How to generate hash code for each build side one of the hash join columns

[weijie tong]

HI All:
  Through implementing the JPPD feature (
https://issues.apache.org/jira/browse/DRILL-6385) , I was blocked by the
problem: how to get the hash code of each build side of the hash join
columns through the dynamic generated java code. Hope someone can give some
advice.

   I supposed to add methods as below to the HashTableTemplate :

public long getBuild64HashCode(int incomingRowIdx, int seedValue, int
fieldId) throws SchemaChangeException{
    return getBuild64HashCodeInner(incomingRowIdx, seedValue, fieldId);
}

protected abstract long
getBuild64HashCodeInner(@Named("incomingRowIdx") int incomingRowIdx,
@Named("seedValue") int seedValue, @Named("fieldId") int fieldId)
throws SchemaChangeException;


   The high level code to invoke the getBuild64HashCode method is at the
HashJoinBatch's executeBuildPhase() :

//create runtime filter
if (cycleNum == 0 && enableRuntimeFilter) {
  //create runtime filter and send out async
  int condFieldIndex = 0;
  for (BloomFilter bloomFilter : bloomFilters) {
    //VV
    for (int ind = 0; ind < currentRecordCount; ind++) {
      long hashCode = partitions[0].getBuild64HashCode(ind, condFieldIndex);
      bloomFilter.insert(hashCode);
    }
    condFieldIndex++;
  }
  //TODO sered out async
}


  As you know, the abstract method getBuild64HashCodeInner needs to
calculate the hash codes of each build side column by the fieldId input
parameter. In order to achieve this target, I plan to have different
solving parts corresponding to different column ValueVector , using the if
statement to distinguish different solving parts through the id of the
column.   The corresponding method to generate the dynamic codes  is as
below:

private void setupGetBuild64Hash(ClassGenerator<HashTable> cg,
MappingSet incomingMapping, VectorAccessible batch,
LogicalExpression[] keyExprs, TypedFieldId[] buildKeyFieldIds)
  throws SchemaChangeException {
  cg.setMappingSet(incomingMapping);
  if (keyExprs == null || keyExprs.length == 0) {
    cg.getEvalBlock()._return(JExpr.lit(0));
  }
  String seedValue = "seedValue";
  String fieldId = "fieldId";
  LogicalExpression seed =
ValueExpressions.getParameterExpression(seedValue,
Types.required(TypeProtos.MinorType.INT));

  LogicalExpression fieldIdParamExpr =
ValueExpressions.getParameterExpression(fieldId,
Types.required(TypeProtos.MinorType.INT) );
  HoldingContainer fieldIdParamHolder = cg.addExpr(fieldIdParamExpr);
  int i = 0;
  for (LogicalExpression expr : keyExprs) {
    TypedFieldId targetTypeFieldId = buildKeyFieldIds[i];
    ValueExpressions.IntExpression targetBuildFieldIdExp = new
ValueExpressions.IntExpression(targetTypeFieldId.getFieldIds()[0],
ExpressionPosition.UNKNOWN);
    JFieldRef targetBuildSideFieldId =
cg.addExpr(targetBuildFieldIdExp,
ClassGenerator.BlkCreateMode.TRUE_IF_BOUND).getValue();
    JBlock ifBlock =
cg.getEvalBlock()._if(fieldIdParamHolder.getValue().eq(targetBuildSideFieldId))._then();

    LogicalExpression hashExpression =
HashPrelUtil.getHashExpression(expr, seed, incomingProbe != null);
    LogicalExpression materializedExpr =
ExpressionTreeMaterializer.materializeAndCheckErrors(hashExpression,
batch, context.getFunctionRegistry());
    HoldingContainer hash = cg.addExpr(materializedExpr,
ClassGenerator.BlkCreateMode.FALSE);


    ifBlock._return(hash.getValue());
    i++;
  }
  cg.getEvalBlock()._return(JExpr.lit(0));

}

But unfortunately, the generated codes are not what I expected. The codes
to read ValueVector , calculate hash code of the read value do not stay in
the if block.  So how can I let the related codes stay in the if block ?