html_url,issue_url,id,node_id,user,user_label,created_at,updated_at,author_association,body,reactions,issue,issue_label,performed_via_github_app
https://github.com/simonw/datasette/issues/859#issuecomment-648234787,https://api.github.com/repos/simonw/datasette/issues/859,648234787,MDEyOklzc3VlQ29tbWVudDY0ODIzNDc4Nw==,9599,simonw,2020-06-23T15:22:51Z,2020-06-23T15:22:51Z,OWNER,"I wonder if this is a SQLite caching issue then?

Datasette has a configuration option for this but I haven't spent much time experimenting with it so I don't know how much of an impact it can have: https://datasette.readthedocs.io/en/stable/config.html#cache-size-kb","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",642572841,Database page loads too slowly with many large tables (due to table counts),
https://github.com/simonw/datasette/issues/859#issuecomment-648232645,https://api.github.com/repos/simonw/datasette/issues/859,648232645,MDEyOklzc3VlQ29tbWVudDY0ODIzMjY0NQ==,3243482,abdusco,2020-06-23T15:19:53Z,2020-06-23T15:19:53Z,CONTRIBUTOR,"The issue seems to appear sporadically, like when I return to database page after a while, during which some records have been added to the database.

I've just visited database, page first visit took ~10s, consecutive visits took 0.3s.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",642572841,Database page loads too slowly with many large tables (due to table counts),
https://github.com/simonw/datasette/issues/859#issuecomment-648163272,https://api.github.com/repos/simonw/datasette/issues/859,648163272,MDEyOklzc3VlQ29tbWVudDY0ODE2MzI3Mg==,9599,simonw,2020-06-23T13:52:23Z,2020-06-23T13:52:23Z,OWNER,"I'm chunking inserts at 100 at a time right now: https://github.com/simonw/sqlite-utils/blob/4d9a3204361d956440307a57bd18c829a15861db/sqlite_utils/db.py#L1030

I think the performance is more down to using Faker to create the test data - generating millions of entirely fake, randomized records takes a fair bit of time.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",642572841,Database page loads too slowly with many large tables (due to table counts),
https://github.com/simonw/datasette/issues/859#issuecomment-647925594,https://api.github.com/repos/simonw/datasette/issues/859,647925594,MDEyOklzc3VlQ29tbWVudDY0NzkyNTU5NA==,3243482,abdusco,2020-06-23T05:55:21Z,2020-06-23T06:28:29Z,CONTRIBUTOR,"Hmm, not seeing the problem now.  
I've removed the commented out sections in `database.py` and restarted the process. Database page now loads in <250ms.

I have couple of workers that check some pages regularly and scrape new content and save to the DB. Could it be that datasette tries to recount tables every time database size changes? Normally it keeps a count cache, but as DB gets updated so often (new content every 5 min or so) it's practically recounting every time I go to the database page?

EDIT: 
It turns out it doesn't hold cache with mutable databases.

I'll update the issue with more findings and a better way to reproduce the problem if I encounter it again.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",642572841,Database page loads too slowly with many large tables (due to table counts),
https://github.com/simonw/datasette/issues/859#issuecomment-647936117,https://api.github.com/repos/simonw/datasette/issues/859,647936117,MDEyOklzc3VlQ29tbWVudDY0NzkzNjExNw==,3243482,abdusco,2020-06-23T06:25:17Z,2020-06-23T06:25:17Z,CONTRIBUTOR,"> 
> 
> ```
> sqlite-generate many-cols.db --tables 2 --rows 200000 --columns 50
> ```
> 
> Looks like that will take 35 minutes to run (it's not a particularly fast tool).

Try chunking write operations into batches every 1000 records or so.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",642572841,Database page loads too slowly with many large tables (due to table counts),
https://github.com/simonw/datasette/issues/859#issuecomment-647935300,https://api.github.com/repos/simonw/datasette/issues/859,647935300,MDEyOklzc3VlQ29tbWVudDY0NzkzNTMwMA==,3243482,abdusco,2020-06-23T06:23:01Z,2020-06-23T06:23:01Z,CONTRIBUTOR,"> You said ""200k+, 50+ rows in a couple of tables"" - does that mean 50+ columns? I'll try with larger numbers of columns and see what difference that makes.

Ah that was a typo, I meant 50k.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",642572841,Database page loads too slowly with many large tables (due to table counts),
https://github.com/simonw/datasette/issues/859#issuecomment-647923666,https://api.github.com/repos/simonw/datasette/issues/859,647923666,MDEyOklzc3VlQ29tbWVudDY0NzkyMzY2Ng==,3243482,abdusco,2020-06-23T05:49:31Z,2020-06-23T05:49:31Z,CONTRIBUTOR,"I think I should mention that having FTS on all tables mean I have 5 visible, 25 hidden (FTS) tables displayed on database page.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",642572841,Database page loads too slowly with many large tables (due to table counts),
https://github.com/simonw/datasette/issues/859#issuecomment-647894903,https://api.github.com/repos/simonw/datasette/issues/859,647894903,MDEyOklzc3VlQ29tbWVudDY0Nzg5NDkwMw==,9599,simonw,2020-06-23T04:07:59Z,2020-06-23T04:07:59Z,OWNER,"Just to check: are you seeing the problem on this page: https://latest.datasette.io/fixtures (the database page) - or this page (the table page): https://latest.datasette.io/fixtures/compound_three_primary_keys

If it's the table page then the problem may well be #862.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",642572841,Database page loads too slowly with many large tables (due to table counts),
https://github.com/simonw/datasette/issues/859#issuecomment-647890619,https://api.github.com/repos/simonw/datasette/issues/859,647890619,MDEyOklzc3VlQ29tbWVudDY0Nzg5MDYxOQ==,9599,simonw,2020-06-23T03:48:21Z,2020-06-23T03:48:21Z,OWNER,"    sqlite-generate many-cols.db --tables 2 --rows 200000 --columns 50

Looks like that will take 35 minutes to run (it's not a particularly fast tool).
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",642572841,Database page loads too slowly with many large tables (due to table counts),
https://github.com/simonw/datasette/issues/859#issuecomment-647890378,https://api.github.com/repos/simonw/datasette/issues/859,647890378,MDEyOklzc3VlQ29tbWVudDY0Nzg5MDM3OA==,9599,simonw,2020-06-23T03:47:19Z,2020-06-23T03:47:19Z,OWNER,"I generated a 600MB database using [sqlite-generate](https://github.com/simonw/sqlite-generate) just now - with 100 tables at 100,00 rows and 3 tables at 1,000,000 rows - and performance of the database page was fine, 250ms.

Those tables only had 4 columns each though.

You said ""200k+, 50+ rows in a couple of tables"" - does that mean 50+ columns? I'll try with larger numbers of columns and see what difference that makes.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",642572841,Database page loads too slowly with many large tables (due to table counts),