[FLINK-10734] Temporal joins on heavily filtered tables might fail in planning

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 1.7.0
• Component/s: Table SQL / Planner
• Assignee: Unassigned
• Reporter: Piotr Nowojski
• Created: 31/Oct/18 11:41
• Updated: 06/Jul/21 07:46

Description

Following query:

    val sqlQuery =
      """
        |SELECT
        |  o.amount * r.rate AS amount
        |FROM
        |  Orders AS o,
        |  LATERAL TABLE (Rates(o.rowtime)) AS r
        |WHERE r.currency = o.currency
        |""".stripMargin

with Rates defined as follows:

    tEnv.registerTable("EuroRatesHistory", tEnv.scan("RatesHistory").filter('currency === "Euro"))
    tEnv.registerFunction(
      "Rates",
      tEnv.scan("EuroRatesHistory").createTemporalTableFunction('rowtime, 'currency))

Will fail with:

org.apache.flink.table.api.ValidationException: Only single column join key is supported. Found [] in [InnerJoin(where: (__TEMPORAL_JOIN_CONDITION(rowtime, rowtime0, currency)), join: (amount, rowtime, currency, rate, rowtime0))]

 at org.apache.flink.table.plan.nodes.datastream.DataStreamTemporalJoinToCoProcessTranslator$TemporalJoinConditionExtractor.validateRightPrimaryKey(DataStreamTemporalJoinToCoProcessTranslator.scala:215)
 at org.apache.flink.table.plan.nodes.datastream.DataStreamTemporalJoinToCoProcessTranslator$TemporalJoinConditionExtractor.visitCall(DataStreamTemporalJoinToCoProcessTranslator.scala:183)
 at org.apache.flink.table.plan.nodes.datastream.DataStreamTemporalJoinToCoProcessTranslator$TemporalJoinConditionExtractor.visitCall(DataStreamTemporalJoinToCoProcessTranslator.scala:152)

The problem is that filtering condition ('currency === "Euro") interferes with joining condition, simplifying it to nothing. Note how top LogicalFilter(condition=[=($3, $1)]) changes during optimising and finally disappears:

LogicalProject(amount=[*($0, $4)])
  LogicalFilter(condition=[=($3, $1)])
    LogicalTemporalTableJoin(condition=[__TEMPORAL_JOIN_CONDITION($2, $5, $3)], joinType=[inner])
      LogicalTableScan(table=[[_DataStreamTable_0]])
      LogicalFilter(condition=[=($0, _UTF-16LE'Euro')])
        LogicalTableScan(table=[[_DataStreamTable_1]])

LogicalProject(amount=[*($0, $4)])
  LogicalFilter(condition=[=(_UTF-16LE'Euro', $1)])
    LogicalProject(amount=[$0], currency=[$1], rowtime=[$2], currency0=[$3], rate=[$4], rowtime0=[CAST($5):TIMESTAMP(3) NOT NULL])
      LogicalTemporalTableJoin(condition=[__TEMPORAL_JOIN_CONDITION($2, $5, $3)], joinType=[inner])
        LogicalTableScan(table=[[_DataStreamTable_0]])
        LogicalFilter(condition=[=($0, _UTF-16LE'Euro')])
          LogicalTableScan(table=[[_DataStreamTable_1]])

FlinkLogicalCalc(expr#0..4=[{inputs}], expr#5=[*($t0, $t3)], amount=[$t5])
  FlinkLogicalTemporalTableJoin(condition=[__TEMPORAL_JOIN_CONDITION($1, $4, $2)], joinType=[inner])
    FlinkLogicalCalc(expr#0..2=[{inputs}], expr#3=[_UTF-16LE'Euro'], expr#4=[=($t3, $t1)], amount=[$t0], rowtime=[$t2], $condition=[$t4])
      FlinkLogicalNativeTableScan(table=[[_DataStreamTable_0]])
    FlinkLogicalCalc(expr#0..2=[{inputs}], expr#3=[_UTF-16LE'Euro'], expr#4=[=($t0, $t3)], proj#0..2=[{exprs}], $condition=[$t4])
      FlinkLogicalNativeTableScan(table=[[_DataStreamTable_1]])