Performance MetaDataEditor When Selecting Many Images

[thomaslow]

Related Issues:

• Metadata editor is slow to respond #4196

In a meta data editor with 2000 images, the method DataEditorForm.consecutivePagesSelected is called over 2000 times when selecting an image. For large gallery sections (>100 images) and large selections (>10 images), it's execution time is relatively slow (milliseconds), which adds up when called over 2000 times to multiple seconds.

For example, when selecting 50 images in a gallery section of 500 images:

simplescreenrecorder-2022-05-06_10.39.12.mp4

Or, when selecting:

• 1 image in a gallery section of 80 images: 21.6 ms.
• 1 image in a gallery section of 500 images: 483ms
• 10 images in a gallery section of 80 images: 105ms
• 10 images in a gallery section of 500 images: 2.8 seconds
• 100 images in a gallery section of 500 images: 23.7 seconds

Most of it's execution time seems to be related to the distinct().count() call. For large selections, this should be slower, since it involves pairwise comparisons. However, I'm not sure why it is also slower for large gallery sections, since the size of a gallery section should not have any influence here.

Anyway, the proposed implementation improves the runtime of the method signficantly. The same selection of 50 images loads much faster:

simplescreenrecorder-2022-05-06_10.36.52.mp4

The execution time of DataEditorForm.consecutivePagesSelected is reduced to about 36ms in the worst case (selecting 500 images in a gallery section of 500).

The remaining delay when selecting images is related to the full reloading of the gallery, structure and pagination panel.