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/*
 * 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 io.trino.operator.scalar;

import io.trino.spi.block.Block;
import io.trino.spi.block.BlockBuilder;
import io.trino.spi.function.Convention;
import io.trino.spi.function.Description;
import io.trino.spi.function.OperatorDependency;
import io.trino.spi.function.ScalarFunction;
import io.trino.spi.function.SqlType;
import io.trino.spi.function.TypeParameter;
import io.trino.spi.type.Type;
import io.trino.type.BlockTypeOperators.BlockPositionHashCode;
import io.trino.type.BlockTypeOperators.BlockPositionIsIdentical;

import static io.trino.spi.function.InvocationConvention.InvocationArgumentConvention.BLOCK_POSITION;
import static io.trino.spi.function.InvocationConvention.InvocationReturnConvention.FAIL_ON_NULL;
import static io.trino.spi.function.OperatorType.HASH_CODE;
import static io.trino.spi.function.OperatorType.IDENTICAL;

@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,
            @OperatorDependency(
                    operator = IDENTICAL,
                    argumentTypes = {"E", "E"},
                    convention = @Convention(arguments = {BLOCK_POSITION, BLOCK_POSITION}, result = FAIL_ON_NULL)) BlockPositionIsIdentical identicalOperator,
            @OperatorDependency(
                    operator = HASH_CODE,
                    argumentTypes = "E",
                    convention = @Convention(arguments = BLOCK_POSITION, result = FAIL_ON_NULL)) BlockPositionHashCode elementHashCode,
            @SqlType("array(E)") Block leftArray,
            @SqlType("array(E)") Block rightArray)
    {
        int leftPositionCount = leftArray.getPositionCount();
        int rightPositionCount = rightArray.getPositionCount();

        if (leftPositionCount == 0 || rightPositionCount == 0) {
            return leftArray;
        }

        BlockSet set = new BlockSet(type, identicalOperator, elementHashCode, rightPositionCount + leftPositionCount);
        for (int i = 0; i < rightPositionCount; i++) {
            set.add(rightArray, i);
        }
        BlockBuilder distinctElementBlockBuilder = type.createBlockBuilder(null, leftPositionCount);
        for (int i = 0; i < leftPositionCount; i++) {
            if (set.add(leftArray, i)) {
                type.appendTo(leftArray, i, distinctElementBlockBuilder);
            }
        }
        return distinctElementBlockBuilder.build();
    }
}




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