我想了解特定類型的死鎖是如何發生的。瞭解特定類型的死鎖
我有一個非常簡單的死鎖圖與兩個資源和兩個進程。一個是運行SELECT
另一個UPDATE
聲明。我知道有些情況會導致死鎖,但我不明白在這種情況下會發生什麼。
被害人查詢:
SELECT id_particle, id_event, dt_created, dt_rcvd, tlx_no, from_routename, re, deleted
FROM msg_list
WHERE to_routename = @P0
AND ((dt_answ IS NULL AND b_complete = 0 AND id_event=6) OR (id_event = 10 AND deleted = 0)
OR (from_id_post = 9705 AND deleted = 0))
ORDER BY dt_created ASC
冠軍獎金查詢:
UPDATE msg_list
SET
ID_EVENT=7,
STATUS='Answered',
DT_ANSW={ts '2017-02-12 05:34:14'
WHERE ID_PARTICLE = 46211816
完整的僵局圖:
<deadlock-list>
<deadlock victim="process30aa42d468">
<process-list>
<process id="process30aa42d468" taskpriority="0" logused="0" waitresource="PAGE: 6:1:155679 " waittime="921" ownerId="427175775" transactionname="SELECT" lasttranstarted="2017-02-12T05:34:48.293" XDES="0x3126fbba40" lockMode="S" schedulerid="4" kpid="10648" status="suspended" spid="184" sbid="0" ecid="0" priority="0" trancount="0" lastbatchstarted="2017-02-12T05:34:48.293" lastbatchcompleted="2017-02-12T05:34:48.280" lastattention="1900-01-01T00:00:00.280" clientapp="jTDS" hostname="LNS" hostpid="123" loginname="MsgStore" isolationlevel="read committed (2)" xactid="427175775" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame procname="tempdb.dbo.#jtds000003_____________________________________________________________________________________________________________0042FD9D" line="1" stmtstart="92" stmtend="668" sqlhandle="0x030002005819e1b4efce580018a7000001000000000000000000000000000000000000000000000000000000">
SELECT id_particle, id_event, dt_created, dt_rcvd, tlx_no, from_routename, re, deleted FROM msg_list WHERE to_routename = @P0 AND ((dt_answ IS NULL AND b_complete = 0 AND id_event=6) OR (id_event = 10 AND deleted = 0) OR (from_id_post = 9705 AND deleted = 0)) ORDER BY dt_created AS </frame>
</executionStack>
<inputbuf>
Proc [Database Id = 2 Object Id = -1260316328] </inputbuf>
</process>
<process id="process319282aca8" taskpriority="0" logused="21256" waitresource="PAGE: 6:1:396658 " waittime="869" ownerId="427175573" transactionname="implicit_transaction" lasttranstarted="2017-02-12T05:34:48.210" XDES="0x30c2dbc408" lockMode="IX" schedulerid="4" kpid="11980" status="suspended" spid="99" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2017-02-12T05:34:48.430" lastbatchcompleted="2017-02-12T05:34:48.427" lastattention="2017-02-12T03:34:28.130" clientapp="NotesMover" hostname="LNS" hostpid="8828" loginname="Notesmover" isolationlevel="read committed (2)" xactid="427175573" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128058">
<executionStack>
<frame procname="adhoc" line="1" stmtstart="364" stmtend="812" sqlhandle="0x020000006d523b316d15563a50b97ce8d56da3cf6d8fc4450000000000000000000000000000000000000000">
unknown </frame>
<frame procname="adhoc" line="1" stmtend="554" sqlhandle="0x02000000d8b78713c51b1588947edf24f2d7b69031f4f1d60000000000000000000000000000000000000000">
unknown </frame>
<frame procname="unknown" line="1" sqlhandle="0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000">
unknown </frame>
</executionStack>
<inputbuf>
UPDATE msg_list SET ID_EVENT=7, STATUS='Answered', DT_ANSW={ts '2017-02-12 05:34:14'WHERE ID_PARTICLE = 46211816
</inputbuf>
</process>
</process-list>
<resource-list>
<pagelock fileid="1" pageid="155679" dbid="6" subresource="FULL" objectname="MsgStore.dbo.msg_list" id="lock31683f2400" mode="IX" associatedObjectId="72057594523811840">
<owner-list>
<owner id="process319282aca8" mode="IX"/>
</owner-list>
<waiter-list>
<waiter id="process30aa42d468" mode="S" requestType="wait"/>
</waiter-list>
</pagelock>
<pagelock fileid="1" pageid="396658" dbid="6" subresource="FULL" objectname="MsgStore.dbo.msg_list" id="lock2f80c2e300" mode="S" associatedObjectId="72057594523811840">
<owner-list>
<owner id="process30aa42d468" mode="S"/>
</owner-list>
<waiter-list>
<waiter id="process319282aca8" mode="IX" requestType="wait"/>
</waiter-list>
</pagelock>
</resource-list>
</deadlock>
</deadlock-list>
和它們的圖形表示:
這裏是正在運行這兩個查詢時生成的查詢計劃:
的受害者:
優勝者:
由受害者使用的ncci_rcvd_list
指數是一個非聚集覆蓋索引與單個鍵柱和幾個包含的列。其中一列包括專欄由獲勝者更新。關鍵列未更新。
mgs_list
表有大約500,000條記錄。 SELECT
查詢返回的結果集通常只有幾十行左右(儘管偶爾它可能會更大,可能是幾千)。
有人可以解釋這種情況如何導致僵局嗎?
這是從生產系統捕獲的,這種情況發生頻率很高。我已經通過將事務隔離級別更改爲讀取已提交的快照來解決此問題,這不再是問題,但我想了解發生的事情,然後查看是否存在不同的解決方案。
您可以將執行計劃粘貼爲xml並共享 – TheGameiswar