Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4625#discussion_r140262200
  
    --- Diff: 
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/join/TimeBoundedStreamInnerJoin.scala
 ---
    @@ -131,340 +116,308 @@ class TimeBoundedStreamInnerJoin(
         // Initialize the data caches.
         val leftListTypeInfo: TypeInformation[JList[Row]] = new 
ListTypeInfo[Row](leftType)
         val leftStateDescriptor: MapStateDescriptor[Long, JList[Row]] =
    -      new MapStateDescriptor[Long, JList[Row]](timeIndicator + 
"InnerJoinLeftCache",
    -        BasicTypeInfo.LONG_TYPE_INFO.asInstanceOf[TypeInformation[Long]], 
leftListTypeInfo)
    +      new MapStateDescriptor[Long, JList[Row]](
    +        timeIndicator + "InnerJoinLeftCache",
    +        BasicTypeInfo.LONG_TYPE_INFO.asInstanceOf[TypeInformation[Long]],
    +        leftListTypeInfo)
         leftCache = getRuntimeContext.getMapState(leftStateDescriptor)
     
         val rightListTypeInfo: TypeInformation[JList[Row]] = new 
ListTypeInfo[Row](rightType)
         val rightStateDescriptor: MapStateDescriptor[Long, JList[Row]] =
    -      new MapStateDescriptor[Long, JList[Row]](timeIndicator + 
"InnerJoinRightCache",
    -        BasicTypeInfo.LONG_TYPE_INFO.asInstanceOf[TypeInformation[Long]], 
rightListTypeInfo)
    +      new MapStateDescriptor[Long, JList[Row]](
    +        timeIndicator + "InnerJoinRightCache",
    +        BasicTypeInfo.LONG_TYPE_INFO.asInstanceOf[TypeInformation[Long]],
    +        rightListTypeInfo)
         rightCache = getRuntimeContext.getMapState(rightStateDescriptor)
     
         // Initialize the timer states.
         val leftTimerStateDesc: ValueStateDescriptor[Long] =
    -      new ValueStateDescriptor[Long](timeIndicator + 
"InnerJoinLeftTimerState",
    -        classOf[Long])
    +      new ValueStateDescriptor[Long](timeIndicator + 
"InnerJoinLeftTimerState", classOf[Long])
         leftTimerState = getRuntimeContext.getState(leftTimerStateDesc)
     
         val rightTimerStateDesc: ValueStateDescriptor[Long] =
    -      new ValueStateDescriptor[Long](timeIndicator + 
"InnerJoinRightTimerState",
    -        classOf[Long])
    +      new ValueStateDescriptor[Long](timeIndicator + 
"InnerJoinRightTimerState", classOf[Long])
         rightTimerState = getRuntimeContext.getState(rightTimerStateDesc)
       }
     
       /**
    -    * Process records from the left stream.
    -    *
    -    * @param cRowValue the input record
    -    * @param ctx       the context to register timer or get current time
    -    * @param out       the collector for outputting results
    -    *
    +    * Process rows from the left stream.
         */
       override def processElement1(
    -    cRowValue: CRow,
    -    ctx: CoProcessFunction[CRow, CRow, CRow]#Context,
    -    out: Collector[CRow]): Unit = {
    -    val timeForRecord: Long = getTimeForRecord(ctx, cRowValue, true)
    -    getCurrentOperatorTime(ctx)
    +      cRowValue: CRow,
    +      ctx: CoProcessFunction[CRow, CRow, CRow]#Context,
    +      out: Collector[CRow]): Unit = {
    +    updateOperatorTime(ctx)
    +    val rowTime: Long = getTimeForLeftStream(ctx, cRowValue)
    +    val oppositeLowerBound: Long = rowTime - rightRelativeSize
    +    val oppositeUpperBound: Long = rowTime + leftRelativeSize
         processElement(
           cRowValue,
    -      timeForRecord,
    +      rowTime,
           ctx,
           out,
           leftOperatorTime,
    +      oppositeLowerBound,
    +      oppositeUpperBound,
           rightOperatorTime,
           rightTimerState,
           leftCache,
           rightCache,
    -      true
    +      leftRow = true
         )
       }
     
       /**
    -    * Process records from the right stream.
    -    *
    -    * @param cRowValue the input record
    -    * @param ctx       the context to get current time
    -    * @param out       the collector for outputting results
    -    *
    +    * Process rows from the right stream.
         */
       override def processElement2(
    -    cRowValue: CRow,
    -    ctx: CoProcessFunction[CRow, CRow, CRow]#Context,
    -    out: Collector[CRow]): Unit = {
    -    val timeForRecord: Long = getTimeForRecord(ctx, cRowValue, false)
    -    getCurrentOperatorTime(ctx)
    +      cRowValue: CRow,
    +      ctx: CoProcessFunction[CRow, CRow, CRow]#Context,
    +      out: Collector[CRow]): Unit = {
    +    updateOperatorTime(ctx)
    +    val rowTime: Long = getTimeForRightStream(ctx, cRowValue)
    +    val oppositeLowerBound: Long = rowTime - leftRelativeSize
    +    val oppositeUpperBound: Long =  rowTime + rightRelativeSize
         processElement(
           cRowValue,
    -      timeForRecord,
    +      rowTime,
           ctx,
           out,
           rightOperatorTime,
    +      oppositeLowerBound,
    +      oppositeUpperBound,
           leftOperatorTime,
           leftTimerState,
           rightCache,
           leftCache,
    -      false
    +      leftRow = false
         )
       }
     
       /**
    -    * Put a record from the input stream into the cache and iterate the 
opposite cache to
    -    * output records meeting the join conditions. If there is no timer set 
for the OPPOSITE
    +    * Put a row from the input stream into the cache and iterate the 
opposite cache to
    +    * output join results meeting the conditions. If there is no timer set 
for the OPPOSITE
         * STREAM, register one.
         */
       private def processElement(
    -    cRowValue: CRow,
    -    timeForRecord: Long,
    -    ctx: CoProcessFunction[CRow, CRow, CRow]#Context,
    -    out: Collector[CRow],
    -    myWatermark: Long,
    -    oppositeWatermark: Long,
    -    oppositeTimeState: ValueState[Long],
    -    recordListCache: MapState[Long, JList[Row]],
    -    oppositeCache: MapState[Long, JList[Row]],
    -    leftRecord: Boolean): Unit = {
    -    if (relativeWindowSize > 0) {
    -      //TODO Shall we consider adding a method for initialization with the 
context and collector?
    -      cRowWrapper.out = out
    -
    -      val record = cRowValue.row
    -
    -      //TODO Only if the time of the record is greater than the watermark, 
can we continue.
    -      if (timeForRecord >= myWatermark - allowedLateness) {
    -        val oppositeLowerBound: Long =
    -          if (leftRecord) timeForRecord - rightRelativeSize else 
timeForRecord - leftRelativeSize
    -
    -        val oppositeUpperBound: Long =
    -          if (leftRecord) timeForRecord + leftRelativeSize else 
timeForRecord + rightRelativeSize
    -
    -        // Put the record into the cache for later use.
    -        val recordList = if (recordListCache.contains(timeForRecord)) {
    -          recordListCache.get(timeForRecord)
    -        } else {
    -          new util.ArrayList[Row]()
    -        }
    -        recordList.add(record)
    -        recordListCache.put(timeForRecord, recordList)
    -
    -        // Register a timer on THE OTHER STREAM to remove records from the 
cache once they are
    -        // expired.
    -        if (oppositeTimeState.value == 0) {
    -          registerCleanUpTimer(
    -            ctx, timeForRecord, oppositeWatermark, oppositeTimeState, 
leftRecord, true)
    -        }
    +      cRowValue: CRow,
    +      timeForRow: Long,
    +      ctx: CoProcessFunction[CRow, CRow, CRow]#Context,
    +      out: Collector[CRow],
    +      myWatermark: Long,
    +      oppositeLowerBound: Long,
    +      oppositeUpperBound: Long,
    +      oppositeWatermark: Long,
    +      oppositeTimeState: ValueState[Long],
    +      rowListCache: MapState[Long, JList[Row]],
    +      oppositeCache: MapState[Long, JList[Row]],
    +      leftRow: Boolean): Unit = {
    +    cRowWrapper.out = out
    +    val row = cRowValue.row
    +    if (!checkRowOutOfDate(timeForRow, myWatermark)) {
    --- End diff --
    
    Thanks for your thoughts. I understand your motivation to either emit 
complete results for a row or none but I think it is fine to emit partial 
results. My reasoning is the following:
    
    1. we should try to produce results which are as close to the original 
semantics as possible
    2. being late (later than the allowedLateness) does not necessarily mean 
that we missed matching results. Maybe there were no matching records in the 
matched time frame, so we could still produce exact results.
    3. By not storing a row in the cache, the join result becomes more 
incomplete. Rows of the other stream that would have produced a complete result 
will only produce partial results (which we wanted to avoid by not adding it to 
state).
    
    So, I'd rather unnest the conditions.


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