If it is MyISAM and there is some form of corruption, you might get the symptom you see.
Do CHECK TABLE.
information_schema has the same "flaw" in row count as SHOW TABLE STATUS for InnoDB.
> -----Original Message-----
> From: Stillman, Benjamin [mailto:BStillman@stripped]
> Sent: Tuesday, February 26, 2013 11:04 AM
> To: Zachary Stern; mysql@stripped
> Subject: RE: data loss due to misconfiguration
>
> Are you actually querying the table (select count(*) from table_name),
> or just the stats (show table status)? Is the table Innodb?
>
> If you're using Innodb and aren't doing a select count (or other
> select query) on the table, then yes you'll have varying results. This
> is because unlike MyISAM, Innodb does not keep a count of the records.
> Using show table status gives just an estimation. This would be my
> first path of investigation.
>
> http://dev.mysql.com/doc/refman/5.5/en/show-table-status.html
>
> "The number of rows. Some storage engines, such as MyISAM, store the
> exact count. For other storage engines, such as InnoDB, this value is
> an approximation, and may vary from the actual value by as much as 40
> to 50%. In such cases, use SELECT COUNT(*) to obtain an accurate
> count."
>
>
>
> -----Original Message-----
> From: Zachary Stern [mailto:zs@stripped]
> Sent: Tuesday, February 26, 2013 12:42 PM
> To: mysql@stripped
> Subject: data loss due to misconfiguration
>
> Is such a thing possible? There are no errors or issues, but we can
> query a table, get X number of rows, query it later, and all of the
> sudden be missing a thousand rows.
>
> I know this isn't much to go on, but I'm not even sure what information
> to provide. Will be happy to give anything you guys might be able to
> think of.
>
> TIA.
>
> -Zachary
>
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