.Q.a[012]

Community Support
1

.Q.a0 and .Q.a1 are very similar but have several differences.

  1. Can you explain to me how they are treated differently? I know you are not supposed to meddle with q.k, but this is for my own curiosity.

These funcs comes in very handy when defining my own aggr functions, hence me questioning them. A question was raised quite a while ago regarding this, but wasn’t answered…

https://groups.google.com/forum/#!searchin/personal-kdbplus/.Q.a0/personal-kdbplus/zITo2qRGBLY/Pj3FSQjDOZoJ

  1. What then is .Q.a2?

  2. On a further note, does anyone have every .Q func detailed anywhere as there are many not on code.kx?

Thanks,

Sean

2

.Q.a0 is the list of functions which can be automatically aggregated across partitions

http://code.kx.com/wiki/JB:KdbplusForMortals/partitioned_tables#1.3.4.0_Overview

.Q.a1 is the list of the functions which need special handling.  For example, sum doesn?t need special handling as the total sum across all partitions is the sum of all the individual partition sums (i.e. the function can be applied in the individual partitions, then re-applied to the individual results).  Avg does need special handling as the you can?t average the averages - you need to get the total sum and total count across all partitions, then divide.

.Q.a2 are the corresponding special handlers.

  

3

Thank you very much..this is exactly what I needed.