Prevent Oracle from changing field.null to True

Fixed #17957 -- when using Oracle and character fields, the fields
were set null = True to ease the handling of empty strings. This
caused problems when using multiple databases from different vendors,
or when the character field happened to be also a primary key.

The handling was changed so that NOT NULL is not emitted on Oracle
even if field.null = False, and field.null is not touched otherwise.

Thanks to bhuztez for the report, ramiro for triaging & comments,
ikelly for the patch and alex for reviewing.

1 files changed, 5 insertions, 5 deletions

diff --git a/docs/ref/databases.txt b/docs/ref/databases.txt
index 8fbe4125c9..2dea337d2b 100644
--- a/docs/ref/databases.txt
+++ b/docs/ref/databases.txt
@@ -685,11 +685,11 @@ NULL and empty strings
 
 Django generally prefers to use the empty string ('') rather than
 NULL, but Oracle treats both identically. To get around this, the
-Oracle backend coerces the ``null=True`` option on fields that have
-the empty string as a possible value. When fetching from the database,
-it is assumed that a NULL value in one of these fields really means
-the empty string, and the data is silently converted to reflect this
-assumption.
+Oracle backend ignores an explicit ``null`` option on fields that
+have the empty string as a possible value and generates DDL as if
+``null=True``. When fetching from the database, it is assumed that
+a ``NULL`` value in one of these fields really means the empty
+string, and the data is silently converted to reflect this assumption.
 
 ``TextField`` limitations
 -------------------------