Ticket #17785: pscopg2-introspection.patch

django/db/backends/postgresql_psycopg2/introspection.py

@@ -50 +50 @@
         """
         Returns a dictionary of {field_index: (field_index_other_table, other_table)}
         representing all relationships to the given table. Indexes are 0-based.
+        If a column gets deleted, attnum of the other columns does not change. You can't use attnum as
+        offset in the table description.
         """
+        cursor.execute("SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(table_name))
+        this_table_col_names=[col_desc[0] for col_desc in cursor.description]
         cursor.execute("""
-            SELECT con.conkey, con.confkey, c2.relname
+            SELECT 
+               (SELECT attname FROM pg_attribute WHERE attnum=con.conkey[1] AND attrelid=con.conrelid), 
+               (SELECT attname FROM pg_attribute WHERE attnum=con.confkey[1] AND attrelid=con.confrelid), 
+               c2.relname
             FROM pg_constraint con, pg_class c1, pg_class c2
             WHERE c1.oid = con.conrelid
                 AND c2.oid = con.confrelid
                 AND c1.relname = %s
                 AND con.contype = 'f'""", [table_name])
         relations = {}
-        for row in cursor.fetchall():
-            # row[0] and row[1] are single-item lists, so grab the single item.
-            relations[row[0][0] - 1] = (row[1][0] - 1, row[2])
+        for this_col_name, other_col_name, other_table in list(cursor.fetchall()):
+            cursor.execute("SELECT * FROM %s LIMIT 1" % self.connection.ops.quote_name(other_table))
+            other_table_col_names=[col_desc[0] for col_desc in cursor.description]
+            relations[this_table_col_names.index(this_col_name)] = (other_table_col_names.index(other_col_name), other_table)
         return relations
 
     def get_indexes(self, cursor, table_name):

tests/regressiontests/introspection/tests.py

@@ -4 +4 @@
 
 from django.db import connection
 from django.test import TestCase, skipUnlessDBFeature, skipIfDBFeature
+from django.db.utils import DatabaseError
 
 from .models import Reporter, Article
 
@@ -136 +137 @@
         indexes = connection.introspection.get_indexes(cursor, Article._meta.db_table)
         self.assertEqual(indexes['reporter_id'], {'unique': False, 'primary_key': False})
 
+    def test_introspection_after_drop_column(self):
+        cursor = connection.cursor()
+        cursor.execute('''CREATE TABLE "django_drop_col_other1" ("id" INTEGER CONSTRAINT "other1_pk_id" PRIMARY KEY)''')
+        cursor.execute('''CREATE TABLE "django_drop_col_other2" ("id" INTEGER CONSTRAINT "other2_pk_id" PRIMARY KEY)''')
+        cursor.execute('''CREATE TABLE "django_drop_col_test" (
+                              "id" INTEGER CONSTRAINT "pk_id" PRIMARY KEY, 
+                              "col_to_drop" INTEGER CONSTRAINT "fk_col_to_drop" REFERENCES "django_drop_col_other1" ("id"), 
+                              "col_fk" INTEGER CONSTRAINT "fk_col_fk" REFERENCES "django_drop_col_other2" ("id") 
+                          ) ''')
+        col_names = [col[0] for col in connection.introspection.get_table_description(cursor, "django_drop_col_test")]
+        self.assertEqual(col_names, ['id', 'col_to_drop', 'col_fk'])
+        rels=connection.introspection.get_relations(cursor, "django_drop_col_test")
+        self.assertEqual(rels, {1: (0, u'django_drop_col_other1'), 2: (0, u'django_drop_col_other2')})
+        try:
+            cursor.execute('ALTER TABLE "django_drop_col_test" DROP COLUMN "col_to_drop"')
+        except DatabaseError:
+            return # sqlite does not support drop column
+        col_names = [col[0] for col in connection.introspection.get_table_description(cursor, "django_drop_col_test")]
+        self.assertEqual(col_names, ['id', 'col_fk'])
+        rels=connection.introspection.get_relations(cursor, "django_drop_col_test")
+        self.assertEqual(rels, {1: (0, u'django_drop_col_other2')})
+        
 
 def datatype(dbtype, description):
     """Helper to convert a data type into a string."""