WIP: core nullability

core/src/main/java/org/apache/calcite/adapter/clone/ColumnLoader.java

@@ -196,7 +196,7 @@ public int size() {
         // We have discovered a the first unique key in the table.
         sort[0] = pair.i;
         final Comparable[] values =
-            valueSet.values.toArray(new Comparable[list.size()]);
+            valueSet.values.toArray(new Comparable[0]);
         final Kev[] kevs = new Kev[list.size()];
         for (int i = 0; i < kevs.length; i++) {
           kevs[i] = new Kev(i, values[i]);

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

@@ -48,6 +48,8 @@
 import com.google.common.collect.Multimap;
 import com.google.common.collect.Ordering;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
+
 import java.sql.Connection;
 import java.sql.DatabaseMetaData;
 import java.sql.ResultSet;
@@ -481,15 +483,15 @@ protected Map<String, RelProtoDataType> getTypes() {
     return ImmutableMap.of();
   }
 
-  @Override public RelProtoDataType getType(String name) {
+  @Override public @Nullable RelProtoDataType getType(String name) {
     return getTypes().get(name);
   }
 
   @Override public Set<String> getTypeNames() {
     return getTypes().keySet();
   }
 
-  public Schema getSubSchema(String name) {
+  public @Nullable Schema getSubSchema(String name) {
     // JDBC does not support sub-schemas.
     return null;
   }

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

@@ -117,7 +117,7 @@ public static Function1<ResultSet, Function0<Object[]>> factory(
         try {
           return new ObjectArrayRowBuilder(
               resultSet,
-              Pair.left(list).toArray(new ColumnMetaData.Rep[list.size()]),
+              Pair.left(list).toArray(new ColumnMetaData.Rep[0]),
               Ints.toArray(Pair.right(list)));
         } catch (SQLException e) {
           throw new RuntimeException(e);

core/src/main/java/org/apache/calcite/interpreter/BindableConvention.java

@@ -24,6 +24,8 @@
 import org.apache.calcite.plan.RelTraitSet;
 import org.apache.calcite.rel.RelNode;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
+
 /**
  * Calling convention that returns results as an
  * {@link org.apache.calcite.linq4j.Enumerable} of object arrays.
@@ -52,7 +54,7 @@ public String getName() {
     return "BINDABLE";
   }
 
-  @Override public RelNode enforce(RelNode input, RelTraitSet required) {
+  @Override public @Nullable RelNode enforce(RelNode input, RelTraitSet required) {
     return null;
   }
 

core/src/main/java/org/apache/calcite/interpreter/Context.java

@@ -18,14 +18,16 @@
 
 import org.apache.calcite.DataContext;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
+
 /**
  * Context for executing a scalar expression in an interpreter.
  */
 public class Context {
   public final DataContext root;
 
   /** Values of incoming columns from all inputs. */
-  public Object[] values;
+  public Object @Nullable [] values;
 
   Context(DataContext root) {
     this.root = root;

core/src/main/java/org/apache/calcite/jdbc/CachingCalciteSchema.java

@@ -33,6 +33,8 @@
 import com.google.common.collect.ImmutableSortedMap;
 import com.google.common.collect.ImmutableSortedSet;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
+
 import java.util.Collection;
 import java.util.List;
 import java.util.Set;
@@ -50,11 +52,11 @@ class CachingCalciteSchema extends CalciteSchema {
   private boolean cache = true;
 
   /** Creates a CachingCalciteSchema. */
-  CachingCalciteSchema(CalciteSchema parent, Schema schema, String name) {
+  CachingCalciteSchema(@Nullable CalciteSchema parent, Schema schema, String name) {
     this(parent, schema, name, null, null, null, null, null, null, null, null);
   }
 
-  private CachingCalciteSchema(CalciteSchema parent, Schema schema,
+  private CachingCalciteSchema(@Nullable CalciteSchema parent, Schema schema,
       String name, NameMap<CalciteSchema> subSchemaMap,
       NameMap<TableEntry> tableMap, NameMap<LatticeEntry> latticeMap, NameMap<TypeEntry> typeMap,
       NameMultimap<FunctionEntry> functionMap, NameSet functionNames,

core/src/main/java/org/apache/calcite/jdbc/CalcitePrepare.java

@@ -50,6 +50,8 @@
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
+
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Type;
@@ -58,6 +60,8 @@
 import java.util.List;
 import java.util.Map;
 
+import static org.apache.calcite.linq4j.Nullness.assertNonNull;
+
 /**
  * API for a service that prepares statements for execution.
  */
@@ -172,7 +176,7 @@ private static SparkHandler createHandler() {
         final Class<?> clazz =
             Class.forName("org.apache.calcite.adapter.spark.SparkHandlerImpl");
         Method method = clazz.getMethod("instance");
-        return (CalcitePrepare.SparkHandler) method.invoke(null);
+        return (CalcitePrepare.SparkHandler) assertNonNull(method.invoke(null));
       } catch (ClassNotFoundException e) {
         return new TrivialSparkHandler();
       } catch (IllegalAccessException
@@ -341,7 +345,7 @@ public CalciteSignature(String sql,
         List<RelCollation> collationList,
         long maxRowCount,
         Bindable<T> bindable,
-        Meta.StatementType statementType) {
+        Meta.@Nullable StatementType statementType) {
       super(columns, sql, parameterList, internalParameters, cursorFactory,
           statementType);
       this.rowType = rowType;
@@ -372,11 +376,11 @@ public List<RelCollation> getCollationList() {
    *
    * @param <T> element type */
   class Query<T> {
-    public final String sql;
-    public final Queryable<T> queryable;
-    public final RelNode rel;
+    public final @Nullable String sql;
+    public final @Nullable Queryable<T> queryable;
+    public final @Nullable RelNode rel;
 
-    private Query(String sql, Queryable<T> queryable, RelNode rel) {
+    private Query(@Nullable String sql, @Nullable Queryable<T> queryable, @Nullable RelNode rel) {
       this.sql = sql;
       this.queryable = queryable;
       this.rel = rel;

core/src/main/java/org/apache/calcite/jdbc/CalciteSchema.java

@@ -41,6 +41,8 @@
 import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Lists;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
+
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
@@ -58,7 +60,7 @@
  */
 public abstract class CalciteSchema {
 
-  private final CalciteSchema parent;
+  private final @Nullable CalciteSchema parent;
   public final Schema schema;
   public final String name;
   /** Tables explicitly defined in this schema. Does not include tables in
@@ -70,14 +72,18 @@ public abstract class CalciteSchema {
   protected final NameSet functionNames;
   protected final NameMap<FunctionEntry> nullaryFunctionMap;
   protected final NameMap<CalciteSchema> subSchemaMap;
-  private List<? extends List<String>> path;
-
-  protected CalciteSchema(CalciteSchema parent, Schema schema,
-      String name, NameMap<CalciteSchema> subSchemaMap,
-      NameMap<TableEntry> tableMap, NameMap<LatticeEntry> latticeMap, NameMap<TypeEntry> typeMap,
-      NameMultimap<FunctionEntry> functionMap, NameSet functionNames,
-      NameMap<FunctionEntry> nullaryFunctionMap,
-      List<? extends List<String>> path) {
+  private @Nullable List<? extends List<String>> path;
+
+  protected CalciteSchema(@Nullable CalciteSchema parent, Schema schema,
+      String name,
+      @Nullable NameMap<CalciteSchema> subSchemaMap,
+      @Nullable NameMap<TableEntry> tableMap,
+      @Nullable NameMap<LatticeEntry> latticeMap,
+      @Nullable NameMap<TypeEntry> typeMap,
+      @Nullable NameMultimap<FunctionEntry> functionMap,
+      @Nullable NameSet functionNames,
+      @Nullable NameMap<FunctionEntry> nullaryFunctionMap,
+      @Nullable List<? extends List<String>> path) {
     this.parent = parent;
     this.schema = schema;
     this.name = name;
@@ -662,7 +668,7 @@ public NavigableSet<String> getTableNames() {
       return CalciteSchema.this.getTableNames();
     }
 
-    @Override public RelProtoDataType getType(String name) {
+    @Override public @Nullable RelProtoDataType getType(String name) {
       final TypeEntry entry = CalciteSchema.this.getType(name, true);
       return entry == null ? null : entry.getType();
     }
@@ -679,7 +685,7 @@ public NavigableSet<String> getFunctionNames() {
       return CalciteSchema.this.getFunctionNames();
     }
 
-    public SchemaPlus getSubSchema(String name) {
+    public @Nullable SchemaPlus getSubSchema(String name) {
       final CalciteSchema subSchema =
           CalciteSchema.this.getSubSchema(name, true);
       return subSchema == null ? null : subSchema.plus();

core/src/main/java/org/apache/calcite/jdbc/JavaCollation.java

@@ -18,6 +18,9 @@
 
 import org.apache.calcite.sql.SqlCollation;
 
+import org.checkerframework.checker.initialization.qual.UnderInitialization;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
 import java.nio.charset.Charset;
 import java.text.Collator;
 import java.util.Locale;
@@ -55,11 +58,13 @@ private static String getStrengthString(int strengthValue) {
     }
   }
 
-  @Override protected String generateCollationName(Charset charset) {
+  @Override protected String generateCollationName(
+      @UnderInitialization(SqlCollation.class) JavaCollation this,
+      Charset charset) {
     return super.generateCollationName(charset) + "$JAVA_COLLATOR";
   }
 
-  @Override public Collator getCollator() {
+  @Override public @Nullable Collator getCollator() {
     return collator;
   }
 }

core/src/main/java/org/apache/calcite/package-info.java

@@ -18,4 +18,11 @@
 /**
  * Main package for Calcite, the dynamic data management platform.
  */
+@DefaultQualifier(value = NonNull.class, locations = TypeUseLocation.FIELD)
+@DefaultQualifier(value = NonNull.class, locations = TypeUseLocation.PARAMETER)
+@DefaultQualifier(value = NonNull.class, locations = TypeUseLocation.RETURN)
 package org.apache.calcite;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
+import org.checkerframework.framework.qual.TypeUseLocation;

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

@@ -19,6 +19,8 @@
 import org.apache.calcite.rel.RelNode;
 import org.apache.calcite.rel.core.RelFactories;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
+
 /**
  * Calling convention trait.
  */
@@ -48,7 +50,7 @@ public interface Convention extends RelTrait {
    * or {@code null} if trait enforcement is not allowed or the
    * required traitSet can't be satisfied.
    */
-  default RelNode enforce(RelNode input, RelTraitSet required) {
+  default @Nullable RelNode enforce(RelNode input, RelTraitSet required) {
     throw new RuntimeException(getClass().getName()
         + "#enforce() is not implemented.");
   }

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

@@ -24,6 +24,7 @@
 import org.apache.calcite.util.CancelFlag;
 import org.apache.calcite.util.trace.CalciteTrace;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
 import org.slf4j.Logger;
 
 import java.util.List;
@@ -249,7 +250,7 @@ RelNode register(
    * @param equivRel Relational expression it is equivalent to (may be null)
    * @return Registered relational expression
    */
-  RelNode ensureRegistered(RelNode rel, RelNode equivRel);
+  RelNode ensureRegistered(RelNode rel, @Nullable RelNode equivRel);
 
   /**
    * Determines whether a relational expression has been registered.

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

@@ -550,7 +550,7 @@ public boolean matches(RelOptRuleCall call) {
    * @return Convention of the result of firing this rule, null if
    *   not known
    */
-  public Convention getOutConvention() {
+  public @Nullable Convention getOutConvention() {
     return null;
   }
 
@@ -561,7 +561,7 @@ public Convention getOutConvention() {
    * @return Trait which will be modified as a result of firing this rule,
    *   or null if the rule is not a converter rule
    */
-  public RelTrait getOutTrait() {
+  public @Nullable RelTrait getOutTrait() {
     return null;
   }
 

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

@@ -26,6 +26,7 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 
+import org.checkerframework.checker.nullness.qual.Nullable;
 import org.slf4j.Logger;
 
 import java.util.HashMap;
@@ -54,7 +55,7 @@ public abstract class RelOptRuleCall {
   public final RelOptRule rule;
   public final RelNode[] rels;
   private final RelOptPlanner planner;
-  private final List<RelNode> parents;
+  private final @Nullable List<RelNode> parents;
 
   //~ Constructors -----------------------------------------------------------
 
@@ -77,7 +78,7 @@ protected RelOptRuleCall(
       RelOptRuleOperand operand,
       RelNode[] rels,
       Map<RelNode, List<RelNode>> nodeInputs,
-      List<RelNode> parents) {
+      @Nullable List<RelNode> parents) {
     this.id = nextId++;
     this.planner = planner;
     this.operand0 = operand;
@@ -171,7 +172,7 @@ public <T extends RelNode> T rel(int ordinal) {
    * @param rel Relational expression
    * @return Children of relational expression
    */
-  public List<RelNode> getChildRels(RelNode rel) {
+  public @Nullable List<RelNode> getChildRels(RelNode rel) {
     return nodeInputs.get(rel);
   }
 
@@ -221,7 +222,7 @@ public RelMetadataQuery getMetadataQuery() {
   /**
    * Returns a list of parents of the first relational expression.
    */
-  public List<RelNode> getParents() {
+  public @Nullable List<RelNode> getParents() {
     return parents;
   }