为啥这个查询需要这么长时间?

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【中文标题】为啥这个查询需要这么长时间?【英文标题】:Why does this query take so long?为什么这个查询需要这么长时间? 【发布时间】:2010-09-13 09:34:02 【问题描述】:

我有一个复杂的查询需要在 mysql 服务器上运行。

在我的家庭测试机器上,一个 mac,查询需要 0.00 秒并立即返回结果。

然而,在我的服务器上,一个 ubuntu 机器,相同的查询需要大约 3.30 分钟,使用相同的数据。

数据库使用 InnoDB 表。 ubuntu box有64位内核,mysql就是为此编译的。

为什么 ubuntu 服务器执行查询需要这么长的时间?

这些是来自 ubuntu-box 的配置变量:

mysql> show variables;
+---------------------------------+-----------------------------+
| Variable_name                   | Value                       |
+---------------------------------+-----------------------------+
| auto_increment_increment        | 1                           | 
| auto_increment_offset           | 1                           | 
| automatic_sp_privileges         | ON                          | 
| back_log                        | 50                          | 
| basedir                         | /usr/                       | 
| binlog_cache_size               | 32768                       | 
| bulk_insert_buffer_size         | 8388608                     | 
| character_set_client            | latin1                      | 
| character_set_connection        | latin1                      | 
| character_set_database          | utf8                        | 
| character_set_filesystem        | binary                      | 
| character_set_results           | latin1                      | 
| character_set_server            | latin1                      | 
| character_set_system            | utf8                        | 
| character_sets_dir              | /usr/share/mysql/charsets/  | 
| collation_connection            | latin1_swedish_ci           | 
| collation_database              | utf8_danish_ci              | 
| collation_server                | latin1_swedish_ci           | 
| completion_type                 | 0                           | 
| concurrent_insert               | 1                           | 
| connect_timeout                 | 10                          | 
| datadir                         | /var/lib/mysql/             | 
| date_format                     | %Y-%m-%d                    | 
| datetime_format                 | %Y-%m-%d %H:%i:%s           | 
| default_week_format             | 0                           | 
| delay_key_write                 | ON                          | 
| delayed_insert_limit            | 100                         | 
| delayed_insert_timeout          | 300                         | 
| delayed_queue_size              | 1000                        | 
| div_precision_increment         | 4                           | 
| keep_files_on_create            | OFF                         | 
| engine_condition_pushdown       | OFF                         | 
| expire_logs_days                | 10                          | 
| flush                           | OFF                         | 
| flush_time                      | 0                           | 
| ft_boolean_syntax               | + -><()~*:""&|              | 
| ft_max_word_len                 | 84                          | 
| ft_min_word_len                 | 4                           | 
| ft_query_expansion_limit        | 20                          | 
| ft_stopword_file                | (built-in)                  | 
| group_concat_max_len            | 1024                        | 
| have_archive                    | YES                         | 
| have_bdb                        | NO                          | 
| have_blackhole_engine           | YES                         | 
| have_compress                   | YES                         | 
| have_crypt                      | YES                         | 
| have_csv                        | YES                         | 
| have_dynamic_loading            | YES                         | 
| have_example_engine             | NO                          | 
| have_federated_engine           | DISABLED                    | 
| have_geometry                   | YES                         | 
| have_innodb                     | YES                         | 
| have_isam                       | NO                          | 
| have_merge_engine               | YES                         | 
| have_ndbcluster                 | DISABLED                    | 
| have_openssl                    | DISABLED                    | 
| have_ssl                        | DISABLED                    | 
| have_query_cache                | YES                         | 
| have_raid                       | NO                          | 
| have_rtree_keys                 | YES                         | 
| have_symlink                    | YES                         | 
| hostname                        | databaseserver              | 
| init_connect                    |                             | 
| init_file                       |                             | 
| init_slave                      |                             | 
| innodb_additional_mem_pool_size | 8388608                     | 
| innodb_autoextend_increment     | 8                           | 
| innodb_buffer_pool_awe_mem_mb   | 0                           | 
| innodb_buffer_pool_size         | 1073741824                  | 
| innodb_checksums                | ON                          | 
| innodb_commit_concurrency       | 0                           | 
| innodb_concurrency_tickets      | 500                         | 
| innodb_data_file_path           | ibdata1:10M:autoextend      | 
| innodb_data_home_dir            |                             | 
| innodb_adaptive_hash_index      | ON                          | 
| innodb_doublewrite              | ON                          | 
| innodb_fast_shutdown            | 1                           | 
| innodb_file_io_threads          | 4                           | 
| innodb_file_per_table           | OFF                         | 
| innodb_flush_log_at_trx_commit  | 2                           | 
| innodb_flush_method             | O_DIRECT                    | 
| innodb_force_recovery           | 0                           | 
| innodb_lock_wait_timeout        | 50                          | 
| innodb_locks_unsafe_for_binlog  | OFF                         | 
| innodb_log_arch_dir             |                             | 
| innodb_log_archive              | OFF                         | 
| innodb_log_buffer_size          | 4194304                     | 
| innodb_log_file_size            | 5242880                     | 
| innodb_log_files_in_group       | 2                           | 
| innodb_log_group_home_dir       | ./                          | 
| innodb_max_dirty_pages_pct      | 90                          | 
| innodb_max_purge_lag            | 0                           | 
| innodb_mirrored_log_groups      | 1                           | 
| innodb_open_files               | 300                         | 
| innodb_rollback_on_timeout      | OFF                         | 
| innodb_support_xa               | ON                          | 
| innodb_sync_spin_loops          | 20                          | 
| innodb_table_locks              | ON                          | 
| innodb_thread_concurrency       | 8                           | 
| innodb_thread_sleep_delay       | 10000                       | 
| interactive_timeout             | 28800                       | 
| join_buffer_size                | 131072                      | 
| key_buffer_size                 | 16777216                    | 
| key_cache_age_threshold         | 300                         | 
| key_cache_block_size            | 1024                        | 
| key_cache_division_limit        | 100                         | 
| language                        | /usr/share/mysql/english/   | 
| large_files_support             | ON                          | 
| large_page_size                 | 0                           | 
| large_pages                     | OFF                         | 
| lc_time_names                   | en_US                       | 
| license                         | GPL                         | 
| local_infile                    | ON                          | 
| locked_in_memory                | OFF                         | 
| log                             | OFF                         | 
| log_bin                         | OFF                         | 
| log_bin_trust_function_creators | OFF                         | 
| log_error                       |                             | 
| log_queries_not_using_indexes   | OFF                         | 
| log_slave_updates               | OFF                         | 
| log_slow_queries                | ON                          | 
| log_warnings                    | 1                           | 
| long_query_time                 | 1                           | 
| low_priority_updates            | OFF                         | 
| lower_case_file_system          | OFF                         | 
| lower_case_table_names          | 0                           | 
| max_allowed_packet              | 16777216                    | 
| max_binlog_cache_size           | 18446744073709547520        | 
| max_binlog_size                 | 104857600                   | 
| max_connect_errors              | 10                          | 
| max_connections                 | 100                         | 
| max_delayed_threads             | 20                          | 
| max_error_count                 | 64                          | 
| max_heap_table_size             | 16777216                    | 
| max_insert_delayed_threads      | 20                          | 
| max_join_size                   | 18446744073709551615        | 
| max_length_for_sort_data        | 1024                        | 
| max_prepared_stmt_count         | 16382                       | 
| max_relay_log_size              | 0                           | 
| max_seeks_for_key               | 18446744073709551615        | 
| max_sort_length                 | 1024                        | 
| max_sp_recursion_depth          | 0                           | 
| max_tmp_tables                  | 32                          | 
| max_user_connections            | 0                           | 
| max_write_lock_count            | 18446744073709551615        | 
| multi_range_count               | 256                         | 
| myisam_data_pointer_size        | 6                           | 
| myisam_max_sort_file_size       | 9223372036853727232         | 
| myisam_recover_options          | BACKUP                      | 
| myisam_repair_threads           | 1                           | 
| myisam_sort_buffer_size         | 8388608                     | 
| myisam_stats_method             | nulls_unequal               | 
| ndb_autoincrement_prefetch_sz   | 1                           | 
| ndb_force_send                  | ON                          | 
| ndb_use_exact_count             | ON                          | 
| ndb_use_transactions            | ON                          | 
| ndb_cache_check_time            | 0                           | 
| ndb_connectstring               |                             | 
| net_buffer_length               | 16384                       | 
| net_read_timeout                | 30                          | 
| net_retry_count                 | 10                          | 
| net_write_timeout               | 60                          | 
| new                             | OFF                         | 
| old_passwords                   | OFF                         | 
| open_files_limit                | 1024                        | 
| optimizer_prune_level           | 1                           | 
| optimizer_search_depth          | 62                          | 
| pid_file                        | /var/run/mysqld/mysqld.pid  | 
| plugin_dir                      |                             | 
| port                            | 3306                        | 
| preload_buffer_size             | 32768                       | 
| profiling                       | OFF                         | 
| profiling_history_size          | 15                          | 
| protocol_version                | 10                          | 
| query_alloc_block_size          | 8192                        | 
| query_cache_limit               | 1048576                     | 
| query_cache_min_res_unit        | 4096                        | 
| query_cache_size                | 16777216                    | 
| query_cache_type                | ON                          | 
| query_cache_wlock_invalidate    | OFF                         | 
| query_prealloc_size             | 8192                        | 
| range_alloc_block_size          | 4096                        | 
| read_buffer_size                | 131072                      | 
| read_only                       | OFF                         | 
| read_rnd_buffer_size            | 262144                      | 
| relay_log                       |                             | 
| relay_log_index                 |                             | 
| relay_log_info_file             | relay-log.info              | 
| relay_log_purge                 | ON                          | 
| relay_log_space_limit           | 0                           | 
| rpl_recovery_rank               | 0                           | 
| secure_auth                     | OFF                         | 
| secure_file_priv                |                             | 
| server_id                       | 0                           | 
| skip_external_locking           | ON                          | 
| skip_networking                 | OFF                         | 
| skip_show_database              | OFF                         | 
| slave_compressed_protocol       | OFF                         | 
| slave_load_tmpdir               | /tmp/                       | 
| slave_net_timeout               | 3600                        | 
| slave_skip_errors               | OFF                         | 
| slave_transaction_retries       | 10                          | 
| slow_launch_time                | 2                           | 
| socket                          | /var/run/mysqld/mysqld.sock | 
| sort_buffer_size                | 2097144                     | 
| sql_big_selects                 | ON                          | 
| sql_mode                        |                             | 
| sql_notes                       | ON                          | 
| sql_warnings                    | OFF                         | 
| ssl_ca                          |                             | 
| ssl_capath                      |                             | 
| ssl_cert                        |                             | 
| ssl_cipher                      |                             | 
| ssl_key                         |                             | 
| storage_engine                  | MyISAM                      | 
| sync_binlog                     | 0                           | 
| sync_frm                        | ON                          | 
| system_time_zone                | CEST                        | 
| table_cache                     | 64                          | 
| table_lock_wait_timeout         | 50                          | 
| table_type                      | MyISAM                      | 
| thread_cache_size               | 8                           | 
| thread_stack                    | 131072                      | 
| time_format                     | %H:%i:%s                    | 
| time_zone                       | SYSTEM                      | 
| timed_mutexes                   | OFF                         | 
| tmp_table_size                  | 33554432                    | 
| tmpdir                          | /tmp                        | 
| transaction_alloc_block_size    | 8192                        | 
| transaction_prealloc_size       | 4096                        | 
| tx_isolation                    | REPEATABLE-READ             | 
| updatable_views_with_limit      | YES                         | 
| version                         | 5.0.75-0ubuntu10.5-log      | 
| version_comment                 | (Ubuntu)                    | 
| version_compile_machine         | x86_64                      | 
| version_compile_os              | debian-linux-gnu            | 
| wait_timeout                    | 28800                       | 
+---------------------------------+-----------------------------+

这是查询:

SELECT work.id work \
, count( DISTINCT( u.id ) ) number_of_editions \
, GROUP_CONCAT( DISTINCT( u.main_title ) ) main_title \
, GROUP_CONCAT( DISTINCT( main_author.full_name ) ) main_author \
, CONCAT_WS(' ', \
     GROUP_CONCAT( DISTINCT( u.sub_title_1 ) ) \
    ,GROUP_CONCAT( DISTINCT( u.sub_title_2 ) )  \
    ,GROUP_CONCAT( DISTINCT( u.sub_title_3 ) )  \
    ,GROUP_CONCAT( DISTINCT( u.sub_title_4 ) )  \
    ,GROUP_CONCAT( DISTINCT( u.sub_title_5 ) )  \
    ,GROUP_CONCAT( DISTINCT( u.alternative_title ) )   \
    ,GROUP_CONCAT( DISTINCT( sst.title ) )  \
    ) boktitler \
, GROUP_CONCAT( DISTINCT( a.full_name ) ) authorname \
, GROUP_CONCAT( DISTINCT( lp.name )) literary_award \
, GROUP_CONCAT( DISTINCT( f.name )) publisher \
, GROUP_CONCAT( DISTINCT( st.title )) series \
, GROUP_CONCAT( DISTINCT( otn.time )) about_period \
, GROUP_CONCAT( DISTINCT( ostn.place )) about_place \
, GROUP_CONCAT( DISTINCT( opn.full_name )) about_person \
, GROUP_CONCAT( DISTINCT( eon.tag )) utag \
, GROUP_CONCAT( DISTINCT( pt.title )) parallell_title \
, work.owners number_of_owners \
FROM core_work work \
LEFT \
JOIN core_edition u \
    ON u.work_id = work.id \
LEFT \
JOIN core_author main_author \
    ON main_author.edition_id = u.id AND main_author.nr = 1 \
LEFT \
JOIN core_conjoined_title sst \
    ON sst.edition_id = u.id \
LEFT \
JOIN core_parallell_title pt \
    ON pt.edition_id = u.id \
LEFT \
JOIN core_editiontag eo \
    ON eo.edition_id = u.id \
LEFT \
JOIN core_utag eon \
    ON eon.id = eo.tag_id \
LEFT \
JOIN core_edition_about_persons op \
    ON op.edition_id = u.id \
LEFT \
JOIN core_about_person opn \
    ON opn.id = op.about_person_id \
LEFT \
JOIN core_edition_about_place ost \
    ON ost.edition_id = u.id \
LEFT \
JOIN core_about_place ostn \
    ON ostn.id = ost.about_place_id \
LEFT \
JOIN core_edition_abouttime ot \
    ON ot.edition_id = u.id \
LEFT \
JOIN core_abouttime otn \
    ON otn.id = ot.abouttime_id \
LEFT \
JOIN core_seriesnr vs \
    ON vs.edition_id = u.id \
LEFT  \
JOIN core_series st \
    ON st.id = vs.series_id \
LEFT \
JOIN core_edition_publisher uf \
    ON uf.edition_id = u.id \
LEFT \
JOIN core_publisher f \
    ON f.id = uf.publisher_id \
LEFT \
JOIN core_author a \
    ON a.edition_id = u.id AND a.nr > 1 \
LEFT \
JOIN core_awarded_literary_award tlp \
    ON tlp.edition_id = u.id \
LEFT \
JOIN core_literary_award lp \
    ON tlp.literary_award_id = lp.id \
LEFT \
JOIN core_source source \
    ON u.source_id = source.id \
WHERE u.hidden = 0 \
AND number_of_editions > 0 \
GROUP \
   BY work.id \
LIMIT 1;

两个数据库中的数据应该是相同的(我从一个转储到文件并恢复到另一个)。当我执行 EXPLAIN SELECT 时,答案之间存在差异:(删除了相同的行)

快速测试机:

+----+-------------+-------------+--------+---------------------------------------+---------------------------------------+---------+-----------------------------------+------+-------------+
| id | select_type | table       | type   | possible_keys                         | key                                   | key_len | ref                               | rows | Extra       |
+----+-------------+-------------+--------+---------------------------------------+---------------------------------------+---------+-----------------------------------+------+-------------+
|  1 | SIMPLE      | work        | index  | PRIMARY,work_number_of_editions       | PRIMARY                               | 4       | NULL                              |    2 | Using where |
+----+-------------+-------------+--------+---------------------------------------+---------------------------------------+---------+-----------------------------------+------+-------------+

慢机器:

+----+-------------+-------------+--------+---------------------------------------+---------------------------------------+---------+-----------------------------------+--------+-----------------------------+
| id | select_type | table       | type   | possible_keys                         | key                                   | key_len | ref                               | rows   | Extra                       |
+----+-------------+-------------+--------+---------------------------------------+---------------------------------------+---------+-----------------------------------+--------+-----------------------------+
|  1 | SIMPLE      | work        | range  | PRIMARY,work_number_of_editions       | work_number_of_editions               | 5       | NULL                              | 106796 | Using where; Using filesort | 
+----+-------------+-------------+--------+---------------------------------------+---------------------------------------+---------+-----------------------------------+--------+-----------------------------+

这让我很困惑;为什么 ubuntu 服务器与另一个服务器具有相同的数据时会报告 106796 行?以及为什么慢机器使用文件排序?

【问题讨论】:

您是否比较了两个系统上的计划? 为了更好地比较两台服务器,请添加 SQL_NO_CACHE 选项。 @Dennis Haarbrink:SQL_NO_CACHE 在这里什么都不做。它是查询缓存的控件。 @Morgan Tocker:我知道,但是当查询结果被缓存时,你会得到一个错误的比较。 【参考方案1】:

尝试在两台服务器上使用EXPLAIN SELECT ...。这将显示正在使用哪些索引以及如何使用。如果两台机器上的设置有任何差异,它应该会影响查询计划(例如,某些表在您的服务器上缺少索引)。

两台机器上的数据集是否相同?如果您的家用计算机上只有一小部分数据,而服务器上有完整的“较大”数据集,那也会影响事情。您正在使用 lot 的 DISTINCT 修饰符和 GROUP_CONCATS 并加入大量表。这可能需要使用大量临时表,并且您可能会超出可用内存,从而迫使 MySQL 使用磁盘缓冲,这与内存中的操作相比非常慢。

【讨论】:

现在我已经从 ubuntu 盒子中转储了所有表并导入到测试机器中。它们现在应该是相同的。但是,EXPLAIN SELECT 不一样:我将编辑我的问题以包含不同的响应。 你在 home box 上运行什么版本的 MySQL?从 ubuntu 服务器版本的外观来看,它来自旧版本,因为 Ubuntu 10.04LTS 附带 v5.1.41。 在我的测试机器上,我在 mac 上从 macports 运行 MySQL 5.5.2-m2。 这是一个相当大的区别。 5.5 是具有大量内部更改的开发/前沿版本,这可以解释查询性能的差异。我建议降级到更接近你的 ubuntu 机器上的版本,看看这是否会让你的 Mac 和服务器一样慢。【参考方案2】:

尝试OPTIMIZEANALYZE所有表格

【讨论】:

现在我都做了,一切都OK了。不幸的是,它并没有提高性能。

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