Transaction creation performance (#303) (#320)

* Default autoCommit to false, remove setting of autocommit and only set isolationLevel if it's changed.

* Set default transaction isolation from database config

node-api/src/main/kotlin/net/corda/nodeapi/internal/persistence/CordaPersistence.kt

@@ -35,7 +35,8 @@ enum class TransactionIsolationLevel {
     /**
      * The JDBC constant value of the same name but prefixed with TRANSACTION_ defined in [java.sql.Connection].
      */
-    val jdbcValue: Int = java.sql.Connection::class.java.getField("TRANSACTION_$name").get(null) as Int
+    val jdbcString = "TRANSACTION_$name"
+    val jdbcValue: Int = java.sql.Connection::class.java.getField(jdbcString).get(null) as Int
 }
 
 class CordaPersistence(

node-api/src/main/kotlin/net/corda/nodeapi/internal/persistence/DatabaseTransaction.kt

@@ -20,8 +20,10 @@ class DatabaseTransaction(
         cordaPersistence.dataSource.connection
                 .apply {
                     _connectionCreated = true
-                    autoCommit = false
-                    transactionIsolation = isolation
+                    // only set the transaction isolation level if it's actually changed - setting isn't free.
+                    if (transactionIsolation != isolation) {
+                        transactionIsolation = isolation
+                    }
                 }
     }
 

node/src/main/kotlin/net/corda/node/services/config/NodeConfiguration.kt

@@ -135,6 +135,13 @@ data class NodeConfigurationImpl(
         require(security == null || rpcUsers.isEmpty()) {
             "Cannot specify both 'rpcUsers' and 'security' in configuration"
         }
+
+        // ensure our datasource configuration is sane
+        require(dataSourceProperties.get("autoCommit") != true) { "Datbase auto commit cannot be enabled, Corda requires transactional behaviour" }
+        dataSourceProperties.set("autoCommit", false)
+        if (dataSourceProperties.get("transactionIsolation") == null) {
+            dataSourceProperties["transactionIsolation"] = database.transactionIsolationLevel.jdbcString
+        }
     }
 }