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Peter Eisentraut authored
This adds support for the more or less SQL-conforming USAGE privilege on types and domains. The intent is to be able restrict which users can create dependencies on types, which restricts the way in which owners can alter types. reviewed by Yeb Havinga
Peter Eisentraut authoredThis adds support for the more or less SQL-conforming USAGE privilege on types and domains. The intent is to be able restrict which users can create dependencies on types, which restricts the way in which owners can alter types. reviewed by Yeb Havinga
create_operator.sgml 8.92 KiB
<!--
doc/src/sgml/ref/create_operator.sgml
PostgreSQL documentation
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<refentry id="SQL-CREATEOPERATOR">
<refmeta>
<refentrytitle>CREATE OPERATOR</refentrytitle>
<manvolnum>7</manvolnum>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>CREATE OPERATOR</refname>
<refpurpose>define a new operator</refpurpose>
</refnamediv>
<indexterm zone="sql-createoperator">
<primary>CREATE OPERATOR</primary>
</indexterm>
<refsynopsisdiv>
<synopsis>
CREATE OPERATOR <replaceable>name</replaceable> (
PROCEDURE = <replaceable class="parameter">function_name</replaceable>
[, LEFTARG = <replaceable class="parameter">left_type</replaceable> ] [, RIGHTARG = <replaceable class="parameter">right_type</replaceable> ]
[, COMMUTATOR = <replaceable class="parameter">com_op</replaceable> ] [, NEGATOR = <replaceable class="parameter">neg_op</replaceable> ]
[, RESTRICT = <replaceable class="parameter">res_proc</replaceable> ] [, JOIN = <replaceable class="parameter">join_proc</replaceable> ]
[, HASHES ] [, MERGES ]
)
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>CREATE OPERATOR</command> defines a new operator,
<replaceable class="parameter">name</replaceable>. 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.
</para>
<para>
The operator name is a sequence of up to <symbol>NAMEDATALEN</>-1
(63 by default) characters from the following list:
<literallayout>
+ - * / < > = ~ ! @ # % ^ & | ` ?
</literallayout>
There are a few restrictions on your choice of name:
<itemizedlist>
<listitem>
<para><literal>--</literal> and <literal>/*</literal> cannot appear anywhere in an operator name,
since they will be taken as the start of a comment.
</para>
</listitem>
<listitem>
<para>
A multicharacter operator name cannot end in <literal>+</literal> or
<literal>-</literal>,
unless the name also contains at least one of these characters:
<literallayout>
~ ! @ # % ^ & | ` ?
</literallayout>
For example, <literal>@-</literal> is an allowed operator name,
but <literal>*-</literal> is not.
This restriction allows <productname>PostgreSQL</productname> to
parse SQL-compliant commands without requiring spaces between tokens. </para>
</listitem>
<listitem>
<para>
The use of <literal>=></> as an operator name is deprecated. It may
be disallowed altogether in a future release.
</para>
</listitem>
</itemizedlist>
</para>
<para>
The operator <literal>!=</literal> is mapped to
<literal><></literal> on input, so these two names are always
equivalent.
</para>
<para>
At least one of <literal>LEFTARG</> and <literal>RIGHTARG</> must be defined. For
binary operators, both must be defined. For right unary
operators, only <literal>LEFTARG</> should be defined, while for left
unary operators only <literal>RIGHTARG</> should be defined.
</para>
<para>
The <replaceable class="parameter">function_name</replaceable>
procedure must have been previously defined using <command>CREATE
FUNCTION</command> and must be defined to accept the correct number
of arguments (either one or two) of the indicated types.
</para>
<para>
The other clauses specify optional operator optimization clauses.
Their meaning is detailed in <xref linkend="xoper-optimization">.
</para>
<para>
To be able to create an operator, you must have <literal>USAGE</literal>
privilege on the argument types and the return type, as well
as <literal>EXECUTE</literal> privilege on the underlying function. If a
commutator or negator operator is specified, you must own these operators.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="parameter">name</replaceable></term>
<listitem>
<para>
The name of the operator to be defined. See above for allowable
characters. The name can be schema-qualified, for example
<literal>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
<firstterm>overloading</>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">function_name</replaceable></term>
<listitem>
<para>
The function used to implement this operator.
</para>
</listitem> </varlistentry>
<varlistentry>
<term><replaceable class="parameter">left_type</replaceable></term>
<listitem>
<para>
The data type of the operator's left operand, if any.
This option would be omitted for a left-unary operator.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">right_type</replaceable></term>
<listitem>
<para>
The data type of the operator's right operand, if any.
This option would be omitted for a right-unary operator.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">com_op</replaceable></term>
<listitem>
<para>
The commutator of this operator.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">neg_op</replaceable></term>
<listitem>
<para>
The negator of this operator.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">res_proc</replaceable></term>
<listitem>
<para>
The restriction selectivity estimator function for this operator.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">join_proc</replaceable></term>
<listitem>
<para>
The join selectivity estimator function for this operator.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>HASHES</literal></term>
<listitem>
<para>
Indicates this operator can support a hash join.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>MERGES</literal></term>
<listitem> <para>
Indicates this operator can support a merge join.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
To give a schema-qualified operator name in <replaceable
class="parameter">com_op</replaceable> or the other optional
arguments, use the <literal>OPERATOR()</> syntax, for example:
<programlisting>
COMMUTATOR = OPERATOR(myschema.===) ,
</programlisting></para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>
Refer to <xref linkend="xoper"> for further information.
</para>
<para>
It is not possible to specify an operator's lexical precedence in
<command>CREATE OPERATOR</>, because the parser's precedence behavior
is hard-wired. See <xref linkend="sql-precedence"> for precedence details.
</para>
<para>
The obsolete options <literal>SORT1</>, <literal>SORT2</>,
<literal>LTCMP</>, and <literal>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 <literal>MERGES</> true.
</para>
<para>
Use <xref linkend="sql-dropoperator"> to delete user-defined operators
from a database. Use <xref linkend="sql-alteroperator"> to modify operators in a
database.
</para>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
The following command defines a new operator, area-equality, for
the data type <type>box</type>:
<programlisting>
CREATE OPERATOR === (
LEFTARG = box,
RIGHTARG = box,
PROCEDURE = area_equal_procedure,
COMMUTATOR = ===,
NEGATOR = !==,
RESTRICT = area_restriction_procedure,
JOIN = area_join_procedure,
HASHES, MERGES
);
</programlisting></para>
</refsect1>
<refsect1>
<title>Compatibility</title>
<para> <command>CREATE OPERATOR</command> is a
<productname>PostgreSQL</productname> extension. There are no
provisions for user-defined operators in the SQL standard.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="sql-alteroperator"></member>
<member><xref linkend="sql-createopclass"></member>
<member><xref linkend="sql-dropoperator"></member>
</simplelist>
</refsect1>
</refentry>