This is apparently by design. This policy no longer seems to work as
described, and is actually misleading, perhaps remove it or when this
policy is in effect actually stamp the indexes with the new version
number? [As this is an intentional non-default configuration - my vote
would be to *stamp* with updated version number - with appropriate
warnings added to both the policy class and the policy factory class in
the javadocs]
Based on this, our systems will be stuck at 7.7.3 for a very long time.
See the following post at stackoverflow, segments upgraded remain
*stamped* as being created in an older version even when they are
rewritten into a newer version segment.
https://stackoverflow.com/a/58619742/1341731
<rant>
Not everyone has the luxury of being able reindex from scratch with data
they might not have copies of anymore, say, for copyright reasons, or
because of space constraints that can't be alleviated, or the size of
collection make it unrealistic in time...
</rant>
On 10/12/21 9:44 AM, Michael Conrad wrote:
Attempting to use the merge policy "UpgradeIndexMergePolicy" via the
"UpgradeIndexMergePolicyFactory" seems to result in no merging.
Here is my config fragment:
<mergePolicyFactory
class="org.apache.solr.index.UpgradeIndexMergePolicyFactory">
<str name="wrapped.prefix">mergePolicy</str>
<str
name="mergePolicy.class">org.apache.solr.index.TieredMergePolicyFactory</str>
<int name="mergePolicy.maxMergeAtOnce">2</int>
<int name="mergePolicy.segmentsPerTier">2</int>
<double name="mergePolicy.noCFSRatio">0.0</double>
</mergePolicyFactory>
The description of the policy says:
> This MergePolicy is used for upgrading all existing segments of an
index when calling IndexWriter.forceMerge(int).
> All other methods delegate to the base MergePolicy given to the
constructor. This allows for an as-cheap-as possible
> upgrade of an older index by only upgrading segments that are
created by previous Lucene versions.
> forceMerge does no longer really merge; it is just used to
"forceMerge" older segment versions away.
Based on this description, when I run "forceMerge" via the curl command:
http://solr-0001:8983/solr/collection/update?optimize=true&maxSegments=1
The non-current version segments should get rewritten to new
replacement segments using the current Lucene version without
reindexing being needed.
The documentation does not provide an example of how to actually use
this policy in a collection's config file. My fragment is a best guess
based on Google search results.
Links:
https://lucene.apache.org/core/7_7_3/core/org/apache/lucene/index/UpgradeIndexMergePolicy.html?is-external=true
https://solr.apache.org/docs/7_7_3/solr-core/org/apache/solr/index/UpgradeIndexMergePolicyFactory.html
Help would be appreciated.
-Michael/NewSRX Tech
