Re: [HACKERS] Subselects are in CVS...

From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
To: vadim(at)sable(dot)krasnoyarsk(dot)su (Vadim B(dot) Mikheev)
Cc: hackers(at)postgreSQL(dot)org
Subject: Re: [HACKERS] Subselects are in CVS...
Date: 1998-03-16 05:37:00
Message-ID: 199803160537.AAA22913@candle.pha.pa.us
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers

Added to backend/optimizer/plan/README.

>
> This is some implementation notes and opened issues...
>
> First, implementation uses new type of parameters - PARAM_EXEC - to deal
> with correlation Vars. When query_planner() is called, it first tries to
> replace all upper queries Var referenced in current query with Param of
> this type. Some global variables are used to keep mapping of Vars to
> Params and Params to Vars.
>
> After this, all current query' SubLinks are processed: for each SubLink
> found in query' qual union_planner() (old planner() function) will be
> called to plan corresponding subselect (union_planner() calls
> query_planner() for "simple" query and supports UNIONs). After subselect
> are planned, optimizer knows about is this correlated, un-correlated or
> _undirect_ correlated (references some grand-parent Vars but no parent
> ones: uncorrelated from the parent' point of view) query.
>
> For uncorrelated and undirect correlated subqueries of EXPRession or

--
Bruce Momjian | 830 Blythe Avenue
maillist(at)candle(dot)pha(dot)pa(dot)us | Drexel Hill, Pennsylvania 19026
+ If your life is a hard drive, | (610) 353-9879(w)
+ Christ can be your backup. | (610) 853-3000(h)

In response to

Browse pgsql-hackers by date

  From Date Subject
Next Message Bruce Momjian 1998-03-16 05:45:31 Re: [PORTS] Port Bug Report: Grant select to other user removes owner select permission
Previous Message Bruce Momjian 1998-03-16 05:10:39 Re: [HACKERS] Memory leaks for large objects