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https://issues.apache.org/jira/browse/SOLR-12259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16657001#comment-16657001
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Tomás Fernández Löbbe commented on SOLR-12259:
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Thanks for opening this Jira Erick, upgrading is a major issue for us too.
+1 for not mixing things with the optimize command. I think that one has a
different objective (regardless of if in fact re-writes segments). How do you
feel about making a new Request Handler instead, that we could include in the
solrconfig (or implicit, like /update), that way we don’t pollute the
UpdateHandler with upgrading logic and don’t mix the APIs with different kinds
of parameters that this handler could accept. Something like:
{{/solr/collection_or_core/upgrade}}
In this endpoint we could include logic for upgrading Lucene/Solr versions (now
maybe only upgrading the index, but maybe more things in the future, things
like “MIGRATESTATEFORMAT” collection API could belong here too). I’m also
thinking this endpoint could provide information regarding upgrades (in a sort
of dry-run option), like:
{{/solr/collection_or_core/upgrade?action=status}}
And return something like (this is just a random example):
{code}
index:
creationVersion:Lucene 6.3
codecVersion:Lucene 6.1
segment versions:[...]
canUpgrade: YES
Solr:
runningVersions: [7.3,6.3]
clusterStateFormat: legacy
...
{code}
Then the user could do a:
{{/solr/collection_or_core/upgrade?action=upgradeIndex}} or something like that
to start an upgrade in the index, Solr would then check whatever it can to see
if the upgrade is possible, do core/collections calls, or whatever it needs to
do to upgrade.
> Robustly upgrade indexes
> ------------------------
>
> Key: SOLR-12259
> URL: https://issues.apache.org/jira/browse/SOLR-12259
> Project: Solr
> Issue Type: Improvement
> Security Level: Public(Default Security Level. Issues are Public)
> Reporter: Erick Erickson
> Assignee: Erick Erickson
> Priority: Major
>
> The general problem statement is that the current upgrade path is trappy and
> cumbersome. It would be a great help "in the field" to make the upgrade
> process less painful.
> Additionally one of the most common things users want to do is enable
> docValues, but currently they often have to re-index.
> Issues:
> 1> if I upgrade from 5x to 6x and then 7x, theres no guarantee that when I go
> to 7x all the segments have been rewritten in 6x format. Say I have a segment
> at max size that has no deletions. It'll never be rewritten until it has
> deleted docs. And perhaps 50% deleted docs currently.
> 2> IndexUpgraderTool explicitly does a forcemerge to 1 segment, which is bad.
> 3> in a large distributed system, running IndexUpgraderTool on all the nodes
> is cumbersome even if <2> is acceptable.
> 4> Users who realize specifying docValues on a field would be A Good Thing
> have to re-index. We have UninvertDocValuesMergePolicyFactory. Wouldn't it be
> nice to be able to have this done all at once without forceMerging to one
> segment.
> Proposal:
> Somehow avoid the above. Currently LUCENE-7976 is a start in that direction.
> It will make TMP respect max segments size so can avoid forceMerges that
> result in one segment. What it does _not_ do is rewrite segments with zero
> (or a small percentage) deleted documents.
> So it doesn't seem like a huge stretch to be able to specify to TMP the
> option to rewrite segments that have no deleted documents. Perhaps a new
> parameter to optimize?
> This would likely require another change to TMP or whatever.
> So upgrading to a new solr would look like
> 1> install the new Solr
> 2> execute
> "http://node:port/solr/collection_or_core/update?optimize=true&upgradeAllSegments=true";
> What's not clear to me is whether we'd require
> UninvertDocValuesMergePolicyFactory to be specified and wrap TMP or not.
> Anyway, let's discuss. I'll create yet another LUCENE JIRA for TMP do rewrite
> all segments that I'll link.
> I'll also link several other JIRAs in here, they're coalescing.
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