MySQL Bugs: #73595: Replace usage of StringBuffer in JDBC driver

Bug #73595	Replace usage of StringBuffer in JDBC driver
Submitted:	15 Aug 2014 8:12	Modified:	23 Jan 2015 0:23
Reporter:	Lukas Eder	Email Updates:
Status:	Closed	Impact on me:	None
Category:	Connector / J	Severity:	S5 (Performance)
Version:	5.1.32	OS:	Any
Assigned to:	Alexander Soklakov	CPU Architecture:	Any
Tags:	jdbc, StringBuffer

Description:
While introspecting the sources of com.mysql.jdbc.DatabaseMetaDataUsingInfoSchema, I have discovered that in order to construct SQL strings internally, java.lang.StringBuffer is used instead of java.lang.StringBuilder.

StringBuffer's use is discouraged since JDK 5 as all of its methods are (most often unnecessarily) synchronized. See also the relevant paragraph of the StringBuffer Javadoc:

> As of release JDK 5, this class has been supplemented 
> with an equivalent class designed for use by a single 
> thread, StringBuilder. The StringBuilder class should 
> generally be used in preference to this one, as it 
> supports all of the same operations but it is faster, 
> as it performs no synchronization.

How to repeat:
No steps needed

Suggested fix:
Replace all single-threaded usage of StringBuffer in the JDBC driver by StringBuilder

Hi Lukas,

Thank you for this bug report.

We have been replacing StringBuffer by StringBuilder for some time, but there are still many to replace. So, it was verified as described.

Added the following entry to the Connector/J 5.1.35 changelog:

"All occurrences of the StringBuffer class in the Connector/J code has been replaced with the StringBuilder class, in order to improve code performance."