2
doc/src/sgml/ref/create_opclass.sgml
3
PostgreSQL documentation
6
<refentry id="SQL-CREATEOPCLASS">
8
<refentrytitle>CREATE OPERATOR CLASS</refentrytitle>
9
<manvolnum>7</manvolnum>
10
<refmiscinfo>SQL - Language Statements</refmiscinfo>
14
<refname>CREATE OPERATOR CLASS</refname>
15
<refpurpose>define a new operator class</refpurpose>
18
<indexterm zone="sql-createopclass">
19
<primary>CREATE OPERATOR CLASS</primary>
24
CREATE OPERATOR CLASS <replaceable class="parameter">name</replaceable> [ DEFAULT ] FOR TYPE <replaceable class="parameter">data_type</replaceable>
25
USING <replaceable class="parameter">index_method</replaceable> [ FAMILY <replaceable class="parameter">family_name</replaceable> ] AS
26
{ OPERATOR <replaceable class="parameter">strategy_number</replaceable> <replaceable class="parameter">operator_name</replaceable> [ ( <replaceable class="parameter">op_type</replaceable>, <replaceable class="parameter">op_type</replaceable> ) ] [ FOR SEARCH | FOR ORDER BY <replaceable class="parameter">sort_family_name</replaceable> ]
27
| FUNCTION <replaceable class="parameter">support_number</replaceable> [ ( <replaceable class="parameter">op_type</replaceable> [ , <replaceable class="parameter">op_type</replaceable> ] ) ] <replaceable class="parameter">function_name</replaceable> ( <replaceable class="parameter">argument_type</replaceable> [, ...] )
28
| STORAGE <replaceable class="parameter">storage_type</replaceable>
34
<title>Description</title>
37
<command>CREATE OPERATOR CLASS</command> creates a new operator class.
38
An operator class defines how a particular data type can be used with
39
an index. The operator class specifies that certain operators will fill
40
particular roles or <quote>strategies</> for this data type and this
41
index method. The operator class also specifies the support procedures to
43
the index method when the operator class is selected for an
44
index column. All the operators and functions used by an operator
45
class must be defined before the operator class can be created.
49
If a schema name is given then the operator class is created in the
50
specified schema. Otherwise it is created in the current schema.
51
Two operator classes in the same schema can have the same name only if they
52
are for different index methods.
56
The user who defines an operator class becomes its owner. Presently,
57
the creating user must be a superuser. (This restriction is made because
58
an erroneous operator class definition could confuse or even crash the
63
<command>CREATE OPERATOR CLASS</command> does not presently check
64
whether the operator class definition includes all the operators and
65
functions required by the index method, nor whether the operators and
66
functions form a self-consistent set. It is the user's
67
responsibility to define a valid operator class.
71
Related operator classes can be grouped into <firstterm>operator
72
families</>. To add a new operator class to an existing family,
73
specify the <literal>FAMILY</> option in <command>CREATE OPERATOR
74
CLASS</command>. Without this option, the new class is placed into
75
a family named the same as the new class (creating that family if
76
it doesn't already exist).
80
Refer to <xref linkend="xindex"> for further information.
85
<title>Parameters</title>
89
<term><replaceable class="parameter">name</replaceable></term>
92
The name of the operator class to be created. The name can be
99
<term><literal>DEFAULT</></term>
102
If present, the operator class will become the default
103
operator class for its data type. At most one operator class
104
can be the default for a specific data type and index method.
110
<term><replaceable class="parameter">data_type</replaceable></term>
113
The column data type that this operator class is for.
119
<term><replaceable class="parameter">index_method</replaceable></term>
122
The name of the index method this operator class is for.
128
<term><replaceable class="parameter">family_name</replaceable></term>
131
The name of the existing operator family to add this operator class to.
132
If not specified, a family named the same as the operator class is
133
used (creating it, if it doesn't already exist).
139
<term><replaceable class="parameter">strategy_number</replaceable></term>
142
The index method's strategy number for an operator
143
associated with the operator class.
149
<term><replaceable class="parameter">operator_name</replaceable></term>
152
The name (optionally schema-qualified) of an operator associated
153
with the operator class.
159
<term><replaceable class="parameter">op_type</replaceable></term>
162
In an <literal>OPERATOR</> clause,
163
the operand data type(s) of the operator, or <literal>NONE</> to
164
signify a left-unary or right-unary operator. The operand data
165
types can be omitted in the normal case where they are the same
166
as the operator class's data type.
170
In a <literal>FUNCTION</> clause, the operand data type(s) the
171
function is intended to support, if different from
172
the input data type(s) of the function (for B-tree and hash indexes)
173
or the class's data type (for GIN and GiST indexes). These defaults
174
are always correct, so there is no point in specifying <replaceable
175
class="parameter">op_type</replaceable> in a <literal>FUNCTION</> clause
176
in <command>CREATE OPERATOR CLASS</>, but the option is provided
177
for consistency with the comparable syntax in
178
<command>ALTER OPERATOR FAMILY</>.
184
<term><replaceable class="parameter">sort_family_name</replaceable></term>
187
The name (optionally schema-qualified) of an existing btree operator
188
family that describes the sort ordering associated with an ordering
193
If neither <literal>FOR SEARCH</> nor <literal>FOR ORDER BY</> is
194
specified, <literal>FOR SEARCH</> is the default.
200
<term><replaceable class="parameter">support_number</replaceable></term>
203
The index method's support procedure number for a
204
function associated with the operator class.
210
<term><replaceable class="parameter">function_name</replaceable></term>
213
The name (optionally schema-qualified) of a function that is an
214
index method support procedure for the operator class.
220
<term><replaceable class="parameter">argument_type</replaceable></term>
223
The parameter data type(s) of the function.
229
<term><replaceable class="parameter">storage_type</replaceable></term>
232
The data type actually stored in the index. Normally this is
233
the same as the column data type, but some index methods
234
(currently GIN and GiST) allow it to be different. The
235
<literal>STORAGE</> clause must be omitted unless the index
236
method allows a different type to be used.
243
The <literal>OPERATOR</>, <literal>FUNCTION</>, and <literal>STORAGE</>
244
clauses can appear in any order.
252
Because the index machinery does not check access permissions on functions
253
before using them, including a function or operator in an operator class
254
is tantamount to granting public execute permission on it. This is usually
255
not an issue for the sorts of functions that are useful in an operator
260
The operators should not be defined by SQL functions. A SQL function
261
is likely to be inlined into the calling query, which will prevent
262
the optimizer from recognizing that the query matches an index.
266
Before <productname>PostgreSQL</productname> 8.4, the <literal>OPERATOR</>
267
clause could include a <literal>RECHECK</> option. This is no longer
268
supported because whether an index operator is <quote>lossy</> is now
269
determined on-the-fly at run time. This allows efficient handling of
270
cases where an operator might or might not be lossy.
275
<title>Examples</title>
278
The following example command defines a GiST index operator class
279
for the data type <literal>_int4</> (array of <type>int4</type>). See the
280
<xref linkend="intarray"> module for the complete example.
284
CREATE OPERATOR CLASS gist__int_ops
285
DEFAULT FOR TYPE _int4 USING gist AS
286
OPERATOR 3 &&,
287
OPERATOR 6 = (anyarray, anyarray),
290
OPERATOR 20 @@ (_int4, query_int),
291
FUNCTION 1 g_int_consistent (internal, _int4, int, oid, internal),
292
FUNCTION 2 g_int_union (internal, internal),
293
FUNCTION 3 g_int_compress (internal),
294
FUNCTION 4 g_int_decompress (internal),
295
FUNCTION 5 g_int_penalty (internal, internal, internal),
296
FUNCTION 6 g_int_picksplit (internal, internal),
297
FUNCTION 7 g_int_same (_int4, _int4, internal);
302
<title>Compatibility</title>
305
<command>CREATE OPERATOR CLASS</command> is a
306
<productname>PostgreSQL</productname> extension. There is no
307
<command>CREATE OPERATOR CLASS</command> statement in the SQL
313
<title>See Also</title>
315
<simplelist type="inline">
316
<member><xref linkend="sql-alteropclass"></member>
317
<member><xref linkend="sql-dropopclass"></member>
318
<member><xref linkend="sql-createopfamily"></member>
319
<member><xref linkend="sql-alteropfamily"></member>