[CALCITE-3965] Avoid DiffRepository lock contention
When many test cases using the same DiffRepository instances are running
on multiple threads, it causes lots of contention because all methods
are synchronized. One of the most used method is
DiffRepository#expand(String, String) which do not alter the state of
the tree in most cases.
As the method content itself is thread-safe, remove the synchronized
keyword as it does not bring any extra safety and just increase
artificially the contention around the lock.
diff --git a/core/src/test/java/org/apache/calcite/test/DiffRepository.java b/core/src/test/java/org/apache/calcite/test/DiffRepository.java
index 36593df..875e2dc 100644
--- a/core/src/test/java/org/apache/calcite/test/DiffRepository.java
+++ b/core/src/test/java/org/apache/calcite/test/DiffRepository.java
@@ -235,7 +235,7 @@
* Expands a string containing one or more variables. (Currently only works
* if there is one variable.)
*/
- public synchronized String expand(String tag, String text) {
+ public String expand(String tag, String text) {
if (text == null) {
return null;
} else if (text.startsWith("${")
