Re: New ManyToManyField Approach

On Nov 23, 2010, at 5:40 PM, shane@bogomip.com wrote:
> Without test data I'm not sure where the trade offs are with the
> following. However it should improve the ability to look up items
> that reference a certain set of keys as well as easily check to see if
> a set already exists. This should also help reduce the number of rows
> in a reference table.

It definitely does that. The downsides are:

1. Selects that are looking for a particular individual value ("all items that reference user 1") are going to be a sequential scan.

2. You might get collisions on the adler32 function in real life; I'm not familiar enough with that particular function.

If you are using PostgreSQL, you might look at using intarray or hstore fields instead; those have the same advantages you enumerate, but you can also index on them in ways that will speed up searches for individual values.

--
-- Christophe Pettus
xof@thebuild.com

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