Testschema:
ROLLBACK;
BEGIN;
CREATE TABLE a (
a_id serial PRIMARY KEY NOT NULL,
b_id integer
);
CREATE INDEX a__b_id ON a USING btree (b_id);
CREATE TABLE b (
b_id serial NOT NULL,
c_id integer
);
CREATE INDEX b__c_id ON b USING btree (c_id);
CREATE TABLE c (
c_id serial PRIMARY KEY NOT NULL,
value integer UNIQUE
);
INSERT INTO b (b_id, c_id)
SELECT g.i, g.i FROM generate_series(1, 50000) g(i);
INSERT INTO a(b_id)
SELECT g.i FROM generate_series(1, 50000) g(i);
COMMIT;
ANALYZE;