Suggestion request in concurrency problem
lazarus / 16-Databases

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esvignolo · 2017-02-03 20:42

Hello everyone, I have a problem that I have to see with a table
(tbufdatset) and access to it.
The scenario is as follows: a main form that contains the table in
memory(tbufdatset), but the data of the same is updated by a thread
from time to time. The problem occurs when you are updating the table
in memory (by the thread) and at the same time from the main form you
want to query the same tbufdatset, and this generates memory access
errors.
Ideally update in a second table in memory, and once the second is
updated, this happens to be the main one, but I can not think how to
do it.

The suggestions are appreciated, thank you very much.

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LacaK · 2017-02-04 15:30

You must protect code which modifies/reads TBufDataset using any kind
of synchronization.
See for example: http://wiki.freepascal.org/Multithreaded_Application_
Tutorial#Critical_sections

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esvignolo · 2017-02-04 16:48

Hi LacaK, thanks for your answer. I am already using critical sections
in similar parts, but in the case of the table in memory, the main
form that reads the tbufdataset in 99% of the time only reads it, and
the process of the thread that updates it can take a minute, Which,
thought or tried to find a solution where the load of the thread is
generated in a second tbufdataset, so that when this process of one
minute is finished, become the tbufdataset that uses the main form,
and not have "on hold" reading the main form.

Quote from: LacaK on February 04, 2017, 04:30:46 pmYou must protect
code which modifies/reads TBufDataset using any kind of
synchronization.
See for example: http://wiki.freepascal.org/Multithreaded_Application_
Tutorial#Critical_sections