[jira] [Created] (CALCITE-4161) MergeJoin algorithm should not assume inputs sorted in ascending order

["Lai Zhou (Jira)" <ji...@apache.org>]

Lai Zhou created CALCITE-4161:
---------------------------------

             Summary: MergeJoin algorithm should not assume inputs sorted in ascending order
                 Key: CALCITE-4161
                 URL: https://issues.apache.org/jira/browse/CALCITE-4161
             Project: Calcite
          Issue Type: Bug
          Components: core, linq4j
    Affects Versions: 1.24.0
            Reporter: Lai Zhou


given a sql:
{code:java}
select id,first_name,vs.specialty_id from vets join vet_specialties vs on vets.id = vs.vet_id and vet_id>1 order by id desc limit 100
{code}
the final plan is:

 
{code:java}
EnumerableCalc(expr#0..3=[{inputs}], proj#0..1=[{exprs}], specialty_id=[$t3]) EnumerableLimit(fetch=[100]) EnumerableMergeJoin(condition=[=($0, $2)], joinType=[inner]) EnumerableSort(sort0=[$0], dir0=[DESC]) EnumerableCalc(expr#0..2=[{inputs}], proj#0..1=[{exprs}]) JdbcToEnumerableConverter JdbcFilter(condition=[>($0, 1)]) JdbcTableScan(table=[[default, vets]]) EnumerableSort(sort0=[$0], dir0=[DESC]) JdbcToEnumerableConverter JdbcFilter(condition=[>($0, 1)]) JdbcTableScan(table=[[default, vet_specialties]]) 
{code}
The inputs of EnumerableMergeJoin is sorted in descending order，

but the MergeJoinEnumerator just supports inputs sorted in ascending order,

the result is wrong.

 

I think the MergeJoin should not assume inputs sorted in ascending order,

it should know the inputs sorted order .

 

 



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