Note 'distribute' method is not merged into SQLBase, for 2 reasons:
- SQLQueue still differs from SQLDict because it does not remove duplicate
  messages.
- 'order_validation_text' column only exists in 'message' table

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@37687 20353a03-c40f-0410-a6d1-a30d3c3de9de