Tim

I remember that it wasn't worth the time taken to create them, or the space required to store them to use an index on a boolean field. Is the same true in ElevateDB?

Roy Lambert

Roy

I don't know if it's true with very large tables but with a table from one
of my testcases (100,000 records with 8000 set to true the rest to false)
there's no difference in speed if you index the boolean field.

Furthermore, I don't know if it's the case with EDB but I know from another
DBMS that putting an index on a boolean field increased the CPU usage with
48 % (w/o index 2%, with index 50%).

I never index my boolean fields after I knew that. Perhaps Tim can share
some technical background info on this matter.

Regards, Harry


"Roy Lambert" <roy.lambert@skynet.co.uk> schreef in bericht
news:1DC2E4F8-CEB5-40E4-B9C8-4C9154C2851C@news.elevatesoft.com...
> Tim
>
> I remember that it wasn't worth the time taken to create them, or the
space required to store them to use an index on a boolean field. Is the same
true in ElevateDB?
>
> Roy Lambert

Roy,

<< I remember that it wasn't worth the time taken to create them, or the
space required to store them to use an index on a boolean field. Is the same
true in ElevateDB? >>

It depends upon the row size.  If you're forcing EDB to scan the entire
table and the row size is fairly large (500 bytes or more), then it is more
efficient to index the Boolean column and have EDB use the index.

--
Tim Young
Elevate Software
www.elevatesoft.com

Harry,

<< Furthermore, I don't know if it's the case with EDB but I know from
another DBMS that putting an index on a boolean field increased the CPU
usage with 48 % (w/o index 2%, with index 50%). >>

That is not the case with EDB.  A boolean index will be the same as any
other column type in terms of CPU usage, and no single index in EDB would
double the CPU usage.

--
Tim Young
Elevate Software
www.elevatesoft.com