postgresql

History

Tom Lane 11086f2f2b Repair planner bug introduced in 8.2 by ability to rearrange outer joins: in cases where a sub-SELECT inserts a WHERE clause between two outer joins, that clause may prevent us from re-ordering the two outer joins. The code was considering only the joins' own ON-conditions in determining reordering safety, which is not good enough. Add a "delay_upper_joins" flag to OuterJoinInfo to flag that we have detected such a clause and higher-level outer joins shouldn't be permitted to commute with this one. (This might seem overly coarse, but given the current rules for OJ reordering, it's sufficient AFAICT.) The failure case is actually pretty narrow: it needs a WHERE clause within the RHS of a left join that checks the RHS of a lower left join, but is not strict for that RHS (else we'd have simplified the lower join to a plain join). Even then no failure will be manifest unless the planner chooses to rearrange the join order. Per bug report from Adam Terrey.		2007-05-22 23:23:58 +00:00
..
Makefile	Remove remains of old depend target.	2007-01-20 17:16:17 +00:00
README	make sure the $Id tags are converted to $PostgreSQL as well ...	2003-11-29 22:41:33 +00:00
bitmapset.c	Update CVS HEAD for 2007 copyright. Back branches are typically not	2007-01-05 22:20:05 +00:00
copyfuncs.c	Repair planner bug introduced in 8.2 by ability to rearrange outer joins:	2007-05-22 23:23:58 +00:00
equalfuncs.c	Repair planner bug introduced in 8.2 by ability to rearrange outer joins:	2007-05-22 23:23:58 +00:00
list.c	Update CVS HEAD for 2007 copyright. Back branches are typically not	2007-01-05 22:20:05 +00:00
makefuncs.c	Fix up the remaining places where the expression node structure would lose	2007-03-17 00:11:05 +00:00
nodeFuncs.c	Update CVS HEAD for 2007 copyright. Back branches are typically not	2007-01-05 22:20:05 +00:00
nodes.c	Update CVS HEAD for 2007 copyright. Back branches are typically not	2007-01-05 22:20:05 +00:00
outfuncs.c	Repair planner bug introduced in 8.2 by ability to rearrange outer joins:	2007-05-22 23:23:58 +00:00
params.c	First phase of plan-invalidation project: create a plan cache management	2007-03-13 00:33:44 +00:00
print.c	Turn the rangetable used by the executor into a flat list, and avoid storing	2007-02-22 22:00:26 +00:00
read.c	Update CVS HEAD for 2007 copyright. Back branches are typically not	2007-01-05 22:20:05 +00:00
readfuncs.c	Modify processing of DECLARE CURSOR and EXPLAIN so that they can resolve the	2007-04-27 22:05:49 +00:00
tidbitmap.c	Fix dynahash.c to suppress hash bucket splits while a hash_seq_search() scan	2007-04-26 23:24:46 +00:00
value.c	Update CVS HEAD for 2007 copyright. Back branches are typically not	2007-01-05 22:20:05 +00:00

README

*******************************************************************************
*                                                                             *
* EXPLANATION OF THE NODE STRUCTURES                                          *
*    - Andrew Yu (11/94)                                                      *
*                                                                             *
* Copyright (c) 1994, Regents of the University of California                 *
*                                                                             *
* $PostgreSQL: pgsql/src/backend/nodes/README,v 1.2 2003/11/29 22:39:45 pgsql Exp $
*                                                                             *
*******************************************************************************

INTRODUCTION

The current node structures are plain old C structures. "Inheritance" is
achieved by convention. No additional functions will be generated. Functions
that manipulate node structures reside in this directory.


FILES IN THIS DIRECTORY

    Node manipulation functions:
	copyfuncs.c	- copying a node
	equalfuncs.c	- comparing a node
	outfuncs.c	- convert a node to ascii representation
	readfuncs.c	- convert ascii representation back to a node
	makefuncs.c	- creator functions for primitive nodes

    Node definitions:
	nodes.h		- define node tags (NodeTag)
	pg_list.h	- generic list 
	primnodes.h	- primitive nodes
	parsenodes.h	- parse tree nodes
	plannodes.h	- plan tree nodes
	relation.h	- inner plan tree nodes
	execnodes.h	- executor nodes
	memnodes.h	- memory nodes


STEPS TO ADD A NODE

Suppose you wana define a node Foo:

1. add a tag (T_Foo) to the enum NodeTag in nodes.h (You may have to
   recompile the whole tree after doing this.)
2. add the structure definition to the appropriate ???nodes.h file. If you
   intend to inherit from, say a Plan node, put Plan as the first field of
   you definition.
3. if you intend to use copyObject, equal, nodeToString or stringToNode,
   add an appropriate function to copyfuncs.c, equalfuncs.c, outfuncs.c
   and readfuncs.c accordingly. (Except for frequently used nodes, don't
   bother writing a creator function in makefuncs.c)


HISTORICAL NOTE

Prior to the current simple C structure definitions, the Node structures 
uses a pseudo-inheritance system which automatically generates creator and
accessor functions. Since every node inherits from LispValue, the whole thing
is a mess. Here's a little anecdote:

    LispValue definition -- class used to support lisp structures
    in C.  This is here because we did not want to totally rewrite
    planner and executor code which depended on lisp structures when
    we ported postgres V1 from lisp to C. -cim 4/23/90