/or the list of predefined fields (implicit, partition) might be set by the scanner. For now, all readers have their own implementation of the select set.

Handles both early- and late-schema readers. Early-schema readers provide a table schema, late-schema readers do not.

If the reader (or, later, the scanner) has a SELECT list, then that select list is pushed down into the result set loader created for the reader.

Also handles parsing out various column types, filling in null columns and (via the vector cache), minimizing changes across readers. In the worst case, a reader might have a column "c" in one file, might skip "c" in the second file, and "c" may appear again in a third file. This negotiator, along with the scan projection and vector cache, "smoothes out" schema changes by preserving the vector for "c" across all three files. In the first and third files "c" is a vector written by the reader, in the second, it is a null column filled in by the scan projector (assuming, of course, that "c" is nullable or an array.)

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	SchemaNegotiatorImpl.NegotiatorListener

Field Summary

Fields

Modifier and Type	Field	Description
protected int	batchSize
protected CustomErrorContext	context
protected final ManagedScanFramework	framework
protected boolean	isSchemaComplete
protected long	limit
protected TupleMetadata	providedSchema
protected TupleMetadata	tableSchema

Constructor Summary

Constructors

Constructor	Description
SchemaNegotiatorImpl(ManagedScanFramework framework)

Method Summary

Modifier and Type	Method	Description
void	batchSize(int maxRecordsPerBatch)	Set the preferred batch size (which may be overridden by the result set loader in order to limit vector or batch size.)
void	bind(SchemaNegotiatorImpl.NegotiatorListener listener)
ResultSetLoader	build()	Callback from the schema negotiator to build the schema from information from both the table and scan operator.
OperatorContext	context()
com.typesafe.config.Config	drillConfig()
CustomErrorContext	errorContext()
boolean	hasProvidedSchema()	Report if the execution plan defines a provided schema.
boolean	isProjectionEmpty()	Report whether the projection list is empty, as occurs in two cases: SELECT COUNT(*) ... -- empty project. SELECT a, b FROM table(c d) -- disjoint project.
boolean	isSchemaComplete()
void	limit(long limit)	Push down a LIMIT into the scan.
CustomErrorContext	parentErrorContext()	The context to use as a parent when creating a custom context.
TupleMetadata	providedSchema()	Returns the provided schema, if defined.
OptionSet	queryOptions()
void	setErrorContext(CustomErrorContext context)	Specify an advanced error context which allows the reader to fill in custom context values.
void	tableSchema(TupleMetadata schema, boolean isComplete)	Specify the table schema if this is an early-schema reader.
String	userName()	Name of the user running the query.

Methods inherited from class java.lang.Object

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

Field Details

framework

protected final ManagedScanFramework framework

context

protected CustomErrorContext context

providedSchema

protected TupleMetadata providedSchema

tableSchema

protected TupleMetadata tableSchema

isSchemaComplete

protected boolean isSchemaComplete

batchSize

protected int batchSize

limit

protected long limit

Constructor Details

SchemaNegotiatorImpl

public SchemaNegotiatorImpl(ManagedScanFramework framework)

Method Details

bind

public void bind(SchemaNegotiatorImpl.NegotiatorListener listener)

isProjectionEmpty

public boolean isProjectionEmpty()

Description copied from interface: SchemaNegotiator

Report whether the projection list is empty, as occurs in two cases:

• SELECT COUNT(*) ... -- empty project.

SELECT a, b FROM table(c d) -- disjoint project.