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Teach planner how to rearrange join order for some classes of OUTER JOIN.

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Per my recent proposal.  I ended up basing the implementation on the
existing mechanism for enforcing valid join orders of IN joins --- the
rules for valid outer-join orders are somewhat similar.
This commit is contained in:
Tom Lane
2005-12-20 02:30:36 +00:00
parent 1a6aaaa6c4
commit e3b9852728
23 changed files with 969 additions and 722 deletions
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9
src/include/nodes/primnodes.h
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@@ -10,7 +10,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.109 2005/10/15 02:49:45 momjian Exp $
* $PostgreSQL: pgsql/src/include/nodes/primnodes.h,v 1.110 2005/12/20 02:30:36 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -845,12 +845,7 @@ typedef struct TargetEntry
* or qualified join. Also, FromExpr nodes can appear to denote an
* ordinary cross-product join ("FROM foo, bar, baz WHERE ...").
* FromExpr is like a JoinExpr of jointype JOIN_INNER, except that it
* may have any number of child nodes, not just two. Also, there is an
* implementation-defined difference: the planner is allowed to join the
* children of a FromExpr using whatever join order seems good to it.
* At present, JoinExpr nodes are always joined in exactly the order
* implied by the jointree structure (except the planner may choose to
* swap inner and outer members of a join pair).
* may have any number of child nodes, not just two.
*
* NOTE: the top level of a Query's jointree is always a FromExpr.
* Even if the jointree contains no rels, there will be a FromExpr.