Save offsets in Batch without bind parameters, #253 (#255)

* for better performance since the add-bind approach has round-trips to the db
* basic validation of string parameters

core/src/main/scala/akka/persistence/r2dbc/internal/R2dbcExecutor.scala

@@ -55,6 +55,21 @@ import reactor.core.publisher.Mono
       .asFuture()
   }
 
+  /**
+   * Batch update of SQL statements without bind parameters.
+   */
+  def updateBatchInTx(conn: Connection, statements: immutable.IndexedSeq[String])(implicit
+      ec: ExecutionContext): Future[Int] = {
+    val batch = conn.createBatch()
+    statements.foreach(batch.add)
+    val consumer: BiConsumer[Int, Integer] = (acc, elem) => acc + elem.intValue()
+    Flux
+      .from[Result](batch.execute())
+      .concatMap(_.getRowsUpdated)
+      .collect(() => 0, consumer)
+      .asFuture()
+  }
+
   def updateInTx(statements: immutable.IndexedSeq[Statement])(implicit
       ec: ExecutionContext): Future[immutable.IndexedSeq[Int]] =
     // connection not intended for concurrent calls, make sure statements are executed one at a time

projection/src/main/scala/akka/projection/r2dbc/internal/R2dbcOffsetStore.scala

@@ -186,6 +186,22 @@ private[projection] class R2dbcOffsetStore(
     (projection_name, projection_key, slice, persistence_id, seq_nr, timestamp_offset, timestamp_consumed)
     VALUES (?,?,?,?,?,?, transaction_timestamp())"""
 
+  private def insertTimestampOffsetBatchSql(pid: Pid, seqNr: SeqNr, offsetTimestamp: Instant): String = {
+    def validateStringParam(name: String, value: String): Unit = {
+      if (value.contains('\''))
+        throw new IllegalArgumentException(s"Illegal $name parameter [$value]")
+    }
+    validateStringParam("projectionId.name", projectionId.name)
+    validateStringParam("projectionId.key", projectionId.key)
+    validateStringParam("pid", pid)
+
+    val slice = persistenceExt.sliceForPersistenceId(pid)
+    sql"""
+      INSERT INTO $timestampOffsetTable
+      (projection_name, projection_key, slice, persistence_id, seq_nr, timestamp_offset, timestamp_consumed)
+      VALUES ('${projectionId.name}','${projectionId.key}',$slice,'$pid',$seqNr,'$offsetTimestamp', transaction_timestamp())"""
+  }
+
   // delete less than a timestamp
   private val deleteOldTimestampOffsetSql: String =
     sql"DELETE FROM $timestampOffsetTable WHERE slice BETWEEN ? AND ? AND projection_name = ? AND timestamp_offset < ?"
@@ -499,19 +515,15 @@ private[projection] class R2dbcOffsetStore(
     // FIXME change to trace
     logger.debug("saving timestamp offset [{}], {}", records.last.timestamp, records)
 
-    val statement = conn.createStatement(insertTimestampOffsetSql)
-
     if (records.size == 1) {
+      val statement = conn.createStatement(insertTimestampOffsetSql)
       val boundStatement = bindRecord(statement, records.head)
       R2dbcExecutor.updateOneInTx(boundStatement)
     } else {
-      // TODO Try Batch without bind parameters for better performance. Risk of sql injection for these parameters is low.
-      val boundStatement =
-        records.foldLeft(statement) { (stmt, rec) =>
-          stmt.add()
-          bindRecord(stmt, rec)
-        }
-      R2dbcExecutor.updateBatchInTx(boundStatement)
+      val statements = records.map { rec =>
+        insertTimestampOffsetBatchSql(rec.pid, rec.seqNr, rec.timestamp)
+      }
+      R2dbcExecutor.updateBatchInTx(conn, statements)
     }
   }