Re: [HACKERS] How does postgres store the join predicate for arelation in a given query
| От | Gourav Kumar |
|---|---|
| Тема | Re: [HACKERS] How does postgres store the join predicate for arelation in a given query |
| Дата | |
| Msg-id | CAPzqDmiQOwkei1cCH=7arkxGPmn-WTyS7y_Hr1Xr1iLyuCnMcw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: [HACKERS] How does postgres store the join predicate for arelation in a given query (Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>) |
| Ответы |
Re: [HACKERS] How does postgres store the join predicate for a relation in a given query
|
| Список | pgsql-hackers |
Hi Ashutosh,
I have the RelOptInfo data structure for the relations which are to be joined but when I check their joininfo, it is empty.
Does baserestrictinfo contains base predicates ?
Thanks
Gourav.
On 11 October 2017 at 12:00, Ashutosh Bapat <ashutosh.bapat@enterprisedb.com> wrote:
On Tue, Oct 10, 2017 at 7:29 PM, Gourav Kumar <gourav1905@gmail.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
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