Ejemplo n.º 1
0
short
PhysSequence::codeGen(Generator *generator) 
{
  // Get a local handle on some of the generator objects.
  //
  CollHeap *wHeap = generator->wHeap();
  Space *space = generator->getSpace();
  ExpGenerator *expGen = generator->getExpGenerator();
  MapTable *mapTable = generator->getMapTable();

  // Allocate a new map table for this node. This must be done
  // before generating the code for my child so that this local
  // map table will be sandwiched between the map tables already
  // generated and the map tables generated by my offspring.
  //
  // Only the items available as output from this node will
  // be put in the local map table. Before exiting this function, all of
  // my offsprings map tables will be removed. Thus, none of the outputs 
  // from nodes below this node will be visible to nodes above it except 
  // those placed in the local map table and those that already exist in
  // my ancestors map tables. This is the standard mechanism used in the
  // generator for managing the access to item expressions.
  //
  MapTable *localMapTable = generator->appendAtEnd();

  // Since this operation doesn't modify the row on the way down the tree,
  // go ahead and generate the child subtree. Capture the given composite row
  // descriptor and the child's returned TDB and composite row descriptor.
  //
  ex_cri_desc * givenCriDesc = generator->getCriDesc(Generator::DOWN);
  child(0)->codeGen(generator);
  ComTdb *childTdb = (ComTdb*)generator->getGenObj();
  ex_cri_desc * childCriDesc = generator->getCriDesc(Generator::UP);
  ExplainTuple *childExplainTuple = generator->getExplainTuple();

  // Make all of my child's outputs map to ATP 1. The child row is only 
  // accessed in the project expression and it will be the second ATP 
  // (ATP 1) passed to this expression.
  //
  localMapTable->setAllAtp(1);

  // My returned composite row has an additional tupp.
  //
  Int32 numberTuples = givenCriDesc->noTuples() + 1;
  ex_cri_desc * returnCriDesc 
#pragma nowarn(1506)   // warning elimination 
    = new (space) ex_cri_desc(numberTuples, space);
#pragma warn(1506)  // warning elimination 

  // For now, the history buffer row looks just the return row. Later,
  // it may be useful to add an additional tupp for sequence function
  // itermediates that are not needed above this node -- thus, this
  // ATP is kept separate from the returned ATP.
  //
  const Int32 historyAtp = 0;
  const Int32 historyAtpIndex = numberTuples-1;
#pragma nowarn(1506)   // warning elimination 
  ex_cri_desc *historyCriDesc = new (space) ex_cri_desc(numberTuples, space);
#pragma warn(1506)  // warning elimination 
  ExpTupleDesc *historyDesc = 0;

  //seperate the read and retur expressions
  seperateReadAndReturnItems(wHeap);

  // The history buffer consists of items projected directly from the
  // child, the root sequence functions, the value arguments of the 
  // offset functions, and running sequence functions. These elements must 
  // be materialized in the  history buffer in order to be able to compute 
  // the outputs of this node -- the items projected directly from the child 
  // (projectValues) and the root sequence functions (sequenceFunctions).
  //
  // Compute the set of sequence function items that must be materialized
  // int the history buffer. -- sequenceItems
  //
  // Compute the set of items in the history buffer: the union of the 
  // projected values and the value arguments. -- historyIds
  //
  // Compute the set of items in the history buffer that are computed:
  // the difference between all the elements in the history buffer
  // and the projected items. -- computedHistoryIds
  //

  // KB---will need to return atp with 3 tups only 0,1 and 2 
  // 2 -->values from history buffer after ther are moved to it

 
  addCheckPartitionChangeExpr(generator, TRUE);

  ValueIdSet historyIds;

  historyIds += movePartIdsExpr(); 
  historyIds += sequencedColumns();
  
  ValueIdSet outputFromChild = child(0)->getGroupAttr()->getCharacteristicOutputs();

  getHistoryAttributes(readSeqFunctions(),outputFromChild, historyIds, TRUE, wHeap);

  // Add in the top level sequence functions.
  historyIds += readSeqFunctions();

  getHistoryAttributes(returnSeqFunctions(),outputFromChild, historyIds, TRUE, wHeap);
  // Add in the top level functions.
  historyIds += returnSeqFunctions();
  
  // Layout the work tuple format which consists of the projected
  // columns and the computed sequence functions. First, compute
  // the number of attributes in the tuple.
  //
  ULng32 numberAttributes 
    = ((NOT historyIds.isEmpty()) ? historyIds.entries() : 0);

  // Allocate an attribute pointer vector from the working heap.
  //
  Attributes **attrs = new(wHeap) Attributes*[numberAttributes];

  // Fill in the attributes vector for the history buffer including
  // adding the entries to the map table. Also, compute the value ID
  // set for the elements to project from the child row.
  //
  //??????????re-visit this function??
  computeHistoryAttributes(generator, 
                           localMapTable,
                           attrs,
                           historyIds);

  // Create the tuple descriptor for the history buffer row and
  // assign the offsets to the attributes. For now, this layout is 
  // identical to the returned row. Set the tuple descriptors for
  // the return and history rows.
  //
  ULng32 historyRecLen;
  expGen->processAttributes(numberAttributes,
                            attrs,
                            ExpTupleDesc::SQLARK_EXPLODED_FORMAT,
                            historyRecLen,
                            historyAtp,
                            historyAtpIndex,
                            &historyDesc,
                            ExpTupleDesc::SHORT_FORMAT);
  NADELETEBASIC(attrs, wHeap);
#pragma nowarn(1506)   // warning elimination 
  returnCriDesc->setTupleDescriptor(historyAtpIndex, historyDesc);
#pragma warn(1506)  // warning elimination 
#pragma nowarn(1506)   // warning elimination 
  historyCriDesc->setTupleDescriptor(historyAtpIndex, historyDesc);
#pragma warn(1506)  // warning elimination 

  // If there are any sequence function items, generate the sequence 
  // function expressions.
  //
  ex_expr * readSeqExpr = NULL;
  if(NOT readSeqFunctions().isEmpty())
    {
      ValueIdSet seqVals = readSeqFunctions();
      seqVals += sequencedColumns();
      seqVals += movePartIdsExpr(); 
      expGen->generateSequenceExpression(seqVals,
                                         readSeqExpr);
    }

  ex_expr *checkPartChangeExpr = NULL;
  if (!checkPartitionChangeExpr().isEmpty()) {
    ItemExpr * newCheckPartitionChangeTree= 
        checkPartitionChangeExpr().rebuildExprTree(ITM_AND,TRUE,TRUE);

    expGen->generateExpr(newCheckPartitionChangeTree->getValueId(), 
                         ex_expr::exp_SCAN_PRED,
                         &checkPartChangeExpr);
  }

  //unsigned long rowLength;
  ex_expr * returnExpr = NULL;
  if(NOT returnSeqFunctions().isEmpty())
  {
    expGen->generateSequenceExpression(returnSeqFunctions(),
                                         returnExpr);

  }

  // Generate expression to evaluate predicate on the output
  //
  ex_expr *postPred = 0;

  if (! selectionPred().isEmpty()) {
    ItemExpr * newPredTree = 
      selectionPred().rebuildExprTree(ITM_AND,TRUE,TRUE);

    expGen->generateExpr(newPredTree->getValueId(), ex_expr::exp_SCAN_PRED,
                         &postPred);
  }


  // Reset ATP's to zero for parent.
  //
  localMapTable->setAllAtp(0);


  // Generate expression to evaluate the cancel expression
  //
  ex_expr *cancelExpression = 0;

  if (! cancelExpr().isEmpty()) {
    ItemExpr * newCancelExprTree = 
      cancelExpr().rebuildExprTree(ITM_AND,TRUE,TRUE);

    expGen->generateExpr(newCancelExprTree->getValueId(), ex_expr::exp_SCAN_PRED,
                         &cancelExpression);
  }

  //
  //  For overflow
  //
  // ( The following are meaningless if ! unlimitedHistoryRows() ) 
  NABoolean noOverflow =  
    CmpCommon::getDefault(EXE_BMO_DISABLE_OVERFLOW) == DF_ON ;
  NABoolean logDiagnostics = 
    CmpCommon::getDefault(EXE_DIAGNOSTIC_EVENTS) == DF_ON ;
  NABoolean possibleMultipleCalls = generator->getRightSideOfFlow() ;
  short scratchTresholdPct = 
    (short) CmpCommon::getDefaultLong(SCRATCH_FREESPACE_THRESHOLD_PERCENT);
  // determione the memory usage (amount of memory as percentage from total
  // physical memory used to initialize data structures)
  unsigned short memUsagePercent =
    (unsigned short) getDefault(BMO_MEMORY_USAGE_PERCENT);
  short memPressurePct = (short)getDefault(GEN_MEM_PRESSURE_THRESHOLD);

  historyRecLen = ROUND8(historyRecLen);

  Lng32 maxNumberOfOLAPBuffers;
  Lng32 maxRowsInOLAPBuffer;
  Lng32 minNumberOfOLAPBuffers;
  Lng32 numberOfWinOLAPBuffers;
  Lng32 olapBufferSize;

  computeHistoryParams(historyRecLen,
                       maxRowsInOLAPBuffer,
                       minNumberOfOLAPBuffers,
                       numberOfWinOLAPBuffers,
                       maxNumberOfOLAPBuffers,
                       olapBufferSize);

  ComTdbSequence *sequenceTdb
    = new(space) ComTdbSequence(readSeqExpr,
                                returnExpr,
                                postPred,
                                cancelExpression,
                                getMinFollowingRows(),
#pragma nowarn(1506)   // warning elimination 
                                historyRecLen,
                                historyAtpIndex,
                                childTdb,
                                givenCriDesc,
                                returnCriDesc,
                                (queue_index)getDefault(GEN_SEQFUNC_SIZE_DOWN),
                                (queue_index)getDefault(GEN_SEQFUNC_SIZE_UP),
                                getDefault(GEN_SEQFUNC_NUM_BUFFERS),
                                getDefault(GEN_SEQFUNC_BUFFER_SIZE),
				olapBufferSize,
                                maxNumberOfOLAPBuffers,
                                numHistoryRows(),
                                getUnboundedFollowing(),
				logDiagnostics,
				possibleMultipleCalls,
				scratchTresholdPct,
				memUsagePercent,
				memPressurePct,
                                maxRowsInOLAPBuffer,
                                minNumberOfOLAPBuffers,
                                numberOfWinOLAPBuffers,
                                noOverflow,
                                checkPartChangeExpr);
#pragma warn(1506)  // warning elimination 
  generator->initTdbFields(sequenceTdb);

  // update the estimated value of HistoryRowLength with actual value
  //setEstHistoryRowLength(historyIds.getRowLength());

  double sequenceMemEst = getEstimatedRunTimeMemoryUsage(sequenceTdb);
  generator->addToTotalEstimatedMemory(sequenceMemEst);

  if(!generator->explainDisabled()) {
    Lng32 seqMemEstInKBPerCPU = (Lng32)(sequenceMemEst / 1024) ;
    seqMemEstInKBPerCPU = seqMemEstInKBPerCPU/
      (MAXOF(generator->compilerStatsInfo().dop(),1));
    generator->setOperEstimatedMemory(seqMemEstInKBPerCPU);

    generator->
      setExplainTuple(addExplainInfo(sequenceTdb,
                                     childExplainTuple,
                                     0,
                                     generator));

    generator->setOperEstimatedMemory(0);
  }

  sequenceTdb->setScratchIOVectorSize((Int16)getDefault(SCRATCH_IO_VECTOR_SIZE_HASH));
  sequenceTdb->setOverflowMode(generator->getOverflowMode());

  sequenceTdb->setBmoMinMemBeforePressureCheck((Int16)getDefault(EXE_BMO_MIN_SIZE_BEFORE_PRESSURE_CHECK_IN_MB));
  
  if(generator->getOverflowMode() == ComTdb::OFM_SSD )
    sequenceTdb->setBMOMaxMemThresholdMB((UInt16)(ActiveSchemaDB()->
				   getDefaults()).
			  getAsLong(SSD_BMO_MAX_MEM_THRESHOLD_IN_MB));
  else
    sequenceTdb->setBMOMaxMemThresholdMB((UInt16)(ActiveSchemaDB()->
				   getDefaults()).
			  getAsLong(EXE_MEMORY_AVAILABLE_IN_MB));

  // The CQD EXE_MEM_LIMIT_PER_BMO_IN_MB has precedence over the mem quota sys
  NADefaults &defs = ActiveSchemaDB()->getDefaults();
  UInt16 mmu = (UInt16)(defs.getAsDouble(EXE_MEM_LIMIT_PER_BMO_IN_MB));
  UInt16 numBMOsInFrag = (UInt16)generator->getFragmentDir()->getNumBMOs();
  if (mmu != 0)
    sequenceTdb->setMemoryQuotaMB(mmu);
  else {
    // Apply quota system if either one the following two is true:
    //   1. the memory limit feature is turned off and more than one BMOs 
    //   2. the memory limit feature is turned on
    NABoolean mlimitPerCPU = defs.getAsDouble(EXE_MEMORY_LIMIT_PER_CPU) > 0;

    if ( mlimitPerCPU || numBMOsInFrag > 1 ) {

        double memQuota = 
           computeMemoryQuota(generator->getEspLevel() == 0,
                              mlimitPerCPU,
                              generator->getBMOsMemoryLimitPerCPU().value(),
                              generator->getTotalNumBMOsPerCPU(),
                              generator->getTotalBMOsMemoryPerCPU().value(),
                              numBMOsInFrag, 
                              generator->getFragmentDir()->getBMOsMemoryUsage()
                             );
                                  
        sequenceTdb->setMemoryQuotaMB( UInt16(memQuota) );
    }
  }

  generator->setCriDesc(givenCriDesc, Generator::DOWN);
  generator->setCriDesc(returnCriDesc, Generator::UP);
  generator->setGenObj(this, sequenceTdb);

  return 0;

}
Ejemplo n.º 2
0
short RelInternalSP::codeGen(Generator * generator)
{
  Space * space          = generator->getSpace();
  ExpGenerator * exp_gen = generator->getExpGenerator();
  MapTable * last_map_table = generator->getLastMapTable();

  ex_expr * input_expr  = NULL;
  ex_expr * output_expr = NULL;

  ////////////////////////////////////////////////////////////////////////////
  //
  // Returned atp layout:
  //
  // |--------------------------------|
  // | input data  |  stored proc row |
  // | ( I tupps ) |  ( 1 tupp )      |
  // |--------------------------------|
  // <-- returned row to parent ---->
  //
  // input data:        the atp input to this node by its parent. 
  // stored proc row:   tupp where the row read from SP is moved.
  //
  ////////////////////////////////////////////////////////////////////////////

  ex_cri_desc * given_desc 
    = generator->getCriDesc(Generator::DOWN);

  ex_cri_desc * returned_desc 
    = new(space) ex_cri_desc(given_desc->noTuples() + 1, space);
 
  // cri descriptor for work atp has 3 entries:
  // -- the first two entries for consts and temps.
  // -- Entry 3(index #2) is where the input and output rows will be created.
  ex_cri_desc * work_cri_desc = new(space) ex_cri_desc(3, space);
  const Int32 work_atp = 1;
  const Int32 work_atp_index = 2;
 
  ExpTupleDesc * input_tuple_desc = NULL;
  ExpTupleDesc * output_tuple_desc = NULL;

  // Generate expression to create the input row that will be
  // given to the stored proc.
  // The input value is in sp->getProcAllParams() 
  // and has to be converted to sp->procType().
  // Generate Cast node to convert procParam to ProcType.
  // If procType is a varchar, explode it. This is done
  // so that values could be extracted correctly.
  ValueIdList procVIDList;
  for (CollIndex i = 0; i < procTypes().entries(); i++)
    {
      Cast * cn;

      if ((procTypes())[i].getType().getVarLenHdrSize() > 0) 
	{

// 5/9/98: add support for VARNCHAR
          const CharType& char_type =
                (CharType&)((procTypes())[i].getType());

	  // Explode varchars by moving them to a fixed field
	  // whose length is equal to the max length of varchar.
	  cn = new(generator->wHeap()) 
	    Cast ((getProcAllParamsVids())[i].getItemExpr(), 
		  (new(generator->wHeap())
		   SQLChar(generator->wHeap(),
		           CharLenInfo(char_type.getStrCharLimit(), char_type.getDataStorageSize()),
			   char_type.supportsSQLnull(),
			   FALSE, FALSE, FALSE,
			   char_type.getCharSet(),
			   char_type.getCollation(),
			   char_type.getCoercibility()
/*
                           (procTypes())[i].getType().getNominalSize(),
			   (procTypes())[i].getType().supportsSQLnull()
*/
                          )
                  )
                 );
	  
	  // Move the exploded field to a varchar field since 
	  // procType is varchar.
	  // Can optimize by adding an option to convert node to
	  // blankpad. TBD.
	  //
	  cn = new(generator->wHeap())
	    Cast(cn, &((procTypes())[i].getType()));
	} 
      else
 	cn = new(generator->wHeap()) Cast((getProcAllParamsVids())[i].getItemExpr(),
					  &((procTypes())[i].getType()));

      cn->bindNode(generator->getBindWA());
      procVIDList.insert(cn->getValueId());
    }

  ULng32 inputRowlen_ = 0;
  exp_gen->generateContiguousMoveExpr(procVIDList, -1, /*add conv nodes*/
				      work_atp, work_atp_index,
				      ExpTupleDesc::SQLARK_EXPLODED_FORMAT,
				      inputRowlen_,
				      &input_expr,
				      &input_tuple_desc,
				      ExpTupleDesc::LONG_FORMAT);

  // add all columns from this SP to the map table. 
  ULng32 tupleLength;
  exp_gen->processValIdList(getTableDesc()->getColumnList(),
			    ExpTupleDesc::SQLARK_EXPLODED_FORMAT,
			    tupleLength,
			    work_atp, 
			    work_atp_index);
 
  // Generate expression to move the output row returned by the
  // stored proc back to parent.
  ULng32 outputRowlen_ = 0;
  MapTable * returnedMapTable = 0;
  exp_gen->generateContiguousMoveExpr(getTableDesc()->getColumnList(),
				      -1 /*add conv nodes*/,
				      0, returned_desc->noTuples() - 1,
				      ExpTupleDesc::SQLARK_EXPLODED_FORMAT,
				      outputRowlen_,
				      &output_expr,
				      &output_tuple_desc,
				      ExpTupleDesc::LONG_FORMAT,
				      &returnedMapTable);
 
  // Now generate expressions used to extract or move input or
  // output values. See class ExSPInputOutput.
  ExSPInputOutput * extractInputExpr = NULL;
  ExSPInputOutput * moveOutputExpr = NULL;
  
  generateSPIOExpr(this, generator,
		   extractInputExpr,
		   moveOutputExpr);

  // done with expressions at this operator. Remove the appended map tables.
  generator->removeAll(last_map_table);

  // append the map table containing the returned columns
  generator->appendAtEnd(returnedMapTable);

  NAString procNameAsNAString(procName_);
  char * sp_name = 
    space->allocateAndCopyToAlignedSpace(procNameAsNAString,
					 procNameAsNAString.length(), 0);

  ExpGenerator *expGen = generator->getExpGenerator();

  // expression to conditionally return 0 or more rows.
  ex_expr *predExpr = NULL;

  // generate tuple selection expression, if present
  if(NOT selectionPred().isEmpty())
  {
    ItemExpr* pred = selectionPred().rebuildExprTree(ITM_AND,TRUE,TRUE);
    expGen->generateExpr(pred->getValueId(),ex_expr::exp_SCAN_PRED,&predExpr);
  }

  ComTdbStoredProc * sp_tdb = new(space)
    ComTdbStoredProc(sp_name, 
		     input_expr,
		     inputRowlen_,
		     output_expr,
		     outputRowlen_,
		     work_cri_desc,
		     work_atp_index,
		     given_desc,
		     returned_desc,
		     extractInputExpr,
		     moveOutputExpr,
		     2,
		     1024,
		     (Cardinality) getGroupAttr()->
		     getOutputLogPropList()[0]->
		     getResultCardinality().value(),
		     5,
		     64000,  //10240
		     predExpr,
		     (UInt16) arkcmpInfo_);
		      
  generator->initTdbFields(sp_tdb);

  if(!generator->explainDisabled()) 
    {
      generator->setExplainTuple(
				 addExplainInfo(sp_tdb, 0, 0, generator));
    }
  // Do not infer that any transaction started can 
  // be in READ ONLY mode if ISPs are present.
  generator->setNeedsReadWriteTransaction(TRUE);

  generator->setCriDesc(given_desc, Generator::DOWN);
  generator->setCriDesc(returned_desc, Generator::UP);
  generator->setGenObj(this, sp_tdb);

  // Some built-in functions require a TMF transaction
  // because they get their information from catman
  generator->setTransactionFlag(getRequiresTMFTransaction());

  return 0;
}
short
PhysSample::codeGen(Generator *generator) 
{  
  // Get a local handle on some of the generator objects.
  //
  CollHeap *wHeap = generator->wHeap();
  Space *space = generator->getSpace();
  MapTable *mapTable = generator->getMapTable();
  ExpGenerator *expGen = generator->getExpGenerator();

  // Allocate a new map table for this node. This must be done
  // before generating the code for my child so that this local
  // map table will be sandwiched between the map tables already
  // generated and the map tables generated by my offspring.
  //
  // Only the items available as output from this node will
  // be put in the local map table. Before exiting this function, all of
  // my offsprings map tables will be removed. Thus, none of the outputs 
  // from nodes below this node will be visible to nodes above it except 
  // those placed in the local map table and those that already exist in
  // my ancestors map tables. This is the standard mechanism used in the
  // generator for managing the access to item expressions.
  //
  MapTable *localMapTable = generator->appendAtEnd();

  // Since this operation doesn't modify the row on the way down the tree,
  // go ahead and generate the child subtree. Capture the given composite row
  // descriptor and the child's returned TDB and composite row descriptor.
  //
  ex_cri_desc * givenCriDesc = generator->getCriDesc(Generator::DOWN);
  child(0)->codeGen(generator);
  ComTdb *childTdb = (ComTdb*)generator->getGenObj();
  ex_cri_desc * childCriDesc = generator->getCriDesc(Generator::UP);
  ExplainTuple *childExplainTuple = generator->getExplainTuple();

  // Geneate the sampling expression.
  //
  ex_expr *balExpr = NULL;
  Int32 returnFactorOffset = 0;
  ValueId val;
  val = balanceExpr().init();
  if(balanceExpr().next(val))
    expGen->generateSamplingExpr(val, &balExpr, returnFactorOffset);

  // Alias the sampleColumns() so that they reference the underlying
  // expressions directly. This is done to avoid having to generate and
  // execute a project expression that simply moves the columns from
  // one tupp to another to reflect the application of the sampledCol
  // function.
  //
//   ValueId valId;
//   for(valId = sampledColumns().init();
//       sampledColumns().next(valId);
//       sampledColumns().advance(valId))
//     {
//       MapInfo *mapInfoChild = localMapTable->getMapInfoAsIs
// 	(valId.getItemExpr()->child(0)->castToItemExpr()->getValueId());
//       GenAssert(mapInfoChild, "Sample::codeGen -- no child map info.");
//       Attributes *attr = mapInfoChild->getAttr();
//       MapInfo *mapInfo = localMapTable->addMapInfoToThis(valId, attr);
//       mapInfo->codeGenerated();
//     }
// check if any of the columns inthe sampled columns are lob columns. If so, return an error.
  ValueId valId;
  for(valId = sampledColumns().init();
      sampledColumns().next(valId);
      sampledColumns().advance(valId))
    {
      const NAType &colType = valId.getType();
      if ((colType.getFSDatatype() == REC_BLOB) ||
	  (colType.getFSDatatype() == REC_CLOB))
	{
	   *CmpCommon::diags() << DgSqlCode(-4322);
	   GenExit();
	}
    }
  // Now, remove all attributes from the map table except the 
  // the stuff in the local map table -- the result of this node.
  //
//  localMapTable->removeAll();

  // Generate the expression to evaluate predicate on the sampled row.
  //
  ex_expr *postPred = 0;
  if (!selectionPred().isEmpty()) {
    ItemExpr * newPredTree 
      = selectionPred().rebuildExprTree(ITM_AND,TRUE,TRUE);

    expGen->generateExpr(newPredTree->getValueId(), ex_expr::exp_SCAN_PRED,
			 &postPred);
  }

  // Construct the Sample TDB.
  //
  ComTdbSample *sampleTdb
    = new(space) ComTdbSample(NULL,
			      balExpr,
			      returnFactorOffset,
			      postPred,
			      childTdb,
			      givenCriDesc,
			      childCriDesc,
			      (queue_index)getDefault(GEN_SAMPLE_SIZE_DOWN),
			      (queue_index)getDefault(GEN_SAMPLE_SIZE_UP));
  generator->initTdbFields(sampleTdb);

  if(!generator->explainDisabled()) {
    generator->
      setExplainTuple(addExplainInfo(sampleTdb,
                                     childExplainTuple,
                                     0,
                                     generator));
  }

  generator->setCriDesc(givenCriDesc, Generator::DOWN);
  generator->setCriDesc(childCriDesc, Generator::UP);
  generator->setGenObj(this, sampleTdb);

  return 0;
}