- Postgresql "functional" indexes are necessarily skipped from the

autogenerate process, as the SQLAlchemy backend currently does not
support reflection of these structures.   A warning is emitted
both from the SQLAlchemy backend as well as from the Alembic
backend for Postgresql when such an index is detected.
fixes #282

1 files changed, 21 insertions, 1 deletions

diff --git a/alembic/ddl/postgresql.py b/alembic/ddl/postgresql.py
index ac3a5f4..1002687 100644
--- a/alembic/ddl/postgresql.py
+++ b/alembic/ddl/postgresql.py
@@ -1,10 +1,17 @@
 import re
 
 from .. import compat
+from .. import util
 from .base import compiles, alter_table, format_table_name, RenameTable
 from .impl import DefaultImpl
 from sqlalchemy.dialects.postgresql import INTEGER, BIGINT
-from sqlalchemy import text, Numeric
+from sqlalchemy import text, Numeric, Column
+
+if compat.sqla_08:
+    from sqlalchemy.sql.expression import UnaryExpression
+else:
+    from sqlalchemy.sql.expression import _UnaryExpression as UnaryExpression
+
 import logging
 
 log = logging.getLogger(__name__)
@@ -97,6 +104,19 @@ class PostgresqlImpl(DefaultImpl):
         for name, (uq, ix) in doubled_constraints.items():
             conn_indexes.remove(ix)
 
+        for idx in list(metadata_indexes):
+            if compat.sqla_08:
+                exprs = idx.expressions
+            else:
+                exprs = idx.columns
+            for expr in exprs:
+                if not isinstance(expr, (Column, UnaryExpression)):
+                    util.warn(
+                        "autogenerate skipping functional index %s; "
+                        "not supported by SQLAlchemy reflection" % idx.name
+                    )
+                    metadata_indexes.discard(idx)
+
 
 @compiles(RenameTable, "postgresql")
 def visit_rename_table(element, compiler, **kw):