Skip expression-based index reflection for SQLite

Reflection of an index based on SQL expressions are now skipped with a
warning, in the same way as that of the Postgresql dialect, where we currently
do not support reflecting indexes that have SQL expressions within them.
Previously, an index with columns of None were produced which would break
tools like Alembic.

Fixes: #4431
Change-Id: I1363ade912d206b42669331e2be2bb6f444b65a2

1 files changed, 10 insertions, 3 deletions

diff --git a/lib/sqlalchemy/dialects/sqlite/base.py b/lib/sqlalchemy/dialects/sqlite/base.py
index 1eea2b6c6..424f91fa6 100644
--- a/lib/sqlalchemy/dialects/sqlite/base.py
+++ b/lib/sqlalchemy/dialects/sqlite/base.py
@@ -1941,17 +1941,24 @@ class SQLiteDialect(default.DefaultDialect):
                 "sqlite_autoindex"
             ):
                 continue
-
             indexes.append(dict(name=row[1], column_names=[], unique=row[2]))
 
         # loop thru unique indexes to get the column names.
-        for idx in indexes:
+        for idx in list(indexes):
             pragma_index = self._get_table_pragma(
                 connection, "index_info", idx["name"]
             )
 
             for row in pragma_index:
-                idx["column_names"].append(row[2])
+                if row[2] is None:
+                    util.warn(
+                        "Skipped unsupported reflection of "
+                        "expression-based index %s" % idx["name"]
+                    )
+                    indexes.remove(idx)
+                    break
+                else:
+                    idx["column_names"].append(row[2])
         return indexes
 
     @reflection.cache