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From zellerh <...@git.apache.org>
Subject [GitHub] incubator-trafodion pull request #1051: [TRAAFODION-2568] [TRAFODION-2574]
Date Mon, 10 Apr 2017 18:55:42 GMT
Github user zellerh commented on a diff in the pull request:

    https://github.com/apache/incubator-trafodion/pull/1051#discussion_r110733170
  
    --- Diff: core/sql/optimizer/RelExpr.cpp ---
    @@ -9121,38 +9090,85 @@ NABoolean Scan::updateableIndex(IndexDesc *idx)
       {
         ItemExpr *updateCol = colUpdated[i].getItemExpr();
         CMPASSERT(updateCol->getOperatorType() == ITM_BASECOLUMN);
    -
         for (CollIndex j = 0; j < indexKey.entries(); j++)
         {
           ItemExpr *keyCol = indexKey[j].getItemExpr();
    -
    -      ItemExpr *baseCol = ((IndexColumn*)keyCol)->getDefinition().getItemExpr();
    +      ItemExpr *baseCol = 
    +        ((IndexColumn*)keyCol)->getDefinition().getItemExpr();
           CMPASSERT(baseCol->getOperatorType() == ITM_BASECOLUMN);
    -
    -      // QSTUFF
    -      if (getGroupAttr()->isEmbeddedUpdate()){
    -        if (((BaseColumn*)updateCol)->getColNumber() ==
    +      if (((BaseColumn*)updateCol)->getColNumber() ==
               ((BaseColumn*)baseCol)->getColNumber())
    -          return FALSE;
    -      }
    -      // QSTUFF
    +        return FALSE;
    +    }
    +  }
    +  return TRUE;
    +} // Scan::updateableIndex
    +
    +NABoolean Scan::requiresHalloweenForUpdateUsingIndexScan()
    +{
    +
    +  // Returns TRUE if any non clustering index can be used for a scan 
    +  // during an UPDATE and a key column of that index is in the SET
    +  // clause of the update. If this method returns TRUE we will use a 
    +  // sort node to prevent the "Halloween Update Problem".
    +  //
     
    -      if ((NOT(idx->isUniqueIndex() || idx->isClusteringIndex()))
    -	     ||
    -	  (CmpCommon::getDefault(UPDATE_CLUSTERING_OR_UNIQUE_INDEX_KEY) == DF_OFF))
    +  // preds are in RangeSpec form
    +  ValueIdSet preds = getSelectionPredicates();
    +  const ValueIdList colUpdated = getTableDesc()->getColUpdated();
    +  const LIST(IndexDesc *) & ixlist = getTableDesc()->getIndexes();
    +
    +  if ((colUpdated.entries() == 0) || (preds.entries() == 0) ||
    +      (ixlist.entries() == 1) || // this is the clustering index
    +      (CmpCommon::getDefault(UPDATE_CLUSTERING_OR_UNIQUE_INDEX_KEY) 
    +       == DF_AGGRESSIVE)) // this setting means no Halloween protection
    +    return FALSE;
    +
    +   if (CmpCommon::getDefault(RANGESPEC_TRANSFORMATION) == DF_ON)
    +   {
    +     ValueIdList selectionPredList(preds);
    +     ItemExpr *inputItemExprTree = 
    +       selectionPredList.rebuildExprTree(ITM_AND,FALSE,FALSE);
    +     ItemExpr * resultOld = revertBackToOldTree(STMTHEAP, 
    +                                                inputItemExprTree);
    +     preds.clear();
    +     resultOld->convertToValueIdSet(preds, NULL, ITM_AND);
    +     doNotReplaceAnItemExpressionForLikePredicates(resultOld,preds,
    +                                                   resultOld);
    +   }
     
    +  for (CollIndex indexNo = 0; indexNo < ixlist.entries(); indexNo++)
    +  {
    +    IndexDesc *idx = ixlist[indexNo];
    +    if (idx->isClusteringIndex() || 
    +        (idx->isUniqueIndex() && 
    +        (CmpCommon::getDefault(UPDATE_CLUSTERING_OR_UNIQUE_INDEX_KEY) 
    +         == DF_ON)))
    +      continue ; // skip this idesc
    +
    +    const ValueIdList indexKey = idx->getIndexKey();
    +    // Determine if the columns being updated are key columns. Each key
    +    // column being updated must have an associated equality clause in
    +    // the WHERE clause of the UPDATE for it to be used.
    +    for (CollIndex i = 0; i < colUpdated.entries(); i++)
    --- End diff --
    
    I don't quite understand this comment and the logic below. The existing method, Scan::updateableIndex(),
allows an index if it is a) a unique index or b) has a unique predicate on its key or c) has
an equals predicate on all the index columns of a non-unique index. Do you want to achieve
something different here?


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