EmmyMiao87 commented on issue #1650: Where clause can't push down into the
right table of JOIN clasure
URL:
https://github.com/apache/incubator-doris/issues/1650#issuecomment-521538908
The where predicate could not be pushed down when the predicate is on the
outer join table.
For example: `select * from a left join b on a.id=b.id where b.id=1;`
In some cases, the predicate could be pushed down.
In impala, for example:
Query: explain select * from customer_address a left join customer_address b
on a.ca_address_sk=b.ca_address_sk where b.ca_address_sk=1
++
| Explain String
|
++
| Estimated Per-Host Requirements: Memory=0B VCores=2
|
| WARNING: The following tables are missing relevant table and/or column
statistics. |
| tpcds_hive.customer_address
|
|
|
| PLAN-ROOT SINK
|
| |
|
| 04:EXCHANGE [UNPARTITIONED]
|
| |
|
| 02:HASH JOIN [LEFT OUTER JOIN, BROADCAST]
|
| | hash predicates: a.ca_address_sk = b.ca_address_sk
|
| | other predicates: b.ca_address_sk = 1
|
| |
|
| |--03:EXCHANGE [BROADCAST]
|
| | |
|
| | 01:SCAN HDFS [tpcds_hive.customer_address b]
|
| | partitions=1/1 files=0 size=0B
|
| | predicates: b.ca_address_sk = 1
|
| |
|
| 00:SCAN HDFS [tpcds_hive.customer_address a]
|
|partitions=1/1 files=0 size=0B
|
++
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