Subject Re: [firebird-support] What is the max varchar column I can index?
Author Thomas Steinmaurer
Hi Phil,

> Hi, I have Firebird 1.5.3, and need a varchar(250) column in one of my
> tables and it needs an index for performance reasons.
> 1) I created a table which has a varchar(250) column, codeset none,
> collation none. I can put an index on this column since it is within
> the max size allowed for an index (252 chars, right?).
> 2) If I recreate the table, specifying the column is codeset
> ISO8859-1, collation EN_UK, the largest the column can be (to put an
> index on it) is 83 or 84 characters (I also checked this against
> Ivans(?) online index size checking tool).
> However if I follow step (1) - i.e create the varchar(250) column then
> add an index, I can then modify the column to have codeset ISO8859-1,
> collation EN_UK, and it seems ok.

It seems, but it isn't. Don't do that. A backup/restore cycle will fail,
because the index can't be re-created.

What tool have you used for changing the character set afterwards?

Follow 2). Be aware, the max. index size has been increased with
Firebird 2.0 which is ~ (Page Size / 4) there.

Best Regards,
Thomas Steinmaurer
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