Apache Solr Reference Guide Covering Apache Solr 6.0

timestamp desc
inner
org.apache.solr.index.TieredMergePolicyFactory
10
10
The example above shows Solr's SortingMergePolicyFactory being configured to sort documents in
merged segments by "timestamp desc" , and wrapped around a TieredMergePolicyFactory configur
ed to use the values maxMergeAtOnce=10 and segmentsPerTier=10 via the inner prefix defined by So
rtingMergePolicyFactory's
wrapped.prefix option. For more information on using SortingMergeP
olicyFactory, see the segmentTerminateEarly parameter.
mergeScheduler
The merge scheduler controls how merges are performed. The default ConcurrentMergeScheduler perfo
rms merges in the background using separate threads. The alternative, SerialMergeScheduler, does not
perform merges with separate threads.
mergedSegmentWarmer
When using Solr in for Near Real Time Searching a merged segment warmer can be configured to warm the
reader on the newly merged segment, before the merge commits. This is not required for near real-time
search, but will reduce search latency on opening a new near real-time reader after a merge completes.
Compound File Segments
Each Lucene segment is typically comprised of a dozen or so files. Lucene can be configured to bundle all of
the files for a segment into a single compound file using a file extension of .cfs; it's an abbreviation for
Compound File Segment. CFS segments may incur a minor performance hit for various reasons, depending
on the runtime environment. For example, filesystem buffers are typically associated with open file
descriptors, which may limit the total cache space available to each index. On systems where the number of
open files allowed per process is limited, CFS may avoid hitting that limit. The open files limit might also be
tunable for your OS with the Linux/Unix ulimit command, or something similar for other operating systems.
CFS: New Segments vs Merged Segments
To configure whether newly written segments should use CFS, see the useCompoundFile setting
described above. To configure whether merged segments use CFS, review the Javadocs for your me
rgePolicyFactory .
implementations support and settings
Many Merge Policy noCFSRatio maxCFSSegmentSizeMB wit
h default values that prevent compound files from being used for large segments, but do use
compound files for small segments.
Index Locks
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