Github user sureshsubbiah commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/1051#discussion_r110810480
--- 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) ||
--- End diff --
The old updateableIndex would have returned TRUE if there was no predicate
on the SET clause column. That is why I wrote the current method this way. I
agree that we are open to the halloween problem as the case you mentioned.
Since it is an existing bug I would like to address it in my next checkin which
will be in a day or two.
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