Package org.apache.druid.segment.loading

Class SegmentLocalCacheLoader

java.lang.Object

org.apache.druid.segment.loading.SegmentLocalCacheLoader

All Implemented Interfaces:

SegmentLoader

public class SegmentLocalCacheLoader
extends Object
implements SegmentLoader

Constructor Summary

Constructors

Constructor	Description
SegmentLocalCacheLoader(SegmentCacheManager cacheManager, org.apache.druid.segment.IndexIO indexIO, com.fasterxml.jackson.databind.ObjectMapper mapper)

Method Summary

Modifier and Type	Method	Description
void	cleanup(org.apache.druid.timeline.DataSegment segment)	cleanup any state used by this segment
org.apache.druid.segment.ReferenceCountingSegment	getSegment(org.apache.druid.timeline.DataSegment segment, boolean lazy, org.apache.druid.segment.SegmentLazyLoadFailCallback loadFailed)	Returns a ReferenceCountingSegment that will be added by the SegmentManager to the VersionedIntervalTimeline.
void	loadSegmentIntoPageCache(org.apache.druid.timeline.DataSegment segment, ExecutorService exec)	Asyncly load segment into page cache.

Methods inherited from class java.lang.Object

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

Constructor Detail

SegmentLocalCacheLoader

@Inject
public SegmentLocalCacheLoader(SegmentCacheManager cacheManager,
                               org.apache.druid.segment.IndexIO indexIO,
                               com.fasterxml.jackson.databind.ObjectMapper mapper)

Method Detail

getSegment

public org.apache.druid.segment.ReferenceCountingSegment getSegment(org.apache.druid.timeline.DataSegment segment,
                                                                    boolean lazy,
                                                                    org.apache.druid.segment.SegmentLazyLoadFailCallback loadFailed)
                                                             throws org.apache.druid.segment.loading.SegmentLoadingException

Description copied from interface: SegmentLoader

Returns a ReferenceCountingSegment that will be added by the SegmentManager to the VersionedIntervalTimeline. This method can be called multiple times by the SegmentManager and implementation can either return same ReferenceCountingSegment or a different ReferenceCountingSegment. Caller should not assume any particular behavior. Returning a ReferenceCountingSegment will let custom implementations keep track of reference count for segments that the custom implementations are creating. That way, custom implementations can know when the segment is in use or not.

Specified by:

getSegment in interface SegmentLoader

Parameters:

segment - - Segment to load

lazy - - Whether column metadata de-serialization is to be deferred to access time. Setting this flag to true can speed up segment loading

loadFailed - - Callback to invoke if lazy loading fails during column access.

Throws:

org.apache.druid.segment.loading.SegmentLoadingException - - If there is an error in loading the segment

cleanup

public void cleanup(org.apache.druid.timeline.DataSegment segment)

Description copied from interface: SegmentLoader

cleanup any state used by this segment

Specified by:

cleanup in interface SegmentLoader

loadSegmentIntoPageCache

public void loadSegmentIntoPageCache(org.apache.druid.timeline.DataSegment segment,
                                     ExecutorService exec)

Description copied from interface: SegmentLoader

Asyncly load segment into page cache. Equivalent to `cat segment_files > /dev/null` to force loading the segment index files into page cache so that later when the segment is queried, they are already in page cache and only a minor page fault needs to be triggered instead of a major page fault to make the query latency more consistent.

Specified by:

loadSegmentIntoPageCache in interface SegmentLoader

Parameters:

segment - The segment to load its index files into page cache

exec - The thread pool to use