On Tue, Dec 23, 2003 at 07:07:57PM -0600, Matt W wrote: > Hi Jeremy, > > ----- Original Message ----- > From: "Jeremy Zawodny" > Sent: Monday, December 22, 2003 2:20 PM > Subject: Re: Benefits of MAX_ROWS and AVG_ROW_LENGTH > > > > On Fri, Dec 19, 2003 at 06:40:17PM -0600, Matt W wrote: > > > Hi Mark, > > > > > > I'll tell you what I know. :-) > > > > > > First, AVG_ROW_LENGTH is only needed for dynamic row-length tables > (it's > > > ignored with fixed-length rows) -- more specifically, those with > > > TEXT/BLOB columns. > > > > And VARCHAR/VARBINARY. > > Yes, in that VARCHAR makes variable length rows, but *not* that you > *have to* (or rather "really should") specify AVG_ROW_LENGTH with > MAX_ROWS. Sure, include it if your VARCHARs aren't always going to be > filled to the max length. > > Otherwise, MySQL will just assume that the rows will be as long as the > sum of the max length of all the VARCHAR (and other) columns. When > VARCHAR(n) is specified, and n is the max length that will be stored in > the column, this should be a pretty accurate assumption, no? > > But if you have TEXT/BLOB columns, their max length (well, plain TEXT > anyway; not TINY/MEDIUM/LONG) is equivalent to 255 VARCHAR(255) columns! > And again, MySQL will assume you're going to use it all. That's fine if > you're actually storing 64K in each column, but that's hardly ever the > case. Hence why I said, "more specifically, those with TEXT/BLOB > columns."
Agreed. It's all a matter of scale. If you're dealing with *a lot* of records, you may want to specify those attributes anways. Jeremy -- Jeremy D. Zawodny | Perl, Web, MySQL, Linux Magazine, Yahoo! <[EMAIL PROTECTED]> | http://jeremy.zawodny.com/ -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
