presto-spi/src/main/java/io/prestosql/spi/block/MapHashTables.java/MapHashTables/buildHashTable
class MapHashTables:    synchronized void buildHashTable(Block keyBlock, int keyOffset, int keyCount)
    {
        int[] hashTables = this.hashTables;
        if (hashTables == null) {
            throw new IllegalStateException("hashTables not set");
        }

        buildHashTableInternal(keyBlock, keyOffset, keyCount, hashTables);
        this.hashTables = hashTables;
    }