Oh Wow, i guess you are right.
I just ran example where local runs make use of parallel setup, but not FDW.
i have three servers
2 x pg10
1 x pg11
i run queries on coordinator node ( pg11 ) which makes calls to foreign
server to do a simple count.
the individual nodes run the query in parallel, the setup is repeatable.
but via FDW it runs a simple seq scan.
i guess this is for the same reason as you mentioned wrt declared cursors.
on pg11
create schema pg10;
create schema pg10_qa;
import foreign schema pg10 from server pg10 into pg10;
import foreign schema pg10_qa from server pg10_qa into pg10_qa;
explain (analyze,verbose) SELECT COUNT(1) FROM pg10.tbl_ItemTransactions;
----this query is via FDW
QUERY PLAN
----------------------------------------------------------------------------------------------------
Foreign Scan (cost=108.53..152.69 rows=1 width=8) (actual
time=6584.498..6584.500 rows=1 loops=1)
Output: (count(1))
Relations: Aggregate on (pg10.tbl_itemtransactions)
Remote SQL: SELECT count(1) FROM pg10.tbl_itemtransactions
Planning Time: 0.112 ms
Execution Time: 6585.435 ms
(6 rows)
2019-02-18 09:56:48 UTC LOG: duration: 6593.046 ms plan:
Query Text: DECLARE c1 CURSOR FOR
SELECT count(1) FROM pg10.tbl_itemtransactions
Aggregate (cost=768694.80..768694.81 rows=1 width=8) (actual
time=6593.039..6593.039 rows=1 loops=1)
Output: count(1)
Buffers: shared hit=259476
-> Seq Scan on pg10.tbl_itemtransactions (cost=0.00..666851.04
rows=40737504 width=0) (actual time=0.024..3389.245 rows=40737601 loops=1)
Output: tranid, transactiondate, transactionname
Buffers: shared hit=259476
--------
on pg10 (1) -- foreign server pg10
create schema pg10;
CREATE TABLE pg10.tbl_ItemTransactions
(
TranID SERIAL
,TransactionDate TIMESTAMPTZ
,TransactionName TEXT
);
INSERT INTO pg10.tbl_ItemTransactions
(TransactionDate, TransactionName)
SELECT x, 'dbrnd'
FROM generate_series('2014-01-01 00:00:00'::timestamptz, '2016-08-01
00:00:00'::timestamptz,'2 seconds'::interval) a(x);
explain analyze SELECT count(1) FROM pg10.tbl_itemtransactions; --this
query is local
QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------------
Finalize Aggregate (cost=472650.72..472650.73 rows=1 width=8) (actual
time=2576.053..2576.054 rows=1 loops=1)
-> Gather (cost=472650.50..472650.71 rows=2 width=8) (actual
time=2575.721..2626.980 rows=3 loops=1)
Workers Planned: 2
Workers Launched: 2
-> Partial Aggregate (cost=471650.50..471650.51 rows=1 width=8)
(actual time=2569.302..2569.302 rows=1 loops=3)
-> Parallel Seq Scan on tbl_itemtransactions
(cost=0.00..429215.60 rows=16973960 width=0) (actual time=0.048..1492.144
rows=13579200 loops=3)
Planning time: 0.405 ms
Execution time: 2627.455 ms
(8 rows)
--------
on pg10 (2) -- foreign server pg10_qa
create schema pg10_qa;
CREATE TABLE pg10_qa.tbl_ItemTransactions
(
TranID SERIAL
,TransactionDate TIMESTAMPTZ
,TransactionName TEXT
);
INSERT INTO pg10_qa.tbl_ItemTransactions
(TransactionDate, TransactionName)
SELECT x, 'dbrnd'
FROM generate_series('2014-01-01 00:00:00'::timestamptz, '2016-08-01
00:00:00'::timestamptz,'2 seconds'::interval) a(x);
explain analyze SELECT count(1) FROM pg10_qa.tbl_itemtransactions; -- this
query is local
QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------------
Finalize Aggregate (cost=472650.72..472650.73 rows=1 width=8) (actual
time=2568.469..2568.469 rows=1 loops=1)
-> Gather (cost=472650.50..472650.71 rows=2 width=8) (actual
time=2568.067..2613.006 rows=3 loops=1)
Workers Planned: 2
Workers Launched: 2
-> Partial Aggregate (cost=471650.50..471650.51 rows=1 width=8)
(actual time=2563.893..2563.893 rows=1 loops=3)
-> Parallel Seq Scan on tbl_itemtransactions
(cost=0.00..429215.60 rows=16973960 width=0) (actual time=0.017..1388.417
rows=13579200 loops=3)
Planning time: 0.048 ms
Execution time: 2613.246 ms
(8 rows)
but i guess partition elimination still works across the shards (see
attached). atleast, we'll benefit from here :) in pg11.
Regards,
Vijay
On Mon, Feb 18, 2019 at 3:07 AM Jeff Janes <[email protected]> wrote:
> On Sun, Feb 17, 2019 at 6:32 AM Vijaykumar Jain <[email protected]>
> wrote:
>
>> I am yet to figure out the reason, what we have done is implement fake
>> columns to represent samples and giving them random numbers and keeping
>> other bulls to fake limit.
>>
>> Most of the queries that were impacted were the ones that did not push
>> order by and limit to foreign servers.
>> I am also trying to upgrade pg11 to make use of parallelisation.
>>
>
> postgres_fdw operates through declared cursors, and declared cursors
> inhibit parallel query. This doesn't change in v11, see
> https://www.postgresql.org/docs/11/when-can-parallel-query-be-used.html
>
> I'm not aware of any other changes in v11 that are likely to help you out.
>
> Cheers,
>
> Jeff
>
>>
on mgmt
drop table if exists "flight_bookings";
drop table if exists "hotel_bookings";
drop table if exists "users";
drop table if exists "cities";
# partitions would be on shards
create table "hotel_bookings" (id serial, user_id int, booked_at timestamp,
city_name text, continent text, flight_id int) partition by list (continent);
create table "flight_bookings" (id serial, user_id int, booked_at timestamp,
from_city text, from_continent text, to_city text, to_continent text) partition
by list (to_continent);
# non partitioned table, but hotel_bookings and flight_bookings refer it
create table "users" (id serial, name text, age int);
# create foreign tables which are on shards
create foreign table if not exists "flight_bookings1" partition of
flight_bookings for values in ('Asia', 'Oceania', 'North America') server
gc_bi_shard_1_primary;
create foreign table if not exists "hotel_bookings1" partition of
hotel_bookings for values in ('Asia', 'Oceania', 'North America') server
gc_bi_shard_1_primary;
create foreign table if not exists "flight_bookings2" partition of
flight_bookings for values in ('Europe', 'Africa', 'South and Central America')
server gc_bi_shard_2_primary;
create foreign table if not exists "hotel_bookings2" partition of
hotel_bookings for values in ('Europe', 'Africa', 'South and Central America')
server gc_bi_shard_2_primary;
# for demo purpose, create an unpartitioned table
create table if not exists hotel_bookings_u (like hotel_bookings);
create table if not exists flight_bookings_u (like flight_bookings);
#load data in unpartitioned table first
copy flight_bookings_u from
'/var/tmp/pgconf-asia-demo/testdata/flight_bookings.csv' (format csv);
copy hotel_bookings_u from
'/var/tmp/pgconf-asia-demo/testdata/hotel_bookings.csv' (format csv);
copy users from '/var/tmp/pgconf-asia-demo/testdata/users.csv' (format csv);
#then load the foreign partitoned tables
insert into hotel_bookings select * from hotel_bookings_u;
insert into flight_bookings select * from flight_bookings_u;
# on shard1 create partitioned tables hotel_bookings1 and flight_bookings1 and
further subpartition by booked_at
create table "hotel_bookings1" (id int, user_id int, booked_at timestamp,
city_name text, continent text, flight_id int) partition by range (booked_at);
create table "flight_bookings1" (id int, user_id int, booked_at timestamp,
from_city text, from_continent text, to_city text, to_continent text) partition
by range (booked_at);
# subpartition hotel_bookings1 by booked_at
create table hotel_bookings1_q1 partition of hotel_bookings1 for values from
('2017-01-01') to ('2017-04-01');
create table hotel_bookings1_q2 partition of hotel_bookings1 for values from
('2017-04-01') to ('2017-07-01');
create table hotel_bookings1_q3 partition of hotel_bookings1 for values from
('2017-07-01') to ('2017-10-01');
create table hotel_bookings1_q4 partition of hotel_bookings1 for values from
('2017-10-01') to ('2018-01-01');
create table hotel_bookings1_default partition of hotel_bookings1 DEFAULT;
# subpartition flight_bookings1 by booked_at
create table flight_bookings1_q1 partition of flight_bookings1 for values from
('2017-01-01') to ('2017-04-01');
create table flight_bookings1_q2 partition of flight_bookings1 for values from
('2017-04-01') to ('2017-07-01');
create table flight_bookings1_q3 partition of flight_bookings1 for values from
('2017-07-01') to ('2017-10-01');
create table flight_bookings1_q4 partition of flight_bookings1 for values from
('2017-10-01') to ('2018-01-01');
create table flight_bookings1_default partition of flight_bookings1 DEFAULT;
# on shard2 create partitioned tables hotel_bookings2 and flight_bookings2 and
further subpartition by booked_at
drop table flight_bookings2;
drop table hotel_bookings2;
create table "hotel_bookings2" (id int, user_id int, booked_at timestamp,
city_name text, continent text, flight_id int) partition by range (booked_at);
create table "flight_bookings2" (id int, user_id int, booked_at timestamp,
from_city text, from_continent text, to_city text, to_continent text) partition
by range (booked_at);
# subpartition hotel_bookings2 by booked_at
create table hotel_bookings2_q1 partition of hotel_bookings2 for values from
('2017-01-01') to ('2017-04-01');
create table hotel_bookings2_q2 partition of hotel_bookings2 for values from
('2017-04-01') to ('2017-07-01');
create table hotel_bookings2_q3 partition of hotel_bookings2 for values from
('2017-07-01') to ('2017-10-01');
create table hotel_bookings2_q4 partition of hotel_bookings2 for values from
('2017-10-01') to ('2018-01-01');
create table hotel_bookings2_default partition of hotel_bookings2 DEFAULT;
# subpartition flight_bookings2 by booked_at
create table flight_bookings2_q1 partition of flight_bookings2 for values from
('2017-01-01') to ('2017-04-01');
create table flight_bookings2_q2 partition of flight_bookings2 for values from
('2017-04-01') to ('2017-07-01');
create table flight_bookings2_q3 partition of flight_bookings2 for values from
('2017-07-01') to ('2017-10-01');
create table flight_bookings2_q4 partition of flight_bookings2 for values from
('2017-10-01') to ('2018-01-01');
create table flight_bookings2_default partition of flight_bookings2 DEFAULT;
# no filter conditions, scans all foreign tables
explain select * from flight_bookings join hotel_bookings on flight_bookings.id
= hotel_bookings.flight_id join users on flight_bookings.user_id = users.id;
QUERY PLAN
-----------------------------------------------------------------------------------------------------------
Merge Join (cost=6029.95..17762.67 rows=761410 width=269)
Merge Cond: (hotel_bookings2.flight_id = flight_bookings2.id)
-> Merge Append (cost=830.18..1071.98 rows=7440 width=47)
Sort Key: hotel_bookings2.flight_id
-> Foreign Scan on hotel_bookings2 (cost=339.72..404.81 rows=2893
width=49)
-> Foreign Scan on hotel_bookings1 (cost=490.45..592.76 rows=4547
width=46)
-> Materialize (cost=5199.77..5302.11 rows=20468 width=185)
-> Sort (cost=5199.77..5250.94 rows=20468 width=185)
Sort Key: flight_bookings2.id
-> Hash Join (cost=419.00..1844.16 rows=20468 width=185)
Hash Cond: (flight_bookings2.user_id = users.id)
-> Append (cost=100.00..1243.72 rows=20468 width=54)
-> Foreign Scan on flight_bookings2
(cost=100.00..453.89 rows=7654 width=56)
-> Foreign Scan on flight_bookings1
(cost=100.00..687.49 rows=12814 width=53)
-> Hash (cost=194.00..194.00 rows=10000 width=41)
-> Seq Scan on users (cost=0.00..194.00 rows=10000
width=41)
(16 rows)
# continent filter restricts the scan to shard1 (eliminated shard2) and then
filter on booked_at further restricts scan to q1 partition on tables on shard1
explain select * from flight_bookings join hotel_bookings on flight_bookings.id
= hotel_bookings.flight_id join users on flight_bookings.user_id = users.id
where flight_bookings.to_continent = 'Asia' and hotel_bookings.continent =
'Asia'
and hotel_bookings.booked_at <= '2017-01-02'::timestamp and
flight_bookings.booked_at <= '2017-01-02'::timestamp;
QUERY PLAN
--------------------------------------------------------------------------------------------------
Nested Loop (cost=299.43..575.88 rows=4 width=269)
Join Filter: (flight_bookings1.id = hotel_bookings1.flight_id)
-> Hash Join (cost=199.43..431.08 rows=15 width=185)
Hash Cond: (users.id = flight_bookings1.user_id)
-> Seq Scan on users (cost=0.00..194.00 rows=10000 width=41)
-> Hash (cost=199.25..199.25 rows=15 width=59)
-> Append (cost=100.00..199.25 rows=15 width=59)
-> Foreign Scan on flight_bookings1 (cost=100.00..199.17
rows=15 width=59)
-> Materialize (cost=100.00..143.91 rows=4 width=50)
-> Append (cost=100.00..143.89 rows=4 width=50)
-> Foreign Scan on hotel_bookings1 (cost=100.00..143.87 rows=4
width=50)
(11 rows)
# continent filter restricts the scan to shard1 (eliminated shard2)
explain select * from flight_bookings join hotel_bookings on flight_bookings.id
= hotel_bookings.flight_id join users on flight_bookings.user_id = users.id
where flight_bookings.to_continent = 'Asia' and hotel_bookings.continent =
'Asia';
QUERY PLAN
----------------------------------------------------------------------------------------------------
Merge Join (cost=1582.79..2244.21 rows=40517 width=269)
Merge Cond: (hotel_bookings1.flight_id = flight_bookings1.id)
-> Merge Append (cost=291.62..341.45 rows=1533 width=39)
Sort Key: hotel_bookings1.flight_id
-> Foreign Scan on hotel_bookings1 (cost=291.61..326.11 rows=1533
width=39)
-> Sort (cost=1291.17..1304.38 rows=5286 width=185)
Sort Key: flight_bookings1.id
-> Hash Join (cost=419.00..964.28 rows=5286 width=185)
Hash Cond: (flight_bookings1.user_id = users.id)
-> Append (cost=100.00..572.60 rows=5286 width=53)
-> Foreign Scan on flight_bookings1 (cost=100.00..546.17
rows=5286 width=53)
-> Hash (cost=194.00..194.00 rows=10000 width=41)
-> Seq Scan on users (cost=0.00..194.00 rows=10000
width=41)
(13 rows)
# on shard1, no predicates but on join results in all partition scans
explain select * from flight_bookings1 join hotel_bookings1 on
flight_bookings1.id = hotel_bookings1.flight_id;
QUERY PLAN
---------------------------------------------------------------------------------------------
Hash Join (cost=171.04..659.85 rows=4547 width=99)
Hash Cond: (flight_bookings1_q1.id = hotel_bookings1_q1.flight_id)
-> Append (cost=0.00..331.21 rows=12814 width=53)
-> Seq Scan on flight_bookings1_q1 (cost=0.00..65.83 rows=3183
width=53)
-> Seq Scan on flight_bookings1_q2 (cost=0.00..65.73 rows=3173
width=53)
-> Seq Scan on flight_bookings1_q3 (cost=0.00..67.21 rows=3221
width=53)
-> Seq Scan on flight_bookings1_q4 (cost=0.00..67.35 rows=3235
width=53)
-> Seq Scan on flight_bookings1_default (cost=0.00..1.02 rows=2
width=66)
-> Hash (cost=114.20..114.20 rows=4547 width=46)
-> Append (cost=0.00..114.20 rows=4547 width=46)
-> Seq Scan on hotel_bookings1_q1 (cost=0.00..18.31 rows=931
width=39)
-> Seq Scan on hotel_bookings1_q2 (cost=0.00..18.54 rows=954
width=39)
-> Seq Scan on hotel_bookings1_q3 (cost=0.00..19.12 rows=1012
width=39)
-> Seq Scan on hotel_bookings1_q4 (cost=0.00..18.30 rows=930
width=39)
-> Seq Scan on hotel_bookings1_default (cost=0.00..17.20
rows=720 width=84)
(15 rows)
# on shard1, with predicates using booked_at on table flight_bookings1, scan
restricted to sub partition (q1 and default) but all partitions for
hotel_bookings1
gc_bi_shard_1=> explain select * from flight_bookings1 join hotel_bookings1 on
flight_bookings1.id = hotel_bookings1.flight_id and flight_bookings1.booked_at
<= '2017-01-02'::timestamp;
QUERY PLAN
-----------------------------------------------------------------------------------------------
Hash Join (cost=75.42..207.09 rows=41 width=99)
Hash Cond: (hotel_bookings1_q1.flight_id = flight_bookings1_q1.id)
-> Append (cost=0.00..114.20 rows=4547 width=46)
-> Seq Scan on hotel_bookings1_q1 (cost=0.00..18.31 rows=931
width=39)
-> Seq Scan on hotel_bookings1_q2 (cost=0.00..18.54 rows=954
width=39)
-> Seq Scan on hotel_bookings1_q3 (cost=0.00..19.12 rows=1012
width=39)
-> Seq Scan on hotel_bookings1_q4 (cost=0.00..18.30 rows=930
width=39)
-> Seq Scan on hotel_bookings1_default (cost=0.00..17.20 rows=720
width=84)
-> Hash (cost=74.99..74.99 rows=35 width=53)
-> Append (cost=0.00..74.99 rows=35 width=53)
-> Seq Scan on flight_bookings1_q1 (cost=0.00..73.79 rows=34
width=53)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp
without time zone)
-> Seq Scan on flight_bookings1_default (cost=0.00..1.02
rows=1 width=66)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp
without time zone)
# on shard1, with predicates using booked_at, scan restricted to sub partition
(q1 and default) of both tables
gc_bi_shard_1=> explain select * from flight_bookings1 join hotel_bookings1 on
flight_bookings1.id = hotel_bookings1.flight_id and flight_bookings1.booked_at
<= '2017-01-02'::timestamp and hotel_bookings1.booked_at <= '2017-01-02'::times
tamp;
QUERY PLAN
-----------------------------------------------------------------------------------------------
Hash Join (cost=75.42..117.63 rows=41 width=135)
Hash Cond: (hotel_bookings1_q1.flight_id = flight_bookings1_q1.id)
-> Append (cost=0.00..40.87 rows=247 width=83)
-> Seq Scan on hotel_bookings1_q1 (cost=0.00..20.64 rows=7 width=39)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp without
time zone)
-> Seq Scan on hotel_bookings1_default (cost=0.00..19.00 rows=240
width=84)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp without
time zone)
-> Hash (cost=74.99..74.99 rows=35 width=53)
-> Append (cost=0.00..74.99 rows=35 width=53)
-> Seq Scan on flight_bookings1_q1 (cost=0.00..73.79 rows=34
width=53)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp
without time zone)
-> Seq Scan on flight_bookings1_default (cost=0.00..1.02
rows=1 width=66)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp
without time zone)
(13 rows)
# on shard1 when using predicates using the shard key, both default partition
and matching partition scanned
explain select * from hotel_bookings1 where booked_at <=
'2017-01-02'::timestamp;
QUERY PLAN
-----------------------------------------------------------------------------------
Append (cost=0.00..40.87 rows=247 width=83)
-> Append (cost=0.00..331.21 rows=12814 width=53)
-> Seq Scan on flight_bookings1_q1 (cost=0.00..65.83 rows=3183
width=53)
-> Seq Scan on flight_bookings1_q2 (cost=0.00..65.73 rows=3173
width=53)
-> Seq Scan on flight_bookings1_q3 (cost=0.00..67.21 rows=3221
width=53)
-> Seq Scan on flight_bookings1_q4 (cost=0.00..67.35 rows=3235
width=53)
-> Seq Scan on flight_bookings1_default (cost=0.00..1.02 rows=2
width=66)
-> Hash (cost=114.20..114.20 rows=4547 width=46)
-> Append (cost=0.00..114.20 rows=4547 width=46)
-> Seq Scan on hotel_bookings1_q1 (cost=0.00..18.31 rows=931
width=39)
-> Seq Scan on hotel_bookings1_q2 (cost=0.00..18.54 rows=954
width=39)
-> Seq Scan on hotel_bookings1_q3 (cost=0.00..19.12 rows=1012
width=39)
-> Seq Scan on hotel_bookings1_q4 (cost=0.00..18.30 rows=930
width=39)
-> Seq Scan on hotel_bookings1_default (cost=0.00..17.20
rows=720 width=84)
(15 rows)
# on shard1, with predicates using booked_at on table flight_bookings1, scan
restricted to sub partition (q1 and default) but all partitions for
hotel_bookings1
gc_bi_shard_1=> explain select * from flight_bookings1 join hotel_bookings1 on
flight_bookings1.id = hotel_bookings1.flight_id and flight_bookings1.booked_at
<= '2017-01-02'::timestamp;
QUERY PLAN
-----------------------------------------------------------------------------------------------
Hash Join (cost=75.42..207.09 rows=41 width=99)
Hash Cond: (hotel_bookings1_q1.flight_id = flight_bookings1_q1.id)
-> Append (cost=0.00..114.20 rows=4547 width=46)
-> Seq Scan on hotel_bookings1_q1 (cost=0.00..18.31 rows=931
width=39)
-> Seq Scan on hotel_bookings1_q2 (cost=0.00..18.54 rows=954
width=39)
-> Seq Scan on hotel_bookings1_q3 (cost=0.00..19.12 rows=1012
width=39)
-> Seq Scan on hotel_bookings1_q4 (cost=0.00..18.30 rows=930
width=39)
-> Seq Scan on hotel_bookings1_default (cost=0.00..17.20 rows=720
width=84)
-> Hash (cost=74.99..74.99 rows=35 width=53)
-> Append (cost=0.00..74.99 rows=35 width=53)
-> Seq Scan on flight_bookings1_q1 (cost=0.00..73.79 rows=34
width=53)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp
without time zone)
-> Seq Scan on flight_bookings1_default (cost=0.00..1.02
rows=1 width=66)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp
without time zone)
# on shard1, with predicates using booked_at, scan restricted to sub partition
(q1 and default) of both tables
gc_bi_shard_1=> explain select * from flight_bookings1 join hotel_bookings1 on
flight_bookings1.id = hotel_bookings1.flight_id and flight_bookings1.booked_at
<= '2017-01-02'::timestamp and hotel_bookings1.booked_at <= '2017-01-02'::times
tamp;
QUERY PLAN
-----------------------------------------------------------------------------------------------
Hash Join (cost=75.42..117.63 rows=41 width=135)
Hash Cond: (hotel_bookings1_q1.flight_id = flight_bookings1_q1.id)
-> Append (cost=0.00..40.87 rows=247 width=83)
-> Seq Scan on hotel_bookings1_q1 (cost=0.00..20.64 rows=7 width=39)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp without
time zone)
-> Seq Scan on hotel_bookings1_default (cost=0.00..19.00 rows=240
width=84)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp without
time zone)
-> Hash (cost=74.99..74.99 rows=35 width=53)
-> Append (cost=0.00..74.99 rows=35 width=53)
-> Seq Scan on flight_bookings1_q1 (cost=0.00..73.79 rows=34
width=53)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp
without time zone)
-> Seq Scan on flight_bookings1_default (cost=0.00..1.02
rows=1 width=66)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp
without time zone)
(13 rows)
# on shard1 when using predicates using the shard key, both default partition
and matching partition scanned
explain select * from hotel_bookings1 where booked_at <=
'2017-01-02'::timestamp;
QUERY PLAN
-----------------------------------------------------------------------------------
Append (cost=0.00..40.87 rows=247 width=83)
-> Seq Scan on hotel_bookings1_q1 (cost=0.00..20.64 rows=7 width=39)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp without time
zone)
-> Seq Scan on hotel_bookings1_default (cost=0.00..19.00 rows=240 width=84)
Filter: (booked_at <= '2017-01-02 00:00:00'::timestamp without time
zone)
(5 rows)
