[Info-Ingres] opf_hash_join set on by default at Ingres 9.2 - for a fresh install

[Robert Allely]

Ingres 9.2 with a new  install sets opf_hash_join ON  but if you upgrade the installation from Ingres 2.6 this setting is left off.

Presumable to avoid problems with some existing queries.

 

I assume that set on is going to help efficiency sometimes - does anyone know about this?

 

Interesting that if I hadn't

used a fresh install on one of the installations I would not have known to change it to on.

 

 

Robert Allely

Ports of Auckland NZ

 

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[Roy Hann]

Robert Allely wrote:

> Ingres 9.2 with a new install sets opf_hash_join ON but if you upgrade the installation from Ingres 2.6 this setting is left off.
> Presumable to avoid problems with some existing queries.
>
> I assume that set on is going to help efficiency sometimes - does anyone know about this?
>
> Interesting that if I hadn't
> used a fresh install on one of the installations I would not have known to change it to on.

Unless you have a good reason to turn it off in 9.2 you should turn it
on. Hash joins have been working reliably for quite a while.

Another similar gotcha to look out for is the introduction of new
parameters that don't get added during the upgrade, so you get whatever
the default behaviour is but you don't know you have an option.

--
Roy

UK Ingres User Association Conference 2010 will be on Tuesday June 8 2010
Go to http://www.iua.org.uk/join to get on the mailing list.

[glennr69]

Hi Robert

Yes - we have noticed that too.

During extensive performance testing we found that we got much better
results with it ON.

How is your upgrade going?

Cheers
Glenn