Add basic support of unique constraints reflectionpr/4

Inspection API already supports reflection of table
indexes information and those also include unique
constraints (at least for PostgreSQL and MySQL).
But it could be actually useful to distinguish between
indexes and plain unique constraints (though both are
implemented in the same way internally in RDBMS).

This change adds a new method to Inspection API - get_unique_constraints()
and implements it for SQLite, PostgreSQL and MySQL dialects.

2 files changed, 39 insertions, 0 deletions

diff --git a/lib/sqlalchemy/engine/interfaces.py b/lib/sqlalchemy/engine/interfaces.py
index f623a2a61..d5fe5c5e2 100644
--- a/lib/sqlalchemy/engine/interfaces.py
+++ b/lib/sqlalchemy/engine/interfaces.py
@@ -338,6 +338,25 @@ class Dialect(object):
 
         raise NotImplementedError()
 
+    def get_unique_constraints(self, table_name, schema=None, **kw):
+        """Return information about unique constraints in `table_name`.
+
+        Given a string `table_name` and an optional string `schema`, return
+        unique constraint information as a list of dicts with these keys:
+
+        name
+          the unique constraint's name
+
+        column_names
+          list of column names in order
+
+        \**kw
+          other options passed to the dialect's get_unique_constraints() method.
+
+        """
+
+        raise NotImplementedError()
+
     def normalize_name(self, name):
         """convert the given name to lowercase if it is detected as
         case insensitive.
diff --git a/lib/sqlalchemy/engine/reflection.py b/lib/sqlalchemy/engine/reflection.py
index cf2caf679..1926e693a 100644
--- a/lib/sqlalchemy/engine/reflection.py
+++ b/lib/sqlalchemy/engine/reflection.py
@@ -347,6 +347,26 @@ class Inspector(object):
                                                   schema,
                                             info_cache=self.info_cache, **kw)
 
+    def get_unique_constraints(self, table_name, schema=None, **kw):
+        """Return information about unique constraints in `table_name`.
+
+        Given a string `table_name` and an optional string `schema`, return
+        unique constraint information as a list of dicts with these keys:
+
+        name
+          the unique constraint's name
+
+        column_names
+          list of column names in order
+
+        \**kw
+          other options passed to the dialect's get_unique_constraints() method.
+
+        """
+
+        return self.dialect.get_unique_constraints(
+            self.bind, table_name, schema, info_cache=self.info_cache, **kw)
+
     def reflecttable(self, table, include_columns, exclude_columns=()):
         """Given a Table object, load its internal constructs based on
         introspection.