hstore equality-index performance question

Documentation at "F.13.3. Indexes" says that "hstore has index support
for @> and ? operators..."
=> Therefore no index does support equality-indexes?

If so, then I suppose that following (potentially slow) query
which contains an equality test for all keys 'a' and returns all values...

SELECT id, (kvp->'a') FROM mytable;

... can be accelerated nevertheless by adding following where clause:

SELECT id, (kvp->'a') FROM mytable WHERE kvp ? 'a';

=> Is this correct?

-S.

-- Little test database
CREATE TABLE mytable (
id serial PRIMARY KEY,
kvp HSTORE
);
CREATE INDEX mytable_kvp_idx ON mytable USING GIN(kvp);
INSERT INTO mytable (kvp) VALUES ('a=>x, b=>y');
INSERT INTO mytable (kvp) VALUES ('a=>y, c=>z, d=>a');