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+'\" t
+.\"     Title: CREATE OPERATOR
+.\"    Author: The PostgreSQL Global Development Group
+.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
+.\"      Date: 2021
+.\"    Manual: PostgreSQL 13.4 Documentation
+.\"    Source: PostgreSQL 13.4
+.\"  Language: English
+.\"
+.TH "CREATE OPERATOR" "7" "2021" "PostgreSQL 13.4" "PostgreSQL 13.4 Documentation"
+.\" -----------------------------------------------------------------
+.\" * Define some portability stuff
+.\" -----------------------------------------------------------------
+.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.\" http://bugs.debian.org/507673
+.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
+.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.ie \n(.g .ds Aq \(aq
+.el       .ds Aq '
+.\" -----------------------------------------------------------------
+.\" * set default formatting
+.\" -----------------------------------------------------------------
+.\" disable hyphenation
+.nh
+.\" disable justification (adjust text to left margin only)
+.ad l
+.\" -----------------------------------------------------------------
+.\" * MAIN CONTENT STARTS HERE *
+.\" -----------------------------------------------------------------
+.SH "NAME"
+CREATE_OPERATOR \- define a new operator
+.SH "SYNOPSIS"
+.sp
+.nf
+CREATE OPERATOR \fIname\fR (
+    {FUNCTION|PROCEDURE} = \fIfunction_name\fR
+    [, LEFTARG = \fIleft_type\fR ] [, RIGHTARG = \fIright_type\fR ]
+    [, COMMUTATOR = \fIcom_op\fR ] [, NEGATOR = \fIneg_op\fR ]
+    [, RESTRICT = \fIres_proc\fR ] [, JOIN = \fIjoin_proc\fR ]
+    [, HASHES ] [, MERGES ]
+)
+.fi
+.SH "DESCRIPTION"
+.PP
+\fBCREATE OPERATOR\fR
+defines a new operator,
+\fIname\fR\&. The user who defines an operator becomes its owner\&. If a schema name is given then the operator is created in the specified schema\&. Otherwise it is created in the current schema\&.
+.PP
+The operator name is a sequence of up to
+NAMEDATALEN\-1 (63 by default) characters from the following list:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
++ \- * / < > = ~ ! @ # % ^ & | ` ?
+.fi
+.if n \{\
+.RE
+.\}
+.sp
+There are a few restrictions on your choice of name:
+.sp
+.RS 4
+.ie n \{\
+\h'-04'\(bu\h'+03'\c
+.\}
+.el \{\
+.sp -1
+.IP \(bu 2.3
+.\}
+\-\-
+and
+/*
+cannot appear anywhere in an operator name, since they will be taken as the start of a comment\&.
+.RE
+.sp
+.RS 4
+.ie n \{\
+\h'-04'\(bu\h'+03'\c
+.\}
+.el \{\
+.sp -1
+.IP \(bu 2.3
+.\}
+A multicharacter operator name cannot end in
++
+or
+\-, unless the name also contains at least one of these characters:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+~ ! @ # % ^ & | ` ?
+.fi
+.if n \{\
+.RE
+.\}
+.sp
+For example,
+@\-
+is an allowed operator name, but
+*\-
+is not\&. This restriction allows
+PostgreSQL
+to parse SQL\-compliant commands without requiring spaces between tokens\&.
+.RE
+.sp
+.RS 4
+.ie n \{\
+\h'-04'\(bu\h'+03'\c
+.\}
+.el \{\
+.sp -1
+.IP \(bu 2.3
+.\}
+The use of
+=>
+as an operator name is deprecated\&. It may be disallowed altogether in a future release\&.
+.RE
+.PP
+The operator
+!=
+is mapped to
+<>
+on input, so these two names are always equivalent\&.
+.PP
+At least one of
+LEFTARG
+and
+RIGHTARG
+must be defined\&. For binary operators, both must be defined\&. For right unary operators, only
+LEFTARG
+should be defined, while for left unary operators only
+RIGHTARG
+should be defined\&.
+.if n \{\
+.sp
+.\}
+.RS 4
+.it 1 an-trap
+.nr an-no-space-flag 1
+.nr an-break-flag 1
+.br
+.ps +1
+\fBNote\fR
+.ps -1
+.br
+.PP
+Right unary, also called postfix, operators are deprecated and will be removed in
+PostgreSQL
+version 14\&.
+.sp .5v
+.RE
+.PP
+The
+\fIfunction_name\fR
+function must have been previously defined using
+\fBCREATE FUNCTION\fR
+and must be defined to accept the correct number of arguments (either one or two) of the indicated types\&.
+.PP
+In the syntax of
+CREATE OPERATOR, the keywords
+FUNCTION
+and
+PROCEDURE
+are equivalent, but the referenced function must in any case be a function, not a procedure\&. The use of the keyword
+PROCEDURE
+here is historical and deprecated\&.
+.PP
+The other clauses specify optional operator optimization clauses\&. Their meaning is detailed in
+Section\ \&37.15\&.
+.PP
+To be able to create an operator, you must have
+USAGE
+privilege on the argument types and the return type, as well as
+EXECUTE
+privilege on the underlying function\&. If a commutator or negator operator is specified, you must own these operators\&.
+.SH "PARAMETERS"
+.PP
+\fIname\fR
+.RS 4
+The name of the operator to be defined\&. See above for allowable characters\&. The name can be schema\-qualified, for example
+CREATE OPERATOR myschema\&.+ (\&.\&.\&.)\&. If not, then the operator is created in the current schema\&. Two operators in the same schema can have the same name if they operate on different data types\&. This is called
+overloading\&.
+.RE
+.PP
+\fIfunction_name\fR
+.RS 4
+The function used to implement this operator\&.
+.RE
+.PP
+\fIleft_type\fR
+.RS 4
+The data type of the operator\*(Aqs left operand, if any\&. This option would be omitted for a left\-unary operator\&.
+.RE
+.PP
+\fIright_type\fR
+.RS 4
+The data type of the operator\*(Aqs right operand, if any\&. This option would be omitted for a right\-unary operator\&.
+.RE
+.PP
+\fIcom_op\fR
+.RS 4
+The commutator of this operator\&.
+.RE
+.PP
+\fIneg_op\fR
+.RS 4
+The negator of this operator\&.
+.RE
+.PP
+\fIres_proc\fR
+.RS 4
+The restriction selectivity estimator function for this operator\&.
+.RE
+.PP
+\fIjoin_proc\fR
+.RS 4
+The join selectivity estimator function for this operator\&.
+.RE
+.PP
+HASHES
+.RS 4
+Indicates this operator can support a hash join\&.
+.RE
+.PP
+MERGES
+.RS 4
+Indicates this operator can support a merge join\&.
+.RE
+.PP
+To give a schema\-qualified operator name in
+\fIcom_op\fR
+or the other optional arguments, use the
+OPERATOR()
+syntax, for example:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+COMMUTATOR = OPERATOR(myschema\&.===) ,
+.fi
+.if n \{\
+.RE
+.\}
+.SH "NOTES"
+.PP
+Refer to
+Section\ \&37.14
+for further information\&.
+.PP
+It is not possible to specify an operator\*(Aqs lexical precedence in
+\fBCREATE OPERATOR\fR, because the parser\*(Aqs precedence behavior is hard\-wired\&. See
+Section\ \&4.1.6
+for precedence details\&.
+.PP
+The obsolete options
+SORT1,
+SORT2,
+LTCMP, and
+GTCMP
+were formerly used to specify the names of sort operators associated with a merge\-joinable operator\&. This is no longer necessary, since information about associated operators is found by looking at B\-tree operator families instead\&. If one of these options is given, it is ignored except for implicitly setting
+MERGES
+true\&.
+.PP
+Use
+DROP OPERATOR (\fBDROP_OPERATOR\fR(7))
+to delete user\-defined operators from a database\&. Use
+ALTER OPERATOR (\fBALTER_OPERATOR\fR(7))
+to modify operators in a database\&.
+.SH "EXAMPLES"
+.PP
+The following command defines a new operator, area\-equality, for the data type
+box:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+CREATE OPERATOR === (
+    LEFTARG = box,
+    RIGHTARG = box,
+    FUNCTION = area_equal_function,
+    COMMUTATOR = ===,
+    NEGATOR = !==,
+    RESTRICT = area_restriction_function,
+    JOIN = area_join_function,
+    HASHES, MERGES
+);
+.fi
+.if n \{\
+.RE
+.\}
+.SH "COMPATIBILITY"
+.PP
+\fBCREATE OPERATOR\fR
+is a
+PostgreSQL
+extension\&. There are no provisions for user\-defined operators in the SQL standard\&.
+.SH "SEE ALSO"
+ALTER OPERATOR (\fBALTER_OPERATOR\fR(7)), CREATE OPERATOR CLASS (\fBCREATE_OPERATOR_CLASS\fR(7)), DROP OPERATOR (\fBDROP_OPERATOR\fR(7))