Re: Add index scan progress to pg_stat_progress_vacuum

>    Another idea I came up with is that we can wait for all index vacuums
>    to finish while checking and updating the progress information, and
>    then calls WaitForParallelWorkersToFinish after confirming all index
>    status became COMPLETED. That way, we don’t need to change the
>    parallel query infrastructure. What do you think?

Thinking about this a bit more, the idea of using 
WaitForParallelWorkersToFinish
Will not work if you have a leader worker that is
stuck on a large index. The progress will not be updated
until the leader completes. Even if the parallel workers
finish.

What are your thought about piggybacking on the 
vacuum_delay_point to update progress. The leader can 
perhaps keep a counter to update progress every few thousand
calls to vacuum_delay_point. 

This goes back to your original idea to keep updating progress
while scanning the indexes.

/*
 * vacuum_delay_point --- check for interrupts and cost-based delay.
 *
 * This should be called in each major loop of VACUUM processing,
 * typically once per page processed.
 */
void
vacuum_delay_point(void)
{

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Sami Imseih
Amazon Web Services