postgresql

History

Tom Lane b0c4a50bbb Instead of rechecking lossy index operators by putting them into the regular qpqual ('filter condition'), add special-purpose code to nodeIndexscan.c to recheck them. This ends being almost no net addition of code, because the removal of planner code balances out the extra executor code, but it is significantly more efficient when a lossy operator is involved in an OR indexscan. The old implementation had to recheck the entire indexqual in such cases.		2004-01-06 04:31:01 +00:00
..
Makefile	$Header: -> $PostgreSQL Changes ...	2003-11-29 19:52:15 +00:00
README	make sure the $Id tags are converted to $PostgreSQL as well ...	2003-11-29 22:41:33 +00:00
bitmapset.c	$Header: -> $PostgreSQL Changes ...	2003-11-29 19:52:15 +00:00
copyfuncs.c	Instead of rechecking lossy index operators by putting them into the	2004-01-06 04:31:01 +00:00
equalfuncs.c	Add the ability to extract OR indexscan conditions from OR-of-AND	2004-01-05 05:07:36 +00:00
list.c	$Header: -> $PostgreSQL Changes ...	2003-11-29 19:52:15 +00:00
makefuncs.c	$Header: -> $PostgreSQL Changes ...	2003-11-29 19:52:15 +00:00
nodeFuncs.c	$Header: -> $PostgreSQL Changes ...	2003-11-29 19:52:15 +00:00
nodes.c	$Header: -> $PostgreSQL Changes ...	2003-11-29 19:52:15 +00:00
outfuncs.c	Instead of rechecking lossy index operators by putting them into the	2004-01-06 04:31:01 +00:00
print.c	$Header: -> $PostgreSQL Changes ...	2003-11-29 19:52:15 +00:00
read.c	$Header: -> $PostgreSQL Changes ...	2003-11-29 19:52:15 +00:00
readfuncs.c	$Header: -> $PostgreSQL Changes ...	2003-11-29 19:52:15 +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