Fallback vectorization for FunctionExpr and BaseMacroFunctionExpr.

This patch adds FallbackVectorProcessor, a processor that adapts non-vectorizable
operations into vectorizable ones. It is used in FunctionExpr and BaseMacroFunctionExpr.

In addition:

- Identifiers are updated to offer getObjectVector for ARRAY and COMPLEX in addition
  to STRING. ExprEvalObjectVector is updated to offer ARRAY and COMPLEX as well.

- In SQL tests, cannotVectorize now fails tests if an exception is not thrown. This makes
  it easier to identify tests that can now vectorize.

- Fix a null-matcher bug in StringObjectVectorValueMatcher.

processing/src/main/java/org/apache/druid/math/expr/ExprMacroTable.java

@@ -25,6 +25,8 @@
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Maps;
 import org.apache.druid.java.util.common.StringUtils;
+import org.apache.druid.math.expr.vector.ExprVectorProcessor;
+import org.apache.druid.math.expr.vector.FallbackVectorProcessor;
 
 import javax.annotation.Nullable;
 import java.util.Collections;
@@ -158,6 +160,18 @@ public BindingAnalysis analyzeInputs()
       return analyzeInputsSupplier.get();
     }
 
+    @Override
+    public boolean canVectorize(InputBindingInspector inspector)
+    {
+      return getOutputType(inspector) != null && inspector.canVectorize(args);
+    }
+
+    @Override
+    public <T> ExprVectorProcessor<T> asVectorProcessor(VectorInputBindingInspector inspector)
+    {
+      return FallbackVectorProcessor.create(macro, args, inspector);
+    }
+
     /**
      * Implemented by subclasses to provide the value for {@link #analyzeInputs()}, which uses a memoized supplier.
      */

processing/src/main/java/org/apache/druid/math/expr/FunctionalExpr.java

@@ -24,6 +24,7 @@
 import org.apache.druid.error.DruidException;
 import org.apache.druid.java.util.common.StringUtils;
 import org.apache.druid.math.expr.vector.ExprVectorProcessor;
+import org.apache.druid.math.expr.vector.FallbackVectorProcessor;
 import org.apache.druid.segment.column.Types;
 
 import javax.annotation.Nullable;
@@ -223,13 +224,18 @@ public ExprEval eval(ObjectBinding bindings)
   @Override
   public boolean canVectorize(InputBindingInspector inspector)
   {
-    return function.canVectorize(inspector, args);
+    return function.canVectorize(inspector, args)
+           || (getOutputType(inspector) != null && inspector.canVectorize(args));
   }
 
   @Override
   public ExprVectorProcessor<?> asVectorProcessor(VectorInputBindingInspector inspector)
   {
-    return function.asVectorProcessor(inspector, args);
+    if (function.canVectorize(inspector, args)) {
+      return function.asVectorProcessor(inspector, args);
+    } else {
+      return FallbackVectorProcessor.create(function, args, inspector);
+    }
   }
 
   @Override

processing/src/main/java/org/apache/druid/math/expr/vector/CastToStringVectorProcessor.java

@@ -39,7 +39,7 @@ public ExprEvalVector<Object[]> evalVector(Expr.VectorInputBinding bindings)
     for (int i = 0; i < objects.length; i++) {
       output[i] = Evals.asString(objects[i]);
     }
-    return new ExprEvalObjectVector(output);
+    return new ExprEvalObjectVector(output, ExpressionType.STRING);
   }
 
   @Override

processing/src/main/java/org/apache/druid/math/expr/vector/ExprEvalObjectVector.java

@@ -20,8 +20,10 @@
 package org.apache.druid.math.expr.vector;
 
 import org.apache.druid.common.config.NullHandling;
+import org.apache.druid.error.DruidException;
 import org.apache.druid.math.expr.Evals;
 import org.apache.druid.math.expr.ExprEval;
+import org.apache.druid.math.expr.ExprType;
 import org.apache.druid.math.expr.ExpressionType;
 
 import javax.annotation.Nullable;
@@ -36,9 +38,17 @@ public final class ExprEvalObjectVector extends ExprEvalVector<Object[]>
   @Nullable
   private boolean[] numericNulls;
 
-  public ExprEvalObjectVector(Object[] values)
+  private final ExpressionType type;
+
+  public ExprEvalObjectVector(Object[] values, ExpressionType type)
   {
     super(values, null);
+    this.type = type;
+
+    if (type.isNumeric()) {
+      // Cannot use ExprEvalObjectSelector on types that are innately numbers.
+      throw DruidException.defensive("Expression of type[%s] is numeric", type);
+    }
   }
 
   private void computeNumbers()
@@ -47,16 +57,25 @@ private void computeNumbers()
       longs = new long[values.length];
       doubles = new double[values.length];
       numericNulls = new boolean[values.length];
+      boolean isString = type.is(ExprType.STRING);
       for (int i = 0; i < values.length; i++) {
-        Number n = ExprEval.computeNumber(Evals.asString(values[i]));
-        if (n != null) {
-          longs[i] = n.longValue();
-          doubles[i] = n.doubleValue();
-          numericNulls[i] = false;
+        if (isString) {
+          Number n = ExprEval.computeNumber(Evals.asString(values[i]));
+          if (n != null) {
+            longs[i] = n.longValue();
+            doubles[i] = n.doubleValue();
+            numericNulls[i] = false;
+          } else {
+            longs[i] = 0L;
+            doubles[i] = 0.0;
+            numericNulls[i] = NullHandling.sqlCompatible();
+          }
         } else {
-          longs[i] = 0L;
-          doubles[i] = 0.0;
-          numericNulls[i] = NullHandling.sqlCompatible();
+          // ARRAY, COMPLEX
+          final ExprEval<?> valueEval = ExprEval.bestEffortOf(values[i]);
+          longs[i] = valueEval.asLong();
+          doubles[i] = valueEval.asDouble();
+          numericNulls[i] = valueEval.isNumericNull();
         }
       }
     }
@@ -73,7 +92,7 @@ public boolean[] getNullVector()
   @Override
   public ExpressionType getType()
   {
-    return ExpressionType.STRING;
+    return type;
   }
 
   @Override