On Thu, Dec 18, 2014 at 7:31 PM, Rahila Syed <rahilasye...@gmail.com> wrote:
>>Isn't it better to allocate the memory for compression_scratch in
>>like hdr_scratch?
> I think making compression_scratch a statically allocated global variable
> is the result of  following discussion earlier,
> http://www.postgresql.org/message-id/ca+tgmoaznbuwnls4bpwyqgqteeznoavy7kwdbm0a2-tbarn...@mail.gmail.com

     * Permanently allocate readBuf.  We do it this way, rather than just
     * making a static array, for two reasons: (1) no need to waste the
     * storage in most instantiations of the backend; (2) a static char array
     * isn't guaranteed to have any particular alignment, whereas palloc()
     * will provide MAXALIGN'd storage.

The above source code comment in XLogReaderAllocate() makes me think that
it's better to avoid using a static array. The point (1) seems less important in
this case because most processes need the buffer for WAL compression,


Fujii Masao

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