Joining on a view containing a UNION ALL produces a suboptimal plan on 9.3.4 - Mailing list pgsql-general

Hi everyone -

I have a slow query issue in an app I'm working on. I'm unfortunately
not at liberty to share the query/schema details, but I've put
together a very similar reproduction of the issue:

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CREATE TABLE a (id integer primary key, col integer);
CREATE TABLE b (id integer primary key, col integer);
CREATE TABLE c (id integer primary key, col integer);
CREATE TABLE d (id integer primary key, col integer);
CREATE TABLE e (id integer primary key, col integer);

INSERT INTO a (id, col) SELECT i, floor(random() * 100000) FROM
generate_series(1, 100000, 2) i;
INSERT INTO b (id, col) SELECT i, floor(random() * 100000) FROM
generate_series(1, 100000, 2) i;
INSERT INTO c (id, col) SELECT i, floor(random() * 100000) FROM
generate_series(2, 100000, 2) i;
INSERT INTO d (id, col) SELECT i, floor(random() * 100000) FROM
generate_series(2, 100000, 2) i;
INSERT INTO e (id, col) SELECT i, floor(random() * 100000) FROM
generate_series(1, 100000, 1) i;

ANALYZE;

CREATE VIEW tables AS
  SELECT a.*, b.col AS other_col
  FROM a
  LEFT JOIN b ON a.id = b.id
  UNION ALL
  SELECT c.*, d.col AS other_col
  FROM c
  LEFT JOIN d ON c.id = d.id;

EXPLAIN ANALYZE
SELECT *
FROM tables
WHERE id = 89; -- Index scans, as expected.

EXPLAIN ANALYZE
SELECT *
FROM e
JOIN tables ON e.col = tables.id
WHERE e.id = 568; -- Big merge joins, when simple index scans should
be possible?

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Would this be considered a deficiency in the optimizer? Is there a simple fix?

Thanks!
Chris