MySQL - 我應該使用哪種哈希算法？

Question

我有一個360000字（條目）很大的韻數據庫。每個單詞都有一個類別（例如：'表單'和'見面'具有類別'eet'）。查詢合適的押韻是我的網站空間有點慢，所以我想通過將類別加密成只有數字的散列來加速它。 （我聽說速度更快，是嗎？:)

我應該使用哪種散列算法來加密單個字符串？它應該只包含數字。

或者你有其他建議來加快數據庫查詢嗎？

謝謝！

Answer 1

也許你可以實現levenshtein algorithm到MySQL作爲存儲功能，下面是一個例子，希望它有助於：

DELIMITER // 
CREATE FUNCTION levenshtein(s1 VARCHAR(255), s2 VARCHAR(255)) 
    RETURNS INT 
    DETERMINISTIC 
    BEGIN 
    DECLARE s1_len, s2_len, i, j, c, c_temp, cost INT; 
    DECLARE s1_char CHAR; 
    -- max strlen=255 
    DECLARE cv0, cv1 VARBINARY(256); 
    SET s1_len = CHAR_LENGTH(s1), s2_len = CHAR_LENGTH(s2), cv1 = 0x00, j = 1, i = 1, c = 0; 
    IF s1 = s2 THEN 
     RETURN 0; 
    ELSEIF s1_len = 0 THEN 
     RETURN s2_len; 
    ELSEIF s2_len = 0 THEN 
     RETURN s1_len; 
    ELSE 
     WHILE j <= s2_len DO 
     SET cv1 = CONCAT(cv1, UNHEX(HEX(j))), j = j + 1; 
     END WHILE; 
     WHILE i <= s1_len DO 
     SET s1_char = SUBSTRING(s1, i, 1), c = i, cv0 = UNHEX(HEX(i)), j = 1; 
     WHILE j <= s2_len DO 
      SET c = c + 1; 
      IF s1_char = SUBSTRING(s2, j, 1) THEN 
      SET cost = 0; ELSE SET cost = 1; 
      END IF; 
      SET c_temp = CONV(HEX(SUBSTRING(cv1, j, 1)), 16, 10) + cost; 
      IF c > c_temp THEN SET c = c_temp; END IF; 
      SET c_temp = CONV(HEX(SUBSTRING(cv1, j+1, 1)), 16, 10) + 1; 
      IF c > c_temp THEN 
       SET c = c_temp; 
      END IF; 
      SET cv0 = CONCAT(cv0, UNHEX(HEX(c))), j = j + 1; 
     END WHILE; 
     SET cv1 = cv0, i = i + 1; 
     END WHILE; 
    END IF; 
    RETURN c; 
    END; 

來源http://www.artfulsoftware.com/infotree/queries.php#552（固定加入DELIMITER //）

測試示例腳本

<?php 
//I inserted these test words into a test database 
$words = 'back, lack, pack, rack, sack, tack, yak, black, knack, quack, slack, smack, snack, stack, track, whack, attack,bale, fail, hail, mail, male, nail, pail, tale, rail, sail, stale, scale, snail, whale, detail, email,air, bare, care, chair, dare, fair, hair, pair, rare, wear, chair, flare, stare, scare, share, spare, square, there, where, aware, beware, compare, declare, despair, prepare, repair, unfair,ache, bake, fake, lake, make, rake, take, brake, break, flake, quake, snake, steak, awake, mistake,all, ball, call, doll, hall, fall, tall, crawl, small, baseball, football,an, can, fan, man, pan, ran, tan, van, plan, scan, span, began,and, band, hand, land, sand, bland, command, demand, expand, stand, understand,cap, gap, map, nap, tap, zap, chap, clap, flap, slap, snap, strap, trap, wrap,are, bar, car, far, jar, tar, star, scar, afar, guitar,at, bat, fat, mat, pat, rat, sat, flat, that, splat, combat,ate, date, fate, mate, late, gate, rate, wait, crate, great, plate, skate, slate, state, straight, trait, weight, create,bed, dead, fed, head, led, read, red, said, bread, fled, spread, thread, tread, instead,bell, fell, sell, well, yell, shell, smell, spell, farewell, hotel, motel,den, hen, men, pen, ten, glen, then, when, wren, again,bet, get, jet, let, met, pet, set, vet, wet, yet, threat, barrette, reset, upset,bin, chin, in, pin, tin, grin, thin, twin, skin, begin, within,king, ring, sing, wing, zing, bring, cling, fling, sling, spring, sting, string, swing, thing,bit, fit, hit, it, kit, lit, pit, sit, flit, knit, quit, skit, slit, spit, split, admit, commit, permit,bite, kite, bright, fight, fright, knight, night, might, right, tight, white, write, delight, tonight,go, hoe, low, mow, row, sew, toe, blow, crow, dough, flow, know, glow, grow, know, show, slow, snow, stow, though, throw, ago, although, below,cot, dot, got, hot, lot, not, pot, rot, tot, bought, fought, knot, taught, shot, spot, squat, forgot,crowned, found, ground, hound, mound, pound, round, sound, wound, around, surround,bows, hose, nose, rose, toes, blows, flows, froze, grows, those,cub, rub, sub, tub, club, stub, scrub, shrub ,bun, fun, gun, one, run, son, sun, ton, won, done, none, begun, outdone, undone'; 

//A Class for db connection 
Class DB{ 
    private $db; 

    function __construct($host,$dbname,$user,$pass){ 
     $this->dbhost = $host; 
     $this->dbname = $dbname; 
     $this->dbuser = $user; 
     $this->dbpass = $pass; 
    } 

    private function connect(){ 
     if (!$this->db instanceof PDO){ 
      $this->db = new PDO('mysql:dbname='.$this->dbname.';host='.$this->dbhost, $this->dbuser, $this->dbpass); 
      $this->db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); 
     } 
    } 

    //A Model method for the levenshtein_query. 
    public function levenshtein_query($word,$dist){ 
     $this->connect(); 
     $sql = "SELECT `word` FROM `words` WHERE levenshtein(:word ,`word`) BETWEEN 0 AND $dist"; 
     $statement = $this->db->prepare($sql); 
     $statement->bindParam(':word', $word, PDO::PARAM_STR); 
     $statement->execute(); 
     return $statement->fetchAll(PDO::FETCH_ASSOC); 
    } 
} 

//ini the model class 
$model = new DB('localhost','test_db','root',''); 

//The Word posted 
$word = 'eet'; 
$result = $model->levenshtein_query($word,1); 

print_r($result); 
/* 
//The Result 
Array 
(
    [0] => Array 
     (
      [word] => bet 
     ) 

    [1] => Array 
     (
      [word] => get 
     ) 

    [2] => Array 
     (
      [word] => jet 
     ) 

    [3] => Array 
     (
      [word] => let 
     ) 

    [4] => Array 
     (
      [word] => met 
     ) 

    [5] => Array 
     (
      [word] => pet 
     ) 

    [6] => Array 
     (
      [word] => set 
     ) 

    [7] => Array 
     (
      [word] => vet 
     ) 

    [8] => Array 
     (
      [word] => wet 
     ) 

    [9] => Array 
     (
      [word] => yet 
     ) 

    [10] => Array 
     (
      [word] => meet 
     ) 

) 

*/ 

也許它的某些interes噸...