I notice one interesting problem with the new negative -s mode since 3.1 – query behaviour seems to differ to the point that innocent queries that run properly in positive -s mode fails in negative -s mode.
The code below demonstrates it (note: the problem only shows with splayed tables):
/ Start with negative -s in command line/KDB+ 3.6 2019.04.02 Copyright (C) 1993-2019 Kx Systems/w32/ 8()core 4095MB me my-host xxx.xxx.xxx.xxx NONEXPIRE/ Setup databaseN:1000000;{.Q.dd[:./db;($string x;T;)]set@[;sym;p#].Q.en[:./db]sym xasc([]sym:N?1;px:N?100.;size:N?1000)}each .z.D-til 3;system"l ./db";tables/ Setup parallel slavesports:55500+til neg system"s";(system"start q . -p “,string@)each ports;.z.pd:{n:abs system"s”;$[n=count handles;handles;[hclose each handles;:handles::u#hopen each ports]]}handles:u#int$();system"title MASTER";.z.pd[]@\:({system"title ",string system"p"};)/ Test queryselect size wavg px by sym from T where date=.z.D,sym ina / This runs properlyselect size wavg px by sym from T where date=.z.D,sym inab / This fails with 'length
Note that the last query above would have run properly with the q process was started with a positive -s mode.
My question: Is this indeed a bug in kdb+'s implementation of multi-process mode? Or is this more a “feature,” whose documentation I missed?