org.apache.lens.server.api.driver

Class PartiallyFetchedInMemoryResultSet

java.lang.Object

org.apache.lens.server.api.driver.LensResultSet

org.apache.lens.server.api.driver.InMemoryResultSet

org.apache.lens.server.api.driver.PartiallyFetchedInMemoryResultSet

public class PartiallyFetchedInMemoryResultSet
extends InMemoryResultSet

This is a wrapper over InMemoryResultSet which pre-fetches requested number of rows in memory. All calls are delegated to the underlying InMemoryResultSet except for the calls that access pre-fetched rows. This wrapper was created to support partial streaming of big result sets and complete streaming of SMALL result sets along with persistence. The pre-fetched result available via getPreFetchedRows() can be used for streaming while the persistence logic can iterate over complete result set using hasNext() and next(). Note Streaming and persistence can occur concurrently irrespective of the underlying InMemoryResultSet implementation. Streaming of partial results is not supported at server level as of now.

Constructor Summary

Constructors

Constructor and Description
PartiallyFetchedInMemoryResultSet(InMemoryResultSet inMemoryRS, int reqPreFetchSize) Constructor

Method Summary

Modifier and Type	Method and Description
boolean	canBePurged()
LensResultSetMetadata	getMetadata() Get the result set metadata
List<ResultRow>	getPreFetchedRows()
boolean	hasNext() Whether there is another result row available.
boolean	isComplteleyFetched() Indicates whether the underlying in-memory result has been completely pre-fetched and kept in memory.
ResultRow	next() Read the next result row.
void	setFetchSize(int size) Set number of rows to be fetched at time
void	setFullyAccessed(boolean fullyAccessed)
Integer	size() Get the size of the result set.

Methods inherited from class org.apache.lens.server.api.driver.InMemoryResultSet

getCreationTime, getOutputPath, isHttpResultAvailable, toQueryResult

Methods inherited from class java.lang.Object

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

Constructor Detail

PartiallyFetchedInMemoryResultSet

public PartiallyFetchedInMemoryResultSet(InMemoryResultSet inMemoryRS,
                                         int reqPreFetchSize)
                                  throws LensException

Constructor

Parameters:

inMemoryRS - : Underlying in-memory result set

reqPreFetchSize - : requested number of rows to be pre-fetched and cached.

Throws:

LensException

Method Detail

hasNext

public boolean hasNext()
                throws LensException

Description copied from class: InMemoryResultSet

Whether there is another result row available.

Specified by:

hasNext in class InMemoryResultSet

Returns:

true if next row if available, false otherwise

Throws:

LensException - the lens exception

next

public ResultRow next()
               throws LensException

Description copied from class: InMemoryResultSet

Read the next result row.

Specified by:

next in class InMemoryResultSet

Returns:

The row as list of object

Throws:

LensException - the lens exception

setFetchSize

public void setFetchSize(int size)
                  throws LensException

Description copied from class: InMemoryResultSet

Set number of rows to be fetched at time

Specified by:

setFetchSize in class InMemoryResultSet

Throws:

LensException

size

public Integer size()
             throws LensException

Description copied from class: LensResultSet

Get the size of the result set.

Specified by:

size in class LensResultSet

Returns:

The size if available, -1 if not available.

Throws:

LensException - the lens exception

getMetadata

public LensResultSetMetadata getMetadata()
                                  throws LensException

Description copied from class: LensResultSet

Get the result set metadata

Specified by:

getMetadata in class LensResultSet

Returns:

Returns LensResultSetMetadata

Throws:

LensException

canBePurged

public boolean canBePurged()

Overrides:

canBePurged in class InMemoryResultSet

Returns:

true if the result can be purged

setFullyAccessed

public void setFullyAccessed(boolean fullyAccessed)

Overrides:

setFullyAccessed in class InMemoryResultSet

getPreFetchedRows

public List<ResultRow> getPreFetchedRows()

isComplteleyFetched

@Generated(value="lombok")
public boolean isComplteleyFetched()

Indicates whether the underlying in-memory result has been completely pre-fetched and kept in memory.