id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
33460	Change SQLite backend to generate INSERT statements using VALUES instead of UNION.	Keryn Knight	Keryn Knight	"This is a ticket for tracking this [https://github.com/django/django/pull/15354 pre-emptive PR].

Django's minimum supported version of SQLite is currently documented as 3.9. 

Using `INSERT INTO ... VALUES (...)` instead of `INSERT INTO ... SELECT UNION ALL ...` for multiple rows (i.e. `bulk_create`) was added to SQLite in [http://www.sqlite.org/releaselog/3_7_11.html 3.7.11] released in 2012. 

[https://www.sqlite.org/releaselog/3_8_8.html SQLite 3.8.8], released in 2015, further changed it so that `VALUES(...)` was not subject to the `SQLITE_LIMIT_COMPOUND_SELECT` value, which should subsequently allow for improvements in batch sizes (e.g. investigating changes to `django.db.backends.sqlite3.operations.DatabaseOperations.bulk_batch_size` and `django.db.backends.sqlite3.features.DatabaseFeatures.max_query_params`, the latter of which supports `32766 ` values instead of `999` as of [https://www.sqlite.org/releaselog/3_32_0.html 3.32.0])

The documentation for current SQLite (3.37.2) says, of using `VALUES(...)`:

> The phrase ""VALUES(expr-list)"" means the same thing as ""SELECT expr-list"". The phrase ""VALUES(expr-list-1),...,(expr-list-N)"" means the same thing as ""SELECT expr-list-1 UNION ALL ... UNION ALL SELECT expr-list-N"". Both forms are the same, except that the number of SELECT statements in a compound is limited by SQLITE_LIMIT_COMPOUND_SELECT whereas the number of rows in a VALUES clause has no arbitrary limit.
> There are some restrictions on the use of a VALUES clause that are not shown on the syntax diagrams:
> A VALUES clause cannot be followed by ORDER BY.
> A VALUES clause cannot be followed by LIMIT.

I have run the test suite against `3.37.2` and whatever the CI versions are (I've not checked) ... so far so good. "	Cleanup/optimization	closed	Database layer (models, ORM)	dev	Normal	fixed	sqlite orm bulk_create batch		Ready for checkin	1	0	0	0	0	0