MySQL在存储过程中优化缓慢的UNION查询

时间：2016-06-15 10:10:13

标签： mysql performance stored-procedures optimization

我的存储过程中有以下代码，它基本上将SQL文本连接到while循环中的一个大查询中，然后执行它。我有来自7个不同表的7个UNION ALL语句，其中包含一些输入参数（table_name1...7，start_date，end_date）：

BEGIN

DECLARE v_max INT UNSIGNED DEFAULT 58; 
DECLARE v_counter INT UNSIGNED DEFAULT 1; 
SET @sql_text = '';
WHILE v_counter < v_max DO
-- Build SQL string
SET @sql_text = CONCAT(@sql_text, 
CONCAT(' SELECT 
(SELECT i.name FROM instrument i WHERE i.id =',v_counter,' LIMIT 1) AS Instrument,
(SELECT AVG(p.ask-p.bid) AS avg_spread
FROM ',table_name1,' p
WHERE p.instrument_id=',v_counter,' AND  FROM_UNIXTIME(p.system_datetime/1000000) BETWEEN \'',start_date,'\' AND \'',end_date,'\') AS One

,

(SELECT AVG(p.ask-p.bid) AS avg_spread
FROM ', table_name2,' p
WHERE p.instrument_id=',v_counter,' AND FROM_UNIXTIME(p.system_datetime/1000000) BETWEEN \'',start_date,'\' AND \'', end_date,'\') AS Two

,

(SELECT AVG(p.ask-p.bid) AS avg_spread
FROM ',table_name3,' p
WHERE p.instrument_id=',v_counter,' AND FROM_UNIXTIME(p.system_datetime/1000000) BETWEEN \'', start_date,'\' AND \'',end_date,'\') AS Three

/* ... more unions here ...*/
,

(SELECT AVG(p.ask-p.bid) AS avg_spread
FROM ',table_name7,' p
WHERE p.instrument_id=',v_counter,' AND FROM_UNIXTIME(p.system_datetime/1000000) BETWEEN \'', start_date,'\' AND \'',end_date,'\') AS Seven UNION ALL ')

);


SET v_counter=v_counter+1; 

END WHILE;

-- Remove extra UNION ALL from SQL string
SET @sql_text = LEFT(@sql_text,LENGTH(@sql_text) - LENGTH(' UNION ALL'));
-- SELECT LEFT(@sql_text,LENGTH(@sql_text) - LENGTH(' UNION ALL'));

-- Prepare and execute statement
PREPARE stmt3 FROM @sql_text;
EXECUTE stmt3;
DEALLOCATE PREPARE stmt3;
END

我想知道有没有办法优化这个查询（七个表每个平均包含350万条记录），执行时间在6到25分钟之间？表格是MyISAM，相同，这是它们的结构：

CREATE TABLE `prices_all_2016_06_13_5` (
    `id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT,
    `instrument_id` TINYINT(4) NOT NULL,
    `ask` DECIMAL(12,6) NOT NULL,
    `bid` DECIMAL(12,6) NOT NULL,
    `system_datetime` DECIMAL(20,0) NOT NULL,
    PRIMARY KEY (`id`) USING BTREE,
    INDEX `Index 3` (`instrument_id`) USING HASH,
    INDEX `Index 4` (`system_datetime`)
)
COLLATE='utf8_unicode_ci'
ENGINE=MyISAM
ROW_FORMAT=COMPACT
AUTO_INCREMENT=3882184
;

编辑：这是EXPLAIN：

"id"    "select_type"   "table" "type"  "possible_keys" "key"   "key_len"   "ref"   "rows"  "Extra"
"1" "PRIMARY"   \N  \N  \N  \N  \N  \N  \N  "No tables used"
"9" "SUBQUERY"  \N  \N  \N  \N  \N  \N  \N  "Impossible WHERE noticed after reading const tables"
"8" "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "64566" "Using where"
"7" "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "71061" "Using where"
"6" "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "43979" "Using where"
"5" "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "69852" "Using where"
"4" "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "117355"    "Using where"
"3" "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "70672" "Using where"
"2" "SUBQUERY"  "i" "const" "PRIMARY"   "PRIMARY"   "4" "const" "1" \N
"10"    "UNION" \N  \N  \N  \N  \N  \N  \N  "No tables used"
"18"    "SUBQUERY"  \N  \N  \N  \N  \N  \N  \N  "Impossible WHERE noticed after reading const tables"
"17"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "52505" "Using where"
"16"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "68781" "Using where"
"15"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "40055" "Using where"
"14"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "32054" "Using where"
"13"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "57465" "Using where"
"12"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "33265" "Using where"
"11"    "SUBQUERY"  "i" "const" "PRIMARY"   "PRIMARY"   "4" "const" "1" \N
"19"    "UNION" \N  \N  \N  \N  \N  \N  \N  "No tables used"
"27"    "SUBQUERY"  \N  \N  \N  \N  \N  \N  \N  "Impossible WHERE noticed after reading const tables"
"26"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "75411" "Using where"
"25"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "91574" "Using where"
"24"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "47560" "Using where"
"23"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "80731" "Using where"
"22"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "139225"    "Using where"
"21"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "109131"    "Using where"
"20"    "SUBQUERY"  "i" "const" "PRIMARY"   "PRIMARY"   "4" "const" "1" \N
"28"    "UNION" \N  \N  \N  \N  \N  \N  \N  "No tables used"
"36"    "SUBQUERY"  \N  \N  \N  \N  \N  \N  \N  "Impossible WHERE noticed after reading const tables"
"35"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "67288" "Using where"
"34"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "83522" "Using where"
"33"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "46650" "Using where"
"32"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "50401" "Using where"
"31"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "73280" "Using where"
"30"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "50836" "Using where"
"29"    "SUBQUERY"  "i" "const" "PRIMARY"   "PRIMARY"   "4" "const" "1" \N
"37"    "UNION" \N  \N  \N  \N  \N  \N  \N  "No tables used"
"45"    "SUBQUERY"  \N  \N  \N  \N  \N  \N  \N  "Impossible WHERE noticed after reading const tables"
"44"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "59256" "Using where"
"43"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "54092" "Using where"
"42"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "41561" "Using where"
"41"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "51928" "Using where"
"40"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "64368" "Using where"
"39"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "60471" "Using where"
"38"    "SUBQUERY"  "i" "const" "PRIMARY"   "PRIMARY"   "4" "const" "1" \N
"46"    "UNION" \N  \N  \N  \N  \N  \N  \N  "No tables used"
"54"    "SUBQUERY"  \N  \N  \N  \N  \N  \N  \N  "Impossible WHERE noticed after reading const tables"
"53"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "59213" "Using where"
"52"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "56071" "Using where"
"51"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "47653" "Using where"
"50"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "46033" "Using where"
"49"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "56180" "Using where"
"48"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "47262" "Using where"
"47"    "SUBQUERY"  "i" "const" "PRIMARY"   "PRIMARY"   "4" "const" "1" \N
"55"    "UNION" \N  \N  \N  \N  \N  \N  \N  "No tables used"
"63"    "SUBQUERY"  \N  \N  \N  \N  \N  \N  \N  "Impossible WHERE noticed after reading const tables"
"62"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "69552" "Using where"
"61"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "100487"    "Using where"
"60"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "78156" "Using where"
"59"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "105721"    "Using where"
"58"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "128156"    "Using where"
"57"    "SUBQUERY"  "p" "ref"   "Index 3"   "Index 3"   "1" "const" "114533"    "Using where"
"56"    "SUBQUERY"  "i" "const" "PRIMARY"   "PRIMARY"   "4" "const" "1" ...

1 个答案:

答案 0 :(得分：1)

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    .width(800)
    .height(200)
    .margins({ top: 20, left: 10, right: 10, bottom: 20 })
    .dimension(contractors)
    .group(contractorGroup)
    .ordinalColors(['#3182bd', '#6baed6', '#9ecae1', '#c6dbef', '#dadaeb'])
    .label(function (d) {
        return d.key;
    })
    .title(function (d) {
        return d.value.exceptionCount;
    })
    .elasticX(true)
    .xAxis().ticks(4);

不要隐藏功能中的列;索引不能使用。代替：

FROM_UNIXTIME(p.system_datetime/1000000)
      BETWEEN \'', start_date,'\' AND \'', end_date,'\'

使用p.system_datetime BETWEEN 1000000*UNIX_TIMESTAMP(\'', start_date,'\') AND 1000000*UNIX_TIMESTAMP(\'', end_date,'\') 代替DECIMAL(20,0)的某些原因，从而避免使用DECIMAL(20,6)？另请注意，新的MySQL具有1000000和DATETIME(6)，可为您提供所需的微秒分辨率。

重新构建查询后，TIMESTAMP(6)需要提高查询效率：

p

此外，如果这些表具有相同的结构，那么可能更好地拥有一个表，而不是很多。它可能需要一个额外的列来区分＆＃34; table＆＃34;每一行都属于。你似乎正在通过表名进行分区＆＃34; （INDEX(instrument_id, system_datetime) 等）。

此外，切换到InnoDB，并设计＆＃39;权利＆＃39; prices_all_2016_06_13_5，可能＆＃39;复合＆＃39;，会因为＆＃34;群集＆＃34;而为您带来另一次性能提升。

PRIMARY KEY可能值得也可能不值得做。 （它通常不会产生任何表现。）

我需要更好地了解您的查询是什么，以便进一步提供建议。

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