Re: index scan leads to result that is different from sec scan after upgrading to 8.3.4

Ok, I've done the test case (see attachment).

8.3.3 has passed it.
8.3.4 hasn't passed in ~99% times I run it.

Steps to reproduce:
1. install pg 8.3.4, do initdb, start pg
2. correct PSQL parameter in pg-8.3.4_index_update_test.sh
3. run pg-8.3.4_index_update_test.sh few times

And you will see something like this:

...

------------------------------------------
2nd time obtaining "seq-scan" count and plan...
------------------------------------------
SELECT table1_flag, count(*) FROM table1
GROUP BY table1_flag;
 table1_flag | count
-------------+-------
           1 |   100
(1 row)

EXPLAIN ANALYZE SELECT table1_flag, count(*) FROM table1
GROUP BY table1_flag;
                                                QUERY PLAN
-----------------------------------------------------------------------------------------------------------
 HashAggregate  (cost=15.00..15.01 rows=1 width=2) (actual
time=0.140..0.140 rows=1 loops=1)
   ->  Seq Scan on table1  (cost=0.00..12.00 rows=600 width=2) (actual
time=0.004..0.059 rows=100 loops=1)
 Total runtime: 0.172 ms
(3 rows)

------------------------------------------
2nd time obtaining "index-scan" count and plan...
------------------------------------------
SELECT count(*) FROM table1
WHERE table1_flag = 1;
 count
-------
    98
(1 row)

EXPLAIN ANALYZE SELECT count(*) FROM table1
WHERE table1_flag = 1;
                                                              QUERY
PLAN

--------------------------------------------------------------------------------------------------------------------------------------
 Aggregate  (cost=8.27..8.28 rows=1 width=0) (actual time=0.451..0.451
rows=1 loops=1)
   ->  Index Scan using i_table1__table1_point on table1
(cost=0.00..8.27 rows=1 width=0) (actual time=0.011..0.408 rows=98
loops=1)
 Total runtime: 0.477 ms
(3 rows)

--
Regards,
Sergey Konoplev
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