reverse index ??

[Bastien]

Hi All,

Is there a capablity, as in Oracle, to create a reverse index in mysql? The reverse index could take the key column and read it in reverse to create the index.

Bastien

Cat, the other other white meat

 

[ericbrunson]

I don't believe it does. Though I've always felt there were better ways of dealing with hot blocks and reverse indexes just trade one set of problems for another, including the possibility of hot blocks.

 

[TonyGroves]

Is that just reverse row order as in ORDER BY ... DESC?

 

[ericbrunson]

No, a reverse index actually reverses the characters in a key, so "eric" is indexed as "cire". It's a band-aid for when you have too many keys that start with the same set of characters and you end up creating "hot blocks" or, more aptly, an unbalanced b-tree (which I know is an oxymoron, but no one would have understood if I said "an unb-tree" or a "u-tree" )

 

[Bastien]

no, it read the value of the col from right to left and creates the index from that value...

Bastien

Cat, the other other white meat

 

[TonyGroves]

OK thanks. Interesting concept. I've never heard of it in MySQL, and there's no mention of "reverse index" in the manual.

 

[Bastien]

but i can take the right x characters of a col, correct? I have seen in the manual about a doing that with a left 10 characters...

Bastien

Cat, the other other white meat

 

[TonyGroves]

That's what the [tt]RIGHT(str,len)[/tt] func does.