From: https://www.postgresql.org/docs/9.4/static/sql-createtable.html
"The access method must support amgettuple (see Chapter 55); at present this means GIN cannot be used. Although it's allowed, there is little point in using B-tree or hash indexes with an exclusion constraint, because this does nothing that an ordinary unique constraint doesn't do better. So in practice the access method will always be GiST or SP-GiST." This is misleading. Hash indexes do not support unique constraints directly, but do support them via the EXCLUDE syntax using "WITH =". This is nice if you want a unique index on something that might occasionally exceed 1/3 of 8kB (titin, I'm looking at you) Trivial doc patch attached. Cheers, Jeff
diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml new file mode 100644 index bf2ad64..77d46de *** a/doc/src/sgml/ref/create_table.sgml --- b/doc/src/sgml/ref/create_table.sgml *************** CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY *** 574,583 **** The access method must support <literal>amgettuple</> (see <xref linkend="indexam">); at present this means <acronym>GIN</> cannot be used. Although it's allowed, there is little point in using ! B-tree or hash indexes with an exclusion constraint, because this does nothing that an ordinary unique constraint doesn't do better. ! So in practice the access method will always be <acronym>GiST</> or ! <acronym>SP-GiST</>. </para> <para> --- 574,583 ---- The access method must support <literal>amgettuple</> (see <xref linkend="indexam">); at present this means <acronym>GIN</> cannot be used. Although it's allowed, there is little point in using ! B-tree indexes with an exclusion constraint, because this does nothing that an ordinary unique constraint doesn't do better. ! So in practice the access method will always be <acronym>GiST</>, ! <acronym>SP-GiST</>, or hash. </para> <para>
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