Using the timer function .z.ts in q/kdb+

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q/kdb+ has several pre-defined functions in the dot z namespace such as .z.a to get the IP address, .z.h to get the host, and .z.b to get the dependencies. Today, we will discuss a callback function in the dot z namespace called .z.ts.

.z.ts is a very simple timer function that is invoked at regular pre-configured intervals. The interval is set by \t command and is set to 0 by default.

For example:

q)\t
0i

To invoke a function regularly, you need to set the timer and define the .z.ts function. For example, if I want to print the current timestamp every 5 seconds, here is how I would do that:

First, set the timer using milliseconds:

q)\t 5000

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Then, define .z.ts to print out the timestamp. To do that, we will use another handy pre-defined function in the dot z namespace, .z.P, that returns the current timestamp.

q).z.P
2020.06.16D18:12:36.976243000

As soon as you define .z.ts, you will start seeing timestamps being printed every 5 seconds:

q).z.ts:{0N!.z.P}
q)2020.06.16D18:13:47.490599000
2020.06.16D18:13:52.491541000
2020.06.16D18:13:57.490293000
2020.06.16D18:14:02.493378000
2020.06.16D18:14:07.491536000
2020.06.16D18:14:12.492940000

And that’s all there is to .z.ts. It’s a very simple function but can be very handy and you will encounter it quite frequently. For example, it is used in the sample publisher.q code provided by Kx:

// create timer function to randomly publish
// between 1 and 10 meter records, and between 1 and 5 grid records
.z.ts:{publishmeter[1+rand 10]; publishgrid[1+rand 5]}