[Enhancement]: Improve messages when picking default compression settings

[erimatnor]

What type of enhancement is this?

User experience

What subsystems and features will be improved?

Compression

What does the enhancement do?

The functionality to pick default compression settings when none are given can give a bit strange output:

postgres=# create table mytable (time timestamptz, device int, temp float);
CREATE TABLE
postgres=# select create_hypertable('mytable', 'time');
NOTICE:  adding not-null constraint to column "time"
DETAIL:  Dimensions cannot have NULL values.
  create_hypertable   
----------------------
 (6,public,mytable,t)
(1 row)

postgres=# alter table mytable set (timescaledb.compress);
WARNING:  there was some uncertainty picking the default segment by for the hypertable: You do not have any indexes on columns that can be used for segment_by and thus we are not using segment_by for compression. Please make sure you are not missing any indexes
NOTICE:  default segment by for hypertable "mytable" is set to ""
NOTICE:  default order by for hypertable "mytable" is set to ""time" DESC"
ALTER TABLE

In the above example, the system tells you that there is a segmentby column set to the empty string. Does that mean there is no segmentby or that there is an error in the output?

Also, double quoting happens in ""time" DESC" it would be cleaner to just print '"time" DESC' or "time DESC".

Apart from this, the multiple messages output is a bit jarring and overloads the user with info. I think it would be better to collect this info into one string and output one message.

Implementation challenges

None.

[jrimek-prgs]

is there any workaround how to suppress the warning?

[erimatnor]

is there any workaround how to suppress the warning?

Not currently. Perhaps it is something we can consider in the future.

[jflambert]

I just logged a similar bug #7663

I can confirm that the double-quoting observed here is no longer present in v2.18.0 (so perhaps we could close this one)

However I am also facing confusion regarding the segmentby/orderby WARNINGs, which I'm not sure if I should be heeding or ignoring.