Finer grained progress updates

[brendanheywood]

We currently only update the progress between each column / table combo. We should be able to move this deeper down into plain_text_search and regular_expression_search so that every 100 rows or every 20 seconds we get updates on specific columns that take minutes to run

[bwalkerl]

It appears like the bottleneck is almost entirely on get_recordset_sql(), Breaking this down further would require splitting the search into batches, but I'm not sure this is worth it?

[brendanheywood]

Yeah its low priority, I've taken it off the board. I'd assume the fixed overhead would apply to each batch, or worse it would start ok and then get worse as the pagination progressed so we'd go from potentially O(n) to O(n*n)