Re: postgres optimizer

Tom Lane wrote:
> "Hossein S. Attar" <mhsheikh@softbase.math.uwaterloo.ca> writes:
>
>>I am working on postgres optimizer code to add some statistics
>>collection features for an academic project. At some point in my work, I
>>need to be able to tell if a join is a foreign key join or not. Also in
>>case of a foreign key join, I need to identify which input to the join
>>operator has the primary key attribute and which one has teh foreign
>>key. In other words, when we are making a JoinPath struct, I need to
>>identify if the join between the inner and outer RelOptInfo structs is a
>>foreign key join and if so, which RelOptInfo has the primary key. Does
>>anyone know the best way to do this? Should I go to "joinrestrictinfo"
>>field and go over all expressions? Is there any easier way?

I would be interested in knowing "why" you want to do such a thing? What
is it you expect to gain?

Sincerely,

Joshua D. Drake

>
>
> The planner doesn't think there is any such thing as a "foreign key
> join".  Perhaps you should modify the foreign key triggers (in
> ri_triggers.c) to collect the information you need.
>
>             regards, tom lane
>
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