[KYLIN-3281] OLAPProjectRule can't normal working with projectRel[input=sortRel]

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: v2.3.0
• Fix Version/s: v2.4.0
• Component/s: Query Engine
• Assignee: yiming.xu
• Reporter: yiming.xu
• Created: 09/Mar/18 05:01
• Updated: 23/Jun/18 14:56
• Resolved: 18/Mar/18 18:28

Description

for queries like:
select sum("count") from (SELECT LSTG_FORMAT_NAME , COUNT AS "count" FROM TEST_KYLIN_FACT GROUP BY "LSTG_FORMAT_NAME" ORDER BY "count" DESC) as a
the expected logical plan after volcano is:

OLAPToEnumerableConverter
  OLAPLimitRel(ctx=[], fetch=[50000])
    OLAPAggregateRel(group=[{}], EXPR$0=[SUM($0)], ctx=[])
      OLAPProjectRel(count=[$1], ctx=[])
        OLAPSortRel(sort0=[$1], dir0=[DESC], ctx=[])
          OLAPAggregateRel(group=[{0}], count=[COUNT()], ctx=[])
            OLAPProjectRel(LSTG_FORMAT_NAME=[$3], ctx=[])
              OLAPTableScan(table=[[DEFAULT, TEST_KYLIN_FACT]], ctx=[], fields=[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26]])

however the actual is:

EnumerableLimit(fetch=[50000])
  EnumerableAggregate(group=[{}], EXPR$0=[SUM($0)])
    EnumerableCalc(expr#0..1=[{inputs}], count=[$t1])
      EnumerableSort(sort0=[$1], dir0=[DESC])
        EnumerableAggregate(group=[{0}], count=[COUNT()])
          OLAPToEnumerableConverter
            OLAPProjectRel(LSTG_FORMAT_NAME=[$3], ctx=[])
              OLAPTableScan(table=[[DEFAULT, TEST_KYLIN_FACT]], ctx=[], fields=[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26]])

VolcanoPlanner apply OLAPProjectRule to logicalProject,convert child node should use child traitset not current proejct traitset.
If we use current project trait set, the child node trait set is [olap][0 DESC], it will create a new subset but the subset doesn't have any rel. the cost is inf,
so volcanoPlanner choose a the EnumerableAggregate.