Crash When Using Relationships with Large PostGIS Tables

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Author Name: Jeremy Palmer (@palmerj)
Original Redmine Issue: 9431
Affected QGIS version: master
Redmine category:vectors

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Does this feature support large relationship tables from a database? I tried to build a relationship between PostgreSQL tables where the related table has about 2 million rows (which has foreign key column indexed). However when I tried to do a feature info on the map canvas QGIS hung for 20mins and then crashed. Does it try to fetch and cache all of the relationship data upfront, rather than do a database index look-up each time?

Note relationship fields are defined as int4 in PostgreSQL.

[qgib]

Author Name: Andreas Neumann (@andreasneumann)

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Jeremy - I am not the developer of this feature. But yes - currently, the tables are all fetched to the client and then the relationship is built on the client. This is necessary because QGIS supports also file-based data sources.

However, Matthias, the author of this feature plans to do a QGIS expression to database-expression compiler that should be able to do the filtering in the database. You will have to be patient and wait a bit though. It won't be released with QGIS 2.2.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• os_version was changed from 12.04 to
• crashes_corrupts_data was changed from 0 to 1
• operating_system was changed from Ubuntu to
• priority_id was changed from Normal to High

[qgib]

Author Name: Matthias Kuhn (@m-kuhn)

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Hi Jeremy,

It would be very helpful if you could attach a stacktrace of your crash and check how the memory consumption behaves before the crash, so we could try to figure out, where exactly the problem is.

It indeed does not (yet) make use of indexes, and instead iterates over all the features and filters them locally. I plan to integrate such a functionality in future releases and will be looking for funding for this (probably starting around May). If you are considering to help funding such a development, please contact me via email.

PS: I assume it affects master (this feature was not included in 2.0.1).

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• status_id was changed from Open to Feedback
• version was changed from 2.0.1 to master

[qgib]

Author Name: Matthias Kuhn (@m-kuhn)

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Closed due to lack of feedback.
If this is still an issue, please provide the necessary information and reopen.

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• status_id was changed from Feedback to Closed