FYI, I documented better the peculiarity AndyS
noticed and emailed mariaDB team, see below

Jacek


-------- Original Message --------
Subject: myisam - unexpected file size and myisamchk behavior
Date: Thu, 20 Feb 2014 17:58:58 -0800
From: Jacek Becla <[log in to unmask]>
Organization: SLAC National Accelerator Laboratory
To: [log in to unmask] <[log in to unmask]>,  [log in to unmask] 
<[log in to unmask]>

Hello,

I run into something puzzling when testing 10.0.8.
In essence, I created several 250-million-row MyISAM
tables with different number of columns each by
running something like:

CREATE TABLE x50 AS
    SELECT <50 columns here>
    FROM <huge table>
    LIMIT 25000000;

mysqldump x50 > x50.dump

mysql t < x50.dump

create table x40 as select <40 columns here> from x50;
create table x30 as select <30 columns here> from x40;
create table x20 as select <20 columns here> from x30;
create table x10 as select <10 columns here> from x30;
create table x05 as select < 5 columns here> from x10;
create table x04 as select < 4 columns here> from x05;
create table x03 as select < 3 columns here> from x04;
create table x02 as select < 2 columns here> from x03;
create table x01 as select < 1 column  here> from x02;

size of the 50-column table is very puzzling:

columns	      MYD
	    [bytes]	
50	5,613,095,416
40	7,925,000,000
30	5,900,000,000
20	3,875,000,000
10	1,825,000,000
5	  825,000,000
4	  725,000,000
3	  525,000,000
2	  425,000,000
1	  225,000,000

Also, when I try running myisamchk, it runs (as expected)
for a minute or so, showing the row counter as usually,
and prints:

Data records: 25000000   Deleted blocks:       0
- check file-size
- check record delete-chain
- check key delete-chain
- check index reference
- check record links

while running it on any other table returns immediately with

Data records: 25000000   Deleted blocks:       0
- check file-size
- check record delete-chain
- check key delete-chain
- check index reference

(notice, there is no "check record links")

The actual commands I run are described here:

https://dev.lsstcorp.org/trac/wiki/db/tests/MySql/AriaVsMyISAM

Same thing happens when I try to reproduce it on much small
table. In case you want to reproduce it, the contents of
the two small tables can be found at:

http://www.slac.stanford.edu/~becla/tmp/myisamTest.tar.gz

Does anyone understand why we are seeing this unusual
behavior?

Thanks
Jacek

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