Fixed #12234 -- Create additional indexes that use the appropriate op…

…eration class for PostgreSQL `varchar` and `text` columns when `db_index=True`.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@11912 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/backends/postgresql/creation.py

@@ -35,3 +35,42 @@ def sql_table_creation_suffix(self):
         if settings.TEST_DATABASE_CHARSET:
             return "WITH ENCODING '%s'" % settings.TEST_DATABASE_CHARSET
         return ''
+
+    def sql_indexes_for_field(self, model, f, style):
+        if f.db_index and not f.unique:
+            qn = self.connection.ops.quote_name
+            db_table = model._meta.db_table
+            tablespace = f.db_tablespace or model._meta.db_tablespace
+            if tablespace:
+                sql = self.connection.ops.tablespace_sql(tablespace)
+                if sql:
+                    tablespace_sql = ' ' + sql
+                else:
+                    tablespace_sql = ''
+            else:
+                tablespace_sql = ''
+
+            def get_index_sql(index_name, opclass=''):
+                return (style.SQL_KEYWORD('CREATE INDEX') + ' ' +
+                        style.SQL_TABLE(qn(index_name)) + ' ' +
+                        style.SQL_KEYWORD('ON') + ' ' +
+                        style.SQL_TABLE(qn(db_table)) + ' ' +
+                        "(%s%s)" % (style.SQL_FIELD(qn(f.column)), opclass) +
+                        "%s;" % tablespace_sql)
+
+            output = [get_index_sql('%s_%s' % (db_table, f.column))]
+
+            # Fields with database column types of `varchar` and `text` need
+            # a second index that specifies their operator class, which is
+            # needed when performing correct LIKE queries outside the
+            # C locale. See #12234.
+            db_type = f.db_type()
+            if db_type.startswith('varchar'):
+                output.append(get_index_sql('%s_%s_like' % (db_table, f.column),
+                                            ' varchar_pattern_ops'))
+            elif db_type.startswith('text'):
+                output.append(get_index_sql('%s_%s_like' % (db_table, f.column),
+                                            ' text_pattern_ops'))
+        else:
+            output = []
+        return output

docs/ref/databases.txt

@@ -80,6 +80,21 @@ You should also audit your existing code for any instances of this behavior
 before enabling this feature. It's faster, but it provides less automatic
 protection for multi-call operations.
 
+Indexes for ``varchar`` and ``text`` columns
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.. versionadded:: 1.1.2
+
+When specifying ``db_index=True`` on your model fields, Django typically
+outputs a single ``CREATE INDEX`` statement.  However, if the database type
+for the field is either ``varchar`` or ``text`` (e.g., used by ``CharField``,
+``FileField``, and ``TextField``), then Django will create
+an additional index that uses an appropriate `PostgreSQL operator class`_
+for the column.  The extra index is necessary to correctly perfrom
+lookups that use the ``LIKE`` operator in their SQL, as is done with the
+``contains`` and ``startswith`` lookup types.
+
+.. _PostgreSQL operator class: http://www.postgresql.org/docs/8.4/static/indexes-opclass.html
+
 .. _mysql-notes:
 
 MySQL notes