So you are saying that we do not need to run the IndexUpgrader tool if
we move from 6 to 7. Will the index be then updated automatically or
will we get a problem once we move to 8?
How would one use the IndexUpgrader at all with Solr? Would one need to
run it against the index of every core?
On 14.03.2018 11:14, Shawn Heisey wrote:
On 3/14/2018 3:04 AM, Hendrik Haddorp wrote:
we have a SolrCloud 6.3 with HDFS setup and plan to upgrade to 7.2.1.
The cluster upgrade instructions on
https://lucene.apache.org/solr/guide/7_2/upgrading-a-solr-cluster.html
does not contain any information on changing the luceneMatchVersion.
If we change the luceneMatchVersion manually is it enough to just
reload the collection or do we need to perform an index upgrade like
the IndexUpgrader tool
(https://lucene.apache.org/solr/guide/7_2/indexupgrader-tool.html)
does? If so how would one use that for an index stored in HDFS?
Most people seem to expect that defining luceneMatchVersion will allow
them to build an index with the format of an earlier version.
This is not what happens. Solr builds indexes in the format that the
same version of Lucene chooses by default. As far s I know, you can't
change the index format in Solr.
Somebody who is writing a Lucene program (instead of using Solr) can
choose to use an earlier version's format, but this is not done with
luceneMatchVersion.
The luceneMatchVersion setting is used by the index analysis
components (tokenizers, filters, etc). Sometimes when a component's
behavior is SIGNIFICANTLY changed by a version upgrade, the developer
will put in a luceneMatchVersion check so users can revert to the old
behavior if they want to. Only a minority of changes to analysis
components are controlled by luceneMatchVersion.
Generally there is no need to use the IndexUpgrader tool unless you're
updating at least two major version numbers. This is because a 7.x
version can only read version 6.x indexes. Anything earlier must be
upgraded to 6.x.
But it's my strong opinion that if you're upgrading two major
versions, then you should build a new index from scratch, and use a
new configuration that has been designed from the ground up for the
new version. Users who upgrade that far often find that they cannot
use their configurations in the new version without changes, so they
MUST rebuild.
I actually recommend always building the index from scratch for ANY
Solr upgrade.
Thanks,
Shawn
