Package org.apache.cassandra.index.sai.disk.v1.keystore

Class KeyLookup.Cursor

java.lang.Object

org.apache.cassandra.index.sai.disk.v1.keystore.KeyLookup.Cursor

All Implemented Interfaces:

AutoCloseable

Enclosing class:

KeyLookup

@NotThreadSafe
public class KeyLookup.Cursor
extends Object
implements AutoCloseable

Allows reading the keys from the keys file. Can quickly seek to a random key by point id.

This object is stateful and not thread safe. It maintains a position to the current key as well as a buffer that can hold one key.

Method Summary

Modifier and Type	Method	Description
void	close()
long	clusteredSeekToKey(ByteComparable key, long startingPointId, long endingPointId)	Finds the pointId for a clustering key within a range of pointIds.
void	reset()
ByteSource	seekToPointId(long pointId)	Positions the cursor on the target point id and reads the key at the target to the current key buffer.

Methods inherited from class java.lang.Object

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

Method Details

seekToPointId

@Nonnull
public ByteSource seekToPointId(long pointId)

Positions the cursor on the target point id and reads the key at the target to the current key buffer.

It is allowed to position the cursor before the first item or after the last item; in these cases the internal buffer is cleared.

Parameters:

pointId - point id to lookup

Returns:

The ByteSource containing the key

Throws:

IndexOutOfBoundsException - if the target point id is less than -1 or greater than the number of keys

clusteredSeekToKey

public long clusteredSeekToKey(ByteComparable key,
 long startingPointId,
 long endingPointId)

Finds the pointId for a clustering key within a range of pointIds. The start and end of the range must not exceed the number of keys available. The keys within the range are expected to be in lexographical order.

If the key is not in the block containing the start of the range a binary search is done to find the block containing the search key. That block is then searched to return the pointId that corresponds to the key that is either equal to or next highest to the search key.

Parameters:

key - The key to seek for with the partition

startingPointId - the inclusive starting point for the partition

endingPointId - the exclusive ending point for the partition. Note: this can be equal to the number of keys if this is the last partition

Returns:

a long representing the pointId of the key that is >= to the key passed to the method, or -1 if the key passed is > all the keys.

reset

public void reset()
           throws IOException

Throws:

IOException

close

public void close()

Specified by:

close in interface AutoCloseable