Github user DaveBirdsall commented on a diff in the pull request:
https://github.com/apache/trafodion/pull/1581#discussion_r191576581
--- Diff: core/sql/optimizer/RelExpr.cpp ---
@@ -13341,6 +13345,33 @@ void GenericUpdate::pushdownCoveredExpr(const
ValueIdSet &outputExpr,
newExternalInputs,
predicatesOnParent,
&localExprs);
+
+ if (avoidHalloween() && child(0) && child(0)->getGroupAttr())
+ {
+ ValueIdSet cur_output =
child(0)->getGroupAttr()->getCharacteristicOutputs();
+ if (cur_output.isEmpty())
+ {
+ ValueId exprId;
+ ValueId atLeastOne;
+
+ for (exprId = original_output.init();
+ original_output.next(exprId);
+ original_output.advance(exprId))
+ {
+ atLeastOne = exprId;
+ if
(!(exprId.getItemExpr()->doesExprEvaluateToConstant(FALSE, TRUE)))
+ {
+
child(0)->getGroupAttr()->addCharacteristicOutputs(exprId);
+ break;
+ }
+ }
+ cur_output = child(0)->getGroupAttr()->getCharacteristicOutputs();
+ if (cur_output.isEmpty())
--- End diff --
I don't understand this code path. If cur_output is empty, that means that
the "for" loop did not find a ValueId to add to it. In particular. "atLeastOne"
has its initial value, which I think is the null ValueId, 0. This "if" would
cause us to add the null ValueId to child(0)'s characteristic outputs, which
does not sound correct to me.
---
