org.apache.cassandra.service.pager

Class PartitionRangeQueryPager

java.lang.Object

org.apache.cassandra.service.pager.PartitionRangeQueryPager

All Implemented Interfaces:

QueryPager

public class PartitionRangeQueryPager
extends java.lang.Object

Pages a PartitionRangeReadCommand. Note: this only work for CQL3 queries for now (because thrift queries expect a different limit on the rows than on the columns, which complicates it).

Field Summary

Fields

Modifier and Type	Field and Description
protected ReadCommand	command
protected DataLimits	limits
protected int	protocolVersion

Fields inherited from interface org.apache.cassandra.service.pager.QueryPager

EMPTY

Constructor Summary

Constructors

Constructor and Description
PartitionRangeQueryPager(PartitionRangeReadCommand command, PagingState state, int protocolVersion)

Method Summary

Modifier and Type	Method and Description
ReadExecutionController	executionController() Starts a new read operation.
PartitionIterator	fetchPage(int pageSize, ConsistencyLevel consistency, ClientState clientState) Fetches the next page.
PartitionIterator	fetchPageInternal(int pageSize, ReadExecutionController executionController) Fetches the next page internally (in other, this does a local query).
boolean	isExhausted() Whether or not this pager is exhausted, i.e.
protected boolean	isPreviouslyReturnedPartition(DecoratedKey key)
int	maxRemaining() The maximum number of cells/CQL3 row that we may still have to return.
protected ReadCommand	nextPageReadCommand(int pageSize)
protected void	recordLast(DecoratedKey key, Row last)
protected int	remainingInPartition()
protected void	restoreState(DecoratedKey lastKey, int remaining, int remainingInPartition)
PagingState	state() Get the current state of the pager.

Methods inherited from class java.lang.Object

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

Field Detail

command

protected final ReadCommand command

limits

protected final DataLimits limits

protocolVersion

protected final int protocolVersion

Constructor Detail

PartitionRangeQueryPager

public PartitionRangeQueryPager(PartitionRangeReadCommand command,
                                PagingState state,
                                int protocolVersion)

Method Detail

state

public PagingState state()

Description copied from interface: QueryPager

Get the current state of the pager. The state can allow to restart the paging on another host from where we are at this point.

Returns:

the current paging state. Will return null if paging is at the beginning. If the pager is exhausted, the result is undefined.

nextPageReadCommand

protected ReadCommand nextPageReadCommand(int pageSize)
                                   throws RequestExecutionException

Throws:

RequestExecutionException

recordLast

protected void recordLast(DecoratedKey key,
                          Row last)

isPreviouslyReturnedPartition

protected boolean isPreviouslyReturnedPartition(DecoratedKey key)

executionController

public ReadExecutionController executionController()

Description copied from interface: QueryPager

Starts a new read operation.

This must be called before fetchPageInternal and passed to it to protect the read. The returned object must be closed on all path and it is thus strongly advised to use it in a try-with-ressource construction.

Specified by:

executionController in interface QueryPager

Returns:

a newly started order group for this QueryPager.

fetchPage

public PartitionIterator fetchPage(int pageSize,
                                   ConsistencyLevel consistency,
                                   ClientState clientState)
                            throws RequestValidationException,
                                   RequestExecutionException

Description copied from interface: QueryPager

Fetches the next page.

Specified by:

fetchPage in interface QueryPager

Parameters:

pageSize - the maximum number of elements to return in the next page.

consistency - the consistency level to achieve for the query.

clientState - the ClientState for the query. In practice, this can be null unless consistency is a serial consistency.

Returns:

the page of result.

Throws:

RequestValidationException

RequestExecutionException

fetchPageInternal

public PartitionIterator fetchPageInternal(int pageSize,
                                           ReadExecutionController executionController)
                                    throws RequestValidationException,
                                           RequestExecutionException

Description copied from interface: QueryPager

Fetches the next page internally (in other, this does a local query).

Specified by:

fetchPageInternal in interface QueryPager

Parameters:

pageSize - the maximum number of elements to return in the next page.

executionController - the ReadExecutionController protecting the read.

Returns:

the page of result.

Throws:

RequestValidationException

RequestExecutionException

restoreState

protected void restoreState(DecoratedKey lastKey,
                            int remaining,
                            int remainingInPartition)

isExhausted

public boolean isExhausted()

Description copied from interface: QueryPager

Whether or not this pager is exhausted, i.e. whether or not a call to fetchPage may return more result.

Specified by:

isExhausted in interface QueryPager

Returns:

whether the pager is exhausted.

maxRemaining

public int maxRemaining()

Description copied from interface: QueryPager

The maximum number of cells/CQL3 row that we may still have to return. In other words, that's the initial user limit minus what we've already returned (note that it's not how many we *will* return, just the upper limit on it).

Specified by:

maxRemaining in interface QueryPager

remainingInPartition

protected int remainingInPartition()