Server pagination

[SchrodingersGat]

Adds server-side pagination for (some) data tables which significantly speeds up the UI - especially when there are a large number of records.

Fixes #310

The query is limited on the database side.

For a dataset of ~1000 records, this reduces query time from 6,000ms to ~100ms.

• Check that the "limit" functionality still works for the home page
• Unit testing for the stock list API
• Unit testing for the part list API
• Refactor duplicated "queryParams" function for inventreeTable

[eeintech]

@SchrodingersGat Wow very impressive! Nice work!

Seems like large BOM loading is still slow, any idea why?

[SchrodingersGat]

@eeintech how long does it take to load the BOM table, and how many rows are in the BOM table?

[eeintech]

@SchrodingersGat There are 67 items in the BOM and it can take close to 20 seconds

[SchrodingersGat]

That's pretty slow indeed. With only 67 items I'd say there is something more serious going on that needs to be looked at.

For reference, before I added server-side pagination for the "parts" list, loading all parts on my test database (~1000) took around 6 seconds.

[eeintech]

You're right, we have 200+ parts in our database and the part list is loading almost instantaneously. I'll have to investigate why our BOM doesn't follow the same logic...

[SchrodingersGat]

Using the django debug toolbar, I was actually able to replicate this. The issue is not the data loading into the table

The server request to generate the page takes about 18s

But the subsequent database request is reasonably fast:

[SchrodingersGat]

On further inspection it appears that any of the part detail views are very slow (~15 seconds just to load the "part detail" page).