[QGIS-Developer] QGIS "fast" mode

[Julien Cabieces]

Hi all,

This function is only for PostGres (Tomas use an Oracle database if I
remember correctly).

And from what I inderstand from the code, It only prevents from checking
for unique colomn in a view or materialized view.

However, it looks the good option to deal with this use case, I mean no
check (geometry type, srid, key column...) as soon as this option is set.

Regards,
Julien

> Hi Tomas.
> Check the project property option named "trust". This is exactly what it is
> supposed to do.
> I admit the wording is not nice, any better idea is welcome.
> Best regards
>
>
> Le sam. 14 mars 2020 à 12:55, Tomas Straupis <tomasstraupis at gmail.com> a
> écrit :
>
>> Hello
>>
>>   I would like to know opinion of QGIS developer community on the
>> question of "self-fixing queries" in the context of database layers.
>>
>>   When you add a new database layer, QGIS queries required data, asks
>> user for other information and then saves it in the project file.
>>   Now when you re-open the project, QGIS is re-querying a lot of data
>> which is already saved in the project: geometry type, srid, attributes
>> (table columns/types).
>>   The downsides are:
>>   * these "re-checking" queries take considerable time on large
>> databases: with millions of records from 1minute up to several hours,
>> database is tuned - WMS/WFS queries finish in ~100ms.
>>   * in QGIS server environment these re-checking queries are executed
>> each time when apache launches a new QGIS server process
>>   * QGIS might by itself (without human interaction) decide to  work
>> differently compared to what it was asked to do when the project was
>> created if it finds that "something has changed"
>>   * re-checking during project opening is not 100% correct, as if
>> changes are possible in principle, then data/schema could change
>> during the time QGIS (Desktop/Server) is open/running
>>   * in environments other than development (testing, qa, production),
>> database schema should never change without some clear procedure which
>> should also include updating QGIS project files and testing them as
>> required, therefore such re-checkings should never be required on
>> testing/production environments.
>>
>>   I do understand that the current situation/understanding is
>> different from mine, so in order to satisfy everybody, maybe it would
>> be feasible to add say an environment variable like QGIS_FAST=TRUE (or
>> QGIS_PRODUCTION=TRUE) and if this is set - re-checking queries could
>> be skipped? We've been running modified QGIS without re-checking in
>> production for months and are very happy with results. This should
>> also improve the benchmarks of QGIS Server as it is known that initial
>> opening of the project takes considerable amount of time.
>>
>>   What is your opinion?
>>
>>   Thank you
>>
>> --
>> Tomas
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