Re: Requesting some information about the small portion of source code of postgreSQL

On Tue, Sep 27, 2016 at 11:43 AM, Srinivas Karthik V
<skarthikv.iitb@gmail.com> wrote:
> Dear PostgresSQL Hackers,
>    I am working in optimizer module of postgreSQL 9.4.1. I am trying to
> return a subplan for a query instead of full plan.For this I need to return
> an intermediate plan (or path) from the DP lattice (i.e.  from RelOptInfo
> *standard_join_search() at allpaths.c) instead of the full optimal plan
> (which is from the last level of root->join_rel_level()).

Why do you want to do that?

> while doing so I am getting error :variable not found in subplan target
> lists at function fix_join_expr_mutator at setrefs.c.
>
> It will be great if you can give me some idea about why this error is
> happening, since this error is happening at fix_join_expr_mutator function
> at setrefs.c. Please give me more information about this portion of code.
> Also I would like to know for what targetlist stands for.
>

setref.c implements the final stage of planner, where the
variable/expression references in the parent plan nodes are fixed by
pointing them to expressions/parts of expressions/variables from their
children. This error means that some of the things that parent node is
referring to are not available in the children as expected.

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