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Re: Question about org.h2.store.PageStore's checkpoint() method Noel Grandin Tue Apr 03 05:01:07 2012

I can't be sure, but it looks like it's zero-ing out the header of a page, so I would assume that it's a little necessary.

you could try increasing the page size of your database, that might speed up this operation.


On 2012-04-02 17:15, Steve McLeod wrote:
Hi Thomas,

When running TRUNCATE TABLE on a large table, it is time-consuming. I've done some profiling of the H2 source, and found that a step in PageStore.checkpoint() that consumes one-third of the time needed for TRUNCATE TABLE. In my specific case it uses 69 seconds out of seconds for the whole TRUNCATE execution.

This line is the one consuming the time:

                file.readFully(test, 0, 16);

which is org.h2.store.PageStore.java: line 451 in the current SVN trunk.

It is part of a process of zeroing freed pages on disk. I'm wondering if zeroing is an important part of the workings of the PageStore. Or is it for security reasons? If so, is this step something I could potentially make optional by introducing a "INSECURE_FREE" database option?

I'm running on Mac OS X Lion, using an SSD drive.

Regards,

Steve McLeod



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