/*
 * Licensed 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 com.facebook.presto.operator.scalar;

import com.facebook.presto.common.block.Block;
import com.facebook.presto.common.block.BlockBuilder;
import com.facebook.presto.common.type.Type;
import com.facebook.presto.operator.aggregation.TypedSet;
import com.facebook.presto.spi.function.Description;
import com.facebook.presto.spi.function.ScalarFunction;
import com.facebook.presto.spi.function.SqlType;
import com.facebook.presto.spi.function.TypeParameter;

@ScalarFunction("array_except")
@Description("Returns an array of elements that are in the first array but not the second, without duplicates.")
public final class ArrayExceptFunction
{
    private ArrayExceptFunction() {}

    @TypeParameter("E")
    @SqlType("array(E)")
    public static Block except(
            @TypeParameter("E") Type type,
            @SqlType("array(E)") Block leftArray,
            @SqlType("array(E)") Block rightArray)
    {
        int leftPositionCount = leftArray.getPositionCount();
        int rightPositionCount = rightArray.getPositionCount();

        if (leftPositionCount == 0) {
            return leftArray;
        }
        TypedSet typedSet = new TypedSet(type, leftPositionCount + rightPositionCount, "array_except");
        BlockBuilder distinctElementBlockBuilder = type.createBlockBuilder(null, leftPositionCount);
        for (int i = 0; i < rightPositionCount; i++) {
            typedSet.add(rightArray, i);
        }
        for (int i = 0; i < leftPositionCount; i++) {
            if (typedSet.add(leftArray, i)) {
                type.appendTo(leftArray, i, distinctElementBlockBuilder);
            }
        }
        return distinctElementBlockBuilder.build();
    }
}

@@ -652,62 +652,8 @@
 ck;%0A
-import com.facebook.presto.common.block.BlockBuilder;%0A
 impo
@@ -737,24 +737,33 @@
 aggregation.
+Optimized
 TypedSet;%0Aim
@@ -974,16 +974,51 @@
 meter;%0A%0A
+import static java.lang.Math.max;%0A%0A
 @ScalarF
@@ -1669,24 +1669,25 @@
       %7D%0A
+%0A
         
 TypedSet
@@ -1678,16 +1678,25 @@
         
+Optimized
 TypedSet
@@ -1711,16 +1711,25 @@
 t = new 
+Optimized
 TypedSet
@@ -1735,16 +1735,20 @@
 t(type, 
+max(
 leftPosi
@@ -1760,10 +1760,9 @@
 ount
- +
+,
  rig
@@ -1780,207 +1780,34 @@
 ount
-, %22array_except%22);%0A        BlockBuilder distinctElementBlockBuilder = type.createBlockBuilder(null, leftPositionCount);%0A        for (int i = 0; i %3C rightPositionCount; i++) %7B%0A            typedSet.add
+));%0A        typedSet.union
 (rig
@@ -1813,19 +1813,16 @@
 ghtArray
-, i
 );%0A     
@@ -1828,256 +1828,69 @@
     
-%7D%0A        for (int i = 0; i %3C leftPositionCount; i++) %7B%0A            if (typedSet.add(leftArray, i)) %7B%0A                type.appendTo(leftArray, i, distinctElementBlockBuilder);%0A            %7D%0A        %7D%0A        return distinctElementBlockBuilder.build
+typedSet.except(leftArray);%0A%0A        return typedSet.getBlock
 ();%0A

Optimize array_except by using OptimizedTypedSet