Support for Sequences in MariaDB (#2304)

* Support for Sequneces in MariaDB

* clean up readSequenceValue in test class

* remove flakiness

* remove change for later discussion

* replace deprecated methods

* strictly allow sequences

ebean-api/src/main/java/io/ebean/config/dbplatform/mariadb/MariaDbPlatform.java

@@ -1,6 +1,10 @@
 package io.ebean.config.dbplatform.mariadb;
 
+import javax.sql.DataSource;
+
+import io.ebean.BackgroundExecutor;
 import io.ebean.annotation.Platform;
+import io.ebean.config.dbplatform.PlatformIdGenerator;
 import io.ebean.config.dbplatform.mysql.BaseMySqlPlatform;
 
 /**
@@ -11,6 +15,14 @@ public class MariaDbPlatform extends BaseMySqlPlatform {
   public MariaDbPlatform() {
     super();
     this.platform = Platform.MARIADB;
+    this.sequenceBatchMode = false;
     this.historySupport = new MariaDbHistorySupport();
+    this.dbIdentity.setSupportsSequence(true);
   }
+
+  @Override
+  public PlatformIdGenerator createSequenceIdGenerator(BackgroundExecutor be, DataSource ds, int stepSize, String seqName) {
+    return new MariaDbSequence(be, ds, seqName, stepSize);
+  }
+
 }

ebean-api/src/main/java/io/ebean/config/dbplatform/mariadb/MariaDbSequence.java

@@ -0,0 +1,24 @@
+package io.ebean.config.dbplatform.mariadb;
+
+import io.ebean.BackgroundExecutor;
+import io.ebean.config.dbplatform.SequenceStepIdGenerator;
+
+import javax.sql.DataSource;
+
+public class MariaDbSequence extends SequenceStepIdGenerator {
+
+  private final String nextSql;
+
+  /**
+   * Construct where batchSize is the sequence step size.
+   */
+  public MariaDbSequence(BackgroundExecutor be, DataSource ds, String seqName, int stepSize) {
+    super(be, ds, seqName, stepSize);
+    this.nextSql = "select next value for " + seqName;
+  }
+
+  @Override
+  public String getSql(int batchSize) {
+    return nextSql;
+  }
+}