[Qgis-user] Inefficient SQL

[chris hermansen]

Paul and list,

On Fri, Jul 3, 2020, 05:11 Paul Wittle <paul.wittle at dorsetcouncil.gov.uk>
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
>

Could this be an Oracle table joined by QGIS to a (say) shapefile with the
user selecting a bunch of records (maybe selecting all; or selecting a few
,then inverting the selection; or selecting all records in a bounding box)
which is seen on the Oracle end as such a select?

I don't know this for a fact but it seems plausible. I would think it's
going to be a bunch of OR operators or an IN () with a long list.

>
>
> 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 *
>
> <https://www.dorsetcouncil.gov.uk/>
>
> *Business Solutions Analyst (GIS)*
>
> *ICT Operations *
>
> *Dorset Council*
>
> 01305 228473
> <01305%20228473%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20>
>
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