presto-main/src/main/java/io/prestosql/operator/aggregation/KeyValuePairs.java/KeyValuePairs/KeyValuePairs
class KeyValuePairs:    public KeyValuePairs(Type keyType, Type valueType)
    {
        this.keyType = requireNonNull(keyType, "keyType is null");
        this.valueType = requireNonNull(valueType, "valueType is null");
        keyBlockBuilder = this.keyType.createBlockBuilder(null, EXPECTED_ENTRIES, expectedValueSize(keyType, EXPECTED_ENTRY_SIZE));
        valueBlockBuilder = this.valueType.createBlockBuilder(null, EXPECTED_ENTRIES, expectedValueSize(valueType, EXPECTED_ENTRY_SIZE));
        hashCapacity = arraySize(EXPECTED_ENTRIES, FILL_RATIO);
        this.maxFill = calculateMaxFill(hashCapacity);
        this.hashMask = hashCapacity - 1;
        keyPositionByHash = new int[hashCapacity];
        Arrays.fill(keyPositionByHash, EMPTY_SLOT);
    }