MySQL Bugs: #73547: Contradicting descriptions of bug 16267120 in revision comments and changelog

Bug #73547	Contradicting descriptions of bug 16267120 in revision comments and changelog
Submitted:	12 Aug 2014 8:44	Modified:	12 Aug 2014 14:20
Reporter:	Alexey Kopytov	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Documentation	Severity:	S3 (Non-critical)
Version:	5.6	OS:	Any
Assigned to:	Daniel Price	CPU Architecture:	Any

Description:
The Oracle internal bug 16267120 is described in the changelog for MySQL 5.6.12 as follows:

"
InnoDB: For a compressed table, the “page reorganize” function would ignore the innodb_log_compressed_pages option and always log the entire compressed page, which increased the size of the redo log. The “page reorganize” function now adheres to the innodb_log_compressed_pages option and does not log compressed page images to the redo log when innodb_log_compressed_pages is set to “OFF”. (Bug #16267120)
"

http://dev.mysql.com/doc/relnotes/mysql/5.6/en/news-5-6-12.html

However, this is what I see in the corresponding bzr revision comments:

"
$ bzr log --show-ids -r 5023
------------------------------------------------------------
revno: 5023
revision-id: satya.bodapati@oracle.com-20130418044717-n36fflsodyukpvii
parent: yasufumi.kinoshita@oracle.com-20130418042042-llgzfb1g85vw3pda
committer: Satya Bodapati <satya.bodapati@oracle.com>
branch nick: mysql-5.6
timestamp: Thu 2013-04-18 10:17:17 +0530
message:
  Bug#16267120 - PAGE REORGANIZE ASSUMES INNODB_LOG_COMPRESSED_PAGES=OFF
  
...
  
  The problem is that page reorganize is always being logged as
  MLOG_ZIP_PAGE_REORGANIZE (with the compression level as a parameter),
  which is correct with innodb_log_compressed_pages=OFF.
  
  If innodb_log_compressed_pages=ON, page reorganize should log the
  compressed page image.
  
  Fix:
  ---
  If innodb_log_compressed_pages=ON, log the compressed page and do not
  write a MLOG_COMP_PAGE_REORGANIZE redolog record.
"

They seem to contradict each other: 

- the changelog entry says that the problem was that compressed page image would always be redo-logged, regardless of the innodb_log_compressed_pages value and that the fix was to not log it when innodb_log_compressed_pages is set to “OFF”.

- however, the revision comment says the problem was that compressed page image would never be redo-logged, regardless of the innodb_log_compressed_pages value, and the the fix was to log it when innodb_log_compressed_pages is set to "ON".

From code analysis it appears that the latter one is correct. So this is a request to fix the changelog entry.

How to repeat:
Compare description of the bug in the 5.6.12 changelog, and the corresponding bzr revision.

Hello Alexey Kopytov,

Thank you for the report.

Thanks,
Umesh

The changelog entry has been reviewed by development and revised as follows:

"For compressed tables, a page reorganize operation would always write an
"MLOG_ZIP_PAGE_REORGANIZE" record to the redo log, which is only correct
if "innodb_log_compressed_pages=OFF". When
"innodb_log_compressed_pages=ON", the page reorganize operation should log
the compressed page image."

Thank you for the bug report.