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From "Peter Sturge (JIRA)" <j...@apache.org>
Subject [jira] Created: (SOLR-1709) Distributed Date Faceting
Date Fri, 08 Jan 2010 00:20:54 GMT
Distributed Date Faceting
-------------------------

                 Key: SOLR-1709
                 URL: https://issues.apache.org/jira/browse/SOLR-1709
             Project: Solr
          Issue Type: Improvement
          Components: SearchComponents - other
    Affects Versions: 1.4
            Reporter: Peter Sturge
            Priority: Minor


This patch is for adding support for date facets when using distributed searches.

Date faceting across multiple machines exposes some time-based issues that anyone interested
in this behaviour should be aware of:
Any time and/or time-zone differences are not accounted for in the patch (i.e. merged date
facets are at a time-of-day, not necessarily at a universal 'instant-in-time', unless all
shards are time-synced to the exact same time).
The implementation uses the first encountered shard's facet_dates as the basis for subsequent
shards' data to be merged in.
This means that if subsequent shards' facet_dates are skewed in relation to the first by >1
'gap', these 'earlier' or 'later' facets will not be merged in.
There are several reasons for this:
  * Performance: It's faster to check facet_date lists against a single map's data, rather
than against each other, particularly if there are many shards
  * If 'earlier' and/or 'later' facet_dates are added in, this will make the time range larger
than that which was requested
        (e.g. a request for one hour's worth of facets could bring back 2, 3 or more hours
of data)
    This could be dealt with if timezone and skew information was added, and the dates were
normalized.
One possibility for adding such support is to [optionally] add 'timezone' and 'now' parameters
to the 'facet_dates' map. This would tell requesters what time and TZ the remote server thinks
it is, and so multiple shards' time data can be normalized.

The patch affects 2 files in the Solr core:
  org.apache.solr.handler.component.FacetComponent.java
  org.apache.solr.handler.component.ResponseBuilder.java

The main changes are in FacetComponent - ResponseBuilder is just to hold the completed SimpleOrderedMap
until the finishStage.
One possible enhancement is to perhaps make this an optional parameter, but really, if facet.date
parameters are specified, it is assumed they are desired.
Comments & suggestions welcome.

As a favour to ask, if anyone could take my 2 source files and create a PATCH file from it,
it would be greatly appreciated, as I'm having a bit of trouble with svn (don't shoot me,
but my environment is a Redmond-based os company).


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