postgresql

History

Tom Lane cc5e80b8d1 Teach planner about some cases where a restriction clause can be propagated inside an outer join. In particular, given LEFT JOIN ON (A = B) WHERE A = constant, we cannot conclude that B = constant at the top level (B might be null instead), but we can nonetheless put a restriction B = constant into the quals for B's relation, since no inner-side rows not meeting that condition can contribute to the final result. Similarly, given FULL JOIN USING (J) WHERE J = constant, we can't directly conclude that either input J variable = constant, but it's OK to push such quals into each input rel. Per recent gripe from Kim Bisgaard. Along the way, remove 'valid_everywhere' flag from RestrictInfo, as on closer analysis it was not being used for anything, and was defined backwards anyway.		2005-07-02 23:00:42 +00:00
..
Makefile	Initial implementation of lossy-tuple-bitmap data structures.	2005-04-17 22:24:02 +00:00
README	make sure the $Id tags are converted to $PostgreSQL as well ...	2003-11-29 22:41:33 +00:00
bitmapset.c	Improve hash method for bitmapsets: some examination of actual outputs	2005-06-15 16:24:07 +00:00
copyfuncs.c	Teach planner about some cases where a restriction clause can be	2005-07-02 23:00:42 +00:00
equalfuncs.c	Teach planner about some cases where a restriction clause can be	2005-07-02 23:00:42 +00:00
list.c	Trivial comment tweak.	2005-03-17 05:47:01 +00:00
makefuncs.c	Merge Resdom nodes into TargetEntry nodes to simplify code and save a	2005-04-06 16:34:07 +00:00
nodeFuncs.c	Tag appropriate files for rc3	2004-12-31 22:04:05 +00:00
nodes.c	Tag appropriate files for rc3	2004-12-31 22:04:05 +00:00
outfuncs.c	Teach planner about some cases where a restriction clause can be	2005-07-02 23:00:42 +00:00
params.c	Tag appropriate files for rc3	2004-12-31 22:04:05 +00:00
print.c	Change CREATE TYPE to require datatype output and send functions to have	2005-05-01 18:56:19 +00:00
read.c	Tag appropriate files for rc3	2004-12-31 22:04:05 +00:00
readfuncs.c	Replace pg_shadow and pg_group by new role-capable catalogs pg_authid	2005-06-28 05:09:14 +00:00
tidbitmap.c	Modify hash_search() API to prevent future occurrences of the error	2005-05-29 04:23:07 +00:00
value.c	Some more missed copyright notices. Many of these look like they	2005-01-01 20:44:34 +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