Re: Creste Index with nullable

Lists: pgsql-admin
From: Diego <diego(at)unimedijui(dot)com(dot)br>
To: pgsql-admin(at)postgresql(dot)org
Subject: Creste Index with nullable
Date: 2006-01-17 13:10:58
Message-ID: 43CCECE2.5030300@unimedijui.com.br
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Lists: pgsql-admin

Hi,

I have a question!

create table test (
code int not null,
name varchar(40) not null,
last_name varchar(40) {this field is nullable}
)

I can create a index like
"CREATE INDEX idx_test ON etqmov USING btree (name, last_name)"
using a nullable field? Will work fine?

Thanks...
Diego Ziquinatti
From Brazil


From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Diego <diego(at)unimedijui(dot)com(dot)br>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: Creste Index with nullable
Date: 2006-01-17 15:20:50
Message-ID: 28458.1137511250@sss.pgh.pa.us
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Lists: pgsql-admin

Diego <diego(at)unimedijui(dot)com(dot)br> writes:
> I can create a index like
> "CREATE INDEX idx_test ON etqmov USING btree (name, last_name)"
> using a nullable field? Will work fine?

Sure. Note however that "last_name IS NULL" is not an indexable
operation, so you won't be able to use the index to search for rows
containing nulls. This may or may not matter to you, but if it does
you'll need to think of another way to locate those rows. (Some people
solve this sort of problem with partial indexes.)

regards, tom lane