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

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1

https://learninghub.kx.com/forums/topic/what-is-the-purpose-of-publishing-value-each-t-to-t-in-u-pub

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?

2

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)