我有一个很宽的（很多列）表，里面有大约400,000行，InnoDb，UTF8MB4_Unicode，大约60列和11个索引。
见下面的定义。
当我执行duration时，它仅为表中没有那么多行的用户提供正确的计数。
如果我 RECREATE + ANALYZE ，即当你在InnoDb表上执行SELECT count(*) FROM table_name WHERE user_id = X时MySQL会做什么，它可以很好地计数显示正确的值，直到我们在表中插入新行再次，然后计数关闭。
我在这里遗漏了一些关于SELECT计数的“常识”，或者这是最新MySQL版本中的一个错误，还是因为我的表有很多索引或者其他东西。在升级到5.6.25之前，我从未遇到过这个问题。
我应该提到 my.cnf 只有128 Mb的InnoDb_Pool_Buffer，这可能是针对这个大小的db（不是很大但是从mysqldump gzipped大约300mb）的尺寸。
非常感谢你花时间回答。
编辑从mysqltuner.pl添加输出 - 我非常感谢你们解释它们的任何帮助（我只有Innodb表，没有MyISAM）。请注意它是如何说我有44个碎片表，但我最近刚刚对它们进行了重新创建+分析。这是由于其他参数设置得太低了吗？再次感谢。
删除了Mysql Tuner输出，为更多相关数字提供了位置。
表定义（匿名）：
已删除表定义，因为不再相关
EDIT2 根据要求，提供SHOW GLOBAL STATUS和SHOW VARIABLES的输出
OPTIMIZE TABLE显示变量
Aborted_clients 0
Aborted_connects 5
Binlog_cache_disk_use 0
Binlog_cache_use 0
Binlog_stmt_cache_disk_use 0
Binlog_stmt_cache_use 0
Bytes_received 1392447055
Bytes_sent 20991720246
Com_admin_commands 1739
Com_assign_to_keycache 0
Com_alter_db 0
Com_alter_db_upgrade 0
Com_alter_event 0
Com_alter_function 0
Com_alter_procedure 0
Com_alter_server 0
Com_alter_table 10
Com_alter_tablespace 0
Com_alter_user 0
Com_analyze 0
Com_begin 0
Com_binlog 0
Com_call_procedure 1
Com_change_db 1567913
Com_change_master 0
Com_check 0
Com_checksum 0
Com_commit 0
Com_create_db 0
Com_create_event 0
Com_create_function 0
Com_create_index 0
Com_create_procedure 1
Com_create_server 0
Com_create_table 2
Com_create_trigger 0
Com_create_udf 0
Com_create_user 0
Com_create_view 0
Com_dealloc_sql 0
Com_delete 7717
Com_delete_multi 0
Com_do 0
Com_drop_db 0
Com_drop_event 0
Com_drop_function 0
Com_drop_index 0
Com_drop_procedure 2
Com_drop_server 0
Com_drop_table 2
Com_drop_trigger 0
Com_drop_user 0
Com_drop_view 0
Com_empty_query 0
Com_execute_sql 0
Com_flush 0
Com_get_diagnostics 0
Com_grant 0
Com_ha_close 0
Com_ha_open 0
Com_ha_read 0
Com_help 0
Com_insert 169112
Com_insert_select 37
Com_install_plugin 0
Com_kill 0
Com_load 0
Com_lock_tables 6
Com_optimize 0
Com_preload_keys 0
Com_prepare_sql 0
Com_purge 0
Com_purge_before_date 0
Com_release_savepoint 0
Com_rename_table 0
Com_rename_user 0
Com_repair 0
Com_replace 0
Com_replace_select 0
Com_reset 0
Com_resignal 0
Com_revoke 0
Com_revoke_all 0
Com_rollback 0
Com_rollback_to_savepoint 0
Com_savepoint 0
Com_select 5721646
Com_set_option 3032
Com_signal 0
Com_show_binlog_events 0
Com_show_binlogs 0
Com_show_charsets 0
Com_show_collations 35
Com_show_create_db 86
Com_show_create_event 0
Com_show_create_func 0
Com_show_create_proc 0
Com_show_create_table 587
Com_show_create_trigger 0
Com_show_databases 3
Com_show_engine_logs 0
Com_show_engine_mutex 0
Com_show_engine_status 0
Com_show_events 18
Com_show_errors 0
Com_show_fields 600
Com_show_function_code 0
Com_show_function_status 0
Com_show_grants 0
Com_show_keys 88
Com_show_master_status 0
Com_show_open_tables 0
Com_show_plugins 0
Com_show_privileges 0
Com_show_procedure_code 0
Com_show_procedure_status 0
Com_show_processlist 0
Com_show_profile 0
Com_show_profiles 0
Com_show_relaylog_events 0
Com_show_slave_hosts 0
Com_show_slave_status 0
Com_show_status 1843
Com_show_storage_engines 3
Com_show_table_status 589
Com_show_tables 6
Com_show_triggers 533
Com_show_variables 1956
Com_show_warnings 0
Com_slave_start 0
Com_slave_stop 0
Com_stmt_close 0
Com_stmt_execute 0
Com_stmt_fetch 0
Com_stmt_prepare 0
Com_stmt_reprepare 0
Com_stmt_reset 0
Com_stmt_send_long_data 0
Com_truncate 36
Com_uninstall_plugin 0
Com_unlock_tables 6
Com_update 640052
Com_update_multi 0
Com_xa_commit 0
Com_xa_end 0
Com_xa_prepare 0
Com_xa_recover 0
Com_xa_rollback 0
Com_xa_start 0
Compression OFF
Connection_errors_accept 0
Connection_errors_internal 0
Connection_errors_max_connections 0
Connection_errors_peer_address 0
Connection_errors_select 0
Connection_errors_tcpwrap 0
Connections 1567347
Created_tmp_disk_tables 247145
Created_tmp_files 20174
Created_tmp_tables 386918
Delayed_errors 0
Delayed_insert_threads 0
Delayed_writes 0
Flush_commands 1
Handler_commit 6537068
Handler_delete 33452
Handler_discover 0
Handler_external_lock 20879224
Handler_mrr_init 0
Handler_prepare 0
Handler_read_first 1751492
Handler_read_key 5384829832
Handler_read_last 211053
Handler_read_next 19630786637
Handler_read_prev 6110703982
Handler_read_rnd 73007565
Handler_read_rnd_next 11782800964
Handler_rollback 477
Handler_savepoint 0
Handler_savepoint_rollback 0
Handler_update 3632409114
Handler_write 20236858098
Innodb_buffer_pool_dump_status not started
Innodb_buffer_pool_load_status not started
Innodb_buffer_pool_pages_data 45561
Innodb_buffer_pool_bytes_data 746471424
Innodb_buffer_pool_pages_dirty 10
Innodb_buffer_pool_bytes_dirty 163840
Innodb_buffer_pool_pages_flushed 2075723
Innodb_buffer_pool_pages_free 1024
Innodb_buffer_pool_pages_misc 4614
Innodb_buffer_pool_pages_total 51199
Innodb_buffer_pool_read_ahead_rnd 0
Innodb_buffer_pool_read_ahead 337427
Innodb_buffer_pool_read_ahead_evicted 4272
Innodb_buffer_pool_read_requests 50351166042
Innodb_buffer_pool_reads 2496152
Innodb_buffer_pool_wait_free 0
Innodb_buffer_pool_write_requests 25099776
Innodb_data_fsyncs 680776
Innodb_data_pending_fsyncs 0
Innodb_data_pending_reads 0
Innodb_data_pending_writes 0
Innodb_data_read 46916046848
Innodb_data_reads 2863706
Innodb_data_writes 3201512
Innodb_data_written 69819479040
Innodb_dblwr_pages_written 2075723
Innodb_dblwr_writes 103028
Innodb_have_atomic_builtins ON
Innodb_log_waits 0
Innodb_log_write_requests 3054739
Innodb_log_writes 914722
Innodb_os_log_fsyncs 244890
Innodb_os_log_pending_fsyncs 0
Innodb_os_log_pending_writes 0
Innodb_os_log_written 1752017408
Innodb_page_size 16384
Innodb_pages_created 59717
Innodb_pages_read 2863523
Innodb_pages_written 2075723
Innodb_row_lock_current_waits 0
Innodb_row_lock_time 7419
Innodb_row_lock_time_avg 390
Innodb_row_lock_time_max 1422
Innodb_row_lock_waits 19
Innodb_rows_deleted 33451
Innodb_rows_inserted 5432696
Innodb_rows_read 29436124622
Innodb_rows_updated 596060
Innodb_num_open_files 118
Innodb_truncated_status_writes 0
Innodb_available_undo_logs 128
Key_blocks_not_flushed 0
Key_blocks_unused 6698
Key_blocks_used 6698
Key_read_requests 45635462325
Key_reads 6589434
Key_write_requests 12131142501
Key_writes 9617220
Last_query_cost 0.000000
Last_query_partial_plans 0
Max_used_connections 17
Not_flushed_delayed_rows 0
Open_files 46
Open_streams 0
Open_table_definitions 166
Open_tables 287
Opened_files 1009110
Opened_table_definitions 226
Opened_tables 397
Performance_schema_accounts_lost 0
Performance_schema_cond_classes_lost 0
Performance_schema_cond_instances_lost 0
Performance_schema_digest_lost 0
Performance_schema_file_classes_lost 0
Performance_schema_file_handles_lost 0
Performance_schema_file_instances_lost 0
Performance_schema_hosts_lost 0
Performance_schema_locker_lost 0
Performance_schema_mutex_classes_lost 0
Performance_schema_mutex_instances_lost 0
Performance_schema_rwlock_classes_lost 0
Performance_schema_rwlock_instances_lost 0
Performance_schema_session_connect_attrs_lost 0
Performance_schema_socket_classes_lost 0
Performance_schema_socket_instances_lost 0
Performance_schema_stage_classes_lost 0
Performance_schema_statement_classes_lost 0
Performance_schema_table_handles_lost 0
Performance_schema_table_instances_lost 0
Performance_schema_thread_classes_lost 0
Performance_schema_thread_instances_lost 0
Performance_schema_users_lost 0
Prepared_stmt_count 0
Qcache_free_blocks 1
Qcache_free_memory 1031352
Qcache_hits 0
Qcache_inserts 0
Qcache_lowmem_prunes 0
Qcache_not_cached 5720393
Qcache_queries_in_cache 0
Qcache_total_blocks 1
Queries 9771703
Questions 9640606
Select_full_join 4608
Select_full_range_join 0
Select_range 385947
Select_range_check 0
Select_scan 1745605
Slave_heartbeat_period
Slave_last_heartbeat
Slave_open_temp_tables 0
Slave_received_heartbeats
Slave_retried_transactions
Slave_running OFF
Slow_launch_threads 0
Slow_queries 16
Sort_merge_passes 17244
Sort_range 214894
Sort_rows 199889850
Sort_scan 260475
Ssl_accept_renegotiates 0
Ssl_accepts 0
Ssl_callback_cache_hits 0
Ssl_cipher
Ssl_cipher_list
Ssl_client_connects 0
Ssl_connect_renegotiates 0
Ssl_ctx_verify_depth 0
Ssl_ctx_verify_mode 0
Ssl_default_timeout 0
Ssl_finished_accepts 0
Ssl_finished_connects 0
Ssl_server_not_after
Ssl_server_not_before
Ssl_session_cache_hits 0
Ssl_session_cache_misses 0
Ssl_session_cache_mode NONE
Ssl_session_cache_overflows 0
Ssl_session_cache_size 0
Ssl_session_cache_timeouts 0
Ssl_sessions_reused 0
Ssl_used_session_cache_entries 0
Ssl_verify_depth 0
Ssl_verify_mode 0
Ssl_version
Table_locks_immediate 10362193
Table_locks_waited 49
Table_open_cache_hits 10367123
Table_open_cache_misses 396
Table_open_cache_overflows 0
Tc_log_max_pages_used 0
Tc_log_page_size 0
Tc_log_page_waits 0
Threads_cached 7
Threads_connected 3
Threads_created 30
Threads_running 1
Uptime 520269
Uptime_since_flush_status 520269
答案 0 :(得分：0)
忽略“碎片化” - InnoDB表基本上不是问题。不要运行OPTIMIZE TABLE。 （如果你这样做，请在之前和之后做SHOW TABLE STATUS - 看看它没有多大帮助。）
你有4GB的内存？ innodb_buffer_pool_size可能会提升到600M。
禁用质量控制 - 对于生产系统来说，这通常是“好的”。
很少需要 BIGINT（8字节），除非你期望有超过40亿的东西（INT UNSIGNED - 4字节 - 最多40亿）。
如果您想要更多mysqltuner提供的分析，请向我提供SHOW VARIABLES;和SHOW GLOBAL STATUS;（在服务器启动至少一天后）。
回到主要问题......我认为这个特定查询没有理由错：
SELECT count(*) FROM table_name WHERE user_id = X
如果您执行EXPLAIN SELECT ...，您会看到它将使用索引。 InnoDB中的索引永远不会被破坏。
您建议5.6.25可能有问题。是的，总有这样的机会。 （MySQL因没有回归而享有良好的声誉，这当然也是如此。）请关注bugs.mysql.com。在那里提交一个bug。考虑降级。
VARIABLES / STATUS分析
在设置中找不到很多：
（Key_reads）= 6,589,434 / 520269 = 13 / sec - MyISAM索引读取（从磁盘）速率
（Key_reads + Key_writes）=（6589434 + 9617220）/ 520269 = 31 / sec - MyISAM索引I / O率
你正在使用很多MyISAM; key_buffer_size （8M）应该增加到100M。
（Created_tmp_disk_tables /（Created_tmp_disk_tables + Created_tmp_tables））= 247,145 /（247145 + 386918）= 39.0％ - 溢出到磁盘的临时表的百分比
- 也许增加tmp_table_size和max_heap_table_size;避免blob等。
（Select_scan）= 1,745,605 / 520269 = 3.4 /秒 - 全表扫描
- 添加索引/优化查询（除非它们是小表）
（Select_scan / Com_select）= 1,745,605 / 5721646 = 30.5％ - 执行全表扫描的选择的百分比。 （可能会受到存储例程的愚弄。）
- 添加索引/优化查询
（open_files_limit）= 1,024 - ulimit -n
- 要允许更多文件，请更改 ulimit 或/etc/security/limits.conf或sysctl.conf（kern.maxfiles＆amp; kern.maxfilesperproc）或其他内容（取决于操作系统）
（连接）= 1,567,347 / 520269 = 3 /秒 - 连接
- 增加wait_timeout;使用汇集？
您有半个查询缓存。您应该同时设置query_cache_type = OFF和query_cache_size = 0。 （根据谣言）QC代码中的“错误”会留下一些代码，除非您关闭这两个设置。