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From Martijn v Groningen <>
Subject Re: A rant about field collapsing
Date Thu, 04 Aug 2011 10:58:20 GMT
The development of the field collapse feature is a long and confusing story.
The main point is that SOLR-236 was never going to scale
and the performance in general was bad. A new approach was needed.
This was implemented in SOLR-1682 and added to the trunk (4.0-dev)
around September last year. Later in LUCENE-1421 the code was moved
from Solr to Lucene as a module / contrib. After that the grouping module
and contrib were wired into Solr 3.3 and 4.0-dev in SOLR-2524 and SOLR-2564.

Field collapsing is not gone, but it is just a form of result grouping. The
SOLR-236 feature is in 3.3 / 4.0-dev. Other features that SOLR-236 offered
eventually get in. Like for example post grouping facets.
The http parameters and response have changed without keeping it compatible
the SOLR-236 patches. I think that isn't a problem since SOLR-236 was
never a committed feature. But a widely used feature should never be
attached as a patch
to a Jira issue for 3+ years....

On 3 August 2011 18:33, baronDodd <> wrote:

> I am working on an implementation of search within our application using
> solr.
> About 2 months ago we had the need to group results by a certain field.
> After some searching I came across the JIRA in progress for this - field
> collapsing:
> It was scheduled for the next solr release and had a full set of proper
> subtasks and patch files of almost complete implementations attached. So as
> you can imagine I was happy to apply this patch and build it into our
> application and await for the next release when it would be part of the
> main
> trunk.
> Now imagine my surprise when we have come around to upgrade to see that
> suddenly field collapsing has been thrown away in favour of a totally
> different grouping implementation
> How was it decided that this would be used instead? It was not made very
> clear that LUCENE-1421 was in progress which would effectively make the
> field collapsing work irrelevant by fixing the problem in lucene rather
> than
> primarily in solr. This has cost me days of work to now merge our custom
> changes somehow to the new implementation. I guess it is my own fault for
> basing our custom changes around an unresolved enhancement but as SOLR-236
> had been 3-4 years in progress and SOLR-2524 did not exist at the time it
> seemed pretty safe to assume that the same problem was not being fixed in 2
> totally different ways!
> --
> View this message in context:
> Sent from the Solr - User mailing list archive at

Met vriendelijke groet,

Martijn van Groningen

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