Re: Confusing comment in tidbitmap.c

От:

Tom Lane <tgl@sss.pgh.pa.us>

Дата:

14 декабря 2014 г. в 17:11:33

От:

David Rowley <dgrowleyml@gmail.com>

Дата:

14 декабря 2014 г. в 08:03:37

The following comment above #define PAGES_PER_CHUNK in tibbitmap.c appears to be incorrect:

"But we

* also want PAGES_PER_CHUNK to be a power of 2 to avoid expensive integer

* remainder operations. So, define it like this:"

I don't quite follow this as it does nothing of the kind. Check tbm_page_is_lossy() where we do: bitno = pageno % PAGES_PER_CHUNK;

Or am I missing something about the compiler optimizing that to: bitno = pageno & 255; ?

Regards

David Rowley