Date: Wed, 9 Oct 2013 18:11:42 -0700 (PDT)
From: David Johnston <polobo@yahoo.com>
To: pgsql-sql@postgresql.org
Message-ID: <1381367502833-5773942.post@n5.nabble.com>
In-Reply-To: <1381357909835-5773925.post@n5.nabble.com>
References: 
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Subject: Re: Question about index/constraint definition in a table
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David Johnston wrote
> 
> JORGE MALDONADO wrote
>> I have a table as follows:
>> ------------------------------------------------
>> Table Artist Colaborations
>> ------------------------------------------------
>> * car_id (integer field, primary key)
>> * car_song (integer field, foreign key, foreign table is a catalog of
>> songs)
>> * car_artist (integer field, foreign key, foreign table is a catalog of
>> artists)
>> 
>> So, I added 2 indexes to improve JOIN in queries:
>> 1. An index for car_song which accepts duplicates.
>> 2. An index for car_artist which accepts duplicates.
>> 
>> Now, the combination of "car_song + car_artist" cannot be duplicated so I
>> think that adding a constraint on these 2 fields is the solution.
>> 
>> My question: Is this the correct way to go?
>> 
>> Respectfully,
>> Jorge Maldonado
> Yes.  Why is it this is a question for you?
> 
> Also, the car_id field becomes pointless since your new constraint is the
> true and natural PK.
> 
> David J.

with index only scans it seems that defining a pair of unique indexes (and
no single column indexes) would have value.  How much value I do not know. 
Would still want to drop the artificial id field.

David J.


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