[PATCH] XLogReadRecord returns pointer to currently read page

Hi, hackers!

I propose the patch for fix one small code defect.
The XLogReadRecord() function reads the pages of a WAL segment that 
contain a WAL-record. Then it creates a readRecordBuf buffer in private 
memory of a backend and copy record from the pages to the readRecordBuf 
buffer. Pointer 'record' is set to the beginning of the readRecordBuf 
buffer.

But if the WAL-record is fully placed on one page, the XLogReadRecord() 
function forgets to bind the "record" pointer with the beginning of the 
readRecordBuf buffer. In this case, XLogReadRecord() returns a pointer 
to an internal xlog page. This patch fixes the defect.

Previously, in all cases of using WAL this was not a problem. However if 
you plan to perform some decoding operations before returning the WAL 
record to the caller (this is my case), this can lead to bugs that are 
difficult to catch.


-- 
Andrey Lepikhov
Postgres Professional
https://postgrespro.com
The Russian Postgres Company