Ticket #2495: 2495-against-10914.diff

django/db/backends/mysql/creation.py

@@ -63 +63 @@
                 field.rel.to._meta.db_table, field.rel.to._meta.pk.column)
             ]
         return table_output, deferred
-        
- No newline at end of file
+
+    def sql_indexes_for_field(self, model, f, style):
+        """
+        Modify the return-value of BaseDatabaseCreation.sql_indexes_for_field()
+        to add a  prefix length to the TextField which is currently represented
+        by MySQL's 'longtext' type -- which requires a prefix-length parameter
+        in order to install an index. 
+
+        Use largest possible value allowed - 255 characters.
+
+        All other types are passed unchanged.
+        """
+
+        out = super(DatabaseCreation, self).sql_indexes_for_field(model, f, style)
+
+        if not out or not f.db_type() == self.data_types['TextField']:
+            return out
+
+        qn = self.connection.ops.quote_name
+        field = "%s" % style.SQL_FIELD(qn(f.column))
+
+        newout = []
+        for item in out:
+            # 767-byte prefix length maximum for InnoDB
+            # when using UTF-8 count 3 bytes per character so use 255 as a safe value
+            newout.append(item.replace(field, "%s(255)" % field))
+
+        return newout
+

new file tests/regressiontests/bug2495/models.py

@@ +1 @@
+from unittest import TestCase
+
+from django.db import models, connection
+
+class IndexedTextModel(models.Model):
+    indexed_text = models.TextField(db_index=True)
+
+class TestTextFieldIndices(TestCase):
+    def test_indexed_text_has_an_index(self):
+        try:
+            indexes = connection.introspection.get_indexes(connection.cursor(), IndexedTextModel._meta.db_table)
+        except NotImplementedError:
+            indexes = {}
+        assert 'indexed_text' in indexes
+