爲什麼這個查詢需要這麼長時間？

我有一個複雜的查詢，我需要在MySQL服務器上運行。爲什麼這個查詢需要這麼長時間？

在我的家測試框中，一個mac，查詢需要報告0.00秒，並立即返回reslut。

然而，在我的服務器上，一個Ubuntu的盒子，同樣的查詢需要大約3.30分鐘，使用相同的數據。

數據庫使用InnoDB表。 Ubuntu的盒子有一個64位的內核，並且爲此編譯了mysql。

爲什麼ubuntu服務器需要更長的時間來執行查詢？

這些是從Ubuntu盒的配置變量：

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      | 
+---------------------------------+-----------------------------+

這是查詢：

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;

在兩個數據庫中的數據應該是相同的（I轉儲到從一個文件並恢復到另一個）。當我做EXPLAIN SELECT，有答案之間的區別：（相同的行編輯了）

快速測試機：

+----+-------------+-------------+--------+---------------------------------------+---------------------------------------+---------+-----------------------------------+------+-------------+ 
| 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 | 
+----+-------------+-------------+--------+---------------------------------------+---------------------------------------+---------+-----------------------------------+------+-------------+

慢速機：

+----+-------------+-------------+--------+---------------------------------------+---------------------------------------+---------+-----------------------------------+--------+-----------------------------+ 
| 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 | 
+----+-------------+-------------+--------+---------------------------------------+---------------------------------------+---------+-----------------------------------+--------+-----------------------------+

這讓我爲難;爲什麼ubuntu服務器在與其他數據具有相同數據時報告106796行？爲什麼慢速機器使用文件？

來源

2010-09-13 Hobhouse

您是否比較了兩個系統上的計劃？ – 2010-09-13 09:49:04

要在兩臺服務器之間獲得更好的比較，請添加SQL_NO_CACHE選項。 – 2010-09-13 10:41:45

@Dennis Haarbrink：SQL_NO_CACHE在這裏不做任何事情。它是查詢緩存的控件。 – 2010-09-23 20:13:13

嘗試OPTIMIZE和ANALYZE所有表

來源

2010-09-13 10:36:17 zerkms

現在我已經完成了兩項工作，並取得了所有好成績。不幸的是，它並沒有提高性能。 – Hobhouse 2010-09-13 11:30:38

嘗試在兩臺服務器上使用EXPLAIN SELECT ...。這將顯示哪些索引正在使用以及如何使用。如果兩臺計算機上的設置有所不同，它應該會影響查詢計劃（例如某些表缺少服務器上的索引）。

兩臺機器上的數據集是否相同？如果您的家庭計算機上只有一小部分數據，並且服務器上有完整的「較大」數據集，那麼這也會影響事情。您正在使用DISTINCT修飾符和GROUP_CONCATS的批次並加入大量表格。這可能需要使用相當數量的臨時表，並且您可能會超出可用內存，從而迫使MySQL使用磁盤緩衝，與內存操作相比，這非常緩慢。

來源

2010-09-13 13:41:06

現在我已經把所有的表格都從ubuntu盒子中刪除了，然後導入到測試機器上。他們現在應該是相同的。然而，EXPLAIN SELECT並不相同：我將編輯我的問題以包含不同的響應。 – Hobhouse 2010-09-13 14:52:48

你在家用機器上運行的MySQL版本是什麼？從ubuntu服務器版本的外觀來看，它來自舊版本，Ubuntu 10.04LTS隨附v5.1.41。 – 2010-09-13 15:36:02

在我的測試框中，我在Mac上從macports運行MySQL 5.5.2-m2。 – Hobhouse 2010-09-13 15:58:11

爲什麼這個查詢需要這麼長時間？

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