rianoc

q)t:([] a:1 2 3;s:`lll`h`j;longNameColumn:("ww";"ko";"ooo"))
q)t
a s   longNameColumn
--------------------
1 lll "ww"
2 h   "ko"
3 j   "ooo"

rianoc

`syms _.Q.w[]
used| 10407392
heap| 67108864
peak| 67108864
wmax| 0
mmap| 0
mphy| 8464715776
symw| 1380256

rianoc

Tempting to check against spec

isGuid:{
 t:{all (8 4 4 4 12~count each "-" vs x;all x in "ABCDEFabcdef0123456789");
 $[36=c:count x;t x;38=c;all (x[0 37]~"{}";t x 1+til 36;0b]
 }

Instead faster is testing roundtrip

rianoc

addToBeginning:{x setenv y,":",":" sv {x where not x~\:""}":" vs getenv x}
addToEnd:{x setenv (":" sv {x where not x~\:""}":" vs getenv x),":",y}
remove:{x setenv ":" sv {x where not any x like/:("";y)}[;y]":" vs getenv x}
pushToEnd:{x setenv ":" sv {x iasc x like y}[;y] {x where not x~\:""}":" vs getenv x}
bringForward:{x setenv ":" sv {x idesc x like y}[;y] {x where not x~\:""}":" vs getenv x}

Add where needed:

rianoc

/tab : the table to operate on
/baseCols : the columns not to unpivot
/pivotCols : the columns which you wish to unpivot
/kCol : the key name for unpivoted data
/vCol :  the value name for unpivoted data
unpivot:{[tab;baseCols;pivotCols;kCol;vCol] 
 base:?[tab;();0b;{x!x}(),baseCols];
 newCols:{[k;v;t;p] flip (k;v)!(count[t]#p;t p)}[kCol;vCol;tab] each pivotCols;

rianoc

https://code.kx.com/q/basics/errors/

part
Something wrong with the partitions in the HDB; or med applied over partitions or segments

Make a broken HDB:

rianoc

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

When permforming wj out of box multiple aggregations requires the user to perform positional renaming to tidy up the result.

Instead a helper can be created:

wjr:{[f;w;c;t;q]
 if[not 99h~type q[1];
 :f[w;c;t;q]];

rianoc

In Kdb+ you cannot control the use of '/tmp' during a system call. You may need to avoid this if the drive space is small.

For familiarity use the TMPDIR environment variable:

q)setenv[`TMPDIR] "/my/chosen/path" 

Function to run system commands:

rianoc

Use .p.wrap https://code.kx.com/q/ml/embedpy/userguide/#embedpy-objects_1

Example giving each subplot a title:

plt:.p.import[`matplotlib;`:pyplot]
plts:plt[`:subplots;<;pykwargs `ncols`figsize`dpi!(2;24 8;100)]
.p.wrap[plts[1;0]][`:set_title]"Plot1";
.p.wrap[plts[1;1]][`:set_title]"Plot2";

rianoc

systemWithExitCode:{[c] 
  f:first system"mktemp"; //Make a temp file respecting TMPDIR
  c:c," > ",f," 2>&1;echo $?"; //Add redirect to tmp file and capture of exit code
  e:"J"$first system c; //Execute the command
  f:hsym `$f; 
  r:read0 f; //Read the result of the command 
  hdel f; //Delete the tmp file
  `exitCode`output!(e;r)
 }