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Diffstat (limited to 'doc/src/sgml/citext.sgml')
| -rw-r--r-- | doc/src/sgml/citext.sgml | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/doc/src/sgml/citext.sgml b/doc/src/sgml/citext.sgml index b1fe7101b20..85aa339d8ba 100644 --- a/doc/src/sgml/citext.sgml +++ b/doc/src/sgml/citext.sgml @@ -14,6 +14,16 @@ exactly like <type>text</type>. </para> + <tip> + <para> + Consider using <firstterm>nondeterministic collations</firstterm> (see + <xref linkend="collation-nondeterministic"/>) instead of this module. They + can be used for case-insensitive comparisons, accent-insensitive + comparisons, and other combinations, and they handle more Unicode special + cases correctly. + </para> + </tip> + <sect2> <title>Rationale</title> @@ -246,6 +256,17 @@ SELECT * FROM users WHERE nick = 'Larry'; will be invoked instead. </para> </listitem> + + <listitem> + <para> + The approach of lower-casing strings for comparison does not handle some + Unicode special cases correctly, for example when one upper-case letter + has two lower-case letter equivalents. Unicode distinguishes between + <firstterm>case mapping</firstterm> and <firstterm>case + folding</firstterm> for this reason. Use nondeterministic collations + instead of <type>citext</type> to handle that correctly. + </para> + </listitem> </itemizedlist> </sect2> |