Re: booleans and nulls

Matt L. wrote:

>Out of curiousity, 
>
>1. Does a boolean column occupy 1byte of disk whether
>or not the value is null or not? 
>  
>
I believe so.

>2. Is matching on IS NULL or = 0 more efficient? 
>
>  
>
Hmm... = 0 is the same as IS FALSE.  Not the same as IS NULL.  So I 
guess it is apples v. oranges....

>3. If I ix'd columns w/ null does postgres know
>whatevers not indexed is null or would their be no
>point?
>  
>
>I currently utilize null fields as 'not a value' has
>meaning in a program i've been working on as I don't
>want to put false in every column when i only need a
>couple with a true/false value. 
>
>I'm not joining tables on NULLS, just filtering w/
>them. 
>  
>
Sounds like a partial index would be your best bet.  Something like:
CREATE index ON my_table WHERE my_bool IS NOT NULL

Best Wishes,
Chris Travers
Metatron Technology Consulting