[migrations] Cleanup recent migrations (#5155)

superset/migrations/versions/130915240929_is_sqllab_viz_flow.py

@@ -45,7 +45,7 @@ def upgrade():
     for tbl in session.query(Table).all():
         if tbl.sql:
             tbl.is_sqllab_view = True
-            session.merge(tbl)
+
     session.commit()
     db.session.close()
 

superset/migrations/versions/c5756bec8b47_time_grain_sqla.py

@@ -13,7 +13,7 @@ down_revision = 'e502db2af7be'
 from alembic import op
 import json
 from sqlalchemy.ext.declarative import declarative_base
-from sqlalchemy import Column, Integer, String, Text
+from sqlalchemy import Column, Integer, Text
 
 from superset import db
 
@@ -24,8 +24,6 @@ class Slice(Base):
     __tablename__ = 'slices'
 
     id = Column(Integer, primary_key=True)
-    datasource_type = Column(String(200))
-    slice_name = Column(String(250))
     params = Column(Text)