Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/1272#discussion_r14392261
--- Diff: sql/core/src/main/scala/org/apache/spark/sql/SQLConf.scala ---
@@ -50,8 +50,7 @@ trait SQLConf {
/** ********************** SQLConf functionality methods ************ */
@transient
- private val settings = java.util.Collections.synchronizedMap(
- new java.util.HashMap[String, String]())
+ private val settings = new
java.util.concurrent.ConcurrentHashMap[String, String]()
--- End diff --
We should not be using ConcurrentHashMap because this will be a very low
contention code path. For low contention code path, ConcurrentHashMap is a very
poor choice (as a matter of fact it'll likely be much slower than synchronized,
and use a lot more memory)
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