[GENERAL] Xpath Index in PostgreSQL

[Chris Roffler]

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 TABLE time_series
(
  id bigint NOT NULL,
  "name" character varying NOT NULL,
  "timestamp" timestamp with time zone NOT NULL,
  start_date timestamp with time zone,
  end_date timestamp with time zone,
.............
  external_attributes xml,
 ..............
)
WITH (
  OIDS=FALSE
);


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'