xxhash_64
description
Syntax
BIGINT XXHASH_64(VARCHAR input, ...)
返回输入字符串的64位xxhash值。
注：在计算hash值时，更推荐使用xxhash_64，而不是murmur_hash3_64。
example
mysql> select xxhash_64(NULL);
+-----------------+
| xxhash_64(NULL) |
+-----------------+
| NULL |
+-----------------+
mysql> select xxhash_64("hello");
+----------------------+
| xxhash_64('hello') |
+----------------------+
| -7685981735718036227 |
+----------------------+
mysql> select xxhash_64("hello", "world");
+-----------------------------+
| xxhash_64('hello', 'world') |
+-----------------------------+
| 7001965798170371843 |
+-----------------------------+benchmark
通过TPCH Benchmark测试发现，xxhash_64相比murmur_hash3_64来说性能大幅提升，因此在需要计算hash值的场景下，更推荐使用xxhash_64。
mysql> select count(murmur_hash3_64(l_comment)) from lineitem;
+-----------------------------------+
| count(murmur_hash3_64(l_comment)) |
+-----------------------------------+
| 600037902 |
+-----------------------------------+
1 row in set (17.18 sec)
mysql> select count(xxhash_64(l_comment)) from lineitem;
+-----------------------------+
| count(xxhash_64(l_comment)) |
+-----------------------------+
| 600037902 |
+-----------------------------+
1 row in set (8.41 sec)keywords
XXHASH_64,HASH