1CREATE LANGUAGE(7) SQL Commands CREATE LANGUAGE(7)
2
6 CREATE LANGUAGE - define a new procedural language
7
10 CREATE [ PROCEDURAL ] LANGUAGE name
11 CREATE [ TRUSTED ] [ PROCEDURAL ] LANGUAGE name
12 HANDLER call_handler [ VALIDATOR valfunction ]
13
16 Using CREATE LANGUAGE, a PostgreSQL user can register a new procedural
17 language with a PostgreSQL database. Subsequently, functions and trig‐
18 ger procedures can be defined in this new language.
19 CREATE LANGUAGE effectively associates the language name with a call
21 handler that is responsible for executing functions written in the lan‐
22 guage. Refer to in the documentation for more information about lan‐
23 guage call handlers.
24 There are two forms of the CREATE LANGUAGE command. In the first form,
26 the user supplies just the name of the desired language, and the Post‐
27 greSQL server consults the pg_pltemplate system catalog to determine
28 the correct parameters. In the second form, the user supplies the lan‐
29 guage parameters along with the language name. The second form can be
30 used to create a language that is not defined in pg_pltemplate, but
31 this approach is considered obsolescent.
32 When the server finds an entry in the pg_pltemplate catalog for the
34 given language name, it will use the catalog data even if the command
35 includes language parameters. This behavior simplifies loading of old
36 dump files, which are likely to contain out-of-date information about
37 language support functions.
38 Ordinarily, the user must have the PostgreSQL superuser privilege to
40 register a new language. However, the owner of a database can register
41 a new language within that database if the language is listed in the
42 pg_pltemplate catalog and is marked as allowed to be created by data‐
43 base owners (tmpldbacreate is true). The default is that trusted lan‐
44 guages can be created by database owners, but this can be adjusted by
45 superusers by modifying the contents of pg_pltemplate. The creator of
46 a language becomes its owner and can later drop it, rename it, or
47 assign it to a new owner.
48
50 TRUSTED
51 TRUSTED specifies that the call handler for the language is
52 safe, that is, it does not offer an unprivileged user any func‐
53 tionality to bypass access restrictions. If this key word is
54 omitted when registering the language, only users with the Post‐
55 greSQL superuser privilege can use this language to create new
56 functions.
57 PROCEDURAL
59 This is a noise word.
60 name The name of the new procedural language. The language name is
62 case insensitive. The name must be unique among the languages in
63 the database.
64 For backward compatibility, the name can be enclosed by single
66 quotes.
67 HANDLER call_handler
69 call_handler is the name of a previously registered function
70 that will be called to execute the procedural language func‐
71 tions. The call handler for a procedural language must be writ‐
72 ten in a compiled language such as C with version 1 call conven‐
73 tion and registered with PostgreSQL as a function taking no
74 arguments and returning the language_handler type, a placeholder
75 type that is simply used to identify the function as a call han‐
76 dler.
77 VALIDATOR valfunction
79 valfunction is the name of a previously registered function that
80 will be called when a new function in the language is created,
81 to validate the new function. If no validator function is spec‐
82 ified, then a new function will not be checked when it is cre‐
83 ated. The validator function must take one argument of type
84 oid, which will be the OID of the to-be-created function, and
85 will typically return void.
86 A validator function would typically inspect the function body
88 for syntactical correctness, but it can also look at other prop‐
89 erties of the function, for example if the language cannot han‐
90 dle certain argument types. To signal an error, the validator
91 function should use the ereport() function. The return value of
92 the function is ignored.
93 The TRUSTED option and the support function name(s) are ignored if the
95 server has an entry for the specified language name in pg_pltemplate.
96
98 The createlang(1) program is a simple wrapper around the CREATE LAN‐
99 GUAGE command. It eases installation of procedural languages from the
100 shell command line.
101 Use DROP LANGUAGE [drop_language(7)], or better yet the droplang(1)
103 program, to drop procedural languages.
104 The system catalog pg_language (see in the documentation) records
106 information about the currently installed languages. Also, createlang
107 has an option to list the installed languages.
108 To create functions in a procedural language, a user must have the
110 USAGE privilege for the language. By default, USAGE is granted to PUB‐
111 LIC (i.e., everyone) for trusted languages. This can be revoked if
112 desired.
113 Procedural languages are local to individual databases. However, a
115 language can be installed into the template1 database, which will cause
116 it to be available automatically in all subsequently-created databases.
117 The call handler function and the validator function (if any) must
119 already exist if the server does not have an entry for the language in
120 pg_pltemplate. But when there is an entry, the functions need not
121 already exist; they will be automatically defined if not present in the
122 database. (This might result in CREATE LANGUAGE failing, if the shared
123 library that implements the language is not available in the installa‐
124 tion.)
125 In PostgreSQL versions before 7.3, it was necessary to declare handler
127 functions as returning the placeholder type opaque, rather than lan‐
128 guage_handler. To support loading of old dump files, CREATE LANGUAGE
129 will accept a function declared as returning opaque, but it will issue
130 a notice and change the function's declared return type to lan‐
131 guage_handler.
132
134 The preferred way of creating any of the standard procedural languages
135 is just:
136 CREATE LANGUAGE plpgsql;
138 For a language not known in the pg_pltemplate catalog, a sequence such
141 as this is needed:
142 CREATE FUNCTION plsample_call_handler() RETURNS language_handler
144 AS '$libdir/plsample'
145 LANGUAGE C;
146 CREATE LANGUAGE plsample
147 HANDLER plsample_call_handler;
148
151 CREATE LANGUAGE is a PostgreSQL extension.
152
154 ALTER LANGUAGE [alter_language(7)], CREATE FUNCTION [create_func‐
155 tion(7)], DROP LANGUAGE [drop_language(7)], GRANT [grant(7)], REVOKE
156 [revoke(7)], createlang [createlang(1)], droplang [droplang(1)]
157SQL - Language Statements 2011-09-22 CREATE LANGUAGE(7)