Question on Trigram GIST indexes

[ERR ORR <rd0002@xxxxxxxxx>]

I was trying to make Postgresql use a trigram gist index on a varchar field, but to no avail.

Specifically, I was trying to replicate what is done in this blog post:

http://www.postgresonline.com/journal/archives/212-PostgreSQL-9.1-Trigrams-teaching-LIKE-and-ILIKE-new-tricks.html

I use Postgresql 9.1.7 on Linux FC17 64bit, my locale is UTF8.

My full table definition is

CREATE TABLE "TEST"

(

  "RECID" bigint NOT NULL DEFAULT next_id(),

  "TST_PAYLOAD" character varying(255),

  CONSTRAINT "PK_TEST" PRIMARY KEY ("RECID")

  USING INDEX TABLESPACE local

)

WITH (

  OIDS=FALSE

);

CREATE INDEX "TEST_PAYLOAD_PATTERN_1_IDX"

  ON "TEST"

  USING btree

  ("TST_PAYLOAD" COLLATE pg_catalog."default" varchar_pattern_ops)

TABLESPACE local;

CREATE INDEX "TEST_PAYLOAD_TRIGRAM_GIST_1_IDX"

  ON "TEST"

  USING gist

  ("TST_PAYLOAD" COLLATE pg_catalog."default" gist_trgm_ops)

TABLESPACE local;

CREATE INDEX "TEST_PAYLOAD_TRIGRAM_GIN_1_IDX"

  ON "TEST"

  USING gin

  ("TST_PAYLOAD" COLLATE pg_catalog."default" gin_trgm_ops)

TABLESPACE local;

The field "TST_PAYLOAD" contains 26389 names of cities, all in uppercase.

I have pg_tgrm installed - actually all extensions are present.

Queries which use "WHERE "TST_PAYLOAD" LIKE 'SEAT%'" go to the btree index as it should.

Queries which use "WHERE "TST_PAYLOAD" LIKE '%EAT%'" *should* use the GIST index but do a full table scan instead.

(I am looking for names like 'SEATTLE')

I also tried dropping the btree index but that has no influence on the behavior.

I'd be grateful if anybody could explain to me what I am doing wrong.

Thanks in advance.