That did the trick... thanks!
yes perhaps a minor planner difference just tipped us over the edge previously
=> alter table stock_trans alter column product_id set STATISTICS 1000;
QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------------------------
Limit (cost=3461.10..3461.10 rows=1 width=4) (actual time=0.014..0.014 rows=0 loops=1)
Buffers: shared hit=3
-> Sort (cost=3461.10..3461.75 rows=260 width=4) (actual time=0.013..0.013 rows=0 loops=1)
Sort Key: a.trans_date DESC
Sort Method: quicksort Memory: 25kB
Buffers: shared hit=3
-> Nested Loop (cost=0.87..3459.80 rows=260 width=4) (actual time=0.008..0.008 rows=0 loops=1)
Buffers: shared hit=3
-> Index Scan using stock_trans_product_idx on stock_trans s (cost=0.43..1263.55 rows=260 width=4) (actual time=0.007..0.007 rows=0 loops=1)
Index Cond: (product_id = 2466420)
Filter: (credit_stock_account_id = 3)
Buffers: shared hit=3
-> Index Scan using account_trans_pkey on account_trans a (cost=0.43..8.44 rows=1 width=8) (never executed)
Index Cond: (account_trans_id = s.account_trans_id)
Planning time: 0.255 ms
Execution time: 0.039 ms
(16 rows)
On 19 March 2018 at 16:22, Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
David Osborne <david@xxxxxxxxxxx> writes:
> Hi, yes I've run "analyse" against the newly restored database. Should that
> be enough?
My apologies, you did say that further down in the original message.
It looks like the core of the problem is the poor rowcount estimation
here:
-> Bitmap Index Scan on stock_trans_product_idx (cost=0.00..31.42 rows=1465 width=0) (actual time=0.009..0.009 rows=0 loops=1)
Index Cond: (product_id = 2466420)
Buffers: shared hit=3
You might be able to improve that by raising the statistics target
for stock_trans.product_id. I'm not sure why you weren't getting
bitten by the same issue in 9.1; but the cost estimates aren't
that far apart for the two plans, so maybe you were just lucky ...
regards, tom lane
David Osborne
Qcode Software Limited
T: +44 (0)1463 896484
