Question

这与我的last problem有关。我在列表表格中创建了一个新的两列，一个用于组合视图views_point（每100个视图递增一次），另一个用于发布日期publishedon_hourly（仅按年 - 月 - 小时）制作一些独特的价值观。

这是我的新表：

CREATE TABLE IF NOT EXISTS `listings` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `type` tinyint(1) NOT NULL DEFAULT '1',
  `hash` char(32) NOT NULL,
  `source_id` int(10) unsigned NOT NULL,
  `link` varchar(255) NOT NULL,
  `short_link` varchar(255) NOT NULL,
  `cat_id` mediumint(5) NOT NULL,
  `title` mediumtext NOT NULL,
  `description` mediumtext,
  `content` mediumtext,
  `images` mediumtext,
  `videos` mediumtext,
  `views` int(10) unsigned NOT NULL DEFAULT '0',
  `views_point` int(10) unsigned NOT NULL DEFAULT '0',
  `comments` int(11) DEFAULT '0',
  `comments_update` int(11) NOT NULL DEFAULT '0',
  `editor_id` int(11) NOT NULL DEFAULT '0',
  `auther_name` varchar(255) DEFAULT NULL,
  `createdby_id` int(10) NOT NULL,
  `createdon` int(20) NOT NULL,
  `editedby_id` int(10) NOT NULL,
  `editedon` int(20) NOT NULL,
  `deleted` tinyint(1) NOT NULL,
  `deletedon` int(20) NOT NULL,
  `deletedby_id` int(10) NOT NULL,
  `deletedfor` varchar(255) NOT NULL,
  `published` tinyint(1) NOT NULL DEFAULT '1',
  `publishedon` int(11) unsigned NOT NULL,
  `publishedon_hourly` int(10) unsigned NOT NULL DEFAULT '0',
  `publishedby_id` int(10) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `hash` (`hash`),
  KEY `views_point` (`views_point`),
  KEY `listings` (`publishedon_hourly`,`published`,`cat_id`,`source_id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 ROW_FORMAT=FIXED AUTO_INCREMENT=365513 ;

当我运行这样的查询时：

SELECT *
FROM listings
WHERE (`publishedon_hourly` BETWEEN
       UNIX_TIMESTAMP( '2015-09-5 00:00:00' )
       AND UNIX_TIMESTAMP( '2015-10-5 12:00:00' ))
  AND (published =1)
  AND cat_id IN ( 1, 2, 3, 4, 5 )
ORDER BY by `views_point` DESC
LIMIT 10

这很有效，这个解释如下：

但是当我像这样每月更改日期范围时：

SELECT *
FROM listings
WHERE (`publishedon_hourly` BETWEEN
       UNIX_TIMESTAMP( '2015-09-5 00:00:00' )
       AND UNIX_TIMESTAMP( '2015-09-5 12:00:00' ))
  AND (published =1)
  AND cat_id IN ( 1, 2, 3, 4, 5 )
  ORDER BY `views_point` DESC
  LIMIT 10

然后查询变慢并出现filesort。任何人都知道原因，我该如何解决？

数据样本（来自慢速查询）

INSERT INTO `listings` (`id`, `type`, `hash`, `source_id`, `link`, `short_link`, `cat_id`, `title`, `description`, `content`, `images`, `videos`, `views`, `views_point`, `comments`, `comments_update`, `editor_id`, `auther_name`, `createdby_id`, `createdon`, `editedby_id`, `editedon`, `deleted`, `deletedon`, `deletedby_id`, `deletedfor`, `published`, `publishedon`, `publishedon_hourly`, `publishedby_id`) VALUES
(94189, 1, '44a46d128ce730c72927b19c445ab26e', 8, 'http://Larkin.com/sapiente-laboriosam-omnis-tempore-aliquam-qui-nobis', '', 5, 'And Alice was more and.', 'So they got settled down again very sadly and quietly, and.', 'Dormouse. ''Fourteenth of March, I think it so quickly that the Gryphon only answered ''Come on!'' and ran the faster, while more and more sounds of broken glass, from which she concluded that it was looking down at them, and then a voice sometimes choked with sobs, to sing this:-- ''Beautiful Soup, so rich and green, Waiting in a natural way. ''I thought you did,'' said the Dormouse, without considering at all what had become of it; and as it.', NULL, '', 200, 19700, 0, 0, 0, 'Max', 0, 1441442729, 0, 0, 0, 0, 0, '', 1, 1441442729, 1441440000, 0),
(19030, 1, '3438f6a555f2ce7fdfe03cee7a52882a', 3, 'http://Romaguera.com/voluptatem-rerum-quia-sed', '', 2, 'Dodo said, ''EVERYBODY.', 'I wish I hadn''t to bring but one; Bill''s got the.', 'I wonder what they''ll do well enough; don''t be particular--Here, Bill! catch hold of this remark, and thought to herself. (Alice had no idea what Latitude or Longitude I''ve got to the confused clamour of the other queer noises, would change to dull reality--the grass would be offended again. ''Mine is a long way. So she went on. ''I do,'' Alice said nothing; she had succeeded in curving it down ''important,'' and some were birds,) ''I suppose so,''.', NULL, '', 800, 19400, 0, 0, 0, 'Antonio', 0, 1441447567, 0, 0, 0, 0, 0, '', 1, 1441447567, 1441447200, 0),
(129247, 4, '87d2029a300d8b4314508786eb620a24', 10, 'http://Ledner.com/', '', 4, 'I ever saw one that.', 'The Cat seemed to be a person of authority among them,.', 'I BEG your pardon!'' she exclaimed in a natural way again. ''I wonder what was the same height as herself; and when she looked down at her feet as the question was evidently meant for her. ''I can tell you my history, and you''ll understand why it is I hate cats and dogs.'' It was all dark overhead; before her was another long passage, and the blades of grass, but she had sat down a very little! Besides, SHE''S she, and I''m sure I have dropped them, I wonder?'' As she said to herself; ''his eyes are so VERY tired of being all alone here!'' As she said to itself ''Then I''ll go round a deal.', NULL, '', 1000, 19100, 0, 0, 0, 'Drake', 0, 1441409756, 0, 0, 0, 0, 0, '', 1, 1441409756, 1441407600, 0),
(264582, 2, '5e44fe417f284f42c3b10bccd9c89b14', 8, 'http://www.Dietrich.info/laboriosam-quae-eaque-aut-dolorem', '', 2, 'Alice asked in a very.', 'THINK; or is it directed to?'' said the Mock Turtle,.', 'I can listen all day to such stuff? Be off, or I''ll have you executed.'' The miserable Hatter dropped his teacup and bread-and-butter, and then unrolled the parchment scroll, and read as follows:-- ''The Queen will hear you! You see, she came upon a little of the players to be lost, as she spoke--fancy CURTSEYING as you''re falling through the wood. ''It''s the stupidest tea-party I.', NULL, '', 800, 18700, 0, 0, 0, 'Kevin', 0, 1441441192, 0, 0, 0, 0, 0, '', 1, 1441441192, 1441440000, 0),
(44798, 1, '567cc77ba88c05a4a805dc667816a30c', 14, 'http://www.Hintz.com/distinctio-nulla-quia-incidunt-facere-reprehenderit-sapiente-sint.html', '', 5, 'The Cat seemed to Alice.', 'And the moral of that is--"Be what you mean,'' said Alice..', 'Alice very politely; but she felt very lonely and low-spirited. In a little faster?" said a sleepy voice behind her. ''Collar that Dormouse,'' the Queen said severely ''Who is it directed to?'' said the Footman, and began staring at the Footman''s head: it just at first, but, after watching it a violent blow underneath her chin: it had no pictures or conversations in it, ''and what is the capital of Paris, and Paris is the same thing, you know.'' ''I DON''T.', NULL, '', 300, 17600, 0, 0, 0, 'Rocio', 0, 1441442557, 0, 0, 0, 0, 0, '', 1, 1441442557, 1441440000, 0),
(184472, 1, 'f852e3ed401c7c72c5a9609687385f65', 14, 'https://www.Schumm.biz/voluptatum-iure-qui-dicta-modi-est', '', 4, 'Alice replied, so.', 'I should have liked teaching it tricks very much, if--if.', 'NEVER come to the Dormouse, not choosing to notice this question, but hurriedly went on, ''What''s your name, child?'' ''My name is Alice, so please your Majesty,'' said Two, in a great thistle, to keep back the wandering hair that WOULD always get into her face. ''Wake up, Alice dear!'' said her sister; ''Why, what a dear quiet thing,'' Alice went on, spreading out the answer to shillings and pence. ''Take off your hat,'' the King had said that day. ''No, no!'' said the Gryphon. ''They can''t have anything to say, she simply bowed, and took the watch and looked at it again: but he could.', NULL, '', 900, 17600, 0, 0, 0, 'Billy', 0, 1441407837, 0, 0, 0, 0, 0, '', 1, 1441407837, 1441407600, 0),
(344246, 2, '09dc73287ff642cfa2c97977dc42bc64', 6, 'http://www.Cole.com/sit-maiores-et-quam-vitae-ut-fugiat', '', 1, 'IS the use of a.', 'And when I learn music.'' ''Ah! that accounts for it,'' said.', 'Gryphon answered, very nearly carried it out loud. ''Thinking again?'' the Duchess by this time.) ''You''re nothing but a pack of cards, after all. I needn''t be so stingy about it, you know--'' ''But, it goes on "THEY ALL RETURNED FROM HIM TO YOU,"'' said Alice. ''Call it what you mean,'' the March Hare, ''that "I breathe when I breathe"!'' ''It IS the same side of WHAT? The other guests had taken his watch out of it, and talking over its head. ''Very uncomfortable for the first to speak. ''What size do you like to go and get.', NULL, '', 600, 16900, 0, 0, 0, 'Enrico', 0, 1441406107, 0, 0, 0, 0, 0, '', 1, 1441406107, 1441404000, 0),
(19169, 1, '116c443b5709e870248c93358f9a328e', 12, 'http://www.Gleason.com/et-vero-optio-exercitationem-aliquid-optio-consectetur', '', 4, 'Let this be a lesson to.', 'Sir, With no jury or judge, would be very likely to eat.', 'I wonder who will put on your head-- Do you think I can find them.'' As she said this, she was quite out of sight before the end of every line: ''Speak roughly to your little boy, And beat him when he sneezes; For he can EVEN finish, if he had never heard of such a subject! Our family always HATED cats: nasty, low, vulgar things! Don''t let him know she liked them best, For this must ever be A secret, kept from all the creatures wouldn''t be so kind,'' Alice replied, so eagerly that the way I want to get very tired of being upset, and their curls got entangled together. Alice was not a regular rule: you invented it just grazed his nose, you know?'' ''It''s the thing Mock Turtle would be only.', NULL, '', 700, 16800, 0, 0, 0, 'Unique', 0, 1441407961, 0, 0, 0, 0, 0, '', 1, 1441407961, 1441407600, 0),
(192679, 1, '06a33747b5c95799034630e578e53dc5', 10, 'http://www.Pouros.com/qui-id-molestias-non-dolores-non', '', 5, 'Rabbit just under the.', 'KNOW IT TO BE TRUE--" that''s the jury-box,'' thought Alice,.', 'Mock Turtle, who looked at Two. Two began in a hoarse, feeble voice: ''I heard every word you fellows were saying.'' ''Tell us a story.'' ''I''m afraid I can''t tell you how it was too dark to see what I should say "With what porpoise?"'' ''Don''t you mean by that?'' said the King; and as it was indeed: she was now more than Alice could not make out exactly what they WILL do next! As for pulling me out of court! Suppress him! Pinch him! Off with his head!"'' ''How dreadfully savage!'' exclaimed Alice. ''That''s the first witness,'' said the Duchess. ''Everything''s got a moral, if only you can find it.'' And she squeezed herself up and ran the faster, while more and more faintly came, carried on the end of every line:.', NULL, '', 800, 15900, 0, 0, 0, 'Gene', 0, 1441414720, 0, 0, 0, 0, 0, '', 1, 1441414720, 1441411200, 0),
(251878, 4, '3eafacc53f86c8492c309ca2772fbfe9', 5, 'http://www.Schinner.info/tempora-et-est-qui-nulla', '', 2, 'NOT!'' cried the Mouse,.', 'Twinkle, twinkle--"'' Here the Queen till she heard the.', 'Alice and all of them even when they hit her; and the sounds will take care of the gloves, and she dropped it hastily, just in time to begin at HIS time of life. The King''s argument was, that she had forgotten the Duchess to play croquet with the Dormouse. ''Write that down,'' the King added in an undertone to the fifth bend, I think?'' ''I had NOT!'' cried the Mouse, sharply and very neatly and simply arranged; the only difficulty was, that if something wasn''t done about it in less than a pig, my dear,'' said Alice, a little wider. ''Come, it''s pleased so far,'' said the Gryphon. ''Do you play croquet with the glass table and the King hastily said, and went by without noticing her. Then followed the Knave ''Turn them over!'' The Knave of.', NULL, '', 500, 15900, 0, 0, 0, 'Demarcus', 0, 1441414681, 0, 0, 0, 0, 0, '', 1, 1441414681, 1441411200, 0);

Answer 1

在第一个查询中，ORDER BY使用views_point INDEX完成，因为它在查询的WHERE部分中使用，因此在MySQL中可以用于排序。

在第二个查询中，MySQL使用不同的索引listing_pcs解析WHERE部分。这不能用于满足ORDER BY条件。 MySQL使用filesort，如果不能使用索引，这是最好的选择。

MySQL仅使用索引来排序索引是否与WHERE条件中使用的索引相同。这就是the manual的含义：

在某些情况下，MySQL无法使用索引来解析ORDER BY，尽管它仍然使用索引来查找与WHERE子句匹配的行。这些案例包括以下内容：

用于获取行的键与ORDER BY中使用的键不同：
SELECT * FROM t1 WHERE key2=constant ORDER BY key1;

那你能做什么：

尝试增加sort_buffer_size配置选项，使文件排序尽可能有效。对于排序缓冲区而言太大的大结果会导致MySQL将排序分解为块，这会更慢。

强制MySQL选择不同的索引。值得注意的是，不同的MySQL版本选择不同的默认索引。例如，版本5.1非常糟糕，因为查询优化器已针对此版本进行了大量重写，需要进行大量改进。版本5.6非常好。

SELECT *
FROM listings
FORCE INDEX (views_point)
WHERE (`publishedon_hourly` BETWEEN
       UNIX_TIMESTAMP( '2015-09-5 00:00:00' )
       AND UNIX_TIMESTAMP( '2015-09-5 12:00:00' ))
  AND (published =1)
  AND cat_id IN ( 1, 2, 3, 4, 5 )
ORDER BY `views_point` DESC
LIMIT 10

Answer 2

似乎是某种新闻数据库，所以试着考虑每个月制作某种新闻档案。

想想这个解决方案，它不是最好的，但它可能有所帮助

将这些列添加到列表表中
- publishedmonth tinyint（2）UNSIGNED NOT NULL DEFAULT＆＃39; 0＆＃39;
- publishedyear tinyint（2）UNSIGNED NOT NULL DEFAULT＆＃39; 0＆＃39;
- publishedminute mediumint（6）UNSIGNED NOT NULL DEFAULT＆＃39; 0＆＃39;
将此INDEXING KEY添加到列表表
中
- ADD KEY published_month (publishedmonth,publishedyear,publishedminute)
在插入过程中使用PHP代码中的这些值
- publishedmonth将date('n')
- Publishedyear将date('y')
- publishedminute将date('jHi')

转储大量记录然后测试此查询

SELECT * FROM listings WHERE publishedmonth = 2 AND publishedyear = 17 ORDER BY publishedminute

Answer 3

非常奇怪的行为。很难理解为什么views_point不会用于排序操作而不会看到有问题的数据。您可以尝试为MySQL提供索引提示，以便使用views_point进行排序。

SELECT * FROM listings
  USE INDEX FOR ORDER BY (`views_point`)
WHERE
  (
    `publishedon_hourly` BETWEEN UNIX_TIMESTAMP( '2015-09-5 00:00:00' )
    AND UNIX_TIMESTAMP( '2015-09-5 12:00:00' )
  )
  AND (published =1)
  AND cat_id IN ( 1, 2, 3, 4, 5 )
ORDER BY `views_point` DESC LIMIT 10

Answer 4

EXPLAIN说listings_pcs，但SHOW CREATE TABLE没有列出该索引。我们错过了什么吗？
如果您只需要几列，请不要使用SELECT *。特别是TEXT列将阻止查询期间一种形式的性能加速。
用于计算部分查询的子查询通常显示内容。但是，在您的情况下（大量MEDIUMTEXT被提取，并使用LIMIT），首先在子查询中获取ID可能是有效的，然后获取庞大的列。（“Lazy eval”）见下文。
范围值（publishedon_hourly）最好不要在索引中使用，而不是第一个。
使用=列（published）开始索引通常是最好的。
优化工具有时会选择错误地关注ORDER BY而不是WHERE。（在你的情况下，两者都没有效率）。
INDEX(published, views_point) 可以避免排序，同时帮助一些WHERE。
有一个总是在查询中测试的标志（published）会增加架构的复杂性和低效率。
BETWEEN包含在内，因此第二个查询实际上是扫描12小时加一秒。
将日期拆分为年+月+日通常比帮助更多。
不要将sort_buffer_size设置为大于1％的RAM。否则，您可能会遇到其他问题。
FORCE INDEX今天可能会有所帮助，但明天会在常数发生变化时受伤。注意事项。
将“click_count”或“likes”或“upvotes”放入单独的表中通常会更好。这将快速变化的计数器与庞大的，相对静态的数据分开。因此，两者之间的干扰较少。
如果您执行上述操作，只需从计数器表中删除未发布的行，从而简化了几项操作。
大多数人都对filesort进行了诋毁，但通常还有别的东西 - 在你的情况下，行的数量和大小。
请提供EXPLAIN FORMAT=JSON SELECT ...;可能会有一些有趣的线索。
您的发现很奇怪，可以在bugs.mysql.com上填写错误。

我会按照给定的顺序添加这些索引，并查看优化程序选择的内容：

INDEX(published, views_point) -- aiming at the ORDER BY, plus picking up '=' INDEX(published, cat_id, publishedon_hourly) -- possibly the best for WHERE

或者，也许是
的“懒惰评价”
SELECT L.* FROM listings AS L JOIN ( SELECT id FROM listings WHERE `publishedon_hourly` BETWEEN UNIX_TIMESTAMP(...) AND UNIX_TIMESTAMP(...) AND published = 1 AND cat_id IN ( 1, 2, 3, 4, 5 ) ORDER BY `views_point` DESC LIMIT 10 ) AS s ON L.id = s.id ORDER BY views_point DESC -- with INDEX(published, cat_id, publishedon_hourly, views_point, id)

注意：

子查询将是“使用索引”;也就是说，索引正在覆盖。

将有两种文件排序。一个是在子查询中，但是从索引开始，而不是笨重的文本。一个只有10排，虽然很笨重。

Answer 5

查询优化器并不完美。这是其中一个做出错误决定的案例。它发生在一些边界线情况下。如果表中的数据甚至会改变一小部分，它可能会使用另一个索引并运行更快的查询。

您不会等待它，您可以更改listing_pcs索引。它有source_id，但你没有使用。那么为什么不用view_points替换呢？

KEY `listings` (`publishedon_hourly`,`published`,`point`,`cat_id`)

同样使用tinyint（1）不太用于速度或节省空间。它仍然需要一个完整的字节。同样的mediumint（5）需要3个字节。将deleted，type，catid和published合并为一列，并将索引放在该列上。

MySQL索引和使用filesort

5 个答案: