Parallel query handling

[iqbalaydrus]

Solves #1746

[zoltanbedi]

Hi @iqbalaydrus,
thanks for opening this PR, we are going to take a look at it soon. In the meantime can you please add tests for this?

[iqbalaydrus]

I'm not quite sure what tests I should add for parallelization, do you have any suggestions?

[zoltanbedi]

I'm not quite sure what tests I should add for parallelization, do you have any suggestions?

I thought you might had an idea how to properly test this. 😅

This needs some more time from us to test properly. And I'm also adding @alexanderzobnin as a reviewer.

[iqbalaydrus]

Well parallization just makes things faster without changing any of the app behaviour. So as long as the current tests cover my changes it should be good. But I don't think the tests touch the QueryData method yet. I'll take a look later whether it's possible to add tests to that.

[ivanahuckova]

Hi @iqbalaydrus, thank you for contribution. We have decided that currently we don't want to support parallel query handling because of increased complexity. We will keep the issue open in case we revisit this decision later.