Github user sureshsubbiah commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/1051#discussion_r110809205
--- 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".
--- End diff --
Yes, we can now use a an index to drive an update of an indexed column,
regardless of the type of WHERE predicate. A blocking SORT will be added for
anything other than an equality predicate without a constant. As such there is
no concept of an updateableIndex anymore (not considering embeddedUpdate which
is still retained in the old method). Every index is updateable, some
predicate/index combinations require a blocing sort while others do not. This
method is to help decide whether a blocking sort is needed for an index driven
scan of an update.
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