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Re: Progress on fast path sorting, btree index creation time

Peter Geoghegan <peter@2ndquadrant.com>

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From: Peter Geoghegan <peter@2ndquadrant.com>
To: Josh Berkus <josh@agliodbs.com>
Cc: pgsql-hackers@postgresql.org
Date: 2012-01-10T06:48:11Z
Lists: pgsql-hackers

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  1. During btree index build, sort equal-keyed tuples according to their

On 9 January 2012 19:45, Josh Berkus <josh@agliodbs.com> wrote:
>> Obviously, many indexes are unique and thus won't have duplicates at
>> all.  But if someone creates an index and doesn't make it unique, odds
>> are very high that it has some duplicates.  Not sure how many we
>> typically expect to see, but more than zero...
>
> Peter may not, but I personally admin lots of databases which have
> indexes on values like "category" or "city" which have 100's or 1000's
> of duplicates per value.  I don't think this is uncommon at all.

Uh, then all the more reason to do what I recommend, I imagine. There
is most definitely a large overhead to creating such indexes, at least
for scalar types. As far as I can tell, Tom's complaint is quite
speculative.

-- 
Peter Geoghegan       http://www.2ndQuadrant.com/
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