Timeline for Performance-limits of QGIS expressions
Current License: CC BY-SA 4.0
13 events
| when toggle format | what | by | license | comment | |
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| Jul 6 at 11:24 | vote | accept | Babel | ||
| Jul 6 at 10:52 | answer | added | Houska | timeline score: 2 | |
| Apr 6, 2023 at 15:43 | comment | added | jfmoyen | For "reasonable" use (define reasonable...) I did not find performances to be a limitation. I would not use expressions for heavy duty computation of course, to me they shine when you want to keep everything encompassed and live. This saves the hassle of recreating the layer outside of QGIS, versioning, wrong file and so on. In short it allows for a more streamlined workflow for simple to moderate talks. | |
| S Apr 6, 2023 at 7:34 | history | suggested | e-shirt | CC BY-SA 4.0 |
corrected spelling, deleted false hyperlink
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| Apr 6, 2023 at 7:30 | review | Suggested edits | |||
| S Apr 6, 2023 at 7:34 | |||||
| Aug 23, 2022 at 7:45 | history | edited | Babel | CC BY-SA 4.0 |
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| Dec 2, 2021 at 19:03 | comment | added | pigreco | in my opinion it is a question to ask in the qgis-developer list | |
| Dec 21, 2020 at 18:00 | history | tweeted | twitter.com/StackGIS/status/1341080999304826884 | ||
| Dec 21, 2020 at 12:51 | history | edited | Babel | CC BY-SA 4.0 |
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| Dec 20, 2020 at 10:34 | history | edited | Babel | CC BY-SA 4.0 |
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| Dec 20, 2020 at 10:28 | comment | added | Babel |
Yes, that for sure is a limiting factor, however it is not primarily a limitation of expressions, but of the concept of live rendering/updating and thus in principle affects virtual layers as well. Otherwise put: expressions can also be used with the geometry by expression tool where a new (static) layer is created - so in this case, the aspect of redrawing layers does not play any role. So maybe to be more precise, the question should be more about the performance of the algorithms that are performed in the background when using expressions. Will update the question accordingly.
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| Dec 19, 2020 at 16:36 | comment | added | MrXsquared | For example if you are using an aggregate function on a layer for geometry generator, this will run as many times as you need to redraw your canvas + aggregate the layer as many times as features the source layer has. So this would be quite ineffective and better solved with static layers. Same would be for a virtual layer: it recomputes every time you move your canvas. So they are really nice and useful tools, but in some applications other tools will be way more performant. | |
| Dec 19, 2020 at 16:28 | history | asked | Babel | CC BY-SA 4.0 |