Improve attribute table performance

[qgib]

Author Name: Paolo Cavallini (@pcav)
Original Redmine Issue: 12926

Redmine category:attribute_table

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Loading a large (pg) table requires the loading of all records. This is a real performance killer, and effectively prevents the use of layers with millions of records.
Moreover, even when selection Show only selected in Options, and selecting a few records, apparently all records are read, so this does not speed up.
This beaviour is changed from 1.8 to 2.0. In older versions if you show only selection or show only object visible in map extent qgis was faster. With newer version it has to read all the table data every time it is opened.
See also #19023

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Related issue(s): #19023 (relates), #20496 (relates)
Redmine related issue(s): 10619, 12318

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[qgib]

Author Name: Jürgen Fischer (@jef-n)

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• tracker_id was changed from 1 to 2
• subject was changed from Loading attribute table very slow to Improve attribute table performance
• priority_id was changed from Normal to High

[qgib]

Author Name: Alessandro Pasotti (@elpaso)

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Here is an attempt to speed things up: #2518

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• easy_fix was configured as 0

[qgib]

Author Name: Regis Haubourg (@haubourg)

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Some work has been done here and seems to really improve things: [[https://github.com//pull/4230]]

Some other improvements seem possible again with joined fields.

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• description was changed from Loading a large (pg) table requires the loading of all records. This is a real performance killer, and effectively prevents the use of layers with millions of records.
  Moreover, even when selection Show only selected in Options, and selecting a few records, apparently all records are read, so this does not speed up.
  This beaviour is changed from 1.8 to 2.0. In older versions if you show only selection or show only object visible in map extent qgis was faster. With newer version it has to read all the table data every time it is opened.
  See also Attribute table 'Show features visible on map' option does not speed up loading of large postgis table #19023
  to Loading a large (pg) table requires the loading of all records. This is a real performance killer, and effectively prevents the use of layers with millions of records.
  Moreover, even when selection Show only selected in Options, and selecting a few records, apparently all records are read, so this does not speed up.
  This beaviour is changed from 1.8 to 2.0. In older versions if you show only selection or show only object visible in map extent qgis was faster. With newer version it has to read all the table data every time it is opened.
  See also Attribute table 'Show features visible on map' option does not speed up loading of large postgis table #19023

• status_id was changed from Open to In Progress

[qgib]

Author Name: Paolo Cavallini (@pcav)

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The two PR are closed. Should we close this as well?
Any automatic performance testing?

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• status_id was changed from In Progress to Feedback

[qgib]

Author Name: Giovanni Manghi (@gioman)

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Still slow for large tables if compared to other (gis) software. Better than in the past anyway.

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• resolution was changed from to fixed/implemented
• status_id was changed from Feedback to Closed