SHOW PROCESSLIST顯示哪些線程正在運(yùn)行。您也可以使用MySQLadmin processlist語(yǔ)句得到此信息。如果您有SUPER權(quán)限，您可以看到所有線程。否則，您只能看到您自己的線程（也就是，與您正在使用的MySQL賬戶相關(guān)的線程）。
如果您不使用FULL關(guān)鍵詞，則只顯示每個(gè)查詢的前100個(gè)字符。

本語(yǔ)句報(bào)告TCP/IP連接的主機(jī)名稱（采用host_name:client_port格式），以方便地判定哪個(gè)客戶端正在做什么。


如果您得到“too many connections”錯(cuò)誤信息，并且想要了解正在發(fā)生的情況，本語(yǔ)句是非常有用的。MySQL保留一個(gè)額外的連接，讓擁有SUPER權(quán)限的 賬戶使用，以確保管理員能夠隨時(shí)連接和檢查系統(tǒng)（假設(shè)您沒(méi)有把此權(quán)限給予所有的用戶）。


這個(gè)命令中最關(guān)鍵的就是state列，mysql列出的狀態(tài)主要有以下幾種：

Checking table
　正在檢查數(shù)據(jù)表（這是自動(dòng)的）。
Closing tables
　正在將表中修改的數(shù)據(jù)刷新到磁盤中，同時(shí)正在關(guān)閉已經(jīng)用完的表。這是一個(gè)很快的操作，如果不是這樣的話，就應(yīng)該確認(rèn)磁盤空間是否已經(jīng)滿了或者磁盤是否正處于重負(fù)中。
Connect Out
　復(fù)制從服務(wù)器正在連接主服務(wù)器。
Copying to tmp table on disk
　由于臨時(shí)結(jié)果集大于tmp_table_size，正在將臨時(shí)表從內(nèi)存存儲(chǔ)轉(zhuǎn)為磁盤存儲(chǔ)以此節(jié)省內(nèi)存。
Creating tmp table
　正在創(chuàng)建臨時(shí)表以存放部分查詢結(jié)果。
deleting from main table
　服務(wù)器正在執(zhí)行多表刪除中的第一部分，剛刪除第一個(gè)表。
deleting from reference tables
　服務(wù)器正在執(zhí)行多表刪除中的第二部分，正在刪除其他表的記錄。
Flushing tables
　正在執(zhí)行FLUSH TABLES，等待其他線程關(guān)閉數(shù)據(jù)表。
Killed
　發(fā)送了一個(gè)kill請(qǐng)求給某線程，那么這個(gè)線程將會(huì)檢查kill標(biāo)志位，同時(shí)會(huì)放棄下一個(gè)kill請(qǐng)求。MySQL會(huì)在每次的主循環(huán)中檢查kill標(biāo)志位，不過(guò)有些情況下該線程可能會(huì)過(guò)一小段才能死掉。如果該線程程被其他線程鎖住了，那么kill請(qǐng)求會(huì)在鎖釋放時(shí)馬上生效。
Locked
　被其他查詢鎖住了。
Sending data
　正在處理SELECT查詢的記錄，同時(shí)正在把結(jié)果發(fā)送給客戶端。
Sorting for group
　正在為GROUP BY做排序。
　Sorting for order
　正在為ORDER BY做排序。
Opening tables
　這個(gè)過(guò)程應(yīng)該會(huì)很快，除非受到其他因素的干擾。例如，在執(zhí)ALTER TABLE或LOCK TABLE語(yǔ)句行完以前，數(shù)據(jù)表無(wú)法被其他線程打開(kāi)。正嘗試打開(kāi)一個(gè)表。
Removing duplicates
　正在執(zhí)行一個(gè)SELECT DISTINCT方式的查詢，但是MySQL無(wú)法在前一個(gè)階段優(yōu)化掉那些重復(fù)的記錄。因此，MySQL需要再次去掉重復(fù)的記錄，然后再把結(jié)果發(fā)送給客戶端。
Reopen table
　獲得了對(duì)一個(gè)表的鎖，但是必須在表結(jié)構(gòu)修改之后才能獲得這個(gè)鎖。已經(jīng)釋放鎖，關(guān)閉數(shù)據(jù)表，正嘗試重新打開(kāi)數(shù)據(jù)表。
Repair by sorting
　修復(fù)指令正在排序以創(chuàng)建索引。
Repair with keycache
　修復(fù)指令正在利用索引緩存一個(gè)一個(gè)地創(chuàng)建新索引。它會(huì)比Repair by sorting慢些。
Searching rows for update
　正在講符合條件的記錄找出來(lái)以備更新。它必須在UPDATE要修改相關(guān)的記錄之前就完成了。
Sleeping
　正在等待客戶端發(fā)送新請(qǐng)求.
System lock
　正在等待取得一個(gè)外部的系統(tǒng)鎖。如果當(dāng)前沒(méi)有運(yùn)行多個(gè)mysqld服務(wù)器同時(shí)請(qǐng)求同一個(gè)表，那么可以通過(guò)增加--skip-external-locking參數(shù)來(lái)禁止外部系統(tǒng)鎖。
Upgrading lock
　INSERT DELAYED正在嘗試取得一個(gè)鎖表以插入新記錄。
Updating
　正在搜索匹配的記錄，并且修改它們。
User Lock
　正在等待GET_LOCK()。
Waiting for tables
　該線程得到通知，數(shù)據(jù)表結(jié)構(gòu)已經(jīng)被修改了，需要重新打開(kāi)數(shù)據(jù)表以取得新的結(jié)構(gòu)。然后，為了能的重新打開(kāi)數(shù)據(jù)表，必須等到所有其他線程關(guān)閉這個(gè)表。以下幾種情況下會(huì)產(chǎn)生這個(gè)通知：FLUSH TABLES tbl_name, ALTER TABLE, RENAME TABLE, REPAIR TABLE, ANALYZE TABLE,或OPTIMIZE TABLE。
waiting for handler insert
　INSERT DELAYED已經(jīng)處理完了所有待處理的插入操作，正在等待新的請(qǐng)求。
　大部分狀態(tài)對(duì)應(yīng)很快的操作，只要有一個(gè)線程保持同一個(gè)狀態(tài)好幾秒鐘，那么可能是有問(wèn)題發(fā)生了，需要檢查一下。
　還有其他的狀態(tài)沒(méi)在上面中列出來(lái)，不過(guò)它們大部分只是在查看服務(wù)器是否有存在錯(cuò)誤是才用得著。


mysql 查看當(dāng)前連接數(shù)


命令： show processlist; 
如果是root帳號(hào)，你能看到所有用戶的當(dāng)前連接。如果是其它普通帳號(hào)，只能看到自己占用的連接。 
show processlist;只列出前100條，如果想全列出請(qǐng)使用show full processlist; 
mysql> show processlist;


命令： show status;


Aborted_clients 由于客戶沒(méi)有正確關(guān)閉連接已經(jīng)死掉，已經(jīng)放棄的連接數(shù)量。 
Aborted_connects 嘗試已經(jīng)失敗的MySQL服務(wù)器的連接的次數(shù)。 
Connections 試圖連接MySQL服務(wù)器的次數(shù)。 
Created_tmp_tables 當(dāng)執(zhí)行語(yǔ)句時(shí)，已經(jīng)被創(chuàng)造了的隱含臨時(shí)表的數(shù)量。 
Delayed_insert_threads 正在使用的延遲插入處理器線程的數(shù)量。 
Delayed_writes 用INSERT DELAYED寫入的行數(shù)。 
Delayed_errors 用INSERT DELAYED寫入的發(fā)生某些錯(cuò)誤(可能重復(fù)鍵值)的行數(shù)。 
Flush_commands 執(zhí)行FLUSH命令的次數(shù)。 
Handler_delete 請(qǐng)求從一張表中刪除行的次數(shù)。 
Handler_read_first 請(qǐng)求讀入表中第一行的次數(shù)。 
Handler_read_key 請(qǐng)求數(shù)字基于鍵讀行。 
Handler_read_next 請(qǐng)求讀入基于一個(gè)鍵的一行的次數(shù)。 
Handler_read_rnd 請(qǐng)求讀入基于一個(gè)固定位置的一行的次數(shù)。 
Handler_update 請(qǐng)求更新表中一行的次數(shù)。 
Handler_write 請(qǐng)求向表中插入一行的次數(shù)。 
Key_blocks_used 用于關(guān)鍵字緩存的塊的數(shù)量。 
Key_read_requests 請(qǐng)求從緩存讀入一個(gè)鍵值的次數(shù)。 
Key_reads 從磁盤物理讀入一個(gè)鍵值的次數(shù)。 
Key_write_requests 請(qǐng)求將一個(gè)關(guān)鍵字塊寫入緩存次數(shù)。 
Key_writes 將一個(gè)鍵值塊物理寫入磁盤的次數(shù)。 
Max_used_connections 同時(shí)使用的連接的最大數(shù)目。 
Not_flushed_key_blocks 在鍵緩存中已經(jīng)改變但是還沒(méi)被清空到磁盤上的鍵塊。 
Not_flushed_delayed_rows 在INSERT DELAY隊(duì)列中等待寫入的行的數(shù)量。 
Open_tables 打開(kāi)表的數(shù)量。 
Open_files 打開(kāi)文件的數(shù)量。 
Open_streams 打開(kāi)流的數(shù)量(主要用于日志記載） 
Opened_tables 已經(jīng)打開(kāi)的表的數(shù)量。 
Questions 發(fā)往服務(wù)器的查詢的數(shù)量。 
Slow_queries 要花超過(guò)long_query_time時(shí)間的查詢數(shù)量。 
Threads_connected 當(dāng)前打開(kāi)的連接的數(shù)量。 
Threads_running 不在睡眠的線程數(shù)量。 
Uptime 服務(wù)器工作了多少秒。


After create


This occurs when the thread creates a table (including internal temporary tables), at the end of the function that creates the table. This state is used even if the table could not be created due to some error.


Analyzing


The thread is calculating a MyISAM table key distributions (for example, for ANALYZE TABLE).


checking permissions


The thread is checking whether the server has the required privileges to execute the statement.


Checking table


The thread is performing a table check operation.


cleaning up


The thread has processed one command and is preparing to free memory and reset certain state variables.


closing tables


The thread is flushing the changed table data to disk and closing the used tables. This should be a fast operation. If not, you should verify that you do not have a full disk and that the disk is not in very heavy use.


converting HEAP to MyISAM


The thread is converting an internal temporary table from a MEMORY table to an on-disk MyISAM table.


copy to tmp table


The thread is processing an ALTER TABLE statement. This state occurs after the table with the new structure has been created but before rows are copied into it.


Copying to group table


If a statement has different ORDER BY and GROUP BY criteria, the rows are sorted by group and copied to a temporary table.


Copying to tmp table


The server is copying to a temporary table in memory.


Copying to tmp table on disk


The server is copying to a temporary table on disk. The temporary result set was larger than tmp_table_size and the thread is changing the temporary table from in-memory to disk-based format to save memory.


Creating index


The thread is processing ALTER TABLE ... ENABLE KEYS for a MyISAM table.


Creating sort index


The thread is processing a SELECT that is resolved using an internal temporary table.


creating table


The thread is creating a table. This includes creation of temporary tables.


Creating tmp table


The thread is creating a temporary table in memory or on disk. If the table is created in memory but later is converted to an on-disk table, the state during that operation will be Copying to tmp table on disk.


deleting from main table


The server is executing the first part of a multiple-table delete. It is deleting only from the first table, and saving columns and offsets to be used for deleting from the other (reference) tables.


deleting from reference tables


The server is executing the second part of a multiple-table delete and deleting the matched rows from the other tables.


discard_or_import_tablespace


The thread is processing an ALTER TABLE ... DISCARD TABLESPACE or ALTER TABLE ... IMPORT TABLESPACE statement.


end


This occurs at the end but before the cleanup of ALTER TABLE, CREATE VIEW, DELETE, INSERT, SELECT, or UPDATE statements.


executing


The thread has begun executing a statement.


Execution of init_command


The thread is executing statements in the value of the init_command system variable.


freeing items


The thread has executed a command. This state is usually followed by cleaning up.


Flushing tables


The thread is executing FLUSH TABLES and is waiting for all threads to close their tables.


FULLTEXT initialization


The server is preparing to perform a natural-language full-text search.


init


This occurs before the initialization of ALTER TABLE, DELETE, INSERT, SELECT, or UPDATE statements.


Killed


Someone has sent a KILL statement to the thread and it should abort next time it checks the kill flag. The flag is checked in each major loop in MySQL, but in some cases it might still take a short time for the thread to die. If the thread is locked by some other thread, the kill takes effect as soon as the other thread releases its lock.


Locked


The query is locked by another query.


logging slow query


The thread is writing a statement to the slow-query log.


NULL


This state is used for the SHOW PROCESSLIST state.


login


The initial state for a connection thread until the client has been authenticated successfully.


Opening tables, Opening table


The thread is trying to open a table. This is should be very fast procedure, unless something prevents opening. For example, an ALTER TABLE or a LOCK TABLE statement can prevent opening a table until the statement is finished.


preparing


This state occurs during query optimization.


Purging old relay logs


The thread is removing unneeded relay log files.


query end


This state occurs after processing a query but before the freeing items state.


Reading from net


The server is reading a packet from the network.


Removing duplicates


The query was using SELECT DISTINCT in such a way that MySQL could not optimize away the distinct operation at an early stage. Because of this, MySQL requires an extra stage to remove all duplicated rows before sending the result to the client.


removing tmp table


The thread is removing an internal temporary table after processing a SELECT statement. This state is not used if no temporary table was created.


rename


The thread is renaming a table.


rename result table


The thread is processing an ALTER TABLE statement, has created the new table, and is renaming it to replace the original table.


Reopen tables


The thread got a lock for the table, but noticed after getting the lock that the underlying table structure changed. It has freed the lock, closed the table, and is trying to reopen it.


Repair by sorting


The repair code is using a sort to create indexes.


Repair done


The thread has completed a multi-threaded repair for a MyISAM table.


Repair with keycache


The repair code is using creating keys one by one through the key cache. This is much slower than Repair by sorting.


Rolling back


The thread is rolling back a transaction.


Saving state


For MyISAM table operations such as repair or analysis, the thread is saving the new table state to the .MYI file header. State includes information such as number of rows, the AUTO_INCREMENT counter, and key distributions.


Searching rows for update


The thread is doing a first phase to find all matching rows before updating them. This has to be done if the UPDATE is changing the index that is used to find the involved rows.


Sending data


The thread is processing rows for a SELECT statement and also is sending data to the client.


setup


The thread is beginning an ALTER TABLE operation.


Sorting for group


The thread is doing a sort to satisfy a GROUP BY.


Sorting for order


The thread is doing a sort to satisfy a ORDER BY.


Sorting index


The thread is sorting index pages for more efficient access during a MyISAM table optimization operation.


Sorting result


For a SELECT statement, this is similar to Creating sort index, but for nontemporary tables.


statistics


The server is calculating statistics to develop a query execution plan.


System lock


The thread is going to request or is waiting for an internal or external system lock for the table. If this state is being caused by requests for external locks and you are not using multiple mysqld servers that are accessing the same tables, you can disable external system locks with the --skip-external-locking option. However, external locking is disabled by default, so it is likely that this option will have no effect. For SHOW PROFILE, this state means the thread is requesting the lock (not waiting for it).


Table lock


The next thread state after System lock. The thread has acquired an external lock and is going to request an internal table lock.


Updating


The thread is searching for rows to update and is updating them.


updating main table


The server is executing the first part of a multiple-table update. It is updating only the first table, and saving columns and offsets to be used for updating the other (reference) tables.


updating reference tables


The server is executing the second part of a multiple-table update and updating the matched rows from the other tables.


User lock


The thread is going to request or is waiting for an advisory lock requested with a GET_LOCK() call. For SHOW PROFILE, this state means the thread is requesting the lock (not waiting for it).


Waiting for tables, Waiting for table


The thread got a notification that the underlying structure for a table has changed and it needs to reopen the table to get the new structure. However, to reopen the table, it must wait until all other threads have closed the table in question.


This notification takes place if another thread has used FLUSH TABLES or one of the following statements on the table in question: FLUSH TABLES tbl_name, ALTER TABLE, RENAME TABLE, REPAIR TABLE, ANALYZE TABLE, or OPTIMIZE TABLE.


Waiting on cond


A generic state in which the thread is waiting for a condition to become true. No specific state information is available.


Writing to net


The server is writing a packet to the network.

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