While recently answering a post on the MSDN forum, I realized that the Robert Gold(Vice President of Business Intelligence in Bostwick Laboratories, Inc) was facing the same problem that I was facing couple of years back when I was working as a Team Leader in one of the BPO’s. The MIS Department was reporting to me and one of the main jobs was to create “Trackers” for various departments. My team used to take hours to design a particular tracker only to realize after few days that the users were spoiling the format of the tracker by copying and pasting. Completely protecting it with a password was not the option. Nor did we find any option in Excel which forced selective pasting. It was then we devised this macro which allowed the user to paste but behind the scenes, converted that paste into paste special – values.
The only drawback of this method is that if the macros are disabled then this won’t work. But thanks to the IT Department, they ensured that the macros was enabled on each and every pc. After that we never faced a problem with users messing up the format of the sheet.
So how does this code work? What is the logic behind it? I would explain this in 3 sections.
only loads at most batch-size records into client memory at once, resulting in a more predictable client memory footprint
theoretically requires less server-side resources than selectMethod=cursor
will read the entire result set into client memory (unless the driver natively supports asynchronous result set retrieval) before the client application can iterate over it; this can reduce performance in two ways:
reduced performance with large result sets if the client application is written in such a way as to stop processing after traversing only a fraction of the result set (with directit has already paid the cost of retrieving data it will essentially throw away; with cursorthe waste is limited to at most batch-size – 1 rows — the early termination condition should probably be recoded in SQL anyway e.g. as SELECT TOP or window functions)
reduced performance with large result sets because of potential garbage collection and/or out-of-memory issues associated with an increased memory footprint
Can using selectMethod=cursor lower application performance? — either method can lower performance, for different reasons. Past a certain resultset size, cursor may still be preferable. See below for when to use one or the other
Is selectMethod= an application-transparent setting on a JDBC connection? — it is transparent, but it can still break their app if memory usage grows significantly enough to hog their client system (and, correspondingly, your server) or crash the client altogether
When a sequence is incremented twice when running SELECT NEXT VALUE FOR MYSEQ; and you are using the Microsoft JDBC driver with the selectMethod=cursor, remove the selectMethod=cursor option from the JDBC URL. The sequences will then be incremented correctly.
Spring is a widely used framework today, bringing many powerfull features and extensions to the Java core stack. However most of people tend to use these features without understanding their underlying mechanism.
Since there is no “magic” in real life, we are going to dig into some Spring features related to Transaction and Database in this serie of articles.
By convention, type parameter names are single, uppercase letters. This stands in sharp contrast to the variable naming conventions that you already know about, and with good reason: Without this convention, it would be difficult to tell the difference between a type variable and an ordinary class or interface name.
The most commonly used type parameter names are:
E – Element (used extensively by the Java Collections Framework)
K – Key
N – Number
T – Type
V – Value
S,U,V etc. – 2nd, 3rd, 4th types
You’ll see these names used throughout the Java SE API and the rest of this lesson.