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13.06.2018 12:40, Maksim Milyutin wrote:
On 09.06.2018 22:49, Tom Lane wrote:
Maksim Milyutin <milyutinma@xxxxxxxxx> writes:
On hot standby I faced with the similar problem.
...
is planned 4.940 ms on master and *254.741* ms on standby.
(I wonder though why, if you executed the same query on the master,
its setting of the index-entry-is-dead bits didn't propagate to the
standby.)
I have verified the number dead item pointers (through pageinspect
extension) in the first leaf page of index participating in query
('main.message_instance_pkey') on master and slave nodes and have
noticed a big difference.
SELECT * FROM
monitoring.bt_page_stats('main.message_instance_pkey', 3705);
On master:
blkno | type | live_items | dead_items | avg_item_size |
page_size | free_size | btpo_prev | btpo_next | btpo |
btpo_flags
-------+------+------------+------------+---------------+-----------+-----------+-----------+-----------+------+------------
3705 | l | 1 | 58 | 24
| 8192 | 6496 | 0 | 3719 | 0 |
65
On standby:
blkno | type | live_items | dead_items | avg_item_size |
page_size | free_size | btpo_prev | btpo_next | btpo |
btpo_flags
-------+------+------------+------------+---------------+-----------+-----------+-----------+-----------+------+------------
3705 | l | 59 | 0 | 24
| 8192 | 6496 | 0 | 3719 | 0
| 1
In this point I want to highlight the issue that the changes in lp_flags
bits (namely, set items as dead) for index item pointers doesn't
propagate from master to replica in my case. As a consequence, on
standby I have live index items most of which on master are marked
as dead. And my queries on planning stage are forced to descent to
heap pages under get_actual_variable_range execution that
considerately slows down planning.
Is it bug or restriction of implementation or misconfiguration of
WAL/replication?
--
Regards,
Maksim Milyutin
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