id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,pull_request,body,repo,type,active_lock_reason,performed_via_github_app,reactions,draft,state_reason
688670158,MDU6SXNzdWU2ODg2NzAxNTg=,147,SQLITE_MAX_VARS maybe hard-coded too low,96218,open,0,,,7,2020-08-30T07:26:45Z,2021-02-15T21:27:55Z,,CONTRIBUTOR,,"I came across this while about to open an issue and PR against the documentation for `batch_size`, which is a bit incomplete.

As mentioned in #145, while:

> [`SQLITE_MAX_VARIABLE_NUMBER`](https://www.sqlite.org/limits.html#max_variable_number) ... defaults to 999 for SQLite versions prior to 3.32.0 (2020-05-22) or 32766 for SQLite versions after 3.32.0.

it is common that it is increased at compile time. Debian-based systems, for example, seem to ship with a version of sqlite compiled with SQLITE_MAX_VARIABLE_NUMBER set to 250,000, and I believe this is the case for homebrew installations too.

In working to understand what `batch_size` was actually doing and why, I realized that by setting `SQLITE_MAX_VARS` in `db.py` to match the value my sqlite was compiled with (I'm on Debian), I was able to decrease the time to `insert_all()` my test data set (~128k records across 7 tables) from ~26.5s to ~3.5s.  Given that this about .05% of my total dataset, this is time I am keen to save...

Unfortunately, it seems that `sqlite3` in the python standard library doesn't expose the `get_limit()` C API (even though `pysqlite` used to), so it's hard to know what value sqlite has been compiled with (note that this could mean, I suppose, that it's less than 999, and even hardcoding `SQLITE_MAX_VARS` to the conservative default might not be adequate.  It can also be lowered -- but not raised -- at runtime).  The best I could come up with is `echo """" | sqlite3 -cmd "".limits variable_number""` (only available in `sqlite >= 2015-05-07 (3.8.10)`).

Obviously this couldn't be relied upon in `sqlite_utils`, but I wonder what your opinion would be about exposing `SQLITE_MAX_VARS` as a user-configurable parameter (with suitable ""here be dragons"" warnings)?  I'm going to go ahead and monkey-patch it for my purposes in any event, but it seems like it might be worth considering.",140912432,issue,,,"{""url"": ""https://api.github.com/repos/simonw/sqlite-utils/issues/147/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,