Fixed #23954 -- Added special text/varchar PostgreSQL indexes in migrations

Thanks adityagupta104 for the report and Tim Graham for the review.

4 files changed, 105 insertions, 18 deletions

diff --git a/django/db/backends/postgresql_psycopg2/schema.py b/django/db/backends/postgresql_psycopg2/schema.py
index ceb446c13a..7b479c28b0 100644
--- a/django/db/backends/postgresql_psycopg2/schema.py
+++ b/django/db/backends/postgresql_psycopg2/schema.py
@@ -6,12 +6,34 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
     sql_create_sequence = "CREATE SEQUENCE %(sequence)s"
     sql_delete_sequence = "DROP SEQUENCE IF EXISTS %(sequence)s CASCADE"
     sql_set_sequence_max = "SELECT setval('%(sequence)s', MAX(%(column)s)) FROM %(table)s"
+    sql_create_varchar_index = "CREATE INDEX %(name)s ON %(table)s (%(columns)s varchar_pattern_ops)%(extra)s"
+    sql_create_text_index = "CREATE INDEX %(name)s ON %(table)s (%(columns)s text_pattern_ops)%(extra)s"
 
     def quote_value(self, value):
         # Inner import so backend fails nicely if it's not present
         import psycopg2
         return psycopg2.extensions.adapt(value)
 
+    def _model_indexes_sql(self, model):
+        output = super(DatabaseSchemaEditor, self)._model_indexes_sql(model)
+        if not model._meta.managed or model._meta.proxy or model._meta.swapped:
+            return output
+
+        for field in model._meta.local_fields:
+            db_type = field.db_type(connection=self.connection)
+            if db_type is not None and (field.db_index or field.unique):
+                # 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.
+                if db_type.startswith('varchar'):
+                    output.append(self._create_index_sql(
+                        model, [field], suffix='_like', sql=self.sql_create_varchar_index))
+                elif db_type.startswith('text'):
+                    output.append(self._create_index_sql(
+                        model, [field], suffix='_like', sql=self.sql_create_text_index))
+        return output
+
     def _alter_column_type_sql(self, table, column, type):
         """
         Makes ALTER TYPE with SERIAL make sense.
diff --git a/django/db/backends/schema.py b/django/db/backends/schema.py
index 1b4fdbcd4d..0457bf6907 100644
--- a/django/db/backends/schema.py
+++ b/django/db/backends/schema.py
@@ -226,9 +226,6 @@ class BaseDatabaseSchemaEditor(object):
             if col_type_suffix:
                 definition += " %s" % col_type_suffix
             params.extend(extra_params)
-            # Indexes
-            if field.db_index and not field.unique:
-                self.deferred_sql.append(self._create_index_sql(model, [field], suffix=""))
             # FK
             if field.rel and field.db_constraint:
                 to_table = field.rel.to._meta.db_table
@@ -262,10 +259,10 @@ class BaseDatabaseSchemaEditor(object):
             "definition": ", ".join(column_sqls)
         }
         self.execute(sql, params)
-        # Add any index_togethers
-        for field_names in model._meta.index_together:
-            fields = [model._meta.get_field_by_name(field)[0] for field in field_names]
-            self.execute(self._create_index_sql(model, fields, suffix="_idx"))
+
+        # Add any field index and index_together's (deferred as SQLite3 _remake_table needs it)
+        self.deferred_sql.extend(self._model_indexes_sql(model))
+
         # Make M2M tables
         for field in model._meta.local_many_to_many:
             if field.rel.through._meta.auto_created:
@@ -501,18 +498,12 @@ class BaseDatabaseSchemaEditor(object):
                 rel_fk_names = self._constraint_names(rel.model, [rel.field.column], foreign_key=True)
                 for fk_name in rel_fk_names:
                     self.execute(self._delete_constraint_sql(self.sql_delete_fk, rel.model, fk_name))
-        # Removed an index?
+        # Removed an index? (no strict check, as multiple indexes are possible)
         if (old_field.db_index and not new_field.db_index and
                 not old_field.unique and not
                 (not new_field.unique and old_field.unique)):
             # Find the index for this field
             index_names = self._constraint_names(model, [old_field.column], index=True)
-            if strict and len(index_names) != 1:
-                raise ValueError("Found wrong number (%s) of indexes for %s.%s" % (
-                    len(index_names),
-                    model._meta.db_table,
-                    old_field.column,
-                ))
             for index_name in index_names:
                 self.execute(self._delete_constraint_sql(self.sql_delete_index, model, index_name))
         # Change check constraints?
@@ -802,15 +793,47 @@ class BaseDatabaseSchemaEditor(object):
             index_name = "D%s" % index_name[:-1]
         return index_name
 
-    def _create_index_sql(self, model, fields, suffix=""):
+    def _create_index_sql(self, model, fields, suffix="", sql=None):
+        """
+        Return the SQL statement to create the index for one or several fields.
+        `sql` can be specified if the syntax differs from the standard (GIS
+        indexes, ...).
+        """
+        if len(fields) == 1 and fields[0].db_tablespace:
+            tablespace_sql = self.connection.ops.tablespace_sql(fields[0].db_tablespace)
+        elif model._meta.db_tablespace:
+            tablespace_sql = self.connection.ops.tablespace_sql(model._meta.db_tablespace)
+        else:
+            tablespace_sql = ""
+        if tablespace_sql:
+            tablespace_sql = " " + tablespace_sql
+
         columns = [field.column for field in fields]
-        return self.sql_create_index % {
+        sql_create_index = sql or self.sql_create_index
+        return sql_create_index % {
             "table": self.quote_name(model._meta.db_table),
             "name": self.quote_name(self._create_index_name(model, columns, suffix=suffix)),
             "columns": ", ".join(self.quote_name(column) for column in columns),
-            "extra": "",
+            "extra": tablespace_sql,
         }
 
+    def _model_indexes_sql(self, model):
+        """
+        Return all index SQL statements (field indexes, index_together) for the
+        specified model, as a list.
+        """
+        if not model._meta.managed or model._meta.proxy or model._meta.swapped:
+            return []
+        output = []
+        for field in model._meta.local_fields:
+            if field.db_index and not field.unique:
+                output.append(self._create_index_sql(model, [field], suffix=""))
+
+        for field_names in model._meta.index_together:
+            fields = [model._meta.get_field_by_name(field)[0] for field in field_names]
+            output.append(self._create_index_sql(model, fields, suffix="_idx"))
+        return output
+
     def _create_fk_sql(self, model, field, suffix):
         from_table = model._meta.db_table
         from_column = field.column
diff --git a/docs/releases/1.7.2.txt b/docs/releases/1.7.2.txt
index e3db0d404e..f6b40f32b7 100644
--- a/docs/releases/1.7.2.txt
+++ b/docs/releases/1.7.2.txt
@@ -102,6 +102,7 @@ Bugfixes
 * Fixed ``runserver`` crash when socket error message contained Unicode
   characters (:ticket:`23946`).
 
+<<<<<<< HEAD
 * Fixed serialization of ``type`` when adding a ``deconstruct()`` method
   (:ticket:`23950`).
 
@@ -111,3 +112,7 @@ Bugfixes
 
 * Fixed a crash when adding ``blank=True`` to ``TextField()`` on MySQL
   (:ticket:`23920`).
+
+* Fixed index creation by the migration infrastructure, particularly when
+  dealing with PostgreSQL specific {text|varchar}_pattern_ops indexes
+  (:ticket:`23954`).
diff --git a/tests/indexes/tests.py b/tests/indexes/tests.py
index 786c6b5cb4..411b7646c4 100644
--- a/tests/indexes/tests.py
+++ b/tests/indexes/tests.py
@@ -7,7 +7,10 @@ from django.test import TestCase
 from .models import Article, IndexTogetherSingleList
 
 
-class IndexesTests(TestCase):
+class CreationIndexesTests(TestCase):
+    """
+    Test index handling by the to-be-deprecated connection.creation interface.
+    """
     def test_index_together(self):
         index_sql = connection.creation.sql_indexes_for_model(Article, no_style())
         self.assertEqual(len(index_sql), 1)
@@ -36,3 +39,37 @@ class IndexesTests(TestCase):
         """Test indexes are not created for related objects"""
         index_sql = connection.creation.sql_indexes_for_model(Article, no_style())
         self.assertEqual(len(index_sql), 1)
+
+
+class SchemaIndexesTests(TestCase):
+    """
+    Test index handling by the db.backends.schema infrastructure.
+    """
+    def test_index_together(self):
+        index_sql = connection.schema_editor()._model_indexes_sql(Article)
+        self.assertEqual(len(index_sql), 1)
+
+    def test_index_together_single_list(self):
+        # Test for using index_together with a single list (#22172)
+        index_sql = connection.schema_editor()._model_indexes_sql(IndexTogetherSingleList)
+        self.assertEqual(len(index_sql), 1)
+
+    @skipUnless(connection.vendor == 'postgresql',
+        "This is a postgresql-specific issue")
+    def test_postgresql_text_indexes(self):
+        """Test creation of PostgreSQL-specific text indexes (#12234)"""
+        from .models import IndexedArticle
+        index_sql = connection.schema_editor()._model_indexes_sql(IndexedArticle)
+        self.assertEqual(len(index_sql), 5)
+        self.assertIn('("headline" varchar_pattern_ops)', index_sql[2])
+        self.assertIn('("body" text_pattern_ops)', index_sql[3])
+        # unique=True and db_index=True should only create the varchar-specific
+        # index (#19441).
+        self.assertIn('("slug" varchar_pattern_ops)', index_sql[4])
+
+    @skipUnless(connection.vendor == 'postgresql',
+        "This is a postgresql-specific issue")
+    def test_postgresql_virtual_relation_indexes(self):
+        """Test indexes are not created for related objects"""
+        index_sql = connection.schema_editor()._model_indexes_sql(Article)
+        self.assertEqual(len(index_sql), 1)