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

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Thank you, I reproduce the bug, will fix.

Sergey Konoplev wrote:
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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--
Teodor Sigaev                                   E-mail: teodor@xxxxxxxxx
                                                   WWW: http://www.sigaev.ru/

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