database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-09 22:41:56 +03:00
Code Activity

Very minor improvements in CREATE OPERATOR docs.

Browse Source
This commit is contained in:
Tom Lane
1999-05-20 03:22:01 +00:00
parent c9f8ab6fba
commit c3a4d8ed54
2 changed files with 17 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
src/man/create_operator.l
View File

@ -1,6 +1,6 @@
.\" This is -*-nroff-*-
.\" XXX standard disclaimer belongs here....
.\" $Header: /cvsroot/pgsql/src/man/Attic/create_operator.l,v 1.8 1999/04/15 00:09:00 tgl Exp $
.\" $Header: /cvsroot/pgsql/src/man/Attic/create_operator.l,v 1.9 1999/05/20 03:21:02 tgl Exp $
.TH "CREATE OPERATOR" SQL 11/05/95 PostgreSQL PostgreSQL
.SH NAME
create operator - define a new user operator
@ -88,9 +88,10 @@ and must have one or two arguments.
.\" .(l
.\" MYBOXES2.description A (\*(lq0,0,1,1\*(rq A MYBOXES.description).
.\" .)l
The commutator operator is present so that Postgres can reverse the order
of the operands if it wishes. For example, the operator
area-less-than, >>>, would have a commutator operator,
The commutator operator should be identified if one exists,
so that Postgres can reverse the order of the operands if it wishes.
For example, the operator
area-less-than, >>>, would probably have a commutator operator,
area-greater-than, <<<. Hence, the query optimizer
could freely convert:
.nf
@ -109,9 +110,10 @@ MYBOXES.description <<< "0,0,1,1"::box
This allows the execution code to always use the latter representation
and simplifies the query optimizer somewhat.
.PP
Similarly, if there is a negator operator then it should be identified.
Suppose that an operator, area-equal, ===,
exists, as well as an area not equal, !==.
The negator operator allows the query optimizer to convert
The negator link allows the query optimizer to simplify
.nf
.ce 1
@ -182,7 +184,7 @@ fraction of the instances in MYBOXES that satisfy the clause. The
function res_proc must be a registered function (meaning it is already
defined using
.IR create_function(l))
which accepts one argument of the correct data type and returns a
which accepts arguments of the correct data types and returns a
floating point number. The query optimizer simply calls this
function, passing the parameter "0,0,1,1"
and multiplies the result by the relation size to get the desired