的Apache Derby掛斷執行查詢

Question

我真的很感激一些幫助這裏。 我已經從我的客戶得到這個Derby數據庫及其應用基於Hibernate。我不能讓它工作，因爲Hibernate生成查詢掛斷整個數據庫：

select houses0_.STREET_ID as STREET5_1_, houses0_.ID as ID1_, houses0_.ID as ID42_0_, houses0_.NAME as NAME42_0_, houses0_.SHORT_NAME as SHORT3_42_0_, houses0_.INDEX as INDEX42_0_ from SRG.HOUSE_REFERENCE houses0_ where houses0_.STREET_ID in (select streets0_.ID from SRG.STREET_REFERENCE streets0_ where streets0_.TOWNSHIP_ID in (select townships0_.ID from SRG.TOWNSHIP_REFERENCE townships0_ where townships0_.CITY_ID='555')) 

我沒有看到任何東西在它可疑的，但是當我用它推出德比 - 德比只是什麼都不做。這裏是我的日誌：

2011-10-31 21:58:10.328 GMT Thread[DRDAConnThread_3,5,main] (XID = 1152939), (SESSIONID = 1), (DATABASE = dev), (DRDAID = NF000001.FC97-434877518919679629{1}), Begin compiling prepared statement: select houses0_.STREET_ID as STREET5_1_, houses0_.ID as ID1_, houses0_.ID as ID42_0_, houses0_.NAME as NAME42_0_, houses0_.SHORT_NAME as SHORT3_42_0_, houses0_.INDEX as INDEX42_0_ from HOUSE_REFERENCE houses0_ where houses0_.STREET_ID in (select streets0_.ID from STREET_REFERENCE streets0_ where streets0_.TOWNSHIP_ID in (select townships0_.ID from TOWNSHIP_REFERENCE townships0_ where townships0_.CITY_ID='555')) :End prepared statement 
2011-10-31 21:58:10.682 GMT Thread[DRDAConnThread_3,5,main] (XID = 1152939), (SESSIONID = 1), (DATABASE = dev), (DRDAID = NF000001.FC97-434877518919679629{1}), End compiling prepared statement: select houses0_.STREET_ID as STREET5_1_, houses0_.ID as ID1_, houses0_.ID as ID42_0_, houses0_.NAME as NAME42_0_, houses0_.SHORT_NAME as SHORT3_42_0_, houses0_.INDEX as INDEX42_0_ from SRG.HOUSE_REFERENCE houses0_ where houses0_.STREET_ID in (select streets0_.ID from SRG.STREET_REFERENCE streets0_ where streets0_.TOWNSHIP_ID in (select townships0_.ID from SRG.TOWNSHIP_REFERENCE townships0_ where townships0_.CITY_ID='555')) :End prepared statement 
2011-10-31 21:58:10.758 GMT Thread[DRDAConnThread_3,5,main] (XID = 1152939), (SESSIONID = 1), (DATABASE = dev), (DRDAID = NF000001.FC97-434877518919679629{1}), Executing prepared statement: select houses0_.STREET_ID as STREET5_1_, houses0_.ID as ID1_, houses0_.ID as ID42_0_, houses0_.NAME as NAME42_0_, houses0_.SHORT_NAME as SHORT3_42_0_, houses0_.INDEX as INDEX42_0_ from SRG.HOUSE_REFERENCE houses0_ where houses0_.STREET_ID in (select streets0_.ID from SRG.STREET_REFERENCE streets0_ where streets0_.TOWNSHIP_ID in (select townships0_.ID from SRG.TOWNSHIP_REFERENCE townships0_ where townships0_.CITY_ID='555')) :End prepared statement 

然後什麼都沒有。 我設置一些屬性：

derby.drda.portNumber=1529 

derby.locks.deadlockTrace=true 
derby.locks.monitor=true 

derby.locks.deadlockTimeout=1 
derby.locks.waitTimeout=1 

derby.language.logStatementText=false 
derby.infolog.append=true 

derby.stream.error.logSeverityLevel=0 

derby.drda.logConnections=true 

derby.language.logStatementText=true 

derby.language.logQueryPlan=true 

看看怎麼回事，但有沒有在日誌中，這個查詢只需要永恆的執行，無論是其從休眠或squirrelsql或Derby的ij工具來完成。 正如你可以看到超時是非常小，但德比犯規停止執行查詢時，它留下它做任何查詢想要的。

查詢不是那麼複雜 - 我用它連接改寫了，花了1秒執行。但不是這種形式 - 我沒有明白，爲什麼？你能給我任何提示嗎？

UPD：house_reference包含7508行，選擇從*花費house_reference小於第二，street_reference包含〜44K行，並且子查詢

select streets0_.ID from STREET_REFERENCE streets0_ where streets0_.TOWNSHIP_ID in (select townships0_.ID from TOWNSHIP_REFERENCE townships0_ where townships0_.CITY_ID='52000001000') 

返回111行，在不到一秒鐘。所以選擇從* house_reference在含有111行子句需要分鐘來執行，並將其返回0的結果。這對我來說看起來不錯，但我沒有在數據庫管理方面經歷過的判斷，這就是爲什麼我要求社區:)

Answer 1

指定「in（subquery）」的查詢不能總是被替換爲相應的連接。這個過程被稱爲「扁平化」，爲了給出正確的答案，數據庫必須遵循這些規則。請參閱此文檔：http://db.apache.org/derby/docs/10.8/tuning/ctuntransform36368.html

不幸的是，連接中的子查詢存在顯着的性能問題並不罕見。我很高興你找到了一個解決方法（假設你重寫的查詢實際上是一個可接受的解決方法）。

對象關係映射庫可以產生一些複雜的查詢。如果您可以使查詢最終運行，您可以從查詢計劃中學到一些東西。

另一種可能性是數據庫統計信息變得不準確，從而導致Derby選擇差的查詢計劃。最近的Derby版本改進了對重新計算統計數據的支持，這可以幫助優化器選擇更好的查詢計劃。

有一個在http://db.apache.org/derby/docs/10.8/tuning/index.html