From 018a64c27252f39542ac956f618a08bafb9663cb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johan=20Andr=C3=A9n?= <johan@markatta.com>
Date: Fri, 27 Aug 2021 13:07:55 +0200
Subject: [PATCH] Avoid a bit of work when not using tags #585

---
 .../jdbc/journal/dao/JournalQueries.scala      | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/core/src/main/scala/akka/persistence/jdbc/journal/dao/JournalQueries.scala b/core/src/main/scala/akka/persistence/jdbc/journal/dao/JournalQueries.scala
index 4b70fc0b2..b52357e5f 100644
--- a/core/src/main/scala/akka/persistence/jdbc/journal/dao/JournalQueries.scala
+++ b/core/src/main/scala/akka/persistence/jdbc/journal/dao/JournalQueries.scala
@@ -19,18 +19,22 @@ class JournalQueries(
 
   import profile.api._
 
-  val insertAndReturn =
-    JournalTable.returning(JournalTable.map(_.ordering))
+  val insertAndReturn = JournalTable.returning(JournalTable.map(_.ordering))
   private val TagTableC = Compiled(TagTable)
 
   def writeJournalRows(xs: Seq[(JournalAkkaSerializationRow, Set[String])])(implicit ec: ExecutionContext) = {
     val sorted = xs.sortBy((event => event._1.sequenceNumber))
     val (events, tags) = sorted.unzip
-    for {
-      ids <- insertAndReturn ++= events
-      tagInserts = ids.zip(tags).flatMap { case (id, tags) => tags.map(tag => TagRow(id, tag)) }
-      _ <- TagTableC ++= tagInserts
-    } yield ()
+    if (tags.nonEmpty) {
+      for {
+        ids <- insertAndReturn ++= events
+        tagInserts = ids.zip(tags).flatMap { case (id, tags) => tags.map(tag => TagRow(id, tag)) }
+        _ <- TagTableC ++= tagInserts
+      } yield ()
+    } else {
+      // optimization avoid some work when not using tags
+      insertAndReturn ++= events
+    }
   }
 
   private def selectAllJournalForPersistenceIdDesc(persistenceId: Rep[String]) =