pub/sub and upd

Community Support
1

If I want to publish to table, once I load in u.q in order to subscribe to a table, I need to do define upd correct?

I have defined upd as upd:{[tabname;tabdata] tabname upsert tabdata} but when I call .u.pub nothing gets inserted.  Am I missing something here?

2

Try this: 

http://code.kx.com/wiki/Cookbook/publishsubscribe

Jonny 

3

Right, I have that example working, but I cant figure out why when I do it in my environment upd wont get called.  Seems like I am doing the same as that example.  

  • load u.q
  • create table
  • call .u.init
  • define upd
  • call .u.pub 

I have tried defining upd to show and to insert and neither seem to work.  

4

Did you connect to your publisher process from your subscriber process?
Did you define upd in your subscriber process?

Did you called .. from your subscriber process?

h(`.u.sub;`;`)

On Thursday, January 15, 2015 at 2:21:34 PM UTC, Roni Hoffman wrote:

Right, I have that example working, but I cant figure out why when I do it in my environment upd wont get called.  Seems like I am doing the same as that example.  

  • load u.q
  • create table
  • call .u.init
  • define upd
  • call .u.pub 

I have tried defining upd to show and to insert and neither seem to work.  

5

Oh I see, so pub only works if there are subscribers?  I was wondering if I could use pub to insert and then subscribe when I need to.

6

The publisher and subscriber in this example are two different processes.
In order to get the published data to a subscriber, the subscriber will have to hopen the publisher process port and then send the `.u.sub message shown below.

h:hopen 1234 // publisher port

h(`.u.sub;`;`)

Here’s a breakdown of this call:

h is handle to publisher process

1st arg is calling .u.sub on pub process. So the publisher knows where to send the data.

2nd arg is the table you want. ` is for all tables (symbol)

3rd is the sym from that table you want. ` is for all syms (symbol)

After this, when .u.pub is called on the publisher process it will send the message to the subscriber process.

Shown here in .u.pub

(neg first w)(upd;t;x)`

The subscriber process then calls the upd function with two arguments, table name (symbol) and row data.

7

Oh I see, that makes perfect sense, thanks so much.