query slowness caused by table alias

I don't know if this's really a bug in 7.0, but I
don't see this
problem/feature in 6.5.3.

The system: Linux RedHat 6.0, running postgresql
7.0RC4

The bug: The mixed uses of table names and table alias
in a query results in an extra sequential scan in
query execution

Test cases:

EXPLAIN
SELECT *
FROM part p -- let p alias to part
WHERE part.part_id = 42; -- but don't use p

Nested Loop (cost=0.00..2429.30 rows=50735 width=219)
-> Index Scan using part_pkey on part
(cost=0.00..3.60 rows=1 width=4)
-> Seq Scan on part p (cost=0.00..1918.35
rows=50735 width=215)

# note: a seq scan appears

EXPLAIN
SELECT *
FROM part -- take out the alias
WHERE part.part_id = 42;

Index Scan using part_pkey on part (cost=0.00..3.60
rows=1 width=215)

# note: now the seq scan is gone

EXPLAIN
SELECT *
FROM part p
WHERE p.part_id = 42; -- use alias only

Index Scan using part_pkey on part p (cost=0.00..3.60
rows=1 width=215)

# note: it's also ok

Thanks,

Chi-Fung

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