Filters in Subselect

[Johannes Schulte]

Hi,

I am trying to build something similar to drills way of querying directly
on multiple files, without the columnar layer. I am using the
ProjectableFilterableTable to filter out files not part of the query. No i
got some problems and I hope i can express what I want to say:


select max(path) from y
allows for only checking the path column since it is projected

[EnumerableAggregate(group=[{}], EXPR$0=[MAX($0)])
  EnumerableInterpreter
    BindableTableScan(table=[[ourSchema, ourTable]], projects=[[0]])
]

but when trying to query the maximum path and using it as an filter, the
projects are gone

select * from y where path = (select max(path) from y).

The explain plan then looks like this:

[EnumerableCalc(expr#0..2=[{inputs}], expr#3=[CAST($t0):VARCHAR(1)
CHARACTER SET "ISO-8859-1" COLLATE "ISO-8859-1$en_US$primary"],
expr#4=[CAST($t2):VARCHAR(1) CHARACTER SET "ISO-8859-1" COLLATE
"ISO-8859-1$en_US$primary"], expr#5=[=($t3, $t4)], proj#0..1=[{exprs}],
$condition=[$t5])
  EnumerableJoin(condition=[true], joinType=[left])
    EnumerableInterpreter
      BindableTableScan(table=[[ourSchema, ourTable]])
    EnumerableAggregate(group=[{}], EXPR$0=[MAX($0)])
      EnumerableInterpreter
        BindableTableScan(table=[[ourSchema, ourTable]])
]]

Is there a way to alter the query so ProjectableFilterableTable can still
be used? Or is the only way for getting this a translatable table?

Thanks so far,

Johannes