Paul Rogers created IMPALA-7953:
-----------------------------------
Summary: EXPLAIN does not reliably show table aliases
Key: IMPALA-7953
URL: https://issues.apache.org/jira/browse/IMPALA-7953
Project: IMPALA
Issue Type: Bug
Components: Frontend
Affects Versions: Impala 3.1.0
Reporter: Paul Rogers
Consider one of the queries in {{PlannerTest.testJoins()}}:
{noformat}
# test that on-clause predicates referring to multiple tuple ids
# get registered as eq join conjuncts
select t1.*
from (select * from functional.alltypestiny) t1
join (select * from functional.alltypestiny) t2 on (t1.id = t2.id)
join functional.alltypestiny t3 on (coalesce(t1.id, t2.id) = t3.id)
---- PLAN
PLAN-ROOT SINK
|
04:HASH JOIN [INNER JOIN]
| hash predicates: coalesce(functional.alltypestiny.id,
functional.alltypestiny.id) = t3.id
| runtime filters: RF000 <- t3.id
|
|--02:SCAN HDFS [functional.alltypestiny t3]
| partitions=4/4 files=4 size=460B
|
03:HASH JOIN [INNER JOIN]
| hash predicates: functional.alltypestiny.id = functional.alltypestiny.id
| runtime filters: RF002 <- functional.alltypestiny.id
|
|--01:SCAN HDFS [functional.alltypestiny]
| partitions=4/4 files=4 size=460B
| runtime filters: RF000 -> coalesce(functional.alltypestiny.id,
functional.alltypestiny.id)
|
00:SCAN HDFS [functional.alltypestiny]
partitions=4/4 files=4 size=460B
runtime filters: RF000 -> coalesce(functional.alltypestiny.id,
functional.alltypestiny.id), RF002 -> functional.alltypestiny.id
{noformat}
This query uses self-joins so the table name is not sufficient to explain the
join decisions. Note that the 02 Scan shows the table alias, {{`t3`}}, for that
table. But, the 00 and 01 scans do not. As a result, we can't readily tell
which alias was placed where.
Expected that all scan nodes would show the table alias, if the user provided
one in the SQL.
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