kdb/q: Query multiple handles with hopen

Question

I would like to be able to query several handles at once, where the tables have the same format like:

handles: 8000,8001,8003 tables: foo

Want to do something like:

x:hopen `8000`8001`8003
x select from foo col1,col2

So i get rows from each foo table on each handle.

Is there a way to achieve this?

Thank you

Answer 1

Use 'each' to hopen each handle

  q)h:hopen each 8000 8001 8002
  q)h
  476 480 484i

Use apply each-left to send the same query to each server

  q)r:h@\:"select col1,col2 from foo"
  q)r
  +`col1`col2!(1 2;2 3)
  +`col1`col2!(1 2;2 3)
  +`col1`col2!(1 2;2 3)

Then you'll have to raze the result:

 q)show res:raze r
col1 col2
--------- 
 1    2
 2    3
 1    2
 2    3
 1    2
 2    3