• kdb+

  What is the purpose of publishing value each t to t in .u.pub?

  Posted by mannix on March 17, 2022 at 12:00 am

  if[system“t”;
  	.z.ts:{pub‘[t;value each t];@[`.;t;@[;`sym;`g#]0#];i::j;ts .z.D};
  	upd:{[t;x]
  	if[not -16=type first first x;if[d<“d”$a:.z.P;.z.ts[]];a:“n”$a;x:$[0>type first x;a,x;(enlist(count first x)#a),x]];
  	t insert x;if[l;l enlist (`upd;t;x);j+:1];}];

  What do we use .z.ts to publish “value each t” to the “t” itself, I thought we just added updates to the table, not the whole table itself?

  Why is this?

  mannix replied 8 months, 1 week ago 2 Members · 1 Reply
• 1 Reply

• 

  rocuinneagain

  Member

  March 21, 2022 at 12:00 am

  This is batching mode when the timer t is set. https://code.kx.com/q/basics/syscmds/#t-timer

  In this mode the TP will cache data and only publish it when the timer triggers .z.ts https://code.kx.com/q/ref/dotz/#zts-timer

  In this case t is a list of tables and it calls pub on each of them (' form)  https://code.kx.com/q/ref/maps/#each

  value is called so that the cached data from the TP is populated in pub to send to subscribers (RDB etc.)

  Some more information on batch mode: https://code.kx.com/q/wp/tick-profiling/

   

  q)upd'[t;value each t] 
  //A demo 'upd' which prints the parameters sent to it 
  q)a:([] c1:1 2 3) 
  q)b:([] c2:4 5 6) 
  q)t:tables[] //Create list of tables 
  q)t `s#`a`b 
  q)upd'[t;value each t] (`a;+(,`c1)!,1 2 3) (`b;+(,`c2)!,4 5 6)

   

   

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