MySQL Bugs: #41490: After enlargement of InnoDB page size, the error message become inaccurate.

Bug #41490	After enlargement of InnoDB page size, the error message become inaccurate.
Submitted:	16 Dec 2008 8:39	Modified:	13 Nov 3:26
Reporter:	Meiji KIMURA
Status:	Closed
Category:	Server: InnoDB	Severity:	S3 (Non-critical)
Version:	5.0.x	OS:	Any
Assigned to:	Satya B	Target Version:
Triage:	Triaged: D4 (Minor)

Description:
As MySQL document said, we can enlarge a page size of InnoDB.

"The default database page size in InnoDB is 16KB. By recompiling the code, you can set
it to values ranging from 8KB to 64KB. You must update the values of UNIV_PAGE_SIZE and
UNIV_PAGE_SIZE_SHIFT in the univ.i source file."
http://dev.mysql.com/doc/refman/5.1/en/innodb-restrictions.html

When I want to set 64KB for an InnoDB page size, modify code and recompile.

#define UNIV_PAGE_SIZE (8 * 8192)
#define UNIV_PAGE_SIZE_SHIFT 16

But I try to re-start MySQL with default settings, it fails like this,
081215 22:33:48  mysqld started
InnoDB: Error: tablespace size must be at least 10 MB
081215 22:33:48 Can't init databases
081215 22:33:48 Aborting

I looked into this problem, and I found a cause of this.

Ordinary InnoDB setting is like this,
innodb_data_file_path = ibdata1:10M:autoextend

But I enlarged a page size of InnoDB, 10M is too short to activate MySQL.
We have to enlarge size for innodb_data_file_path, innodb_log_file_size,
innodb_buffer_pool_size according to a page size of InnoDB.

[An example of my.cnf for extended InnoDB]
innodb_data_file_path = ibdata1:100M:autoextend
innodb_log_file_size　=　50M
innodb_buffer_pool_size　=　200M

But why 10M is described in an error message?

I also looked into source codes about an error message. 10M is written as a hard code, so
the error message cannot display proper size for extended InnoDB page size.

in srv0start.c

if (sum_of_new_sizes < 640) {
	  fprintf(stderr,
	  "InnoDB: Error: tablespace size must be at least 10 MB\n");
	  return(DB_ERROR);
}

The program shold modify this part depends on InnoDB page size.

How to repeat:
(1) Enlarge a size of InnoDB page to 64KB.
(2) Compile source code to make a MySQL Binary.
(3) Restart MySQL with default settings.

Suggested fix:
InnoDB shold report to accurate size for error.
The program shold modify the error message depends on InnoDB page size.

in srv0start.c
if (sum_of_new_sizes < 640) {
	  fprintf(stderr,
	  "InnoDB: Error: tablespace size must be at least 10 MB\n");
	  return(DB_ERROR);
}

The 10-megabyte minimum tablespace size is a somewhat arbitrary limit. I would simply
replace the 640 with 10485760/UNIV_PAGE_SIZE. It would be 640 when UNIV_PAGE_SIZE is
16384 bytes.

Note that the implementation of ROW_FORMAT=COMPRESSED in the InnoDB plugin assumes that
UNIV_PAGE_SIZE is at most 16 kilobytes.  In the dense page directory in the compressed
page trailer, pointers to records are 14-bit.  We may change that later.

Several years ago, when I was developing ROW_FORMAT=COMPACT, I also experimented with
different page sizes. I remember seeing this assertion failure in page_rec_check() when
defining UNIV_PAGE_SIZE to 65536:

rec <= page_header_get_ptr(page, PAGE_HEAP_TOP)

This would likely be in MySQL 4.1 or 5.0. I didn't investigate this more closely. So, be
careful when using a larger UNIV_PAGE_SIZE.

If you change UNIV_PAGE_SIZE, you won't be able to exchange any data or log files with
plain InnoDB.  It would be challenging to make UNIV_PAGE_SIZE a configuration parameter,
let alone to make it a table property.  A configureable UNIV_PAGE_SIZE could make InnoDB
noticeably slower.

A patch that replaces the 640 with 10485760 / UNIV_PAGE_SIZE was committed to the InnoDB
6.0 repository.

Pushed into 5.1.41 (revid:joro@sun.com-20091104092152-qz96bzlf2o1japwc) (version source
revid:kristofer.pettersson@sun.com-20091103162305-08l4gkeuif2ozsoj) (merge vers: 5.1.41)
(pib:13)

Pushed into 6.0.14-alpha (revid:alik@sun.com-20091110093407-rw5g8dys2baqkt67) (version
source revid:alik@sun.com-20091109080109-7dxapd5y5pxlu08w) (merge vers: 6.0.14-alpha)
(pib:13)

Pushed into 5.5.0-beta (revid:alik@sun.com-20091109115615-nuohp02h8mdrz8m2) (version
source revid:svoj@sun.com-20091105122958-jyqjx9xus8v4e0yd) (merge vers: 5.5.0-beta)
(pib:13)

Noted in 5.1.41, 5.5.0, 6.0.14 changelog.

With a nonstandard InnoDB page size, some error messages became
inaccurate.

Addition to changelog entry:

Changing the page size is not a supported operation and there is no
guarantee that InnoDB will function normally with a page size other
than 16KB. Problems compiling or running InnoDB may occur. In
particular, ROW_FORMAT=COMPRESSED in the InnoDB Plugin assumes that
the page size is at most 16KB and uses 14-bit pointers. 
    
A version of InnoDB built for one page size cannot use data files or
log files from a version built for a different page size.