On 5/7/20 10:49 AM, Amarendra Konda wrote:
Hi David,
Thanks for the reply.This has optimized number of rows.
Yeah, but your execution time has increased an order of magnitude. Not
sure if that is what you want.
Can you please explain, why it is getting more columns in output, even
though we have asked for only one column ?
EXPLAIN (ANALYZE, COSTS, VERBOSE, BUFFERS) SELECT
pa.process_activity_id AS pa_process_activity_id FROM process_activity
pa WHERE pa.app_id = '126502930200650' AND pa.created > '1970-01-01
00:00:00' AND EXISTS ( SELECT 1 FROM process_instance pi where
pi.app_id = pa.app_id AND pi.user_id = '137074931866340') ORDER BY
pa.process_instance_id,m.created limit 50;
QUERY PLAN
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-----------------
Limit (cost=1.14..37.39 rows=50 width=24) (actual
time=821.283..891.629 rows=50 loops=1)
Output: pa.process_activity_id, pa.process_instance_id, pa.created
Buffers: shared hit=274950
-> Nested Loop Semi Join (cost=1.14..266660108.78 rows=367790473
width=24) (actual time=821.282..891.607 rows=50 loops=1)
Output: pa.process_activity_id, pa.process_instance_id, pa.created
Buffers: shared hit=274950
-> Index Scan using
process_activity_process_instance_id_app_id_created_idx on
public.process_activity pa (cost=0.70..262062725.21 rows=367790473
width=32) (actual time=821.253..891.517 rows=50 loops=1)
* Output: pa.process_activity_id, pa.process_activity_type,
pa.voice_url, pa.process_activity_user_id, pa.app_id,
pa.process_instance_id, pa.alias, pa.read_by_user, pa.source,
pa.label_category_id, pa.label_id, pa.csat_response_id,
m.process_activity_fragments, pa.created, pa.updated, pa.rule_id,
pa.marketing_reply_id, pa.delivered_at, pa.reply_fragments,
pa.status_fragment, pa.internal_meta, pa.interaction_id,
pa.do_not_translate, pa.should_translat
e, pa.in_reply_to*
Index Cond: ((m.app_id = '126502930200650'::bigint) AND
(m.created > '1970-01-01 00:00:00'::timestamp without time zone))
Buffers: shared hit=274946
-> Materialize (cost=0.43..2.66 rows=1 width=8) (actual
time=0.001..0.001 rows=1 loops=50)
Output: pi.app_id
Buffers: shared hit=4
-> Index Scan using fki_conv_konotor_user_user_id on
public.process_instance pi (cost=0.43..2.66 rows=1 width=8) (actual
time=0.020..0.020 rows=1 loops=1)
Output: pi.app_id
Index Cond: (pi.user_id = '137074931866340'::bigint)
Filter: (pi.app_id = '126502930200650'::bigint)
Buffers: shared hit=4
Planning time: 0.297 ms
Execution time: 891.686 ms
(20 rows)
On Thu, May 7, 2020 at 9:17 PM David G. Johnston
<david.g.johnston@xxxxxxxxx <mailto:david.g.johnston@xxxxxxxxx>> wrote:
On Thu, May 7, 2020 at 7:40 AM Adrian Klaver
<adrian.klaver@xxxxxxxxxxx <mailto:adrian.klaver@xxxxxxxxxxx>> wrote:
On 5/7/20 4:19 AM, Amarendra Konda wrote:
> Hi,
>
> PostgreSQL version : PostgreSQL 9.6.2 on x86_64-pc-linux-gnu,
compiled
> by gcc (GCC) 4.8.3 20140911 (Red Hat 4.8.3-9), 64-bit
>
> We have noticed huge difference interms of execution plan (
response
> time) , When we pass the direct values Vs inner query to IN
clause.
>
> High level details of the use case are as follows
>
> * As part of the SQL there are 2 tables named Process_instance
> (master) and Process_activity ( child)
> * Wanted to fetch TOP 50 rows from Process_activity table
for the
> given values of the Process_instance.
> * When we used Inner Join / Inner query ( query1) between
parent
> table and child table , LIMIT is not really taking in to
account.
> Instead it is fetching more rows and columns that
required, and
> finally limiting the result
It is doing what you told it to do which is SELECT all
process_instance_i's for user_id='317079413683604' and app_id =
'427380312000560' and then filtering further. I am going to
guess that
if you run the inner query alone you will find it returns ~23496
rows.
You might have better results if you an actual join between
process_activity and process_instance. Something like
below(obviously
not tested):
What the OP seems to want is a semi-join:
(not tested)
SELECT pa.process_activity_id
FROM process_activity pa WHERE pa.app_id = '427380312000560' AND
pa.created > '1970-01-01 00:00:00'
ANDEXISTS (
SELECT 1 FROM process_instance pi WHERE pi.app_id = pa.app_id AND
pi.user_id = '317079413683604'
)
ORDER BY
pa.process_instance_id,
pa.created limit 50;
I'm unsure exactly how this will impact the plan choice but it
should be an improvement, and in any case more correctly defines
what it is you are looking for.
David J.
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
