Feature Request: Verification Step

[langsharpe]

Has anyone else had a need to for a verification step. An assurance that the migration has completed successfully. e.g.

Lhm.change_table :my_table do |table|
  table.ddl "ALTER TABLE `#{table.name}` DEFAULT CHARACTER SET utf8mb4, DEFAULT COLLATE utf8mb4_unicode_ci"
  verification do |table|
    result = table.query "SELECT count(*) FROM {#table.name) as new_table JOIN #{table.name} as old_table USING (id) WHERE new_table.name != old_table.name"
    result.first[0] == 0
  end
end

The verification block would be executed after the Chunker and before the Switcher. If it evaluated to false the change would be rolled back.

Does anyone else have a need for this and what strategies do you currently use? Does a feature like this fit into this gem?

[arthurnn]

wondering if we were doing that check manually or not. @camilo @sroysen do you know?

[camilo]

no, but the metadata lock should prevent any rows from being inserted/changed ( within the kown potential problems the replace/triggers have) I don't think is needed cc @sroysen