Re: Thoughts on statistics for continuously advancing columns - Mailing list pgsql-hackers

From Greg Smith
Subject Re: Thoughts on statistics for continuously advancing columns
Date
Msg-id 4B3B83F9.6070308@2ndquadrant.com
Whole thread Raw
In response to Re: Thoughts on statistics for continuously advancing columns  ("Joshua D. Drake" <jd@commandprompt.com>)
Responses Re: Thoughts on statistics for continuously advancing columns  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: Thoughts on statistics for continuously advancing columns  ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
List pgsql-hackers
Joshua D. Drake wrote:
> We normally don't notice because most sets won't incur a penalty. We got a customer who
> has a single table that is over 1TB in size... We notice. Granted that is the extreme
> but it would only take a quarter of that size (which is common) to start seeing issues.
>   

Right, and the only thing that makes this case less painful is that you 
don't really need the stats to be updated quite as often in situations 
with that much data.  If, say, your stats say there's 2B rows in the 
table but there's actually 2.5B, that's a big error, but unlikely to 
change the types of plans you get.  Once there's millions of distinct 
values it's takes a big change for plans to shift, etc.

-- 
Greg Smith    2ndQuadrant   Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com  www.2ndQuadrant.com



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