Re: _rowid

[Michael T. Babcock]

Dean Harding wrote:

The thing with Oracle is that once a row is assigned a ROWID, it never
changes.  It doesn't matter if the row grows and has to move within the
block (or if it has to move to another block, for that matter).  That's
why ROWIDs work in Oracle.

Neither does an auto_increment index value that you put in the table yourself. I'm still waiting to hear a proponent of _rowid tell me why _rowid is _better_ for _database_admins_ than using an auto_increment column value. The '_rowid takes no space' argument is hogwash; its stored by Oracle in space that MySQL doesn't allocate internally, so its still taking up a few bytes per row of memory, like it or not.

But apparently, that's not the case with MySQL (personally, I see that
as a design flaw, but that's just my opinion :)

Like I said above, could you please clarify on why an internal row identifier even matters to you as a database admin? How MyISAM and/or InnoDB and/or HEAP and/or Gemini decide to store their table structures is something I'm quite happy to ignore if they work -- why would it be intrinsically better to use an internal _rowid type value than to do what they do? Oh, and make sure you show me that you understand the current structures first -- but more importantly, why does it matter to you, or me, or anyone else building DB software??

so a ROWID in MySQL is
really just a synonym for the primary key, and is probably only useful
to people who are porting from Oracle (or some other database which has
ROWIDs).

Precisely why it was added, as far as I can ascertain from the list archives. It is otherwise completely pointless / useless because of a different in-memory/on-disk data structuring.

--
Michael T. Babcock
C.T.O., FibreSpeed Ltd.
http://www.fibrespeed.net/~mbabcock



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