diff --git a/avatica-server/pom.xml b/avatica-server/pom.xml
index 52a2e5b8a0c3..6c340baed193 100644
--- a/avatica-server/pom.xml
+++ b/avatica-server/pom.xml
@@ -20,12 +20,12 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <artifactId>calcite-avatica-server</artifactId>
   <packaging>jar</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
   <name>Calcite Avatica Server</name>
   <description>JDBC server.</description>
 
diff --git a/avatica/pom.xml b/avatica/pom.xml
index 6d6c1339e528..1ad6136fa83f 100644
--- a/avatica/pom.xml
+++ b/avatica/pom.xml
@@ -20,12 +20,12 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <artifactId>calcite-avatica</artifactId>
   <packaging>jar</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
   <name>Calcite Avatica</name>
   <description>JDBC driver framework.</description>
 
diff --git a/core/pom.xml b/core/pom.xml
index 3e443ee9bbdc..962d867f9769 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -20,12 +20,12 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <artifactId>calcite-core</artifactId>
   <packaging>jar</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
   <name>Calcite Core</name>
   <description>Core Calcite APIs and engine.</description>
 
diff --git a/core/src/main/java/org/apache/calcite/plan/ConventionTraitDef.java b/core/src/main/java/org/apache/calcite/plan/ConventionTraitDef.java
index 9de4762ed96a..dccaa6625ab5 100644
--- a/core/src/main/java/org/apache/calcite/plan/ConventionTraitDef.java
+++ b/core/src/main/java/org/apache/calcite/plan/ConventionTraitDef.java
@@ -25,18 +25,22 @@
 import org.apache.calcite.util.graph.DirectedGraph;
 import org.apache.calcite.util.graph.Graphs;
 
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
 import com.google.common.collect.HashMultimap;
 import com.google.common.collect.Multimap;
 
 import java.util.List;
-import java.util.WeakHashMap;
+import javax.annotation.Nonnull;
 
 /**
  * Definition of the the convention trait.
  * A new set of conversion information is created for
  * each planner that registers at least one {@link ConverterRule} instance.
  *
- * <p>Conversion data is held in a {@link WeakHashMap} so that the JVM's garbage
+ * <p>Conversion data is held in a {@link LoadingCache}
+ * with weak keys so that the JVM's garbage
  * collector may reclaim the conversion data after the planner itself has been
  * garbage collected. The conversion information consists of a graph of
  * conversions (from one calling convention to another) and a map of graph arcs
@@ -51,12 +55,16 @@ public class ConventionTraitDef extends RelTraitDef<Convention> {
   //~ Instance fields --------------------------------------------------------
 
   /**
-   * Weak-key map of RelOptPlanner to ConversionData. The idea is that when
-   * the planner goes away, so does the map entry.
+   * Weak-key cache of RelOptPlanner to ConversionData. The idea is that when
+   * the planner goes away, so does the cache entry.
    */
-  private final WeakHashMap<RelOptPlanner, ConversionData>
-  plannerConversionMap =
-      new WeakHashMap<RelOptPlanner, ConversionData>();
+  private final LoadingCache<RelOptPlanner, ConversionData> conversionCache =
+      CacheBuilder.newBuilder().weakKeys().build(
+          new CacheLoader<RelOptPlanner, ConversionData>() {
+            public ConversionData load(@Nonnull RelOptPlanner key) {
+              return new ConversionData();
+            }
+          });
 
   //~ Constructors -----------------------------------------------------------
 
@@ -198,13 +206,7 @@ public boolean canConvert(
   }
 
   private ConversionData getConversionData(RelOptPlanner planner) {
-    ConversionData conversionData = plannerConversionMap.get(planner);
-    if (conversionData == null) {
-      // Create new, empty ConversionData
-      conversionData = new ConversionData();
-      plannerConversionMap.put(planner, conversionData);
-    }
-    return conversionData;
+    return conversionCache.getUnchecked(planner);
   }
 
   //~ Inner Classes ----------------------------------------------------------
diff --git a/core/src/main/java/org/apache/calcite/prepare/CalciteCatalogReader.java b/core/src/main/java/org/apache/calcite/prepare/CalciteCatalogReader.java
index 75fca834b9e6..8348694b04a5 100644
--- a/core/src/main/java/org/apache/calcite/prepare/CalciteCatalogReader.java
+++ b/core/src/main/java/org/apache/calcite/prepare/CalciteCatalogReader.java
@@ -154,7 +154,7 @@ private Collection<Function> getFunctionsFrom(List<String> names) {
     return functions2;
   }
 
-  private CalciteSchema getSchema(Iterable<String> schemaNames) {
+  protected CalciteSchema getSchema(Iterable<String> schemaNames) {
     CalciteSchema schema = rootSchema;
     for (String schemaName : schemaNames) {
       schema = schema.getSubSchema(schemaName, caseSensitive);
diff --git a/example/csv/pom.xml b/example/csv/pom.xml
index 9e125815a55a..453cff3f772f 100644
--- a/example/csv/pom.xml
+++ b/example/csv/pom.xml
@@ -20,12 +20,12 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite-example</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <artifactId>calcite-example-csv</artifactId>
   <packaging>jar</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
   <name>Calcite Example CSV</name>
   <description>An example Calcite provider that reads CSV files</description>
 
diff --git a/example/pom.xml b/example/pom.xml
index 9db037ebfe2d..c89b1c13f550 100644
--- a/example/pom.xml
+++ b/example/pom.xml
@@ -20,13 +20,13 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <!-- The basics. -->
   <artifactId>calcite-example</artifactId>
   <packaging>pom</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
   <name>Calcite Examples</name>
   <description>Calcite examples</description>
 
diff --git a/linq4j/pom.xml b/linq4j/pom.xml
index 5f61f5b5c39a..94e96ddf7e78 100644
--- a/linq4j/pom.xml
+++ b/linq4j/pom.xml
@@ -20,12 +20,12 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <artifactId>calcite-linq4j</artifactId>
   <packaging>jar</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
   <name>Calcite Linq4j</name>
   <description>Calcite APIs for LINQ (Language-Integrated Query) in Java</description>
 
diff --git a/mongodb/pom.xml b/mongodb/pom.xml
index 3bb5f9adac22..dff19b1de882 100644
--- a/mongodb/pom.xml
+++ b/mongodb/pom.xml
@@ -20,12 +20,12 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <artifactId>calcite-mongodb</artifactId>
   <packaging>jar</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
   <name>Calcite MongoDB</name>
   <description>MongoDB adapter for Calcite</description>
 
diff --git a/plus/pom.xml b/plus/pom.xml
index dd5d8c4321ac..5d5c27b8f45a 100644
--- a/plus/pom.xml
+++ b/plus/pom.xml
@@ -20,12 +20,12 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <artifactId>calcite-plus</artifactId>
   <packaging>jar</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
   <name>Calcite Plus</name>
   <description>Miscellaneous extras for Calcite</description>
 
diff --git a/pom.xml b/pom.xml
index 1591e13e42eb..a301e3489418 100644
--- a/pom.xml
+++ b/pom.xml
@@ -27,7 +27,7 @@ limitations under the License.
   <groupId>org.apache.calcite</groupId>
   <artifactId>calcite</artifactId>
   <packaging>pom</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
 
   <!-- More project information. -->
   <name>Calcite</name>
@@ -88,34 +88,34 @@ limitations under the License.
       <dependency>
         <groupId>org.apache.calcite</groupId>
         <artifactId>calcite-avatica</artifactId>
-        <version>1.4.0-drill-r19</version>
+        <version>1.4.0-drill-r20-test</version>
       </dependency>
       <dependency>
         <groupId>org.apache.calcite</groupId>
         <artifactId>calcite-avatica</artifactId>
-        <version>1.4.0-drill-r19</version>
+        <version>1.4.0-drill-r20-test</version>
         <type>test-jar</type>
       </dependency>
       <dependency>
         <groupId>org.apache.calcite</groupId>
         <artifactId>calcite-avatica-server</artifactId>
-        <version>1.4.0-drill-r19</version>
+        <version>1.4.0-drill-r20-test</version>
       </dependency>
       <dependency>
         <groupId>org.apache.calcite</groupId>
         <artifactId>calcite-core</artifactId>
-        <version>1.4.0-drill-r19</version>
+        <version>1.4.0-drill-r20-test</version>
       </dependency>
       <dependency>
         <groupId>org.apache.calcite</groupId>
         <artifactId>calcite-core</artifactId>
         <type>test-jar</type>
-        <version>1.4.0-drill-r19</version>
+        <version>1.4.0-drill-r20-test</version>
       </dependency>
       <dependency>
         <groupId>org.apache.calcite</groupId>
         <artifactId>calcite-linq4j</artifactId>
-        <version>1.4.0-drill-r19</version>
+        <version>1.4.0-drill-r20-test</version>
       </dependency>
 
       <!-- Now third-party dependencies, sorted by groupId and artifactId. -->
diff --git a/spark/pom.xml b/spark/pom.xml
index ba9fd6138ff0..73a070737b08 100644
--- a/spark/pom.xml
+++ b/spark/pom.xml
@@ -20,12 +20,12 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <artifactId>calcite-spark</artifactId>
   <packaging>jar</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
   <name>Calcite Spark</name>
 
   <properties>
diff --git a/splunk/pom.xml b/splunk/pom.xml
index e14bafe20848..45ac0406e7af 100644
--- a/splunk/pom.xml
+++ b/splunk/pom.xml
@@ -20,12 +20,12 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <artifactId>calcite-splunk</artifactId>
   <packaging>jar</packaging>
-  <version>1.4.0-drill-r19</version>
+  <version>1.4.0-drill-r20-test</version>
   <name>Calcite Splunk</name>
   <description>Splunk adapter for Calcite; also a JDBC driver for Splunk</description>
 
diff --git a/ubenchmark/pom.xml b/ubenchmark/pom.xml
index 997252537be5..009b8be94abd 100644
--- a/ubenchmark/pom.xml
+++ b/ubenchmark/pom.xml
@@ -20,7 +20,7 @@ limitations under the License.
   <parent>
     <groupId>org.apache.calcite</groupId>
     <artifactId>calcite</artifactId>
-    <version>1.4.0-drill-r19</version>
+    <version>1.4.0-drill-r20-test</version>
   </parent>
 
   <properties>