presto-spi/src/main/java/io/prestosql/spi/block/MapBlockBuilder.java/MapBlockBuilder/MapBlockBuilder
class MapBlockBuilder:    private MapBlockBuilder(
            MapType mapType,
            @Nullable BlockBuilderStatus blockBuilderStatus,
            BlockBuilder keyBlockBuilder,
            BlockBuilder valueBlockBuilder,
            int[] offsets,
            boolean[] mapIsNull)
    {
        super(mapType);

        this.blockBuilderStatus = blockBuilderStatus;

        this.positionCount = 0;
        this.offsets = requireNonNull(offsets, "offsets is null");
        this.mapIsNull = requireNonNull(mapIsNull, "mapIsNull is null");
        this.keyBlockBuilder = requireNonNull(keyBlockBuilder, "keyBlockBuilder is null");
        this.valueBlockBuilder = requireNonNull(valueBlockBuilder, "valueBlockBuilder is null");

        int[] hashTable = new int[mapIsNull.length * HASH_MULTIPLIER];
        Arrays.fill(hashTable, -1);
        this.hashTables = new MapHashTables(mapType, Optional.of(hashTable));
    }