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 comparison functions
174 or the class's data type (for B-tree sort support functions and all
175 functions in GiST and GIN operator classes). These defaults
176 are correct, and so <replaceable
177 class="parameter">op_type</replaceable> need not be specified in
178 <literal>FUNCTION</> clauses, except for the case of a B-tree sort
179 support function that is meant to support cross-data-type comparisons.
185 <term><replaceable class="parameter">sort_family_name</replaceable></term>
188 The name (optionally schema-qualified) of an existing <literal>btree</literal> operator
189 family that describes the sort ordering associated with an ordering
194 If neither <literal>FOR SEARCH</> nor <literal>FOR ORDER BY</> is
195 specified, <literal>FOR SEARCH</> is the default.
201 <term><replaceable class="parameter">support_number</replaceable></term>
204 The index method's support procedure number for a
205 function associated with the operator class.
211 <term><replaceable class="parameter">function_name</replaceable></term>
214 The name (optionally schema-qualified) of a function that is an
215 index method support procedure for the operator class.
221 <term><replaceable class="parameter">argument_type</replaceable></term>
224 The parameter data type(s) of the function.
230 <term><replaceable class="parameter">storage_type</replaceable></term>
233 The data type actually stored in the index. Normally this is
234 the same as the column data type, but some index methods
235 (currently GIN and GiST) allow it to be different. The
236 <literal>STORAGE</> clause must be omitted unless the index
237 method allows a different type to be used.
244 The <literal>OPERATOR</>, <literal>FUNCTION</>, and <literal>STORAGE</>
245 clauses can appear in any order.
253 Because the index machinery does not check access permissions on functions
254 before using them, including a function or operator in an operator class
255 is tantamount to granting public execute permission on it. This is usually
256 not an issue for the sorts of functions that are useful in an operator
261 The operators should not be defined by SQL functions. A SQL function
262 is likely to be inlined into the calling query, which will prevent
263 the optimizer from recognizing that the query matches an index.
267 Before <productname>PostgreSQL</productname> 8.4, the <literal>OPERATOR</>
268 clause could include a <literal>RECHECK</> option. This is no longer
269 supported because whether an index operator is <quote>lossy</> is now
270 determined on-the-fly at run time. This allows efficient handling of
271 cases where an operator might or might not be lossy.
276 <title>Examples</title>
279 The following example command defines a GiST index operator class
280 for the data type <literal>_int4</> (array of <type>int4</type>). See the
281 <xref linkend="intarray"> module for the complete example.
285 CREATE OPERATOR CLASS gist__int_ops
286 DEFAULT FOR TYPE _int4 USING gist AS
287 OPERATOR 3 &&,
288 OPERATOR 6 = (anyarray, anyarray),
291 OPERATOR 20 @@ (_int4, query_int),
292 FUNCTION 1 g_int_consistent (internal, _int4, int, oid, internal),
293 FUNCTION 2 g_int_union (internal, internal),
294 FUNCTION 3 g_int_compress (internal),
295 FUNCTION 4 g_int_decompress (internal),
296 FUNCTION 5 g_int_penalty (internal, internal, internal),
297 FUNCTION 6 g_int_picksplit (internal, internal),
298 FUNCTION 7 g_int_same (_int4, _int4, internal);
303 <title>Compatibility</title>
306 <command>CREATE OPERATOR CLASS</command> is a
307 <productname>PostgreSQL</productname> extension. There is no
308 <command>CREATE OPERATOR CLASS</command> statement in the SQL
314 <title>See Also</title>
316 <simplelist type="inline">
317 <member><xref linkend="sql-alteropclass"></member>
318 <member><xref linkend="sql-dropopclass"></member>
319 <member><xref linkend="sql-createopfamily"></member>
320 <member><xref linkend="sql-alteropfamily"></member>