postgresql

History

Tom Lane 4e5fbb34b3 Change the division of labor between grouping_planner and query_planner so that the latter estimates the number of groups that grouping will produce. This is needed because it is primarily query_planner that makes the decision between fast-start and fast-finish plans, and in the original coding it was unable to make more than a crude rule-of-thumb choice when the query involved grouping. This revision helps us make saner choices for queries like SELECT ... GROUP BY ... LIMIT, as in a recent example from Mark Kirkwood. Also move the responsibility for canonicalizing sort_pathkeys and group_pathkeys into query_planner; this information has to be available anyway to support the first change, and doing it this way lets us get rid of compare_noncanonical_pathkeys entirely.		2005-08-27 22:13:44 +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	Add NOWAIT option to SELECT FOR UPDATE/SHARE.	2005-08-01 20:31:16 +00:00
equalfuncs.c	Add NOWAIT option to SELECT FOR UPDATE/SHARE.	2005-08-01 20:31:16 +00:00
list.c	Fix a bunch of bad interactions between partial indexes and the new	2005-07-28 20:26:22 +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	Change the division of labor between grouping_planner and query_planner	2005-08-27 22:13:44 +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	Add NOWAIT option to SELECT FOR UPDATE/SHARE.	2005-08-01 20:31:16 +00:00
tidbitmap.c	Fix logic error in tbm_intersect: the intersection of a normal page and	2005-07-24 02:25:26 +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