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

Class PostingsReader

java.lang.Object

org.apache.cassandra.index.sai.disk.v1.postings.PostingsReader

All Implemented Interfaces:

Closeable, AutoCloseable, OrdinalPostingList, PostingList

@NotThreadSafe
public class PostingsReader
extends Object
implements OrdinalPostingList

Reads, decompresses and decodes postings lists written by PostingsWriter.

Holds exactly one posting block in memory at a time. Does binary search over skip table to find a postings block to load.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	PostingsReader.BlocksSummary

Nested classes/interfaces inherited from interface org.apache.cassandra.index.sai.postings.PostingList

PostingList.EmptyPostingList

Field Summary

Fields inherited from interface org.apache.cassandra.index.sai.postings.PostingList

EMPTY, END_OF_STREAM, OFFSET_NOT_FOUND

Constructor Summary

Constructors

Constructor	Description
PostingsReader(org.apache.lucene.store.IndexInput input, long summaryOffset, QueryEventListener.PostingListEventListener listener)
PostingsReader(org.apache.lucene.store.IndexInput input, PostingsReader.BlocksSummary summary, QueryEventListener.PostingListEventListener listener)

Method Summary

Modifier and Type	Method	Description
long	advance(long targetRowID)	Advances to the first row ID beyond the current that is greater than or equal to the target, and returns that row ID.
void	close()
long	getOrdinal()
long	nextPosting()	Retrieves the next segment row ID, not including row IDs that have been returned by PostingList.advance(long).
long	size()	Returns the upper bound of postings in the list.

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.index.sai.postings.PostingList

maximum, minimum

Constructor Details

PostingsReader

public PostingsReader(org.apache.lucene.store.IndexInput input,
 long summaryOffset,
 QueryEventListener.PostingListEventListener listener)
               throws IOException

Throws:

IOException

PostingsReader

public PostingsReader(org.apache.lucene.store.IndexInput input,
 PostingsReader.BlocksSummary summary,
 QueryEventListener.PostingListEventListener listener)
               throws IOException

Throws:

IOException

Method Details

getOrdinal

public long getOrdinal()

Specified by:

getOrdinal in interface OrdinalPostingList

Returns:

the ordinal of the posting that will be returned on the next call to PostingList.nextPosting()

close

public void close()

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface PostingList

size

public long size()

Description copied from interface: PostingList

Returns the upper bound of postings in the list. During a merge individual postings may be de-duplicated, so we can't return the exact size only the upper bound of the size.

Specified by:

size in interface PostingList

advance

public long advance(long targetRowID)
             throws IOException

Advances to the first row ID beyond the current that is greater than or equal to the target, and returns that row ID. Exhausts the iterator and returns PostingList.END_OF_STREAM if the target is greater than the highest row ID.

Does binary search over the skip table to find the next block to load into memory.

Note: Callers must use the return value of this method before calling nextPosting(), as calling that method will return the next posting, not the one to which we have just advanced.

Specified by:

advance in interface PostingList

Parameters:

targetRowID - target row ID to advance to

Returns:

first segment row ID which is >= the target row ID or PostingList.END_OF_STREAM if one does not exist

Throws:

IOException

nextPosting

public long nextPosting()
                 throws IOException

Description copied from interface: PostingList

Retrieves the next segment row ID, not including row IDs that have been returned by PostingList.advance(long).

Specified by:

nextPosting in interface PostingList

Returns:

next segment row ID

Throws:

IOException