parfeval with fetch not working

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HILTON MARQUES SANTANA
HILTON MARQUES SANTANA 2022년 7월 12일
편집: HILTON MARQUES SANTANA 2022년 7월 14일
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?

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Edric Ellis
Edric Ellis 2022년 7월 13일
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)
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HILTON MARQUES SANTANA
HILTON MARQUES SANTANA 2022년 7월 14일
편집: HILTON MARQUES SANTANA 2022년 7월 14일
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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