[CALCITE-3753] Remove rule queue importance

Since we are going to execute all the rules anyway, sorting the rule matches
will do more harm than good.

Also removed ambitious and impatient mode. User could override checkCancel and
throw VolcanoTimeoutException when appropriate (i.e. exceed 60 seconds, exceed
1000 ticks etc.) so that the VolcanoPlanner will stop exhaustive searching and
return the best plan so far.

Close apache#1840

core/src/main/java/org/apache/calcite/adapter/jdbc/JdbcRules.java

@@ -801,6 +801,11 @@ public JdbcSort(
           offset, fetch);
     }
 
+    @Override public RelOptCost computeSelfCost(RelOptPlanner planner,
+        RelMetadataQuery mq) {
+      return super.computeSelfCost(planner, mq).multiplyBy(0.9);
+    }
+
     public JdbcImplementor.Result implement(JdbcImplementor implementor) {
       return implementor.implement(this);
     }

core/src/main/java/org/apache/calcite/plan/AbstractRelOptPlanner.java

@@ -63,7 +63,7 @@ public abstract class AbstractRelOptPlanner implements RelOptPlanner {
 
   private Pattern ruleDescExclusionFilter;
 
-  private final AtomicBoolean cancelFlag;
+  protected final AtomicBoolean cancelFlag;
 
   private final Set<Class<? extends RelNode>> classes = new HashSet<>();
 

core/src/main/java/org/apache/calcite/plan/volcano/RelSet.java

@@ -337,7 +337,6 @@ void mergeWith(
 
     // merge subsets
     for (RelSubset otherSubset : otherSet.subsets) {
-      planner.ruleQueue.subsetImportances.remove(otherSubset);
       RelSubset subset =
           getOrCreateSubset(
               otherSubset.getCluster(),

core/src/main/java/org/apache/calcite/plan/volcano/RelSubset.java

@@ -366,8 +366,7 @@ void propagateCostImprovements0(VolcanoPlanner planner, RelMetadataQuery mq,
         // since best was changed, cached metadata for this subset should be removed
         mq.clearCache(this);
 
-        // Recompute subset's importance and propagate cost change to parents
-        planner.ruleQueue.recompute(this);
+        // Propagate cost change to parents
         for (RelNode parent : getParents()) {
           // removes parent cached metadata since its input was changed
           mq.clearCache(parent);
@@ -386,18 +385,6 @@ void propagateCostImprovements0(VolcanoPlanner planner, RelMetadataQuery mq,
     }
   }
 
-  public void propagateBoostRemoval(VolcanoPlanner planner) {
-    planner.ruleQueue.recompute(this);
-
-    if (boosted) {
-      boosted = false;
-
-      for (RelSubset parentSubset : getParentSubsets(planner)) {
-        parentSubset.propagateBoostRemoval(planner);
-      }
-    }
-  }
-
   @Override public void collectVariablesUsed(Set<CorrelationId> variableSet) {
     variableSet.addAll(set.variablesUsed);
   }