Busy night Rainer? Great to hear this is implemented :-) Too bad we just cut a release :-s
On Fri, Dec 3, 2010 at 9:30 AM, Rainer Döbele <[email protected]> wrote: > Hi Kenji, > > good news for you: it's all "prepared" now :-) > Most of it was already there, but a few bits and pieces were missing. > However you have to take the latest sources directly from our SVN repository. > > In DBDatabase you now have a property called "preparedStatementsEnabled" > which you can enable or disable. > If enabled Empire-db will use prepared statements for all database operations > on DBRecord. > > If you create your own commands using DBCommand you will have to explicitly > declare the parameters using DBCommand.addCmdParam() which will return a > DBCommandParam (I have renamed this inner class from DBCmdParameter!) except > for set() operations. > > I have added an example to the empire-db-example-advanced > (SampleAdvApp.java). The commandParamsSample() method shows how to use > command params. > By additionally setting preparedStatementsEnabled to enabled, also all > operations performed by Empire-db itself will use prepared statements. > You can easily see it in the log. > And the good thing is, you can easily switch between prepared and > non-prepared (non-prepared statements are still better for debugging). > > Let me know, if you have problems or need any more help. > Best regards, > > Rainer > > > Kenji Nakamura wrote: >> from: Kenji Nakamura [mailto:[email protected]] >> to: [email protected] >> re: Re: Prepared statement support? >> >> Hi Rainer, >> >> Yes, this is exactly what I was looking for. >> Regarding statement pooling, it is a part of JDBC 3.0 spec and I think >> it is a job of connection pool utility. >> We use c3p0 and it has statement pooling capability. It is highly >> configurable and has lots of features. >> >> http://www.mchange.com/projects/c3p0/index.html#configuring_statement_po >> oling >> >> I really appreciate if you can include the bug fix of DBReader in the >> next release as this is crucial feature to persuade DBAs and security >> auditors. >> >> Thanks a lot! >> >> Kenji Nakamura >> >> On Dec 2, 2010, at 19:29, Rainer Döbele <[email protected]> wrote: >> >> > Hi everyone, >> > >> > thanks for your comment Matt. >> > >> > To my own surprise I have overlooked that there is already substantial >> support for prepared statement generation in Empire-db now, but you have >> to explicitly declare the parameters. >> > Here is an example of how to generate a prepared statement phrase and >> execute it with the corresponding parameters: >> > >> > // Define the query >> > DBCommand cmd = db.createCommand(); >> > >> > // Create parameters >> > DBCmdParameter depIdParam = cmd.addCmdParam(1); >> > DBCmdParameter genderParam = cmd.addCmdParam('F'); >> > >> > // create statement >> > cmd.select(EMP.getColumns()); >> > cmd.where(EMP.DEPARTMENT_ID.is(depIdParam)); >> > cmd.where(EMP.GENDER.is(genderParam)); >> > >> > // First execution >> > String sql = cmd.getSelect(); >> > ResultSet r = db.executeQuery(sql, cmd.getCmdParams(), false, >> conn); >> > // do something >> > r.close(); >> > >> > // Modify command parameters >> > depIdParam.setValue(2); >> > genderParam.setValue('M'); >> > >> > // Second execution >> > r = db.executeQuery(sql, cmd.getCmdParams(), false, conn); >> > // do something >> > r.close(); >> > >> > This will result in the following SQL: >> > >> > SELECT t2.EMPLOYEE_ID, t2... >> > FROM EMPLOYEES t2 >> > WHERE t2.DEPARTMENT_ID=? AND t2.GENDER=? >> > >> > And set the parameter to 1 and 'F' for the first query and to 2 and >> 'M' for the second. >> > >> > Unfortunately there is a bug in DBReader so that cmd params are not >> properly set. >> > This is the reason why I used db.executeQuery(..) instead of a >> DBReader in the example above. >> > I will fix this bug as soon as possible. >> > >> > Another thing we should do is to use the prepared statements for >> DBRecord.read (which in turn uses DBRowSet.readRecord(...)). >> > >> > As far as the pooling of prepared statements is concerned, if it's not >> done by the data source already it can also be done by subclassing the >> DBDatabaseDriver and overriding executeQuery() and / or executeSQL() and >> do it yourself. But it is not necessary for Empire-db to provide this. >> > >> > Kenji will this satisfy your needs? >> > >> > Regards, >> > Rainer >> > >> > >> > >> > Matthew Bond wrote: >> >> from: Matthew Bond [mailto:[email protected]] >> >> to: [email protected]; empire-db- >> >> re: AW: Prepared statement support? >> >> >> >> Hi Rainer, Hi Kenji, >> >> >> >> Rainer's comments are true in a Web Application scenario where the >> >> connection if got for a short time and then released again. Empire DB >> >> can also be used in other scenarios, like a Fat Clients or Command >> Line >> >> Utility tools, where a connection will probably be held for the whole >> >> duration of the application lifetime and PooledStatements could >> bring >> >> more performance. So it really depends on what you application type >> you >> >> are programming. >> >> >> >> FYI: WebSphere too pools prepared statements (see page 2 of >> http://www- >> >> >> 03.ibm.com/systems/resources/systems_i_advantages_perfmgmt_pdf_stmntcach >> >> e.pdf "WebSphere, however, will do the caching automatically. When >> you >> >> execute a query, WebSphere determines if the SQL text is already in >> the >> >> cache and if so, it will use that cached statement instead of >> preparing >> >> a new one." ). So if EmpireDB was extended to make more use of >> Prepared >> >> Statements it would be advantageous. >> >> >> >> However as Rainer describes, the big benefit of using EmpireDB is >> that >> >> the selects are going to be way better than other ORM's as the >> developer >> >> hand crafts the "SQL" statement. >> >> >> >> The great thing is that it is Open Source so if you feel strongly >> about >> >> the use of PreparedStatements, you could submit a Patch adding this >> >> functionality. >> >> >> >> Cheers >> >> Matt >> >> >> >> -----Ursprüngliche Nachricht----- >> >> Von: Rainer Döbele [mailto:[email protected]] >> >> Gesendet: Donnerstag, 2. Dezember 2010 00:11 >> >> An: [email protected]; empire-db- >> >> [email protected] >> >> Betreff: re: Prepared statement support? >> >> >> >> Dear Kenji, >> >> >> >> I have reviewed our code and thought about this subject again. >> >> As you mentioned there is both a performance and a security issue to >> >> consider. >> >> For the moment I would like to focus on the performance issue as >> >> security can as well be established by other measures. >> >> >> >> It's pretty obvious to understand that creating a prepared statement >> and >> >> executing it multiple times with varying parameters is superior over >> >> creating a normal statement each time. But as far as I understand it, >> >> the advantage of a ps exists only as long as the statement lives, and >> >> ends when you close it. >> >> >> >> The problem is, that a prepared statement is created for a particular >> >> connection. In a web-application we usually use a connection pool and >> >> the connection is fetched for a particular request. It is extremely >> >> rare, that the same statement is executed multiple times within a >> single >> >> request - whereas it is very likely that the same statement needs to >> be >> >> executed by other users' requests. As those other users have >> different >> >> connections they cannot share the same prepared statement. >> >> >> >> Here is a thread discussing this issue: >> >> http://www.velocityreviews.com/forums/t644638-jdbc-preparedstatement- >> in- >> >> a-multi-threaded-environment.html >> >> >> >> As Empire-db does not store or maintain a connection, it is not >> sensible >> >> for us to store the actual JDBC prepared statement object. But this >> >> might not be necessary as it could be done on another level. Possibly >> >> the solution lies just in another Apache Project: Apache Commons >> DBCP. >> >> http://commons.apache.org/dbcp/index.html >> >> >> >> From my understanding it should be possible to use a commons-dbcp >> >> connection pool that will also pool prepared statements. The >> connections >> >> returned by the pool can be used with Empire db just like a normal >> JDBC >> >> connection. >> >> Of course we still need to enforce and extend the generation of >> prepared >> >> statement phrases beyond the CUD operations. >> >> >> >> Still we must keep in mind, that probably for most real world >> >> applications the performance benefit of prepared statements over >> simple >> >> statements is negligible, and it is our primary goal to maintain >> >> simplicity and transparency. >> >> It is IMO far more important to be able to create efficient >> statements - >> >> and avoid the problem of OR-Mappers that usually work with lots of >> >> simple operations. After all, one clever statement with server side >> db >> >> logic will still execute a lot faster than 10 prepared statements >> with >> >> trailed Java logic. >> >> (Still the gloal is to have it all of course) >> >> >> >> Any more suggestions or remarks on this topic? >> >> >> >> Regards >> >> Rainer >> >> >> >> >> >> Kenji Nakamura wrote: >> >>> from: Kenji Nakamura [mailto:[email protected]] >> >>> to: [email protected] >> >>> re Re: Prepared statement support? >> >>> >> >>> Rainer, >> >>> >> >>> Thank you for your reply. My comment are inline. >> >>> >> >>> On Wed, Dec 1, 2010 at 2:14 AM, Rainer Döbele <[email protected]> >> >>> wrote: >> >>>> Hi Kenji, >> >>>> >> >>>> thanks for your interesting links about this subject. >> >>>> >> >>>> It is certainly true, that the performance of a prepared statements >> >>> is better when you execute it multiple times with varying parameter >> >>> values. >> >>>> This is not always possible when varying statements with >> conditional >> >>> joins are created at runtime. >> >>>> For a one-time statement using a prepared statement does not >> execute >> >>> faster than a normal statement. >> >>> >> >>> I understand the issue that the use of PreparedStatement seems to >> have >> >>> overhead and actually it may take longer if we measure it with a >> >>> single execution from application developer's point of view, but the >> >>> compiled result of the statement is kept added to Oracle's cache and >> >>> it flushes the compiled results of the PreparedStatement invoked >> from >> >>> different applications as the cache is managed per SID in Oracle. So >> >>> it has negative impact from the DBA's point of view. It is not an >> >>> issue as long as the DB is used as the data storage of a web >> >>> application server and the performance of the app is only concern, >> but >> >>> the assumption is not true when the DB is also used in data >> >>> processing. >> >>> >> >>>> The inclusion of parameter values in the SQL text when assembling >> >>> statements is an advantage when it comes to logging (logging of >> >>> parameterized statements is not sufficient to track errors) or for >> the >> >>> creation of SQL scripts that are saved and executed later. >> >>> >> >>> I see your point. >> >>> >> >>>> >> >>>> Currently Empire-db uses prepared statements by default only for >> >>> statements with BLOB and CLOB fields. >> >>>> >> >>>> However at least as far as update and insert statements are >> >>>> concerned >> >>> you can override the method useCmdParam() in DBCommandOracle, but >> you >> >>> need to subclass the DBDatabaseDriverOracle and override >> createCommand >> >>> first. If you return true in useCmdParam(), then Empire-DB will use >> a >> >>> prepared statement and supply this value as a prepared statement >> >>> parameter. >> >>> >> >>> From the point of view of Oracle administrator, the primary interest >> >>> is how to reduce the # of hard parse and increase the hit rate of >> the >> >>> cache, and using PreparedStatement only for CUD operation is not >> >>> sufficient if the ratio of Select outweigh CUD operations. From >> >>> security point of view, Select statement with parameters embedding >> >>> user's input is as vulnerable as other DMLs, so the option to use >> >>> PreparedStatement for CUD operation doesn't address those concerns, >> >>> while it may be useful to improve the performance on iterative >> >>> operations. >> >>> >> >>>> >> >>>> Personally I have used Empire-DB in many projects and performance >> or >> >>> security have never been a problem. However, if you except to >> execute >> >>> 10.000 sql statements a minute then certainly this needs to be >> >>> thoroughly checked. >> >>> >> >>> It is nice to know the framework has been proven in production >> >>> environments. Our current performance test also doesn't show the >> hard >> >>> parse is the primary culprit of the performance bottleneck, so it is >> >>> not an urgent problem, but I'd like prepare to answer the questions >> >>> from our DB engineers. >> >>> >> >>>> >> >>>> I have created a new Jira (EMPIREDB-91) issue for us to check, how >> >>> and where we can increase and optimize the use of prepared >> statements. >> >>> >> >>> Thank you for the reaction. I registered myself to the watch list. >> Let >> >>> me know if I can do something to make this forward. >> >>> >> >>> Lastly, I really thank you to share the framework in public. I have >> >>> used Toplink, Hibernate, and iBatis, but I favor empire-db a lot >> >>> because of the simplicity and type-safe coding. It is very >> >>> straightforward to customize to fulfill our specific needs such as >> the >> >>> support of TableFunction in Oracle. >> >>> >> >>> Regards, >> >>> >> >>> Kenji >> >>> >> >>>> >> >>>> Regards >> >>>> Rainer >> >>>> >> >>>> >> >>>> Kenji Nakamura wrote: >> >>>>> from: Kenji Nakamura [mailto:[email protected]] >> >>>>> to: [email protected] >> >>>>> re: Prepared statement support? >> >>>>> >> >>>>> Hi, >> >>>>> >> >>>>> I got a question from one of our DB engineer about the use of >> >>> prepared >> >>>>> statements. >> >>>>> According to him, or a thread in AskTom, it is always preferred to >> >>> use >> >>>>> PreparedStatement instead of Statement whenever possible. >> >>>>> >> >>> >> http://asktom.oracle.com/pls/asktom/f?p=100:11:7607696421577136::::P11 >> >>> _ >> >>> Q >> >>>>> UESTION_ID:1993620575194 >> >>>>> >> >>>>> As far as I looked at the code, PreparedStatement is not used >> other >> >>>>> than DBDatabaseDriver class and the method is not used from other >> >>>>> code. >> >>>>> >> >>>>> My understanding is that creation of PreparedStatement has certain >> >>>>> overhead, but statement pooling introduced in JDBC 3.0 mitigates >> >>>>> the impact especially from application server point of view. >> >>>>> We use Oracle, and the DB engineer explained that the use of >> >>> statement >> >>>>> floods the library cache in SGA and reduce the hit rate of >> >>>>> pre-compiled statements so it has negative impact on entire db, >> and >> >>>>> using PreparedStatement simply reduces the cost of hard parse. >> >>>>> >> >>>>> Another aspect is about SQL injection prevention. I noticed single >> >>>>> quotes are escaped at DBDatabaseDriver#getValueString() method, >> but >> >>>>> the preferred way to prevent SQL injection is to use >> >>> PreparedStatement >> >>>>> according to OWASP website. >> >>>>> >> http://www.owasp.org/index.php/SQL_Injection_Prevention_Cheat_Sheet >> >>>>> >> >>>>> Would you tell me the design philosophy or reasons not to use or >> >>>>> provide the option to use prepared statement? Is it possible, or >> >>> have >> >>>>> a plan to support PreparedStatement? >> >>>>> >> >>>>> Thanks, >> >>>>> >> >>>>> Kenji Nakamura >> >>>> > -- http://www.somatik.be Microsoft gives you windows, Linux gives you the whole house.
