On 13 Dec 1999, Manuel Lemos wrote:
> Hello,
>
> I am using PostgreSQL 6.4.2. and it seems I can't create indexes on
> BOOL columns. I tried this:
>
> ...snip...
>
> However, if I change the BOOL type to CHAR (1) it works.
I'm not a developer, so I don't know if it's a bug or a logic error
you're pointing out, or even if it's an error at all. However, I could
rationalize that it is not an error on the premise that BOOLEAN
identifiers can only have two values: true or false.
Obviously, you cannot use a UNIQUE index on such an column. A Clustered
index would not do much better, logically, since you're only splitting
up the data into two groups. Therefore, what is the point of indexing
on boolean columns, really? I suppose it would depend upon the data in
the table. If you see one value predominantly over the other, splitting
out the smaller group via the index *may* help your search. However, if
the values are fairly even in proportion, you won't gain much.
I'd say stick with your work-around, and post the question to the devel
team.
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