Re: exclusion constraint for ranges of IP

On 2011-08-23, Herouth Maoz <herouth@unicell.co.il> wrote:

>     EXCLUDE USING GIST  ( customer_id WITH =, is_default WITH AND )


> Basically, each customer can have several rows in this table, but only =
> one per customer is allowed to have is_default =3D true. Is this exclude =
> constraint correct?

I don't really understand exclude, but instead of EXCLUDE... I would do

CREATE UNIQUE INDEX "invoice_definitions-unique-default"  ON invoice_definitions(customer_id) WHERE is_default;

Which would create a smaller (and probably faster) BTREE index 
containing only the rows with is_default true.

There seems to be no way to create this in the create-table 
command. (using 8.4 here)


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