How to sort columns in a HDB to apply the p attribute

I have a HDB that is date partitioned. I want to apply the p attribute historically to a specific column. As far as I am aware, to do this, I need to first ensure this column is sorted in a way that all common occurrences are adjacent. Currently, this is not the case. How can I sort this HDB so that this column in each partition has common values adjacent to each other.

Thank you!

Solution

You can use xasc on disk.

https://code.kx.com/q/ref/asc/#xasc

You'd want to sort each partition and apply the parted attribute. Could build up the paths with .Q.PD & .Q.PV as I don't think this is something that exists in dbmaint.q.

This is just a general idea, it is untested so use on some test data and modify to meet your hdb structure if needed.
You may need to modify the xasc part if you want additional sorting within each part.

{[tbl;sortPartCol]
  {[sortPartCol;path] sortPartCol xasc path;@[path;sortPartCol;`p#] 
   }[sortPartCol] each distinct ` sv/: (.Q.PD cross `$string .Q.PV) cross tbl
   }

https://code.kx.com/q/ref/dotq/#qpv-partition-values https://code.kx.com/q/ref/dotq/#qpd-partition-locations