Expressions: Add ExprMacros.

benchmarks/src/main/java/io/druid/benchmark/ExpressionBenchmark.java

@@ -31,6 +31,7 @@
 import io.druid.query.aggregation.BufferAggregator;
 import io.druid.query.aggregation.DoubleSumAggregatorFactory;
 import io.druid.query.aggregation.JavaScriptAggregatorFactory;
+import io.druid.query.expression.TestExprMacroTable;
 import io.druid.segment.ColumnSelectorFactory;
 import io.druid.segment.Cursor;
 import io.druid.segment.FloatColumnSelector;
@@ -112,7 +113,8 @@ public void setup() throws Exception
     this.expressionAggregatorFactory = new DoubleSumAggregatorFactory(
         "name",
         null,
-        "if(x>0,1.0+x,y+1)"
+        "if(x>0,1.0+x,y+1)",
+        TestExprMacroTable.INSTANCE
     );
   }
 

benchmarks/src/main/java/io/druid/benchmark/query/SqlBenchmark.java

@@ -148,6 +148,7 @@ protected Map<String, Table> getTableMap()
         Calcites.createRootSchema(druidSchema),
         walker,
         CalciteTests.createOperatorTable(),
+        CalciteTests.createExprMacroTable(),
         plannerConfig,
         new ServerConfig()
     );

common/src/main/java/io/druid/math/expr/Expr.java

@@ -20,14 +20,39 @@
 package io.druid.math.expr;
 
 import com.google.common.math.LongMath;
+import com.google.common.primitives.Ints;
 import io.druid.java.util.common.IAE;
+import io.druid.java.util.common.ISE;
 
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.util.List;
 
 /**
  */
 public interface Expr
 {
+  default boolean isLiteral()
+  {
+    // Overridden by things that are literals.
+    return false;
+  }
+
+  /**
+   * Returns the value of expr if expr is a literal, or throws an exception otherwise.
+   *
+   * @return expr's literal value
+   *
+   * @throws IllegalStateException if expr is not a literal
+   */
+  @Nullable
+  default Object getLiteralValue()
+  {
+    // Overridden by things that are literals.
+    throw new ISE("Not a literal");
+  }
+
+  @Nonnull
   ExprEval eval(ObjectBinding bindings);
 
   interface ObjectBinding
@@ -45,6 +70,12 @@ interface Visitor
 
 abstract class ConstantExpr implements Expr
 {
+  @Override
+  public boolean isLiteral()
+  {
+    return true;
+  }
+
   @Override
   public void visit(Visitor visitor)
   {
@@ -61,12 +92,20 @@ public LongExpr(Long value)
     this.value = value;
   }
 
+  @Nullable
+  @Override
+  public Object getLiteralValue()
+  {
+    return value;
+  }
+
   @Override
   public String toString()
   {
     return String.valueOf(value);
   }
 
+  @Nonnull
   @Override
   public ExprEval eval(ObjectBinding bindings)
   {
@@ -83,12 +122,20 @@ public StringExpr(String value)
     this.value = value;
   }
 
+  @Nullable
+  @Override
+  public Object getLiteralValue()
+  {
+    return value;
+  }
+
   @Override
   public String toString()
   {
     return value;
   }
 
+  @Nonnull
   @Override
   public ExprEval eval(ObjectBinding bindings)
   {
@@ -105,12 +152,20 @@ public DoubleExpr(Double value)
     this.value = value;
   }
 
+  @Nullable
+  @Override
+  public Object getLiteralValue()
+  {
+    return value;
+  }
+
   @Override
   public String toString()
   {
     return String.valueOf(value);
   }
 
+  @Nonnull
   @Override
   public ExprEval eval(ObjectBinding bindings)
   {
@@ -133,6 +188,7 @@ public String toString()
     return value;
   }
 
+  @Nonnull
   @Override
   public ExprEval eval(ObjectBinding bindings)
   {
@@ -148,11 +204,13 @@ public void visit(Visitor visitor)
 
 class FunctionExpr implements Expr
 {
+  final Function function;
   final String name;
   final List<Expr> args;
 
-  public FunctionExpr(String name, List<Expr> args)
+  public FunctionExpr(Function function, String name, List<Expr> args)
   {
+    this.function = function;
     this.name = name;
     this.args = args;
   }
@@ -163,10 +221,11 @@ public String toString()
     return "(" + name + " " + args + ")";
   }
 
+  @Nonnull
   @Override
   public ExprEval eval(ObjectBinding bindings)
   {
-    return Parser.getFunction(name).apply(args, bindings);
+    return function.apply(args, bindings);
   }
 
   @Override
@@ -203,6 +262,7 @@ class UnaryMinusExpr extends UnaryExpr
     super(expr);
   }
 
+  @Nonnull
   @Override
   public ExprEval eval(ObjectBinding bindings)
   {
@@ -237,6 +297,7 @@ class UnaryNotExpr extends UnaryExpr
     super(expr);
   }
 
+  @Nonnull
   @Override
   public ExprEval eval(ObjectBinding bindings)
   {
@@ -290,6 +351,7 @@ public BinaryEvalOpExprBase(String op, Expr left, Expr right)
     super(op, left, right);
   }
 
+  @Nonnull
   @Override
   public ExprEval eval(ObjectBinding bindings)
   {
@@ -347,7 +409,7 @@ class BinPowExpr extends BinaryEvalOpExprBase
   @Override
   protected final long evalLong(long left, long right)
   {
-    return LongMath.pow(left, (int)right);
+    return LongMath.pow(left, Ints.checkedCast(right));
   }
 
   @Override
@@ -606,6 +668,7 @@ class BinAndExpr extends BinaryOpExprBase
     super(op, left, right);
   }
 
+  @Nonnull
   @Override
   public ExprEval eval(ObjectBinding bindings)
   {
@@ -621,6 +684,7 @@ class BinOrExpr extends BinaryOpExprBase
     super(op, left, right);
   }
 
+  @Nonnull
   @Override
   public ExprEval eval(ObjectBinding bindings)
   {

common/src/main/java/io/druid/math/expr/ExprListenerImpl.java

@@ -19,6 +19,7 @@
 
 package io.druid.math.expr;
 
+import io.druid.java.util.common.RE;
 import io.druid.math.expr.antlr.ExprBaseListener;
 import io.druid.math.expr.antlr.ExprParser;
 import org.antlr.v4.runtime.tree.ParseTree;
@@ -36,11 +37,13 @@
 public class ExprListenerImpl extends ExprBaseListener
 {
   private final Map<ParseTree, Object> nodes;
+  private final ExprMacroTable macroTable;
   private final ParseTree rootNodeKey;
 
-  ExprListenerImpl(ParseTree rootNodeKey)
+  ExprListenerImpl(ParseTree rootNodeKey, ExprMacroTable macroTable)
   {
     this.rootNodeKey = rootNodeKey;
+    this.macroTable = macroTable;
     this.nodes = new HashMap<>();
   }
 
@@ -285,15 +288,22 @@ public void exitPowOpExpr(ExprParser.PowOpExprContext ctx)
   public void exitFunctionExpr(ExprParser.FunctionExprContext ctx)
   {
     String fnName = ctx.getChild(0).getText();
-    if (!Parser.hasFunction(fnName)) {
-      throw new RuntimeException("function " + fnName + " is not defined.");
+    final List<Expr> args = ctx.getChildCount() > 3
+                            ? (List<Expr>) nodes.get(ctx.getChild(2))
+                            : Collections.emptyList();
+
+    Expr expr = macroTable.get(fnName, args);
+
+    if (expr == null) {
+      // Built-in functions.
+      final Function function = Parser.getFunction(fnName);
+      if (function == null) {
+        throw new RE("function '%s' is not defined.", fnName);
+      }
+      expr = new FunctionExpr(function, fnName, args);
     }
 
-    List<Expr> args = ctx.getChildCount() > 3 ? (List<Expr>) nodes.get(ctx.getChild(2)) : Collections.<Expr>emptyList();
-    nodes.put(
-        ctx,
-        new FunctionExpr(fnName, args)
-    );
+    nodes.put(ctx, expr);
   }
 
   @Override

common/src/main/java/io/druid/math/expr/ExprMacroTable.java

@@ -0,0 +1,75 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets 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 io.druid.math.expr;
+
+import javax.annotation.Nullable;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public class ExprMacroTable
+{
+  private static final ExprMacroTable NIL = new ExprMacroTable(Collections.emptyList());
+
+  private final Map<String, ExprMacro> macroMap;
+
+  public ExprMacroTable(final List<ExprMacro> macros)
+  {
+    this.macroMap = macros.stream().collect(
+        Collectors.toMap(
+            m -> m.name().toLowerCase(),
+            m -> m
+        )
+    );
+  }
+
+  public static ExprMacroTable nil()
+  {
+    return NIL;
+  }
+
+  /**
+   * Returns an expr corresponding to a function call if this table has an entry for {@code functionName}.
+   * Otherwise, returns null.
+   *
+   * @param functionName function name
+   * @param args         function arguments
+   *
+   * @return expr for this function call, or null
+   */
+  @Nullable
+  public Expr get(final String functionName, final List<Expr> args)
+  {
+    final ExprMacro exprMacro = macroMap.get(functionName.toLowerCase());
+    if (exprMacro == null) {
+      return null;
+    }
+
+    return exprMacro.apply(args);
+  }
+
+  public interface ExprMacro
+  {
+    String name();
+
+    Expr apply(final List<Expr> args);
+  }
+}

common/src/main/java/io/druid/math/expr/Function.java

@@ -24,7 +24,6 @@
 import org.joda.time.format.DateTimeFormat;
 import org.joda.time.format.DateTimeFormatter;
 import org.joda.time.format.ISODateTimeFormat;
-import com.google.common.base.Supplier;
 
 import java.util.List;
 
@@ -36,10 +35,6 @@ interface Function
 
   ExprEval apply(List<Expr> args, Expr.ObjectBinding bindings);
 
-  // optional interface to be used when function should be created per reference in expression
-  interface FunctionFactory extends Supplier<Function>, Function {
-  }
-
   abstract class SingleParam implements Function
   {
     @Override