Yes, we do have a large number of unique field names in that index, because 
they are driven by user named fields in our application (with some cleaning to 
remove illegal chars).

This slowness problem has appeared very suddenly in the last couple of weeks 
and the number of unique field names has not spiked in the last few weeks. Have 
we crept over some threshold with our linear growth in the number of unique 
field names? Perhaps there is a limit driven by the amount of RAM in the 
machine that we are violating? Are there any guidelines for the maximum number, 
or suggested number, of unique fields names in an index or segment? Any 
suggestions for potentially mitigating the problem? 

Thanks,
Mark


On Nov 3, 2010, at 2:02 PM, Michael McCandless wrote:

> On Wed, Nov 3, 2010 at 4:27 PM, Mark Kristensson
> <mark.kristens...@smartsheet.com> wrote:
>> 
>> I've run checkIndex against the index and the results are below. That net is 
>> that it's telling me nothing is wrong with the index.
> 
> Thanks.
> 
>> I did not have any instrumentation around the opening of the IndexSearcher 
>> (we don't use an IndexReader), just around the actual query execution so I 
>> had to add some additional logging. What I found surprised me, opening a 
>> search against this index takes the same 6 to 8 seconds that closing the 
>> indexWriter takes.
> 
> IndexWriter opens a SegmentReader for each segment in the index, to
> apply deletions, so I think this is the source of the slowness.
> 
> From the CheckIndex output, it looks like you have many (296,713)
> unique fields names on that one large segment -- does that sound
> right?  I suspect such a very high field count is the source of the
> slowness...
> 
> Mike
> 
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