Re: How does postgres store the join predicate for a relation in a given query

On Tue, Oct 10, 2017 at 7:29 PM, Gourav Kumar <gourav1905(at)gmail(dot)com> wrote:
> Hi all,
>
> When you fire a query in postgresql, it will first parse the query and
> create the data structures for storing various aspects of the query and
> executing the query. (Like RangeTblEntry, PlannerInfo, RangeOptInfo etc.).
>
> I want to know how does postgresql stores the join predicates of a query.
> Like which data structure is used to store the join predicates.
>
> How can we find the join predicates applied on a relation from relid, Oid or
> RangeTblEntry ?
>

Every relation has a RelOptInfo associated with it. Predicates
applicable to it are stored in this RelOptInfo as a list. For base
relations (simple tables) it's in baserestrictinfo. The join
predicates applicable are in joininfo. You can get RelOptInfo of a
given simple table using find_base_rel().

HTH.

--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company