[CALCITE-3753] Remove rule queue importance

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/SubstitutionRule.java

@@ -0,0 +1,26 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.calcite.plan;
+
+/**
+ * A rule that implements this interface indicates that the new RelNode
+ * is definitely better than the old one, which will be pruned by setting
+ * importance to 0.
+ */
+public interface SubstitutionRule {
+
+}

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(),
@@ -421,7 +420,7 @@ void mergeWith(
     // once to fire again.)
     for (RelNode rel : rels) {
       assert planner.getSet(rel) == this;
-      planner.fireRules(rel, true);
+      planner.fireRules(rel);
     }
   }
 }

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);
   }