QTable resize problem with large tables

I have a problem with large tables. My table has about 120000 rows. If I want to resize the table, it freezes. Is this a bug?
Has anybody else this problem?
Here is the example code:

Code:

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table->setNumRows(120000); // still ok
table->setNumRows(6000); // freeze

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There is some warning for use big table . Read in doc for QTable section Large tables. Hope this help :)

I have already read this section, but this is no help because my large tables are full of Data.
I found out that this problem seems to be a debugger problem, because it doesn't freeze if you run the exe without debugger.
But I have no idea why.

Maybe it just runs faster when not processing all the debugging code.