Re: Xpath Index in PostgreSQL

Chris Roffler <croffler(at)earthlink(dot)net> writes:
> I am trying to setup an index on an xpath expression but the query never
> uses the index.
> Could someone enlighten me please ?

> Here is the setup :

> CREATE INDEX xml_index
> ON time_series
> USING btree
> ((xpath('/AttributeList/Attributes/Attribute/Name/text()'::text,
> external_attributes)::text[]));

> And here is the query :

> select id, name
> from
> time_series
> where
> (xpath('/AttributeList/Attributes/Attribute/Name/text()',
> external_attributes))[1]::text='Attribute100'

Doesn't work that way --- subscripting isn't an indexable operation.
To make that query fast with a standard index, you'd need the index to
be on
(xpath('/AttributeList/Attributes/Attribute/Name/text()',
external_attributes))[1]::text

regards, tom lane