Re: [HACKERS] increasing the default WAL segment size

On 03/10/2017 11:23 AM, Beena Emerson wrote:

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.

We (Prabhat and I) have started basic  testing of this feature -
2 quick issue -

1)at the time of initdb, we have set - "--wal-segsize 4"  ,so all the WAL file size should be 4 MB each  but in the postgresql.conf file , it is  mentioned

#wal_keep_segments = 0          # in logfile segments, 16MB each; 0 disables

so the comment  (16MB ) mentioned against parameter 'wal_keep_segments'  looks wrong , either we should remove this or modify it .

2)Getting "Aborted (core dumped)"  error at the time of running pg_basebackup  , (this issue is only coming on Linux32 ,not on Linux64)
 we have  double check to confirm it .

Steps to reproduce on Linux32
===================
fetch the sources
apply both the patches
 ./configure --with-zlib   --enable-debug  --enable-cassert  --enable-depend --prefix=$PWD/edbpsql --with-openssl CFLAGS="-g -O0"; make all install
Performed initdb with switch "--wal-segsize 4"

start the server
run pg_basebackup

[centos@tushar-centos bin]$ ./pg_basebackup -v -D /tmp/myslave
*** glibc detected *** ./pg_basebackup: free(): invalid pointer: 0x08da7f00 ***

[centos@tushar-centos bin]$

same scenario is working fine against HEAD (v10 ) on Linux32 [i.e no patch applied] 

[centos@tushar-centos bin]$ ./pg_basebackup --verbose -D /tmp/slave11
pg_basebackup: initiating base backup, waiting for checkpoint to complete
pg_basebackup: checkpoint completed
pg_basebackup: transaction log start point: 0/2800024 on timeline 1
pg_basebackup: starting background WAL receiver
pg_basebackup: transaction log end point: 0/28000E4
pg_basebackup: waiting for background process to finish streaming ...
pg_basebackup: base backup completed
[centos@tushar-centos bin]$