Limits of string transformations in q, stars in TOK

Question

I'm trying to convert int values to minutes, and in some cases it gives me stars * in the result:

string "U"$"99:59" / "99:59"
string "U"$"100:00" / "**:00"

What are the rules for this stars to appear?

Update for seconds:

string "V"$"1000" / "10:00:00"
string "V"$"10000" / "**:00:00"
string "V"$"100000" / "10:00:00"
string "V"$"1000000" / "**:00:00"

Is it possible to configure this rules, say to stop smudging the origin values?

Looks to be when there are more than two digits before the colon, and at least one the digits before the first two is non zero — Adam Bonham, Sep 07 '20 at 11:53

score 3 · Answer 1 · edited Sep 07 '20 at 13:27

I think the stars that appear are just kdb's way of saying that the result couldn't be displayed. The minute and second datatypes have the form hh:mm and hh:mm:ss, respectively. So if kdb reads the hour part as having more than 3 digits (i.e greater than 99), the stars will appear.

If you're casting a string into a minute datatype, then kdb converts the last two chars into minutes, and the rest into hours, eg

"U"$"1234" / 12:34
"U"$"12345" / **:45

Something similar occurs when you convert a string into seconds. If the length of the string is 6 or greater, then the last two chars are converted into seconds. Otherwise, the seconds are set to 00. The rest of the string is then converted into hh:mm as above. To illustrate this, look at:

"V"$"1234" / 12:34:00
"V"$"12345" / **:45:00
"V"$"123456" / 12:34:56
"V"$"1123456" / **:34:56

I should also note that even though stars appear, you can still do things like temporal arithmetic as usual, eg

"U"$"100:00 / **:00
("U"$"100:00")-"U"$"1:00" / 99:00

Limits of string transformations in q, stars in TOK

1 Answers1