org.apache.cassandra.service.pager

Class SliceQueryPager

java.lang.Object

org.apache.cassandra.service.pager.SliceQueryPager

All Implemented Interfaces:

QueryPager, SinglePartitionPager

public class SliceQueryPager
extends java.lang.Object
implements SinglePartitionPager

Pager over a SliceFromReadCommand.

Field Summary

Fields

Modifier and Type	Field and Description
protected CFMetaData	cfm
protected IDiskAtomFilter	columnFilter

Method Summary

Modifier and Type	Method and Description
ColumnCounter	columnCounter()
protected boolean	containsPreviousLast(Row first) Checks to see if the first row of a new page contains the last row from the previous page.
protected java.util.List<Row>	discardFirst(java.util.List<Row> rows)
java.util.List<Row>	fetchPage(int pageSize) Fetches the next page.
protected Cell	firstNonStaticCell(ColumnFamily cf) Returns the first non-static cell in the ColumnFamily.
boolean	isExhausted() Whether or not this pager is exhausted, i.e.
protected boolean	isReversed()
java.nio.ByteBuffer	key()
protected static Cell	lastCell(ColumnFamily cf)
int	maxRemaining() The maximum number of cells/CQL3 row that we may still have to return.
protected java.util.List<Row>	queryNextPage(int pageSize, ConsistencyLevel consistencyLevel, boolean localQuery)
protected boolean	recordLast(Row last) Saves the paging state by recording the last seen partition key and cell name (where applicable).
protected void	restoreState(int remaining, boolean shouldFetchExtraRow)
PagingState	state() Get the current state of the pager.
long	timestamp()

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.cassandra.service.pager.SinglePartitionPager

columnCounter

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

fetchPage, isExhausted, maxRemaining

Field Detail

cfm

protected final CFMetaData cfm

columnFilter

protected final IDiskAtomFilter columnFilter

Method Detail

key

public java.nio.ByteBuffer key()

Specified by:

key in interface SinglePartitionPager

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.

Specified by:

state in interface QueryPager

Returns:

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

queryNextPage

protected java.util.List<Row> queryNextPage(int pageSize,
                                            ConsistencyLevel consistencyLevel,
                                            boolean localQuery)
                                     throws RequestValidationException,
                                            RequestExecutionException

Throws:

RequestValidationException

RequestExecutionException

containsPreviousLast

protected boolean containsPreviousLast(Row first)

Checks to see if the first row of a new page contains the last row from the previous page.

Parameters:

first - the first row of the new page

Returns:

true if first contains the last from from the previous page and it is live, false otherwise

recordLast

protected boolean recordLast(Row last)

Saves the paging state by recording the last seen partition key and cell name (where applicable).

Parameters:

last - the last row in the current page

Returns:

true if an extra row should be fetched in the next page,false otherwise

isReversed

protected boolean isReversed()

fetchPage

public java.util.List<Row> fetchPage(int pageSize)
                              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.

Returns:

the page of result.

Throws:

RequestValidationException

RequestExecutionException

restoreState

protected void restoreState(int remaining,
                            boolean shouldFetchExtraRow)

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

timestamp

public long timestamp()

columnCounter

public ColumnCounter columnCounter()

discardFirst

protected java.util.List<Row> discardFirst(java.util.List<Row> rows)

firstNonStaticCell

protected Cell firstNonStaticCell(ColumnFamily cf)

Returns the first non-static cell in the ColumnFamily. This is necessary to avoid recording a static column as the "last" cell seen in a reversed query. Because we will always query static columns alongside the normal data for a page, they are not a good indicator of where paging should resume. When we begin the next page, we need to start from the last non-static cell.

lastCell

protected static Cell lastCell(ColumnFamily cf)