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

Class KeyStoreWriter

java.lang.Object

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

All Implemented Interfaces:

Closeable, AutoCloseable

@NotThreadSafe
public class KeyStoreWriter
extends Object
implements Closeable

Writes a sequence of partition keys or clustering keys for use with KeyLookup.

Partition keys are written unordered and clustering keys are written in ordered partitions determined by calls to startPartition(). In either case keys can be of varying lengths.

The blockShift field is used to quickly determine the id of the current block based on a point id or to check if we are exactly at the beginning of the block.

Keys are organized in blocks of (2 ^ blockShift) keys.

The blocks should not be too small because they allow prefix compression of the keys except the first key in a block.

The blocks should not be too large because we can't just randomly jump to the key inside the block, but we have to iterate through all the keys from the start of the block.

See Also:

• KeyLookup

Constructor Summary

Constructors

Constructor	Description
KeyStoreWriter(String componentName, MetadataWriter metadataWriter, org.apache.lucene.store.IndexOutput keysOutput, NumericValuesWriter keysBlockOffsets, int blockShift, boolean clustering)	Creates a new writer.

Method Summary

Modifier and Type	Method	Description
void	add(ByteComparable key)	Appends a key at the end of the sequence.
void	close()	Flushes any in-memory buffers to the output streams.
void	startPartition()

Methods inherited from class java.lang.Object

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

Constructor Details

KeyStoreWriter

public KeyStoreWriter(String componentName,
 MetadataWriter metadataWriter,
 org.apache.lucene.store.IndexOutput keysOutput,
 NumericValuesWriter keysBlockOffsets,
 int blockShift,
 boolean clustering)
               throws IOException

Creates a new writer.

It does not own the components, so you must close the components by yourself after you're done with the writer.

Parameters:

componentName - the component name for the KeyLookupMeta

metadataWriter - the MetadataWriter for storing the KeyLookupMeta

keysOutput - where to write the prefix-compressed keys

keysBlockOffsets - where to write the offsets of each block of keys

blockShift - the block shift that is used to determine the block size

clustering - determines whether the keys will be written as ordered partitions

Throws:

IOException

Method Details

startPartition

public void startPartition()

add

public void add(@Nonnull
 ByteComparable key)
         throws IOException

Appends a key at the end of the sequence.

Throws:

IOException - if write to disk fails

IllegalArgumentException - if the key is not greater than the previous added key

close

public void close()
           throws IOException

Flushes any in-memory buffers to the output streams. Does not close the output streams. No more writes are allowed.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException