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

Class BaseScanOperatorExecTest.MockEarlySchemaReader

java.lang.Object

org.apache.drill.exec.physical.impl.scan.BaseScanOperatorExecTest.BaseMockBatchReader

org.apache.drill.exec.physical.impl.scan.BaseScanOperatorExecTest.MockEarlySchemaReader

All Implemented Interfaces:

ManagedReader<SchemaNegotiator>

Enclosing class:

BaseScanOperatorExecTest

protected static class BaseScanOperatorExecTest.MockEarlySchemaReader
extends BaseScanOperatorExecTest.BaseMockBatchReader

Mock reader that pretends to have a schema at open time like an HBase or JDBC reader.

Field Summary

Fields inherited from class org.apache.drill.exec.physical.impl.scan.BaseScanOperatorExecTest.BaseMockBatchReader

batchCount, batchLimit, closeCalled, openCalled, startIndex, tableLoader

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	MockEarlySchemaReader()

Method Summary

Modifier and Type	Method and Description
boolean	next() Read the next batch.
boolean	open(SchemaNegotiator schemaNegotiator) Setup the record reader.

Methods inherited from class org.apache.drill.exec.physical.impl.scan.BaseScanOperatorExecTest.BaseMockBatchReader

close, makeBatch, writeRow

Methods inherited from class java.lang.Object

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

Constructor Detail

MockEarlySchemaReader

protected MockEarlySchemaReader()

Method Detail

open

public boolean open(SchemaNegotiator schemaNegotiator)

Description copied from interface: ManagedReader

Setup the record reader. Called just before the first call to next(). Allocate resources here, not in the constructor. Example: open files, allocate buffers, etc.

Parameters:

schemaNegotiator - mechanism to negotiate select and table schemas, then create the row set reader used to load data into value vectors

Returns:

true if the reader is open and ready to read (possibly no) rows. false for a "soft" failure in which no schema or data is available, but the scanner should not fail, it should move onto another reader

next

public boolean next()

Description copied from interface: ManagedReader

Read the next batch. Reading continues until either EOF, or until the mutator indicates that the batch is full. The batch is considered valid if it is non-empty. Returning true with an empty batch is valid, and is helpful on the very first batch (returning schema only.) An empty batch with a false return code indicates EOF and the batch will be discarded. A non-empty batch along with a false return result indicates a final, valid batch, but that EOF was reached and no more data is available.

This somewhat complex protocol avoids the need to allocate a final batch just to find out that no more data is available; it allows EOF to be returned along with the final batch.

Returns:

true if more data may be available (and so next() should be called again, false to indicate that EOF was reached