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https://issues.apache.org/jira/browse/SOLR-8621?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15123372#comment-15123372
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Christine Poerschke commented on SOLR-8621:
-------------------------------------------
proposed in SOLR-5730:
bq. ... out-of-the-box factories for all existing non-wrapping merge policies
e.g.
{code}
<!-- public TieredMergePolicy() { -->
<mergePolicyFactory class="TieredMergePolicyFactory">
<int name="segmentsPerTier">42</int>
</mergePolicyFactory>
{code}
bq. An out-of-the-box factory ... for existing plain wrapping merge policies
e.g.
{code}
<!-- public UpgradeIndexMergePolicy(MergePolicy base) { -->
<mergePolicyFactory class="UpgradeIndexMergePolicyFactory">
<str name="base">TieredMergePolicyFactory</str>
<int name="base.segmentsPerTier">42</int>
</mergePolicyFactory>
{code}
bq. The factory for building sorting merge policies \[in SOLR-5730\] could look
something like this:
{code}
<!-- public SortingMergePolicy(MergePolicy in, Sort sort) { -->
<mergePolicyFactory class="SortingMergePolicyFactory">
<str name="in">TieredMergePolicyFactory</str>
<int name="in.segmentsPerTier">42</int>
<str name="sort">timestamp desc</str>
</mergePolicyFactory>
{code}
bq. For consistency ... conceptually support wrapping of wrapping merge
policies e.g. someone could go and create their own
MyInstrumentedMergePolicyFactory factory and use it like this:
{code}
<!-- public MyInstrumentedMergePolicy(MergePolicy mergePolicy) { -->
<mergePolicyFactory class="MyInstrumentedMergePolicyFactory">
<str name="mergePolicy">SortingMergePolicyFactory</str>
<str name="mergePolicy.in">TieredMergePolicyFactory</str>
<int name="mergePolicy.in.segmentsPerTier">42</int>
<str name="mergePolicy.sort">timestamp desc</str>
<int name="instrumentationLevel">42</int>
</mergePolicyFactory>
{code}
> solrconfig.xml: deprecate/replace <mergePolicy> with <mergePolicyFactory>
> -------------------------------------------------------------------------
>
> Key: SOLR-8621
> URL: https://issues.apache.org/jira/browse/SOLR-8621
> Project: Solr
> Issue Type: Task
> Reporter: Christine Poerschke
> Assignee: Christine Poerschke
>
> *<mergePolicyFactory> end-user benefits:*
> * Lucene's UpgradeIndexMergePolicy can be configured in Solr
> * (with SOLR-5730) Lucene's SortingMergePolicy can be configured in Solr
> * customisability: arbitrary merge policies including wrapping/nested merge
> policies can be created and configured
> *roadmap:*
> * solr 5.5 introduces <mergePolicyFactory> support
> * solr 5.5(\?) deprecates (but maintains) <mergePolicy> support
> * solr 6.0(\?) removes <mergePolicy> support
> *ticket todos*
> * add <mergePolicyFactory> examples to this ticket
> * work-in-progress git branch off master - to be created (Christine)
> * Solr Reference Guide update (at/towards the very end i.e. master and
> branch_5x commits)
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