#11740 , solved the problem that the query memory statistics are higher than the actual physical memory, because PODArray does not have memset 0 when allocating memory, and the query mem tracker is virtual memory.
But in extreme cases, such as csv load, PODArray frequent insert will cause performance problems. So revert part of #11740 and part of #12820.
The accuracy of the query mem tracker, there is currently no feedback, no further attention.
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