Github user zellerh commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/1254#discussion_r142535910
--- Diff: core/sql/optimizer/OptLogRelExpr.cpp ---
@@ -2394,7 +2394,7 @@ Join::synthConstraints(NormWA * normWAPtr)
(void) leftGA.hasCardConstraint(minLeft,maxLeft);
(void) rightGA.hasCardConstraint(minRight,maxRight);
- if (maxLeft == 1)
+ if (maxLeft == 1 || isIndexJoin_)
--- End diff --
The non-unique index contains one row for each base table row, and it
contains the clustering key of that row. So, there is still a 1:1 match between
the non-unique index and the base table/clustering index, and a probe cache
would not have any cache hits.
---
