kdb part error while loading splayed tables from HDB - kdb

Question

I am saving a table which is enumerated and to be splayed on my hdb. After which we load the hdb directory
There was a corruption which caused
'2022.01.01T00:00:01.000 part
(.Q.L) error"
https://code.kx.com/q/ref/dotq/#ql-load/
This is due to load, and I tried corrupting partition to replicate:
Corrupted .d file
Corrupted splayed column(s)
Removed entire partition
Most of the above cases are handled in our exception.
".\2022.01.1\tbl. OS reports: No such file or directory"
but I couldn't replicate the use case where .Q.l happened nor find why it happened from my logs.
Can someone please suggest what kind of corruption could have caused the part error during load.

Answer 1

One possible cause would be a partition folder without correct read permissions:
$ mkdir -p badHDB/2001.01.01/tab1
$ mkdir -p badHDB/20011.01.01/tab2
$ mkdir -p badHDB/2002.01.01
$ chmod 000 badHDB/2002.01.01
Running it we see the error:
q badHDB
'part
[2] (.Q.L)
[0] \l badHDB
You could write a small function to try to narrow down the issues:
// https://code.kx.com/q/ref/system/#capture-stderr-output
q)tmp:first system"mktemp"
q)tab:flip `part`date`osError`files`error!flip {d:1_string x;{y:string y;(y;"D"$y),{r:system x;$[0~"J"$last r;(0b;-1_r;"");(1b;();first r)]} "ls ",x,"/",y," > ",tmp," 2>&1;echo $? >> ",tmp,";cat ",tmp}[d] each key x} `:badHDB
This would result in:
part date osError files error
-----------------------------------------------------------------------------------------------------------
"2001.01.01" 2001.01.01 0 ,"tab1" ""
"20011.01.01" 0 ,"tab2" ""
"2002.01.01" 2002.01.01 1 () "ls: cannot open directory 'badHDB/2002.01.01': Permission denied"
For a larger HDB filter down to partitions with issues:
select from tab where or[null date;osError]