Add has_index function

sqlalchemy_utils/__init__.py

@@ -19,6 +19,7 @@ from .functions import (
     get_referencing_foreign_keys,
     get_tables,
     group_foreign_keys,
+    has_index,
     identity,
     merge_references,
     mock_engine,
@@ -93,6 +94,7 @@ __all__ = (
     get_referencing_foreign_keys,
     get_tables,
     group_foreign_keys,
+    has_index,
     identity,
     instrumented_list,
     merge_references,

sqlalchemy_utils/functions/__init__.py

@@ -3,10 +3,11 @@ from .mock import create_mock_engine, mock_engine
 from .render import render_expression, render_statement
 from .sort_query import sort_query, QuerySorterException
 from .database import (
-    database_exists,
     create_database,
+    database_exists,
     drop_database,
     escape_like,
+    has_index,
     is_auto_assigned_date_column,
 )
 from .foreign_keys import (

sqlalchemy_utils/functions/database.py

@@ -1,6 +1,5 @@
 from sqlalchemy.engine.url import make_url
 import sqlalchemy as sa
-from sqlalchemy.schema import MetaData, Table, ForeignKeyConstraint
 from sqlalchemy.exc import ProgrammingError, OperationalError
 import os
 from copy import copy
@@ -31,6 +30,69 @@ def escape_like(string, escape_char='*'):
     )
 
 
+def has_index(column):
+    """
+    Return whether or not given column has an index. A column has an index if
+    it has a single column index or it is the first column in compound column
+    index.
+
+    :param column: SQLAlchemy Column object
+
+    .. versionadded: 0.26.2
+
+    ::
+
+        from sqlalchemy_utils import has_index
+
+
+        class Article(Base):
+            __tablename__ = 'article_translation'
+            id = sa.Column(sa.Integer, primary_key=True)
+            title = sa.Column(sa.String(100))
+            is_published = sa.Column(sa.Boolean)
+            is_deleted = sa.Column(sa.Boolean)
+            is_archived = sa.Column(sa.Boolean)
+
+            __table_args__ = (
+            )
+
+
+        table = Article.__table__
+
+        has_index(table.c.is_published) # True
+        has_index(table.c.is_deleted)   # True
+        has_index(table.c.is_archived)  # False
+
+
+    Also supports primary key indexes
+
+    ::
+
+        from sqlalchemy_utils import has_index
+
+
+        class ArticleTranslation(Base):
+            __tablename__ = 'article_translation'
+            id = sa.Column(sa.Integer, primary_key=True)
+            locale = sa.Column(sa.String(10), primary_key=True)
+            title = sa.Column(sa.String(100))
+
+
+        table = ArticleTranslation.__table__
+
+        has_index(table.c.locale)   # False
+        has_index(table.c.id)       # True
+    """
+    return (
+        column is column.table.primary_key.columns.values()[0]
+        or
+        any(
+            index.columns.values()[0] is column
+            for index in column.table.indexes
+        )
+    )
+
+
 def is_auto_assigned_date_column(column):
     """
     Returns whether or not given SQLAlchemy Column object's is auto assigned

sqlalchemy_utils/functions/orm.py

@@ -3,7 +3,6 @@ try:
 except ImportError:
     from ordereddict import OrderedDict
 from functools import partial
-from itertools import groupby
 from inspect import isclass
 from operator import attrgetter
 import sqlalchemy as sa
@@ -16,7 +15,6 @@ from sqlalchemy.orm.mapper import Mapper
 from sqlalchemy.orm.query import _ColumnEntity
 from sqlalchemy.orm.session import object_session
 from sqlalchemy.orm.util import AliasedInsp
-from ..query_chain import QueryChain
 
 
 def get_mapper(mixed):

tests/functions/test_has_index.py

@@ -0,0 +1,35 @@
+import sqlalchemy as sa
+from sqlalchemy.ext.declarative import declarative_base
+
+from sqlalchemy_utils import has_index
+
+
+class TestHasIndex(object):
+    def setup_method(self, method):
+        Base = declarative_base()
+
+        class ArticleTranslation(Base):
+            __tablename__ = 'article_translation'
+            id = sa.Column(sa.Integer, primary_key=True)
+            locale = sa.Column(sa.String(10), primary_key=True)
+            title = sa.Column(sa.String(100))
+            is_published = sa.Column(sa.Boolean, index=True)
+            is_deleted = sa.Column(sa.Boolean)
+            is_archived = sa.Column(sa.Boolean)
+
+            __table_args__ = (
+                sa.Index('my_index', is_deleted, is_archived),
+            )
+
+        self.table = ArticleTranslation.__table__
+
+    def test_compound_primary_key(self):
+        assert has_index(self.table.c.id)
+        assert not has_index(self.table.c.locale)
+
+    def test_single_column_index(self):
+        assert has_index(self.table.c.is_published)
+
+    def test_compound_column_index(self):
+        assert has_index(self.table.c.is_deleted)
+        assert not has_index(self.table.c.is_archived)