Feedback of replacement process

[brendanheywood]

When doing a replacement and there are skipped or errors records its hard to know which records were affected

• when updating the progress bar, if there are errors and just the errors, emit these into a table under the progress. This could be either as it updates, or at the end which ever is easiest
• if we are in 4.3 then we could stream these updates see https://tracker.moodle.org/browse/MDL-73734
• we only need a subset of data to identify the row, eg table name, column, id, rownumber (or equivalent for file replaces)
• we could add the whole row but large chunks of escaped html might mess up the UI due to their size

Advanced full version

• a more advanced version would be to write the output back to a new csv identical to the input, but with one more column added with the status and then when it is finishes you can download the file
• need a cron task to clean these files up after some time eg 24 hours