CODEWITHSUNDEEP
kdb+
eliquinox
eliquinox

Reputation: 33

'length error in the tickerplant kdb+/q

When I start up the tick.q with sym.q and feed.q with files provided as follows:

q tick.q sym -p 5010
q feed.q

Github links: https://github.com/KxSystems/cookbook/tree/master/start/tick , https://github.com/KxSystems/kdb-tick

The tickerplant process prints 'length error on every update, which usually occurs when incorrect number of elements is passed: https://code.kx.com/wiki/Errors

I suspect that this happens when the feed process calls .u.upd

Any suggestions as to how to solve this problem?

Upvotes: 1

Views: 1736

Answers (3)

nyi
nyi

Reputation: 3229

Open a new q session on some port (9999), add your schema definition there and define insert as .u.upd or something like this :

.u.upd:{[t;d]
 .test.t:t;
 .test.d:d;
 t upsert d
}

Now point your feed to this q session and stream some data; this will enable you to analyse the test variables in case of the errors.

Upvotes: 0

Alex R.
Alex R.

Reputation: 721

If you are using the plain vanilla tick setup from KX there is no reason for that error to appear.

Also, I think you need to start the feed as feed.q -t 200 otherwise you will get no data coming through.

Usually the 'length error appears when the table schema does not match. So if you have the sym.q file (and it is loaded correctly) you should not have that issue.

Just to confirm this is the structure of your directory: 

.
├── feed.q
├── README.md
├── tick
│   ├── r.q
│   ├── sym.q
│   └── u.q
└── tick.q

The sym.q file contains your table schema. If you change something in the feedhandler the table schema in the sym.q must match that change (i.e if you add a column in the feed you must also add a holder in the table for that column)

Upvotes: 0

Mark Kelly
Mark Kelly

Reputation: 1780

Entering \e 1 into the command line will suspend execution and run the debugger allowing you to see what failed and query the variables which should help pinpoint what is causing the issues.

More about debugging here https://code.kx.com/q/ref/debug/

Upvotes: 1

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