parfeval with fetch not working

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Hello guys. When I call the fetch() function with parfeval, I get the following error:
parfeval(@fetch,1,database,query)
Error: 'Dot indexing is not supported for variables of this type.'
On the other hand, without parfeval, the function works perfectly. What could it be?

Accepted Answer

Edric Ellis
Edric Ellis on 13 Jul 2022
You cannot pass database connection objects to workers directly like this. You should use createConnectionForPool . There are examples on that doc page that show you how to set up and use this. You'll end up with something like this:
c = createConnectionForPool(..);
% Wrap the call to "fetch" to unpick the .Value out of the pool connection
% object 'c'.
fut = parfeval(@(c, varargin) fetch(c.Value, varargin{:}), 1, c, query)
  1 Comment
HILTON MARQUES SANTANA
HILTON MARQUES SANTANA on 14 Jul 2022
Edited: HILTON MARQUES SANTANA on 14 Jul 2022
Thanks! It's working. Just another question. I am trying to speed up some queries on a online database on this way:
f = parfeval(@(c, varargin) fetch(c.Value, varargin{:}), 1, c, query1);
f(end+1) = parfeval(@(c, varargin) fetch(c.Value, varargin{:}), 1, c, query2);
f(end+1) = parfeval(@(c, varargin) fetch(c.Value, varargin{:}), 1, c, query3);
res1 = fetchOutputs(f(1));
res2 = fetchOutputs(f(3));
res3 = fetchOutputs(f(2));
But the time is not decreasing too much. There is a more efficient approach?
Thanks in advance

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