[lucene-solr] branch master updated: Adding forceMergeDeletePctAllowed and deletesPctAllowed to TieredMergePolicy documentation

[er...@apache.org]

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erick pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/lucene-solr.git


The following commit(s) were added to refs/heads/master by this push:
     new eb9f59f  Adding forceMergeDeletePctAllowed and deletesPctAllowed to TieredMergePolicy documentation
eb9f59f is described below

commit eb9f59f04196970a7eb4b408622b488841498a4e
Author: Erick Erickson <Er...@gmail.com>
AuthorDate: Thu Aug 27 14:38:33 2020 -0400

    Adding forceMergeDeletePctAllowed and deletesPctAllowed to TieredMergePolicy documentation
---
 solr/solr-ref-guide/src/indexconfig-in-solrconfig.adoc | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/solr/solr-ref-guide/src/indexconfig-in-solrconfig.adoc b/solr/solr-ref-guide/src/indexconfig-in-solrconfig.adoc
index 7759674..8615a4b8 100644
--- a/solr/solr-ref-guide/src/indexconfig-in-solrconfig.adoc
+++ b/solr/solr-ref-guide/src/indexconfig-in-solrconfig.adoc
@@ -82,6 +82,9 @@ Other policies available are the `LogByteSizeMergePolicy`, `LogDocMergePolicy`,
 <mergePolicyFactory class="org.apache.solr.index.TieredMergePolicyFactory">
   <int name="maxMergeAtOnce">10</int>
   <int name="segmentsPerTier">10</int>
+  <double name="forceMergeDeletesPctAllowed">10.0</double>
+  <double name="deletesPctAllowed">33.0</double>
+
 </mergePolicyFactory>
 ----
 
@@ -104,6 +107,13 @@ Choosing the best merge factors is generally a trade-off of indexing speed vs. s
 
 Conversely, keeping more segments can accelerate indexing, because merges happen less often, making an update is less likely to trigger a merge. But searches become more computationally expensive and will likely be slower, because search terms must be looked up in more index segments. Faster index updates also means shorter commit turnaround times, which means more timely search results.
 
+=== Controlling Deleted Document Percentages
+
+When a document is deleted or updated, the document is marked as deleted but it not removed from the index until the segment is merged. There are two parameters that can can be adjusted when using the default TieredMergePolicy that influence the number of deleted documents in an index.
+
+* `forceMergeDeletesPctAllowed (default 10.0)`. When the external expungeDeletes command is issued, any segment that has more than this percent deleted documents will be merged into a new segment and the data associated with the deleted documents will be purged. A value of 0.0 will make expungeDeletes behave essentially identically to `optimize`.
+* `deletesPctAllowed (default 33.0)`. During normal segment merging, a "best effort" is made to insure that the total percentage of deleted documents in the index is below this threshold.  Valid settings are between 20% and 50%. 33% was chosen as the default because as this setting approaches 20%, considerable load is added to the system.
+
 === Customizing Merge Policies
 
 If the configuration options for the built-in merge policies do not fully suit your use case, you can customize them: either by creating a custom merge policy factory that you specify in your configuration, or by configuring a {solr-javadocs}/solr-core/org/apache/solr/index/WrapperMergePolicyFactory.html[merge policy wrapper] which uses a `wrapped.prefix` configuration option to control how the factory it wraps will be configured: