Test fetch ID only

ebean-core/src/main/java/io/ebeaninternal/server/querydefn/OrmQueryDetail.java

@@ -5,11 +5,13 @@
 import io.ebean.util.SplitName;
 import io.ebeaninternal.api.SpiQueryManyJoin;
 import io.ebeaninternal.server.deploy.BeanDescriptor;
+import io.ebeaninternal.server.deploy.BeanProperty;
 import io.ebeaninternal.server.deploy.BeanPropertyAssoc;
+import io.ebeaninternal.server.deploy.BeanPropertyAssocOne;
 import io.ebeaninternal.server.el.ElPropertyDeploy;
 import io.ebeaninternal.server.el.ElPropertyValue;
-
 import jakarta.persistence.PersistenceException;
+
 import java.io.Serializable;
 import java.util.*;
 
@@ -326,6 +328,41 @@ private void sortFetchPaths(BeanDescriptor<?> d, OrmQueryProperties p, LinkedHas
     }
   }
 
+  /**
+   * After sorting, we try to convert id only fetches of a bean into a select of the parent bean.
+   */
+  private void convertIdFetches(BeanDescriptor<?> desc, Set<String> nonRemovable) {
+    String[] paths = fetchPaths.keySet().toArray(new String[0]);
+    int i = paths.length;
+    // iterate backwards - otherwise we might detect id only fetches, which are later converted
+    while (i-- > 0) {
+      String path = paths[i];
+      ElPropertyDeploy el = desc.elPropertyDeploy(path);
+      OrmQueryProperties prop = fetchPaths.get(path);
+      if (nonRemovable.contains(path)) {
+        // do not remove
+      } else if (el == null) {
+        throw new PersistenceException("Invalid fetch path " + path + " from " + desc.fullName());
+      } else if (el.beanProperty() instanceof BeanPropertyAssocOne) {
+        BeanPropertyAssocOne assoc = (BeanPropertyAssocOne) el.beanProperty();
+        if (assoc.hasForeignKeyConstraint()) {
+          // check, if we have exactly the ID selected and convert these fetches to a select of the parent bean
+          if (prop.includesExactly(assoc.descriptor().idName())) {
+            OrmQueryProperties parentProp = prop.getParentPath() == null ? baseProps : fetchPaths.get(prop.getParentPath());
+            if (parentProp.hasProperties()) {
+              parentProp.addInclude(assoc.name());
+              fetchPaths.remove(path);
+              prop = null;
+            }
+          }
+        }
+      }
+      if (prop != null && prop.getParentPath() != null) {
+        nonRemovable.add(prop.getParentPath());
+      }
+    }
+  }
+
   /**
    * Mark 'fetch joins' to 'many' properties over to 'query joins' where needed.
    *
@@ -343,6 +380,8 @@ SpiQueryManyJoin markQueryJoins(BeanDescriptor<?> beanDescriptor, String lazyLoa
     boolean fetchJoinFirstMany = allowOne;
 
     sortFetchPaths(beanDescriptor, addIds);
+
+    convertIdFetches(beanDescriptor, new HashSet<>());
     List<FetchEntry> pairs = sortByFetchPreference(beanDescriptor);
 
     for (FetchEntry pair : pairs) {

ebean-core/src/main/java/io/ebeaninternal/server/querydefn/OrmQueryProperties.java

@@ -87,7 +87,7 @@ public OrmQueryProperties(String path, String rawProperties, FetchConfig fetchCo
     this.parentPath = SplitName.parent(path);
     OrmQueryPropertiesParser.Response response = OrmQueryPropertiesParser.parse(rawProperties);
     this.allProperties = response.allProperties;
-    this.included = response.included;
+    this.included = response.included; // modifiable
     if (fetchConfig != null) {
       this.fetchConfig = fetchConfig;
       this.cache = fetchConfig.isCache();
@@ -104,7 +104,7 @@ public OrmQueryProperties(String path, Set<String> included) {
   OrmQueryProperties(String path, Set<String> included, FetchConfig fetchConfig) {
     this.path = path;
     this.parentPath = SplitName.parent(path);
-    this.included = included;
+    this.included = (included == null) ? null : new LinkedHashSet<>(included);
     this.allProperties = false;
     this.fetchConfig = fetchConfig;
     this.cache = fetchConfig.isCache();
@@ -114,7 +114,7 @@ public OrmQueryProperties(String path, Set<String> included) {
     this.path = path;
     this.parentPath = SplitName.parent(path);
     this.allProperties = other.allProperties;
-    this.included = other.included;
+    this.included = (other.included == null) ? null : new LinkedHashSet<>(other.included);
     this.fetchConfig = fetchConfig;
     this.cache = fetchConfig.isCache();
   }
@@ -191,7 +191,7 @@ private SpiExpressionList<?> getFilterManyTrimPath(int trimPath) {
    * Adjust filterMany expressions for inclusion in main query.
    */
   public void filterManyInline() {
-    if (filterMany != null){
+    if (filterMany != null) {
       filterMany.prefixProperty(path);
     }
   }
@@ -431,4 +431,15 @@ public void queryPlanHash(StringBuilder builder) {
     builder.append('}');
   }
 
+  boolean includesExactly(String property) {
+    return included != null
+      && included.size() == 1
+      && included.contains(property);
+  }
+
+  void addInclude(String prop) {
+    if (!allProperties) {
+      included.add(prop);
+    }
+  }
 }

ebean-test/src/test/java/io/ebean/xtest/internal/server/grammer/EqlParserTest.java

@@ -629,7 +629,7 @@ void select_agg_sum() {
     List<OrderDetail> details = query.findList();
 
     assertThat(details).isNotEmpty();
-    assertSql(query).contains("select sum(t0.order_qty), t1.id from o_order_detail t0 join o_order t1 on t1.id = t0.order_id group by t1.id");
+    assertSql(query).contains("select sum(t0.order_qty), t0.order_id from o_order_detail t0 group by t0.order_id");
   }
 
   @Test

ebean-test/src/test/java/org/tests/lazyforeignkeys/TestLazyForeignKeys.java

@@ -77,7 +77,7 @@ public void testFindListWithSelect() {
     List<MainEntityRelation> list = query.findList();
     assertEquals(1, list.size());
 
-    assertSql(query).contains("t0.id, t0.attr1, t0.id1, t0.id2, t1.id, t2.id");
+    assertSql(query).isEqualTo("select t0.id, t0.attr1, t0.id1, t0.id2, t1.id, t2.id from main_entity_relation t0 left join main_entity t1 on t1.id = t0.id1 left join main_entity t2 on t2.id = t0.id2");
 
     MainEntityRelation rel1 = list.get(0);
     assertEquals("ent1", rel1.getEntity1().getId());

ebean-test/src/test/java/org/tests/merge/TestMergeCustomer.java

@@ -93,7 +93,7 @@ public void customerWithAddresses_setClientGeneratedIds_expect_selectAndUpdate()
 
     List<String> sql = LoggedSql.stop();
     assertThat(sql).hasSize(6);
-    assertSql(sql.get(0)).contains("select t0.id, t2.id, t1.id from mcustomer t0 left join maddress t2 on t2.id = t0.shipping_address_id left join maddress t1 on t1.id = t0.billing_address_id where t0.id = ?");
+    assertSql(sql.get(0)).contains("select t0.id, t0.billing_address_id, t0.shipping_address_id from mcustomer t0 where t0.id = ?");
     assertSql(sql.get(1)).contains("update maddress set street=?, city=?, version=? where id=? and version=?");
     assertSqlBind(sql, 2, 3);
     assertThat(sql.get(5)).contains("update mcustomer set name=?, version=?, shipping_address_id=?, billing_address_id=? where id=? and version=?");
@@ -122,7 +122,7 @@ public void customerWithAddresses_newAddress_setClientGeneratedIds_expect_insert
 
     List<String> sql = LoggedSql.stop();
     assertThat(sql).hasSize(8);
-    assertSql(sql.get(0)).contains("select t0.id, t2.id, t1.id from mcustomer t0 left join maddress t2 on t2.id = t0.shipping_address_id left join maddress t1 on t1.id = t0.billing_address_id where t0.id = ?");
+    assertSql(sql.get(0)).contains("select t0.id, t0.billing_address_id, t0.shipping_address_id from mcustomer t0 where t0.id = ?");
     assertSql(sql.get(1)).contains("insert into maddress (id, street, city, version) values (?,?,?,?)");
     assertSqlBind(sql.get(2));
     assertThat(sql.get(4)).contains("update maddress set street=?, city=?, version=? where id=? and version=?");
@@ -155,7 +155,7 @@ public void customerWithAddresses_newAddressWithId_setClientGeneratedIds_expect_
 
     List<String> sql = LoggedSql.stop();
     assertThat(sql).hasSize(9);
-    assertSql(sql.get(0)).contains("select t0.id, t2.id, t1.id from mcustomer t0 left join maddress t2 on t2.id = t0.shipping_address_id left join maddress t1 on t1.id = t0.billing_address_id where t0.id = ?");
+    assertSql(sql.get(0)).contains("select t0.id, t0.billing_address_id, t0.shipping_address_id from mcustomer t0 where t0.id = ?");
 
     // Additional check to see if the address with the unknown UUID is 'insert' or 'update'
     assertSql(sql.get(1)).contains("select t0.id from maddress t0 where t0.id = ?");
@@ -317,7 +317,7 @@ public void fullMonty() {
     List<String> sql = LoggedSql.stop();
     if (isPersistBatchOnCascade()) {
 
-      assertSql(sql.get(0)).contains("select t0.id, t3.id, t1.id, t2.id from mcustomer t0 left join maddress t3 on t3.id = t0.shipping_address_id left join maddress t1 on t1.id = t0.billing_address_id left join mcontact t2 on t2.customer_id = t0.id where t0.id = ?");
+      assertSql(sql.get(0)).contains("select t0.id, t0.shipping_address_id, t0.billing_address_id, t1.id from mcustomer t0 left join mcontact t1 on t1.customer_id = t0.id where t0.id = ? order by t0.id");
       if (isH2() || isHana()) {
         // with nested OneToMany .. we need a second query to read the contact message ids
         assertSql(sql.get(1)).contains("select t0.contact_id, t0.id from mcontact_message t0 where (t0.contact_id) in (?,?,?,?,?,?,?,?,?,?)");

ebean-test/src/test/java/org/tests/query/TestFetchIdOnly.java

@@ -0,0 +1,57 @@
+package org.tests.query;
+
+import io.ebean.DB;
+import io.ebean.Query;
+import io.ebean.test.LoggedSql;
+import io.ebean.text.PathProperties;
+import io.ebean.xtest.BaseTestCase;
+import org.junit.jupiter.api.Test;
+import org.tests.model.basic.Order;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class TestFetchIdOnly extends BaseTestCase {
+
+  @Test
+  void test_withFetchPath() {
+    PathProperties root = PathProperties.parse("status,customer(id)");
+    LoggedSql.start();
+    Query<Order> query = DB.find(Order.class).apply(root);
+    query.findList();
+    List<String> sql = LoggedSql.stop();
+    assertThat(sql).hasSize(1);
+    assertThat(sql.get(0)).contains("select t0.id, t0.status, t0.kcustomer_id from o_order t0;");
+  }
+
+  @Test
+  void test_withSelect() {
+    LoggedSql.start();
+    Query<Order> query = DB.find(Order.class).select("status, customer");
+    query.findList();
+    List<String> sql = LoggedSql.stop();
+    assertThat(sql).hasSize(1);
+    assertThat(sql.get(0)).contains("select t0.id, t0.status, t0.kcustomer_id from o_order t0;");
+  }
+
+  @Test
+  void test_withFetch() {
+    LoggedSql.start();
+    Query<Order> query = DB.find(Order.class).select("status").fetch("customer", "id");
+    query.findList();
+    List<String> sql = LoggedSql.stop();
+    assertThat(sql).hasSize(1);
+    assertThat(sql.get(0)).contains("select t0.id, t0.status, t0.kcustomer_id from o_order t0;");
+  }
+
+  @Test
+  void test_withChildFetch() {
+    LoggedSql.start();
+    Query<Order> query = DB.find(Order.class).select("status").fetch("customer.shippingAddress", "id");
+    query.findList();
+    List<String> sql = LoggedSql.stop();
+    assertThat(sql).hasSize(1);
+    assertThat(sql.get(0)).contains("select t0.id, t0.status, t1.id, t1.shipping_address_id from o_order t0 join o_customer t1 on t1.id = t0.kcustomer_id;");
+  }
+}

ebean-test/src/test/java/org/tests/query/TestSubQuery.java

@@ -75,9 +75,9 @@ public void test_IsInWithFetchSubQuery1() {
     Query<OrderDetail> debugSq = sq.copy();
     debugSq.findSingleAttribute();
     if (isPostgresCompatible()) {
-      assertThat(debugSq.getGeneratedSql()).isEqualTo("select t1.id from o_order_detail t0 join o_order t1 on t1.id = t0.order_id where t0.product_id = any(?)");
+      assertThat(debugSq.getGeneratedSql()).isEqualTo("select t0.order_id from o_order_detail t0 where t0.product_id = any(?)");
     } else {
-      assertSql(debugSq.getGeneratedSql()).isEqualTo("select t1.id from o_order_detail t0 join o_order t1 on t1.id = t0.order_id where t0.product_id in (?)");
+      assertSql(debugSq.getGeneratedSql()).isEqualTo("select t0.order_id from o_order_detail t0 where t0.product_id in (?)");
     }
 
     Query<Order> query = DB.find(Order.class).select("shipDate").where().isIn("id", sq).query();

ebean-test/src/test/java/org/tests/query/joins/TestQueryJoinOnFormula.java

@@ -333,6 +333,20 @@ public void test_ChildPersonParentFindCount() {
     assertThat(loggedSql.get(0)).contains("where coalesce(f2.child_age, 0) = ?");
   }
 
+  @Test
+  public void test_fetch_only() {
+
+    LoggedSql.start();
+
+    DB.find(ChildPerson.class).select("name").fetch("parent.effectiveBean").findList();
+
+    List<String> loggedSql = LoggedSql.stop();
+    assertThat(loggedSql.get(0)).contains("from child_person t0 "
+      + "left join parent_person t1 on t1.identifier = t0.parent_identifier "
+      + "left join grand_parent_person j1 on j1.identifier = t1.parent_identifier "
+      + "left join e_basic t2 on t2.id = coalesce(t1.some_bean_id, j1.some_bean_id)");
+  }
+
   @Test
   public void test_softRef() {