写一段Murmurhash3的sql代码
时间: 2024-03-13 13:44:28 浏览: 28
MurmurHash3是一种非加密哈希函数,常用于哈希表、分布式系统等场景。以下是一个使用MurmurHash3进行哈希的SQL代码示例:
```sql
CREATE FUNCTION murmurhash3(IN input TEXT, IN seed INTEGER)
RETURNS INTEGER
DETERMINISTIC
BEGIN
DECLARE h1, k1, c1, c2, r1, r2, m, n INTEGER;
DECLARE i, len INTEGER;
DECLARE tail VARBINARY(4);
SET len = CHAR_LENGTH(input);
SET m = 0x5bd1e995;
SET r1 = 15;
SET r2 = 13;
SET n = 4;
SET c1 = 0x85ebca6b;
SET c2 = 0xc2b2ae35;
SET h1 = seed;
SET tail = SUBSTRING(CONCAT(input, CHAR(0) * (n - MOD(len, n))), -n);
SET i = 1;
WHILE i <= len DO
SET k1 = ORD(SUBSTRING(input, i, 1));
SET k1 = k1 + BIT_SHIFTLEFT(ORD(SUBSTRING(input, i + 1, 1)), 8);
SET k1 = k1 + BIT_SHIFTLEFT(ORD(SUBSTRING(input, i + 2, 1)), 16);
SET k1 = k1 + BIT_SHIFTLEFT(ORD(SUBSTRING(input, i + 3, 1)), 24);
SET k1 = k1 * m;
SET k1 = BIT_XOR(k1, BIT_SHIFTRIGHT(k1, r1));
SET k1 = k1 * m;
SET h1 = BIT_XOR(h1, k1);
SET h1 = BIT_XOR(h1, BIT_SHIFTRIGHT(h1, r2));
SET h1 = h1 * m;
SET h1 = BIT_XOR(h1, BIT_SHIFTRIGHT(h1, 16));
SET i = i + n;
END WHILE;
SET k1 = 0;
IF MOD(len, n) = 3 THEN
SET k1 = k1 + BIT_SHIFTLEFT(ORD(SUBSTRING(input, len - 1, 1)), 16);
END IF;
IF MOD(len, n) >= 2 THEN
SET k1 = k1 + BIT_SHIFTLEFT(ORD(SUBSTRING(input, len, 1)), 8);
END IF;
SET k1 = k1 + ORD(SUBSTRING(tail, 1, 1));
SET k1 = k1 * m;
SET k1 = BIT_XOR(k1, BIT_SHIFTRIGHT(k1, r1));
SET k1 = k1 * m;
SET h1 = BIT_XOR(h1, k1);
SET h1 = BIT_XOR(h1, BIT_SHIFTRIGHT(h1, r2));
SET h1 = h1 * m;
SET h1 = BIT_XOR(h1, BIT_SHIFTRIGHT(h1, 16));
RETURN h1;
END;
```
该函数接受两个参数:待哈希的字符串和种子值,返回一个整数值作为哈希结果。在该函数中,使用了一些SQL语法中的函数和运算符,例如`ORD`函数可以获取字符的ASCII码,`BIT_XOR`可以进行按位异或运算,`BIT_SHIFTLEFT`和`BIT_SHIFTRIGHT`可以进行位移运算等。
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