Comments

• By chrisaycock 2026-03-0122:363 reply

  I first encountered q/kdb+ at a quant job in 2007. I learned so much from the array semantics about how to concisely represent time-series logic that I can't imagine ever using a scalar language for research.

  Fun fact: the aj (asof join) function was my inspiration for pandas.merge_asof. I added the extra parameters (direction, tolerance, allow_exact_matches) because of the limitations I kept hitting in kdb.

  https://code.kx.com/q/ref/aj/

  https://pandas.pydata.org/docs/reference/api/pandas.merge_as...

  By zX41ZdbW 2026-03-0123:03

  Similarly, this is how it was introduced in ClickHouse in 2019: https://github.com/ClickHouse/ClickHouse/pull/4774

  By leprechaun1066 2026-03-020:071 reply

  The aj function at its heart is a bin (https://code.kx.com/q/ref/bin/) search between the two tables, on the requested columns, to find the indices of the right table to zip onto the left table.

    aj[`sym`time;t;q]
  

  becomes

    t,'(`sym`time _q)(`sym`time#q)bin`sym`time#t
  

  The rest of the aj function internals are there to handle edge cases, handling missing columns and options for filling nulls.

  A lot of the joins can be distilled to the core operators/functions in a similar manner. For example the plus-join is

    x+0i^y(cols key y)#x

  By chrisaycock 2026-03-020:58

  Indeed, my very first attempt used numpy.searchsorted:

  https://numpy.org/doc/2.2/reference/generated/numpy.searchso...

  I couldn't figure-out how Arthur's bin matched on symbol though, so I switched to a linear scan on the right table to record the last-seen index for each "by" element. While it worked, my hash table was messy because I relied on Python to handle a whole tuple as a key, which had some issues during initial testing.

  The asof join I wrote for Empirical properly categorizes the keys before they are matched. That approach worked far better.

  https://www.empirical-soft.com/tutorial.html#dataframes

  By sceadu 2026-03-0221:58

  dang I had no idea you wrote the asof join for pandas. thank you for that

• By koolala 2026-03-020:101 reply

  I wish there was a language like K that worked with single precision floats. Would be great to use with graphics.

  By ksherlock 2026-03-020:471 reply

  q is like k and has single precision floats.

  By koolala 2026-03-021:56

  q is closed source so it isn't really viable to build anything out of it unfortunately. I wonder how they made floats work since it is based on k.

• By jjtheblunt 2026-03-020:451 reply

  the github repo linked, under "manual.md", has a link which redirects to malware, such as that ostensibly to "k6".

  By tosh 2026-03-0210:13

  ty, I made a pull request: https://github.com/JohnEarnest/ok/pull/111