#2021 - Use smarter persistence context for findEach/iterate/stream queries - improve performance of un-tuned findEach/iterate/stream queries that invoke lazy loading

src/test/java/org/tests/query/TestQueryFindEach.java

@@ -4,18 +4,31 @@ import io.ebean.BaseTestCase;
 import io.ebean.DB;
 import io.ebean.FetchConfig;
 import io.ebean.Query;
+import io.ebean.Transaction;
+import io.ebean.annotation.Transactional;
+import io.ebean.bean.PersistenceContext;
+import io.ebeaninternal.api.SpiTransaction;
+import org.ebeantest.LoggedSqlCollector;
 import org.junit.Test;
+import org.tests.model.basic.Contact;
 import org.tests.model.basic.Customer;
 import org.tests.model.basic.ResetBasicData;
+import org.tests.o2m.OmBasicChild;
+import org.tests.o2m.OmBasicParent;
 
+import java.util.List;
+import java.util.Random;
 import java.util.concurrent.atomic.AtomicInteger;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.fail;
 
 public class TestQueryFindEach extends BaseTestCase {
 
+  private final Random random = new Random();
+
   @Test
   public void test() {
 
@@ -36,6 +49,34 @@ public class TestQueryFindEach extends BaseTestCase {
     assertEquals(2, counter.get());
   }
 
+  @Test
+  public void persistenceContext_scope() {
+
+    ResetBasicData.reset();
+
+    Query<Contact> query = DB.find(Contact.class);
+
+    try (final Transaction transaction = DB.beginTransaction()) {
+      // effectively loads customers into persistence context
+      final List<Customer> customerList = DB.find(Customer.class)
+        .select("name")
+        .findList();
+
+      SpiTransaction spiTxn = (SpiTransaction) transaction;
+      PersistenceContext pc = spiTxn.getPersistenceContext();
+      assertThat(pc.size(Customer.class)).isEqualTo(customerList.size());
+
+      LoggedSqlCollector.start();
+      query.findEach(contact -> {
+        // use customer from persistence context (otherwise would invoke lazy loading)
+        assertNotNull(contact.getCustomer().getName());
+      });
+
+      final List<String> sql = LoggedSqlCollector.stop();
+      assertThat(sql).hasSize(1);
+    }
+  }
+
   /**
    * Test the behaviour when an exception is thrown inside the findVisit().
    */
@@ -60,4 +101,45 @@ public class TestQueryFindEach extends BaseTestCase {
 
     fail("Never get here - exception thrown");
   }
+
+  @Test
+  public void iterateResetLimit() {
+
+    DB.find(OmBasicChild.class).delete();
+    DB.find(OmBasicParent.class).delete();
+    insertData();
+
+    LoggedSqlCollector.start();
+    try (final Transaction transaction = DB.beginTransaction()) {
+      // DB.find(OmBasicParent.class).findList();
+      DB.find(OmBasicChild.class)
+        .setLazyLoadBatchSize(100)
+        //.fetchQuery("parent","name")
+        //.fetch("parent","name")
+        .findEach(child -> {
+          assertNotNull(child.getParent().getName());
+        });
+    }
+
+    final List<String> sql = LoggedSqlCollector.stop();
+    assertThat(sql.size()).isLessThan(50);
+  }
+
+  @Transactional(batchSize = 40)
+  private void insertData() {
+    for (int i = 0; i < 150; i++) {
+      insertData2(i);
+    }
+  }
+
+  private void insertData2(int i) {
+    OmBasicParent p = new OmBasicParent("bl_" + i);
+    DB.save(p);
+
+    int children = 20 + random.nextInt(10);
+    for (int j = 0; j < children; j++) {
+      OmBasicChild c = new OmBasicChild("bl_" + i + "_" + j, p);
+      DB.save(c);
+    }
+  }
 }