[Qgis-community-team] Materialised / Rule based views

[Andreas Neumann]

Hi all, 

I agree with Richard. Thanks for referencing the PG docs. Normally,
materialized views are not meant to be manipulated
(insert/update/delete). They are usually used to improve performance of
complex queries. 

Yes - with the power of PostgreSQL one could probably somehow also
update also materialized views (with rules and triggers) - but in most
cases it would not make sense and I wouldn't encourage it. 

Greetings,
Andreas 

On 2018-01-12 10:41, Richard Duivenvoorde wrote:

> Hi,
> 
> just because I stumbled upon this last month:
> 
> A materialized view is originally just a table based on a query. So you
> should not update the 'view' as upon a refresh, those edits will be
> overwritten.
> 
> Postgresql has an 'official' materialized view
> 
> https://www.postgresql.org/docs/9.3/static/sql-creatematerializedview.html
> 
> which you can 'refresh' using a query:
> 
> https://www.postgresql.org/docs/9.3/static/sql-refreshmaterializedview.html
> 
> I think the heading in the training_manual should be something like:
> 'rule based updates' or so?
> 
> Regards,
> 
> Richard Duivenvoorde
> 
> On 11-01-18 23:32, Tim Sutton wrote: Hi
> 
> I (or whoever wrote it) could probably have chosen a better example.
> Materialised views change something that is normally read only (a view)
> into something that can be treated as a writable table (with the correct
> transactions being deferred to the tables that were used to create the
> view). So agreed we should either change the example or the heading :-)
> 
> Regards
> 
> Tim
> 
> On 11 Jan 2018, at 23:24, Anita Graser <anitagraser at gmx.at
> <mailto:anitagraser at gmx.at>> wrote:
> 
> Hi,
> 
> I'm wondering about the term 
> ​"
> Materialised Views (Rule based views)
> ​" in the lesson about rules:​
> ​
> https://docs.qgis.org/testing/en/docs/training_manual/database_concepts/rules.html
> 
> Maybe I'm missing something, but it doesn't seem like the example has
> anything to do with views. It's a nice rule that writes into a regular
> table, as far as I can tell. 
> 
> It would be good to provide an example that deals with inserting data
> into a view. 
> 
> What do you think about changing the subheading to "Creating a logging
> rule"?
> 
> Regards,
> Anita
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> *Tim Sutton*
> 
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