#1181 - ENH: Add @FetchPreference support - Secondary query generation is based on order of fetch statements

src/test/java/org/tests/query/other/TestFetchPreference.java

@@ -0,0 +1,69 @@
+package org.tests.query.other;
+
+import io.ebean.BaseTestCase;
+import io.ebean.Ebean;
+import io.ebean.Query;
+import org.junit.Test;
+import org.tests.model.converstation.Conversation;
+
+import static org.assertj.core.api.StrictAssertions.assertThat;
+
+public class TestFetchPreference extends BaseTestCase {
+
+  @Test
+  public void fetchPreference_overrideOrder() {
+
+    Query<Conversation> query = Ebean.find(Conversation.class)
+      // FetchPreference overrides so participants is joined and messages query joined
+      .fetch("messages")
+      .fetch("participants");
+
+    query.findList();
+    String sql = sqlOf(query, 1);
+    assertThat(sql).contains(" from c_conversation t0 left join c_participation t1 ");
+  }
+
+
+  @Test
+  public void fetchPreference_sr() {
+
+    Query<Conversation> query = Ebean.find(Conversation.class)
+      // without FetchPreference this ToMany would be our first ToMany join
+      // and participants would be query joined
+      .fetch("group.users")
+      .fetch("messages")
+      .fetch("participants");
+
+    query.findList();
+    String sql = sqlOf(query, 1);
+
+    // join to group (the ToOne part only) and participants (our preferred ToMany path)
+    assertThat(sql).contains(" from c_conversation t0 left join c_group t1 on t1.id = t0.group_id  left join c_participation t2");
+  }
+
+  @Test
+  public void fetchPreference_inOrder() {
+
+    Query<Conversation> query = Ebean.find(Conversation.class)
+      .fetch("participants")
+      .fetch("messages");
+
+    query.findList();
+    String sql = sqlOf(query, 1);
+    assertThat(sql).contains(" from c_conversation t0 left join c_participation t1 ");
+  }
+
+  @Test
+  public void fetchQuery_onlyOneJoinCandidate() {
+
+    Query<Conversation> query = Ebean.find(Conversation.class)
+      .fetch("messages")
+      .fetchQuery("participants");
+
+    query.findList();
+    String sql = sqlOf(query, 1);
+
+    // participants is explicitly a "query join" so we can join to message
+    assertThat(sql).contains(" from c_conversation t0 left join c_message t1 ");
+  }
+}