?? ????? ??? ???? ??? ???? ?????, ?? ??? ??? ?? ???? ?? ??? ?? ??? ???? ?? ??????.

??? ?? ???? ??? ???? ? ?? ??? ?? ??, ??? ?? ???? ???? ?? ?? ???? ??? ???? ?? ????.

??? ??? ?? ?????????. ???? MySQL 5.7.26 ????

??? ??

???? 1,000? ?? ??? ??? ?? ???? ?

??? ??? ?? ?? ? ????

??? ??? ???????

1?? ?? ???

?? ?????. ?? ?????. ??? ? ?? ?? ?? ?? ?? ???. ?????? ????? ???? ?? ??? ??? ? ????.

Create table

CREATE TABLE `user_operation_log`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` varchar(64) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `ip` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `op_data` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr1` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr2` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr3` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr4` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr5` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr6` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr7` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr8` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr9` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr10` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr11` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  `attr12` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;

Create data script

?? ??? ???? ???? ?? ????, ??? ?? ?? ??? 1000? ???? ????? ???? ?????. ?? ??? ?????

DELIMITER ;;
CREATE PROCEDURE batch_insert_log()
BEGIN
  DECLARE i INT DEFAULT 1;
  DECLARE userId INT DEFAULT 10000000;
 set @execSql = 'INSERT INTO `test`.`user_operation_log`(`user_id`, `ip`, `op_data`, `attr1`, `attr2`, `attr3`, `attr4`, `attr5`, `attr6`, `attr7`, `attr8`, `attr9`, `attr10`, `attr11`, `attr12`) VALUES';
 set @execData = '';
  WHILE i<=10000000 DO
   set @attr = "&#39;測(cè)試很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)很長(zhǎng)的屬性&#39;";
  set @execData = concat(@execData, "(", userId + i, ", &#39;10.0.69.175&#39;, &#39;用戶(hù)登錄操作&#39;", ",", @attr, ",", @attr, ",", @attr, ",", @attr, ",", @attr, ",", @attr, ",", @attr, ",", @attr, ",", @attr, ",", @attr, ",", @attr, ",", @attr, ")");
  if i % 1000 = 0
  then
     set @stmtSql = concat(@execSql, @execData,";");
    prepare stmt from @stmtSql;
    execute stmt;
    DEALLOCATE prepare stmt;
    commit;
    set @execData = "";
   else
     set @execData = concat(@execData, ",");
   end if;
  SET i=i+1;
  END WHILE;

END;;
DELIMITER ;

??? ??

? ??? ??? ????? ????: win10 ?? ?? i5, ?? ? ?? ? 500MB SSD

?? ???? ?? ? ???? ?? ??? ???? 3148000????. ???? 5G(?? ??? ??)? 38? ?? ???????. ??? ??? ?? ???? ???? ?? ?? ???? ???? ??? ? ????

SELECT count(1) FROM `user_operation_log`

?? ??: 3148000

? ?? ?? ??? ??? ????.

• 14060 ms
• 13755 ms
• 13447 ms

普通分頁(yè)查詢(xún)

MySQL 支持 LIMIT 語(yǔ)句來(lái)選取指定的條數(shù)數(shù)據(jù)， Oracle 可以使用 ROWNUM 來(lái)選取。

MySQL分頁(yè)查詢(xún)語(yǔ)法如下：

SELECT * FROM table LIMIT [offset,] rows | rows OFFSET offset

• 第一個(gè)參數(shù)指定第一個(gè)返回記錄行的偏移量
• 第二個(gè)參數(shù)指定返回記錄行的最大數(shù)目

下面我們開(kāi)始測(cè)試查詢(xún)結(jié)果：

SELECT * FROM `user_operation_log` LIMIT 10000, 10

查詢(xún)3次時(shí)間分別為：

• 59 ms
• 49 ms
• 50 ms

這樣看起來(lái)速度還行，不過(guò)是本地?cái)?shù)據(jù)庫(kù)，速度自然快點(diǎn)。

換個(gè)角度來(lái)測(cè)試

相同偏移量，不同數(shù)據(jù)量

SELECT * FROM `user_operation_log` LIMIT 10000, 10
SELECT * FROM `user_operation_log` LIMIT 10000, 100
SELECT * FROM `user_operation_log` LIMIT 10000, 1000
SELECT * FROM `user_operation_log` LIMIT 10000, 10000
SELECT * FROM `user_operation_log` LIMIT 10000, 100000
SELECT * FROM `user_operation_log` LIMIT 10000, 1000000

查詢(xún)時(shí)間如下：

從上面結(jié)果可以得出結(jié)束：數(shù)據(jù)量越大，花費(fèi)時(shí)間越長(zhǎng)

相同數(shù)據(jù)量，不同偏移量

SELECT * FROM `user_operation_log` LIMIT 100, 100
SELECT * FROM `user_operation_log` LIMIT 1000, 100
SELECT * FROM `user_operation_log` LIMIT 10000, 100
SELECT * FROM `user_operation_log` LIMIT 100000, 100
SELECT * FROM `user_operation_log` LIMIT 1000000, 100

從上面結(jié)果可以得出結(jié)束：偏移量越大，花費(fèi)時(shí)間越長(zhǎng)

SELECT * FROM `user_operation_log` LIMIT 100, 100
SELECT id, attr FROM `user_operation_log` LIMIT 100, 100

如何優(yōu)化

既然我們經(jīng)過(guò)上面一番的折騰，也得出了結(jié)論，針對(duì)上面兩個(gè)問(wèn)題：偏移大、數(shù)據(jù)量大，我們分別著手優(yōu)化

優(yōu)化偏移量大問(wèn)題

采用子查詢(xún)方式

我們可以先定位偏移位置的 id，然后再查詢(xún)數(shù)據(jù)

SELECT * FROM `user_operation_log` LIMIT 1000000, 10

SELECT id FROM `user_operation_log` LIMIT 1000000, 1

SELECT * FROM `user_operation_log` WHERE id >= (SELECT id FROM `user_operation_log` LIMIT 1000000, 1) LIMIT 10

查詢(xún)結(jié)果如下：

從上面結(jié)果得出結(jié)論：

• 第一條花費(fèi)的時(shí)間最大，第三條比第一條稍微好點(diǎn)
• 子查詢(xún)使用索引速度更快

缺點(diǎn)：只適用于id遞增的情況

id非遞增的情況可以使用以下寫(xiě)法，但這種缺點(diǎn)是分頁(yè)查詢(xún)只能放在子查詢(xún)里面

注意：某些 mysql 版本不支持在 in 子句中使用 limit，所以采用了多個(gè)嵌套select

SELECT * FROM `user_operation_log` WHERE id IN (SELECT t.id FROM (SELECT id FROM `user_operation_log` LIMIT 1000000, 10) AS t)

采用 id 限定方式

這種方法要求更高些，id必須是連續(xù)遞增，而且還得計(jì)算id的范圍，然后使用 between，sql如下

SELECT * FROM `user_operation_log` WHERE id between 1000000 AND 1000100 LIMIT 100

SELECT * FROM `user_operation_log` WHERE id >= 1000000 LIMIT 100

查詢(xún)結(jié)果如下：

從結(jié)果可以看出這種方式非?？?/p>

注意：這里的 LIMIT 是限制了條數(shù)，沒(méi)有采用偏移量

優(yōu)化數(shù)據(jù)量大問(wèn)題

返回結(jié)果的數(shù)據(jù)量也會(huì)直接影響速度

SELECT * FROM `user_operation_log` LIMIT 1, 1000000

SELECT id FROM `user_operation_log` LIMIT 1, 1000000

SELECT id, user_id, ip, op_data, attr1, attr2, attr3, attr4, attr5, attr6, attr7, attr8, attr9, attr10, attr11, attr12 FROM `user_operation_log` LIMIT 1, 1000000

查詢(xún)結(jié)果如下：

???? ?? ??? ?? ???? ?? ??? ? ??? ?? ???? ? ? ????.

? ??? ? ?? ?? ??? ?? ?????. ?? ??? ??? ?? ????. ?? ?? ??? ???? *? ?? ????

MySQL ??? ?????? ??? ???? ???? ??? ?? ??? ?????? MySQL? ??? ???? ? ????.

SELECT * ?? ?? ???

??? *? ?????. ???? ?????? ??? ???? SELECT *。難道簡(jiǎn)單無(wú)腦，它不香嗎？

主要兩點(diǎn)：

1. 用 "SELECT * " 數(shù)據(jù)庫(kù)需要解析更多的對(duì)象、字段、權(quán)限、屬性等相關(guān)內(nèi)容，在 SQL 語(yǔ)句復(fù)雜，硬解析較多的情況下，會(huì)對(duì)數(shù)據(jù)庫(kù)造成沉重的負(fù)擔(dān)。
2. 增大網(wǎng)絡(luò)開(kāi)銷(xiāo)，*
   ?? ? ?? ?:
"SELECT * " ??????? ? ?? ??, ??, ??, ?? ?? ?? ???? ???. ??, SQL ?? ???? ?? ??? ??? ??????? ? ??? ?? ???.