it seems a bug for querying on an external table because I found
ucloud_pay_tenanid ulist was a external table which using gpfdist.
CREATE EXTERNAL TABLE ucloud_pay_tenanid (
customercode character varying(255),
customername character varying(255),
prefixflag character varying(255),
customertype character varying(255),
comments character varying(255)
) LOCATION (
'gpfdist://hdptest02.hddomain.cn:8087/ucloud_pay_tenanid_*.csv'
) FORMAT 'text' (delimiter E';' null E'' escape E'OFF')
ENCODING 'UTF8';
then I create an internal table using:
create table ucloudtest as select * from ucloud_pay_tenanid;
run the explain,it lookks like the right query plan:
hdb=# explain select cp.tenantid,
hdb-# (select ulist.customertype from ucloudtest ulist where
ulist.customercode=cp.tenantid),cp.orderuuid from cptest cp;
QUERY PLAN
---------------------------------------------------------------------------------------------------------
Gather Motion 1:1 (slice2; segments: 1) (cost=0.00..219.50 rows=100
width=42)
-> Append-only Scan on cptest cp (cost=0.00..219.50 rows=100 width=42)
SubPlan 1
-> Result (cost=2.18..2.19 rows=1 width=7)
Filter: ulist.customercode::text = $0::text
-> Materialize (cost=2.18..2.19 rows=1 width=7)
-> Broadcast Motion 1:1 (slice1; segments: 1)
(cost=0.00..2.17 rows=1 width=7)
-> Append-only Scan on ucloudtest ulist
(cost=0.00..2.17 rows=1 width=7)
Settings: default_hash_table_bucket_number=18; optimizer=off
Optimizer status: legacy query optimizer
(10 rows)
run the query,get the correct result:
hdb=# select cp.tenantid,
(select ulist.customertype from ucloudtest ulist where
ulist.customercode=cp.tenantid),cp.orderuuid from cptest cp;
tenantid | ?column? | orderuuid
----------+----------+----------------------------------
sxve7r6c | 便利 | e6d9b57a0c55484392448ea908c1fe49
sxve7r6c | 便利 | 22a80697bfc74d63b7f28eee246c4368
3e7rph46 | 专卖 | 420ad3e45762459e91860b975e9f2751
3e7rph46 | 专卖 | 0634e7e3539a4116b9917a7493838f51
7jvfka5m | 专卖 | a7b96194fe9f48379e2711ac6000191b
6xydfh4y | 便利 | 7a55e97119784623a53f6e65ef9680c7
sxve7r6c | 便利 | 227f3d22aec14723bb51efc4e2a6f0b4
3e7rph46 | 专卖 | f3d02cc77a2348829be2f72ce24bf846
6xydfh4y | 便利 | bab722ac7d5748408d3ad2973d292ab5
On 05/18/2017 11:11 AM, tao tony wrote:
> hi guys,
>
> The different explains as below make me confused these days,could you
> please help me to explain why ulist.customertype is null.
>
> explain :
>
> hdb=# explain select cp.tenantid,
> (select ulist.customertype from ucloud_pay_tenanid ulist where
> ulist.customercode=cp.tenantid),cp.orderuuid from cptest cp;
> QUERY PLAN
> --------------------------------------------------------------------------------------------------
> Gather Motion 18:1 (slice1; segments: 18) (cost=0.00..1350002.00
> rows=100 width=42)
> -> Append-only Scan on cptest cp (cost=0.00..1350002.00 rows=6
> width=42)
> SubPlan 1
> -> External Scan on ucloud_pay_tenanid ulist
> (cost=0.00..13500.00 rows=56 width=516)
> Filter: customercode::text = $0::text
> Settings: default_hash_table_bucket_number=18; optimizer=off
> Optimizer status: legacy query optimizer
> (7 rows)
>
>
> hdb=# explain select a,(select d from test1 s where t.b=s.e) from test2 t;
> QUERY PLAN
> ---------------------------------------------------------------------------------------------------------
> Gather Motion 1:1 (slice2; segments: 1) (cost=0.00..10.20 rows=9
> width=6)
> -> Append-only Scan on test2 t (cost=0.00..10.20 rows=9 width=6)
> SubPlan 1
> -> Result (cost=1.01..1.02 rows=1 width=4)
> Filter: $0::text = s.e::text
> -> Materialize (cost=1.01..1.02 rows=1 width=4)
> -> Broadcast Motion 1:1 (slice1; segments: 1)
> (cost=0.00..1.01 rows=1 width=4)
> -> Append-only Scan on test1 s
> (cost=0.00..1.01 rows=1 width=4)
> Settings: default_hash_table_bucket_number=18; optimizer=off
> Optimizer status: legacy query optimizer
> (10 rows)
>
> test data:
>
> query1:
>
> hdb-# (select ulist.customertype from ucloud_pay_tenanid ulist where
> ulist.customercode=cp.tenantid),cp.orderuuid from cptest cp;
> tenantid | ?column? | orderuuid
> ----------+----------+----------------------------------
> sxve7r6c | | 901cf777a3144907899226de86ab8cfe
> k5r9qcfj | | 54c8cbdbe64f4dcca5cacb40b7ab52d6
> 3e7rph46 | | f5e777a5189e409da607182d059ec0d5
> 3e7rph46 | | 478d8a0921ab444ca80dc03ce97d3a94
> 3e7rph46 | | 25808c4a66e34ecaad02d2fc183920ca
> 3e7rph46 | | 0a62832067ea4db68641cce35385aae7
> 3e7rph46 | | 4c9e91233af947518c5c5767a2bd8b3c
> 6xydfh4y | | b2fa1af123384452b23bbc5e0794da56
> 6xydfh4y | | ade5731d97044a0eb9d74836ea7dbf48
> pejg93wh | | da2d037765bb4262a82764715cb4453d
> sxve7r6c | | b02df6c998ff4e448b575e3b1fae8e35
> 3e7rph46 | | 4c9e91233af947518c5c5767a2bd8b3c
>
> query 2:
>
> hdb=# select a,(select d from test1 s where t.b=s.e) from test2 t;
> a | ?column?
> ---+----------
> 1 | 1
> 2 | 2
> 3 | 3
> 4 | 4
> 5 | 5
> 6 | 7
> 7 | 8
> 8 | 9
> 9 | 10
> (9 rows)
>
> another query equal to query1,customertype is not null:
>
> hdb=# select tenantid,ulist.customertype,cp.orderuuid from cptest
> cp,ucloud_pay_tenanid ulist
> hdb-# where cp.tenantid = ulist.customercode;
> tenantid | customertype | orderuuid
> ----------+--------------+----------------------------------
> 7jvfka5m | 专卖 | f10771c9eb4e434dadcc82dc7cda0d4d
> 7jvfka5m | 专卖 | 246a13ed45174ee083fd9f743532ab4c
> 7jvfka5m | 专卖 | e2687954d3e94ab0bf1366369bdc9887
> 7jvfka5m | 专卖 | 018ef9e35db94901b4822509494bd6b5
> 7jvfka5m | 专卖 | 9054d2d5d7264a8aa4b41baddf1198e8
> 7jvfka5m | 专卖 | 9054d2d5d7264a8aa4b41baddf1198e8
> 7jvfka5m | 专卖 | a7b96194fe9f48379e2711ac6000191b
> u642nk35 | 便利 | df4ef8599c154c978d021b6765edb55b
> u642nk35 | 便利 | d60c5d3ac0f44ef1a278d50d84847c2f
> u642nk35 | 便利 | df6ca3d8fb444f8fba604db8611c6292
> u642nk35 | 便利 | df4ef8599c154c978d021b6765edb55b
>
