Weird Stuff I Saw While ... Supporting a Java Team Rick Lowe rick@data-flowe.com @dataflowe Rick’s Upcoming eLearning Courses Performance Monitoring – July 27 MSSQL on AWS – August 9 Code that Kills Performance – Sep 13

What I’m Not I am not a Java Expert I deny that I’m a developer Probably not especially knowledgeable about using MSSQL from Java … I am interested in starting a conversation about these issues 2 | 10/10/2015 Session Title Here

Day 1 : Lets tune their worst query 3 | 10/10/2015 Session Title Here

SelectMethod Options “SelectMethod = full” : client retrieves entire result set “SelectMethod = cursor” : server side cursor “responseBuffering=adaptive” : Results retrieved as they are needed Some are unaware of adaptive buffering. Adaptive buffering is default in JDBC 2.0 and later 4 | 10/10/2015 Session Title Here

Server Side Cursors Works much like a normal cursor Cursor is created from a query and opened Results are read back row-by-agonizing-row Every single one of these steps involves a trip across the network One row at a time minimizes memory requirements on the client 5 | 10/10/2015 Session Title Here

Removing server side cursors Not just annoying - potential performance issue In recent JDBC versions, simply remove “SelectMethod=cursor” from URL Evaluate on test system first Possible issue if code repeatedly accesses same row Workloads do exist where cursors are appropriate from a client side perspective 6 | 10/10/2015 Session Title Here

Day 8 : Conversion to CRUD 7 | 10/10/2015 Session Title Here

How things work in ADO.Net try { mySqlCommand.executeUpdate(); } catch …. executeUpdate() is not actually void, it returns # of rows impacted. … except we usually use NOCOUNT which means the return is always 0 And errors are more interesting than counts 8 | 10/10/2015 Session Title Here

How things work in Java PreparedStatement.executeUpdate() returns the number of rows impacted … and it often actually gets paid attention to When inserting, often check for return == 1 Quick fix is to remove “SET NOCOUNT ON” from Create stored procedures 9 | 10/10/2015 Session Title Here

Day 31 : OUTPUT parameters 10 | 10/10/2015 Session Title Here

It all seemed so easy… PreparedStatement.executeUpdate() will not allow you to simply ignore parameters PreparedStatement does not understand output parameters Must use PreparedCall instead To add confusion, there’s a new weird syntax you can use 11 | 10/10/2015 Session Title Here

Windows Authentication Doesn’t work. Just kidding, it works. It just doesn’t work by default. Setup depends on version 12 | 10/10/2015 Session Title Here

Prior to JDBC 4 Copy sqljdbc_auth.dll from <jdbc>\sqljdbc_version\<language>\auth\<arch> to windows\system32 Be sure to grab the correct architecture – x86 vs x64 Then integratedSecurity=SSPI will work as expected. Alternately, use the –Djava.library.path 13 | 10/10/2015 Session Title Here

Starting With JDBC 4 Can still use sqljdbc_auth Alternately, can use Java Kerberos authenticationScheme=JavaKerberos integratedSecurity=true Must now specify FQDN for server name 14 | 10/10/2015 Session Title Here

V1 Enterprise Java Beans Enterprise Java Beans help encapsulate DB code Developers implement methods to Create, Update, and Delete records Called automatically as code works with objects Issue with early versions – update method can be called whether or not data changes 15 | 10/10/2015 Session Title Here

The Talk 16 | 10/10/2015 Session Title Here

Query Hints In .Net shops, the NOLOCK wars rage on Abusing hints is a bad habit … … So we shouldn’t expect that getting folks to stop using NOLOCK just because we tell them the 101st time. We usually settle for making our personal sandbox a “no smoking zone” 17 | 10/10/2015 Session Title Here

Query Hints Contd. Java people typically aren’t stovepiped to the Microsoft stack This may be a new discussion for them Sometimes easier to change habits in this community 18 | 10/10/2015 Session Title Here

Stopping NOLOCK: What May Not Work 9 out of 10 DBAs agree : NOLOCK is bad If you don’t care about getting the correct answer, why are we using a database? Sure it works in test, but trust me – strange things could happen in prod. 19 | 10/10/2015 Session Title Here

What Might Work A dirty read doesn’t mean you get an old value. If a page is splitting it could be anything. What happens if we return the wrong person’s SSN? Have you heard about Read Committed Snapshot Isolation? If I could promise writers won’t block readers, can we stop using NOLOCK? 20 | 10/10/2015 Session Title Here