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From Andy Seaborne <>
Subject Re: sdb and UNION
Date Sat, 11 Jun 2011 12:39:38 GMT
Nothing specifically known.

In SDB, UNIONs are not done in the SQL database,.  They are the 
concatenation of each subpart.  if that's combined with an earlier 
pattern that is joined to the union, there can be a lot of calls to the 
database, each with JDBC latency overhead.

Again, something that works a whole lot better in TDB.


On 06/06/11 15:36, Simon Helsen wrote:
> Hi,
> I am currently doing experiments to evaluate SDB in terms of performance
> and scalability. I noticed that queries with a large number of UNIONs do
> not behave well (meaning, taking more than a minute on a small store). Are
> there known problems with these kind of queries? I am still on SDB 1.3.2
> thanks,
> Simon

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