[Qgis-user] Inefficient SQL

[Raymond Nijssen]

Hi Paul,

Not sure what causes this in QGIS, but I can imagine this happens when 
you need data for a manual selection. So you select 200 features on your 
screen (by dragging a box) and then export them to a file? Or maybe QGIS 
does this better but a plugin doesn't?

To add to this, I remember hitting a "maximum where clauses of 1000" in 
Oracle a while ago, so this doesn't only affect performance but can 
cause errors as well.

Regards,
Raymond



On 03-07-2020 14:11, Paul Wittle wrote:
> Hi,
> 
> We noticed that one of our users was accidentally sending inefficient 
> (or possibly just massive) SQL statements to the Oracle database. I need 
> to do more work to try and replicate the behaviour but is anyone 
> familiar with how it can happen?
> 
> The query is in the form of select [statement] from table where ID = :a 
> OR ID = :b … OR ID = :xxab
> 
> We wondered why that would happen as normally you would just do a 
> spatial query or perhaps do that for a small number of rows but it 
> seemed to be doing it for a large number of rows.
> 
> Any tips to what might be the cause would help me to replicate the 
> issue; my working theory is trying to load too many features in the 
> attribute table but I’m not sure.
> 
> Thanks,
> 
> *Paul Wittle *
> 
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