tree 561802a97903370f8c43e863494f442af2215058
parent 34e4a4ff9010b0a25c0a1546f012184a1a72e2e3
author Haisheng Yuan <h.yuan@alibaba-inc.com> 1579480079 -0600
committer Haisheng Yuan <15352793+hsyuan@users.noreply.github.com> 1579815819 -0800

[CALCITE-3744] Duplicate rule matches when RelSet gets merged

Some times RelSet can get merged. e.g.

Each number represet Rel id, and they are in different RelSet.

 1            4
   \         /
     2      /
       \   /
         3
Assume in the rulequeue, we have rule match with name of 12, 23, 43. For
simplicity, omit the rule name, first digit represent the parent RelNode,
second represent the child.

If after some rule, we merged the set of 3 into the set of 2, and RelNode 4's
input is replaced by RelSubset of 2. We will retrigger rules and try to add
rulematch 12, 42, 43 into rule queue.

12 will be filtered out, because there is duplicate in the RuleMatch names set.
But for 43, it now has different rulematch digest with previous match, because
RelNode #4's input RelSubset changed, its digest also changed. So we can't
detect the duplication and will re-apply rulematch 43 twice.