Re: progress reporting views and TimestampTz fields

On 25/02/2020 09:13, Fujii Masao wrote:
> Hi,
>
> I'm thinking to change the progress reporting views like
> pg_stat_progress_vacuum so that they also report the time when
> the target command was started and the time when the phase was
> last changed. IMO this is very helpful to estimate the remaining
> time required to complete the current phase. For example,
> if pg_stat_progress_vacuum reports that the current phase
> "scanning heap" started 1 hour before and the progress percentage
> is 50%, we can imagine the remaining time of this phase would be
> approximately 1 hour. Of course, this is not the exact estimation,
> but would be helpful as a hint for operations. Thought?
>
>     ProgressCommandType st_progress_command;
>     Oid            st_progress_command_target;
>     int64        st_progress_param[PGSTAT_NUM_PROGRESS_PARAM];
>
> We cannnot add those timestamp fields simply in the progress
> reporting views because the type of the fields in PgBackendStatus
> struct is only int64 for now, as the above. So I'm thinking to add
> new TimestampTz fields (maybe four fields are enough even for
> future usager?) into PgBackendStatus and make pg_stat_get_progress_info()
> report those fields as timestamp. This change leads to increase
> in the size of PgBackendStatus, as demerit. But I like this approach
> because it's simple and intuitive.
>
> Another idea is to store TimestampTz values in int64 fields
> (for example, always store TimestampTz values in the last two int64
> fields) and make pg_stat_get_progress_info() report not only int64
> but also those TimestampTz fields. This approach doesn't increase
> the struct size, but is a bit tricky. Also int64 fields that TimestampTz
> values will be stored into might be already used to store int64 values
> in some existing extensions. If we need to handle this case, further
> tricky way might need to be implemented. That sounds not good.
>
> Therefore, I'd like to implement the first idea that I described, to
> add the timestamp fields in the progress reporting view. Thought?

+1 on the idea. No opinion on the implementation.
--
Vik Fearing