1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
|
'\" t
.\" Title: CREATE COLLATION
.\" Author: The PostgreSQL Global Development Group
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\" Date: 2022
.\" Manual: PostgreSQL 14.5 Documentation
.\" Source: PostgreSQL 14.5
.\" Language: English
.\"
.TH "CREATE COLLATION" "7" "2022" "PostgreSQL 14.5" "PostgreSQL 14.5 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_COLLATION \- define a new collation
.SH "SYNOPSIS"
.sp
.nf
CREATE COLLATION [ IF NOT EXISTS ] \fIname\fR (
[ LOCALE = \fIlocale\fR, ]
[ LC_COLLATE = \fIlc_collate\fR, ]
[ LC_CTYPE = \fIlc_ctype\fR, ]
[ PROVIDER = \fIprovider\fR, ]
[ DETERMINISTIC = \fIboolean\fR, ]
[ VERSION = \fIversion\fR ]
)
CREATE COLLATION [ IF NOT EXISTS ] \fIname\fR FROM \fIexisting_collation\fR
.fi
.SH "DESCRIPTION"
.PP
\fBCREATE COLLATION\fR
defines a new collation using the specified operating system locale settings, or by copying an existing collation\&.
.PP
To be able to create a collation, you must have
CREATE
privilege on the destination schema\&.
.SH "PARAMETERS"
.PP
IF NOT EXISTS
.RS 4
Do not throw an error if a collation with the same name already exists\&. A notice is issued in this case\&. Note that there is no guarantee that the existing collation is anything like the one that would have been created\&.
.RE
.PP
\fIname\fR
.RS 4
The name of the collation\&. The collation name can be schema\-qualified\&. If it is not, the collation is defined in the current schema\&. The collation name must be unique within that schema\&. (The system catalogs can contain collations with the same name for other encodings, but these are ignored if the database encoding does not match\&.)
.RE
.PP
\fIlocale\fR
.RS 4
This is a shortcut for setting
LC_COLLATE
and
LC_CTYPE
at once\&. If you specify this, you cannot specify either of those parameters\&.
.RE
.PP
\fIlc_collate\fR
.RS 4
Use the specified operating system locale for the
LC_COLLATE
locale category\&.
.RE
.PP
\fIlc_ctype\fR
.RS 4
Use the specified operating system locale for the
LC_CTYPE
locale category\&.
.RE
.PP
\fIprovider\fR
.RS 4
Specifies the provider to use for locale services associated with this collation\&. Possible values are:
icu,
libc\&.
libc
is the default\&. The available choices depend on the operating system and build options\&.
.RE
.PP
DETERMINISTIC
.RS 4
Specifies whether the collation should use deterministic comparisons\&. The default is true\&. A deterministic comparison considers strings that are not byte\-wise equal to be unequal even if they are considered logically equal by the comparison\&. PostgreSQL breaks ties using a byte\-wise comparison\&. Comparison that is not deterministic can make the collation be, say, case\- or accent\-insensitive\&. For that, you need to choose an appropriate
LC_COLLATE
setting
\fIand\fR
set the collation to not deterministic here\&.
.sp
Nondeterministic collations are only supported with the ICU provider\&.
.RE
.PP
\fIversion\fR
.RS 4
Specifies the version string to store with the collation\&. Normally, this should be omitted, which will cause the version to be computed from the actual version of the collation as provided by the operating system\&. This option is intended to be used by
\fBpg_upgrade\fR
for copying the version from an existing installation\&.
.sp
See also
ALTER COLLATION (\fBALTER_COLLATION\fR(7))
for how to handle collation version mismatches\&.
.RE
.PP
\fIexisting_collation\fR
.RS 4
The name of an existing collation to copy\&. The new collation will have the same properties as the existing one, but it will be an independent object\&.
.RE
.SH "NOTES"
.PP
\fBCREATE COLLATION\fR
takes a
SHARE ROW EXCLUSIVE
lock, which is self\-conflicting, on the
pg_collation
system catalog, so only one
\fBCREATE COLLATION\fR
command can run at a time\&.
.PP
Use
\fBDROP COLLATION\fR
to remove user\-defined collations\&.
.PP
See
Section\ \&24.2.2.3
for more information on how to create collations\&.
.PP
When using the
libc
collation provider, the locale must be applicable to the current database encoding\&. See
CREATE DATABASE (\fBCREATE_DATABASE\fR(7))
for the precise rules\&.
.SH "EXAMPLES"
.PP
To create a collation from the operating system locale
fr_FR\&.utf8
(assuming the current database encoding is
UTF8):
.sp
.if n \{\
.RS 4
.\}
.nf
CREATE COLLATION french (locale = \*(Aqfr_FR\&.utf8\*(Aq);
.fi
.if n \{\
.RE
.\}
.PP
To create a collation using the ICU provider using German phone book sort order:
.sp
.if n \{\
.RS 4
.\}
.nf
CREATE COLLATION german_phonebook (provider = icu, locale = \*(Aqde\-u\-co\-phonebk\*(Aq);
.fi
.if n \{\
.RE
.\}
.PP
To create a collation from an existing collation:
.sp
.if n \{\
.RS 4
.\}
.nf
CREATE COLLATION german FROM "de_DE";
.fi
.if n \{\
.RE
.\}
.sp
This can be convenient to be able to use operating\-system\-independent collation names in applications\&.
.SH "COMPATIBILITY"
.PP
There is a
\fBCREATE COLLATION\fR
statement in the SQL standard, but it is limited to copying an existing collation\&. The syntax to create a new collation is a
PostgreSQL
extension\&.
.SH "SEE ALSO"
ALTER COLLATION (\fBALTER_COLLATION\fR(7)), DROP COLLATION (\fBDROP_COLLATION\fR(7))
|
