Re: [HACKERS] increasing the default WAL segment size - Mailing list pgsql-hackers

From Beena Emerson
Subject Re: [HACKERS] increasing the default WAL segment size
Date
Msg-id CAOG9ApEhqTX66=UeAQJjQG3jPnnFZiz9voVVWVZwyOA=drzjgQ@mail.gmail.com
Whole thread Raw
In response to Re: [HACKERS] increasing the default WAL segment size  (Ashutosh Sharma <ashu.coek88@gmail.com>)
Responses Re: [HACKERS] increasing the default WAL segment size  (tushar <tushar.ahuja@enterprisedb.com>)
List pgsql-hackers
Hello,

On Tue, Mar 7, 2017 at 10:46 AM, Ashutosh Sharma <ashu.coek88@gmail.com> wrote:
Hi,

I took a look at this patch. Overall, the patch looks good to me.
However, there are some review comments that I would like to share,

1. I think the macro 'PATH_MAX' used in pg_waldump.c file is specific
to Linux. It needs to be changed to some constant value or may be
MAXPGPATH inorder to make it platform independent.

2. As already mentioned by Jim and Kuntal upthread, you are trying to
detect the configured WAL segment size in pg_waldump.c and
pg_standby.c files based on the size of the random WAL file which
doesn't look like a good idea. But, then I think the only option we
have is to pass the location of pg_control file to pg_waldump module
along with the start and end wal segments.

3. When trying to compile '02-initdb-walsegsize-v2.patch' on Windows,
I got this warning message,

Warning    1    warning C4005: 'DEFAULT_XLOG_SEG_SIZE' : macro
redefinition
c:\users\ashu\postgresql\src\include\pg_config_manual.h    20

Apart from these, I am not having any comments as of now. I am still
validating the patch on Windows. If I find any issues i will update
it.

Thank you for your reviews Kuntal, Jim, Ashutosh

Attached in an updated 02 patch which:
  1. Call RetrieveXLogSegSize(conn) in pg_receivewal.c
  2. Remove the warning in Windows
  3. Change PATH_MAX in pg_waldump with MAXPGPATH
Regarding the usage of the wal file size as the XLogSegSize, I agree with what Robert has said. Generally, the wal size will be of the expected wal_segment_size and to have it any other size, esspecially of a valid power2 value is extremely rare and I feel it is not a major cause of concern.

Thank you,

Beena Emerson
EnterpriseDB: http://www.enterprisedb.com

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