bulk_create() crashes with mixed length arguments on LOB fields on Oracle.

[Mark Gordon]

Consider the below model, containing one LOB field

from django.db import models

class Bar(models.Model):
    baz = models.TextField()

When you make a bulk_create request, e.g. Bar.objects.bulk_create([b0, b1]) you will get generate a query like below.

INSERT INTO "PROJECT_BAR" ("BAZ") SELECT * FROM (SELECT :arg1 col_0 FROM DUAL UNION ALL SELECT :arg0 FROM DUAL)

This works most of the time, however at some point logic was added to automatically convert a string's type to Database.CLOB when it exceeded 4000 bytes from a normal string literal type. When this conversion happens for some of the arguments but not all of the arguments in the ephemeral table Oracle will complain that the type of the column of the unified table is inconsistent and fail the query.

E.g. the following will fail

Bar.objects.bulk_create([Bar(baz='aaa'), Bar(baz='a'*5000)])

Generating the error

django.db.utils.DatabaseError: ORA-01790: expression must have same datatype as corresponding expression

Note that when both objects have a long or both have a short baz field this query succeeds.

I'm working on a patch

[Mariusz Felisiak]

Thanks for the report. Reproduced at 1d25354fb5f87d35968cd78b53d9560fd75f5b1a.

​PR

[Mariusz Felisiak]

​Alternative PR

[Mariusz Felisiak <felisiak.mariusz@…>]

In dc890bef:

Fixed #30510 -- Fixed crash of QuerySet.bulk_create() with mixed-length texts on Oracle.

Text with more than 4000 characters must be set to as a CLOB on Oracle
what caused a mixed datatype error (ORA-01790) when shorter text
appeared in the same operation.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 9dc13f4:

[3.0.x] Fixed #30510 -- Fixed crash of QuerySet.bulk_create() with mixed-length texts on Oracle.

Text with more than 4000 characters must be set to as a CLOB on Oracle
what caused a mixed datatype error (ORA-01790) when shorter text
appeared in the same operation.

Backport of dc890bef5ad8e9fccce55f3e64af72103ea6e8c1 from master