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-.\" $Header: /cvsroot/pgsql/src/man/Attic/create_index.l,v 1.3 1996/12/11 00:27:14 momjian Exp $
+.\" $Header: /cvsroot/pgsql/src/man/Attic/create_index.l,v 1.4 1997/01/13 17:22:25 momjian Exp $
.TH "CREATE INDEX" SQL 11/05/95 PostgreSQL PostgreSQL
.SH NAME
create index \(em construct a secondary index
Obviously, the decision to build a functional index represents a
tradeoff between space (for the index) and execution time.
.PP
+The \fBunique\fR keyword causes the system to check for duplicate
+values when the index is created (if data already exist) and each
+time data is added.
+Attempts to insert or update non-duplicate data will generate an error.
+.PP
Postgres provides btree, rtree and hash access methods for
secondary indices. The btree access method is an implementation of
the Lehman-Yao high-concurrency btrees. The rtree access method