This page in other versions: 9.1 / 9.2 / 9.3  |  Development versions: devel / 9.4

11.10. Indexes and Collations

An index can support only one collation per index column. If multiple collations are of interest, multiple indexes may be needed.

Consider these statements:

CREATE TABLE test1c (
    id integer,
    content varchar COLLATE "x"
);

CREATE INDEX test1c_content_index ON test1c (content);

The index automatically uses the collation of the underlying column. So a query of the form

SELECT * FROM test1c WHERE content > constant;

could use the index, because the comparison will by default use the collation of the column. However, this index cannot accelerate queries that involve some other collation. So if queries of the form, say,

SELECT * FROM test1c WHERE content > constant COLLATE "y";

are also of interest, an additional index could be created that supports the "y" collation, like this:

CREATE INDEX test1c_content_y_index ON test1c (content COLLATE "y");

Add Comment

Please use this form to add your own comments regarding your experience with particular features of PostgreSQL, clarifications of the documentation, or hints for other users. Please note, this is not a support forum, and your IP address will be logged. If you have a question or need help, please see the faq, try a mailing list, or join us on IRC. Note that submissions containing URLs or other keywords commonly found in 'spam' comments may be silently discarded. Please contact the webmaster if you think this is happening to you in error.

Proceed to the comment form.

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group