add support for findSingleAttributeSet

ebean-api/src/main/java/io/ebean/ExpressionList.java

@@ -383,6 +383,15 @@ public interface ExpressionList<T> {
    */
   <A> List<A> findSingleAttributeList();
 
+  /**
+   * Executes the query returning a set of values for a single property.
+   *
+   * This can be used to cache sets.
+   *
+   * @return a HashSet of values for the selegted property
+   */
+  <A> Set<A> findSingleAttributeSet();
+
   /**
    * Execute a query returning a single value of a single property/column.
    * <pre>{@code

ebean-api/src/main/java/io/ebean/ExtendedServer.java

@@ -368,6 +368,11 @@ public interface ExtendedServer {
    */
   <A, T> List<A> findSingleAttributeList(Query<T> query, Transaction transaction);
 
+  /**
+   * Execute the query returning a hashset of values for a single property.
+   */
+  <A, T> Set<A> findSingleAttributeSet(Query<T> query, Transaction transaction);
+
   /**
    * Execute the query returning at most one entity bean or null (if no matching
    * bean is found).

ebean-api/src/main/java/io/ebean/Query.java

@@ -925,6 +925,11 @@ public interface Query<T> extends CancelableQuery {
    */
   <A> List<A> findSingleAttributeList();
 
+  /**
+   * Execute the query returning a hashset of values for a single property.
+   */
+  <A> Set<A> findSingleAttributeSet();
+
   /**
    * Execute a query returning a single value of a single property/column.
    * <p>

ebean-autotune/src/main/java/io/ebeaninternal/server/autotune/service/BaseQueryTuner.java

@@ -143,6 +143,7 @@ public class BaseQueryTuner {
     switch (type) {
       case COUNT:
       case ATTRIBUTE:
+      case ATTRIBUTE_SET:
       case ID_LIST:
       case UPDATE:
       case DELETE:

ebean-core/src/main/java/io/ebeaninternal/api/SpiQuery.java

@@ -92,6 +92,11 @@ public interface SpiQuery<T> extends Query<T>, SpiQueryFetch, TxnProfileEventCod
      */
     ATTRIBUTE(FIND_ATTRIBUTE, "findAttribute", false, false),
 
+    /**
+     * Find single attribute set.
+     */
+    ATTRIBUTE_SET(FIND_ATTRIBUTE_SET, "findAttributeSet", false, false),
+
     /**
      * Find rowCount.
      */

ebean-core/src/main/java/io/ebeaninternal/api/TxnProfileEventCodes.java

@@ -28,6 +28,7 @@ public interface TxnProfileEventCodes {
   String FIND_ID_LIST = "fi";
   String FIND_EXISTS = "ex";
   String FIND_ATTRIBUTE = "fa";
+  String FIND_ATTRIBUTE_SET = "fas";
   String FIND_COUNT = "fc";
   String FIND_SUBQUERY = "fs";
 

ebean-core/src/main/java/io/ebeaninternal/server/core/DefaultServer.java

@@ -364,7 +364,7 @@ public final class DefaultServer implements SpiServer, SpiEbeanServer {
     startQueryPlanCapture();
   }
 
-  
+
   @Override
   public void start() {
     for (Plugin plugin : serverPlugins) {
@@ -1189,7 +1189,23 @@ public final class DefaultServer implements SpiServer, SpiEbeanServer {
     }
     try {
       request.initTransIfRequired();
-      return request.findSingleAttributeList();
+      return request.findSingleAttributeCollection(new ArrayList<>());
+    } finally {
+      request.endTransIfRequired();
+    }
+  }
+
+  @Override
+  @SuppressWarnings("unchecked")
+  public <A, T> Set<A> findSingleAttributeSet(Query<T> query, Transaction transaction) {
+    SpiOrmQueryRequest<T> request = createQueryRequest(Type.ATTRIBUTE_SET, query, transaction);
+    Object result = request.getFromQueryCache();
+    if (result != null) {
+      return (Set<A>) result;
+    }
+    try {
+      request.initTransIfRequired();
+      return request.findSingleAttributeCollection(new LinkedHashSet<>());
     } finally {
       request.endTransIfRequired();
     }

ebean-core/src/main/java/io/ebeaninternal/server/core/OrmQueryEngine.java

@@ -6,6 +6,7 @@ import io.ebean.bean.BeanCollection;
 
 import javax.persistence.PersistenceException;
 import java.sql.SQLException;
+import java.util.Collection;
 import java.util.List;
 
 /**
@@ -29,11 +30,11 @@ public interface OrmQueryEngine {
   <T> BeanCollection<T> findMany(OrmQueryRequest<T> request);
 
   /**
-   * Execute the findSingleAttributeList query.
+   * Execute the findSingleAttributeCollection query.
    */
-  <A> List<A> findSingleAttributeList(OrmQueryRequest<?> request);
+  <A extends Collection<?>> A findSingleAttributeCollection(OrmQueryRequest<?> request, A collection);
 
-  /**
+   /**
    * Execute the findVersions query.
    */
   <T> List<Version<T>> findVersions(OrmQueryRequest<T> request);

ebean-core/src/main/java/io/ebeaninternal/server/core/OrmQueryRequest.java

@@ -431,8 +431,8 @@ public final class OrmQueryRequest<T> extends BeanRequest implements SpiOrmQuery
   }
 
   @Override
-  public <A> List<A> findSingleAttributeList() {
-    return queryEngine.findSingleAttributeList(this);
+  public <A extends Collection<?>> A findSingleAttributeCollection(A collection) {
+    return queryEngine.findSingleAttributeCollection(this, collection);
   }
 
   /**

ebean-core/src/main/java/io/ebeaninternal/server/core/SpiOrmQueryRequest.java

@@ -7,6 +7,7 @@ import io.ebeaninternal.api.SpiQuery;
 import io.ebeaninternal.server.deploy.BeanDescriptor;
 import io.ebeanservice.docstore.api.DocQueryRequest;
 
+import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -120,9 +121,9 @@ public interface SpiOrmQueryRequest<T> extends BeanQueryRequest<T>, DocQueryRequ
   <K> Map<K, T> findMap();
 
   /**
-   * Execute the findSingleAttributeList query.
+   * Execute the findSingleAttributeCollection query.
    */
-  <A> List<A> findSingleAttributeList();
+  <A extends Collection<?>> A findSingleAttributeCollection(A collection);
 
   /**
    * Execute returning the ResultSet.

ebean-core/src/main/java/io/ebeaninternal/server/expression/DefaultExpressionList.java

@@ -467,6 +467,11 @@ public class DefaultExpressionList<T> implements SpiExpressionList<T> {
     return query.findSingleAttributeList();
   }
 
+  @Override
+  public <A> Set<A> findSingleAttributeSet() {
+    return query.findSingleAttributeSet();
+  }
+
   @Override
   public boolean exists() {
     return query.exists();

ebean-core/src/main/java/io/ebeaninternal/server/expression/JunctionExpression.java

@@ -464,6 +464,11 @@ final class JunctionExpression<T> implements SpiJunction<T>, SpiExpression, Expr
     return exprList.findSingleAttributeList();
   }
 
+  @Override
+  public <A> Set<A> findSingleAttributeSet() {
+    return exprList.findSingleAttributeSet();
+  }
+
   @Override
   public PagedList<T> findPagedList() {
     return exprList.findPagedList();

ebean-core/src/main/java/io/ebeaninternal/server/query/CQueryEngine.java

@@ -24,11 +24,7 @@ import org.slf4j.Logger;
 import javax.persistence.PersistenceException;
 import java.sql.ResultSet;
 import java.sql.SQLException;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 
 /**
  * Handles the Object Relational fetching.
@@ -91,16 +87,16 @@ public final class CQueryEngine {
   /**
    * Build and execute the findSingleAttributeList query.
    */
-  public <A> List<A> findSingleAttributeList(OrmQueryRequest<?> request) {
+  public <A extends Collection<?>> A findSingleAttributeList(OrmQueryRequest<?> request, A collection) {
     CQueryFetchSingleAttribute rcQuery = queryBuilder.buildFetchAttributeQuery(request);
     request.setCancelableQuery(rcQuery);
-    return findAttributeList(request, rcQuery);
+    return findAttributeCollection(request, rcQuery, collection);
   }
 
   @SuppressWarnings("unchecked")
-  private <A> List<A> findAttributeList(OrmQueryRequest<?> request, CQueryFetchSingleAttribute rcQuery) {
+  private <A extends Collection<?>> A findAttributeCollection(OrmQueryRequest<?> request, CQueryFetchSingleAttribute rcQuery, A collection) {
     try {
-      List<A> list = (List<A>) rcQuery.findList();
+      rcQuery.findCollection(collection);
       if (request.logSql()) {
         logGeneratedSql(request, rcQuery.getGeneratedSql(), rcQuery.getBindLog(), rcQuery.micros());
       }
@@ -109,13 +105,22 @@ public final class CQueryEngine {
       }
       if (request.isQueryCachePut()) {
         request.addDependentTables(rcQuery.getDependentTables());
-        list = Collections.unmodifiableList(list);
-        request.putToQueryCache(list);
-        if (Boolean.FALSE.equals(request.query().isReadOnly())) {
-          list = new ArrayList<>(list);
+        if (collection instanceof List) {
+          collection = (A) Collections.unmodifiableList((List<?>) collection);
+          request.putToQueryCache(collection);
+          if (Boolean.FALSE.equals(request.query().isReadOnly())) {
+            collection = (A) new ArrayList<>(collection);
+          }
+        } else if (collection instanceof Set) {
+          collection = (A) Collections.unmodifiableSet((Set<?>) collection);
+          request.putToQueryCache(collection);
+          if (Boolean.FALSE.equals(request.query().isReadOnly())) {
+            collection = (A) new LinkedHashSet<>(collection);
+          }
         }
+
       }
-      return list;
+      return collection;
     } catch (SQLException e) {
       throw translate(request, rcQuery.getBindLog(), rcQuery.getGeneratedSql(), e);
     }
@@ -144,7 +149,7 @@ public final class CQueryEngine {
   public <A> List<A> findIds(OrmQueryRequest<?> request) {
     CQueryFetchSingleAttribute rcQuery = queryBuilder.buildFetchIdsQuery(request);
     request.setCancelableQuery(rcQuery);
-    return findAttributeList(request, rcQuery);
+    return findAttributeCollection(request, rcQuery, new ArrayList<>());
   }
 
   private <T> void logGeneratedSql(OrmQueryRequest<T> request, String sql, String bindLog, long micros) {

ebean-core/src/main/java/io/ebeaninternal/server/query/CQueryFetchSingleAttribute.java

@@ -16,6 +16,7 @@ import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.SQLException;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 import java.util.Set;
 import java.util.concurrent.locks.ReentrantLock;
@@ -76,11 +77,10 @@ final class CQueryFetchSingleAttribute implements SpiProfileTransactionEvent, Ca
   /**
    * Execute the query returning the row count.
    */
-  List<Object> findList() throws SQLException {
+  void findCollection(Collection result) throws SQLException {
     long startNano = System.nanoTime();
     try {
       prepareExecute();
-      List<Object> result = new ArrayList<>();
       while (dataReader.next()) {
         Object value = reader.read(dataReader);
         if (containsCounts) {
@@ -95,7 +95,6 @@ final class CQueryFetchSingleAttribute implements SpiProfileTransactionEvent, Ca
         queryPlan.captureBindForQueryPlan(predicates, executionTimeMicros);
       }
       getTransaction().profileEvent(this);
-      return result;
     } finally {
       close();
     }

ebean-core/src/main/java/io/ebeaninternal/server/query/DefaultFetchGroupQuery.java

@@ -286,6 +286,11 @@ final class DefaultFetchGroupQuery<T> implements SpiFetchGroupQuery<T>, SpiQuery
     throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");
   }
 
+  @Override
+  public <A> Set<A> findSingleAttributeSet() {
+    throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");
+  }
+
   @Override
   public <A> A findSingleAttribute() {
     throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");

ebean-core/src/main/java/io/ebeaninternal/server/query/DefaultOrmQueryEngine.java

@@ -17,6 +17,7 @@ import javax.persistence.PersistenceException;
 import java.sql.SQLException;
 import java.util.Collection;
 import java.util.List;
+import java.util.Set;
 
 /**
  * Main Finder implementation.
@@ -97,9 +98,9 @@ public final class DefaultOrmQueryEngine implements OrmQueryEngine {
   }
 
   @Override
-  public <A> List<A> findSingleAttributeList(OrmQueryRequest<?> request) {
+  public <A extends Collection<?>> A findSingleAttributeCollection(OrmQueryRequest<?> request, A collection) {
     flushJdbcBatchOnQuery(request);
-    return queryEngine.findSingleAttributeList(request);
+    return queryEngine.findSingleAttributeList(request, collection);
   }
 
   @Override

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

@@ -1498,6 +1498,10 @@ public class DefaultOrmQuery<T> extends AbstractQuery implements SpiQuery<T> {
     return (List<A>) server.findSingleAttributeList(this, transaction);
   }
 
+  @Override
+  public final <A> Set<A> findSingleAttributeSet() {
+    return (Set<A>) server.findSingleAttributeSet(this, transaction);
+  }
   @Override
   public final <A> A findSingleAttribute() {
     List<A> list = findSingleAttributeList();

ebean-test/src/test/java/io/ebean/xtest/internal/api/TDSpiEbeanServer.java

@@ -695,6 +695,11 @@ public class TDSpiEbeanServer extends TDSpiServer implements SpiEbeanServer {
     return null;
   }
 
+  @Override
+  public <A, T> Set<A> findSingleAttributeSet(Query<T> query, Transaction transaction) {
+    return null;
+  }
+
   @Override
   public <T> T findOne(Query<T> query, Transaction transaction) {
     return null;

ebean-test/src/test/java/org/tests/cache/TestQueryCache.java

@@ -1,21 +1,23 @@
 package org.tests.cache;
 
-import io.ebean.xtest.BaseTestCase;
 import io.ebean.CacheMode;
 import io.ebean.DB;
 import io.ebean.ExpressionList;
 import io.ebean.bean.BeanCollection;
 import io.ebean.cache.ServerCache;
 import io.ebean.test.LoggedSql;
+import io.ebean.xtest.BaseTestCase;
 import org.junit.jupiter.api.Test;
 import org.tests.model.basic.Customer;
 import org.tests.model.basic.ResetBasicData;
 import org.tests.model.cache.EColAB;
 
 import java.util.List;
+import java.util.Set;
 import java.util.function.Consumer;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.junit.jupiter.api.Assertions.*;
 
 public class TestQueryCache extends BaseTestCase {
@@ -50,7 +52,7 @@ public class TestQueryCache extends BaseTestCase {
   }
 
   @Test
-  public void findSingleAttribute() {
+  public void findSingleAttributeList() {
 
     DB.find(EColAB.class).delete();
     new EColAB("03", "SingleAttribute").save();
@@ -76,6 +78,7 @@ public class TestQueryCache extends BaseTestCase {
 
     assertThat(colA_Second).isSameAs(colA_first);
 
+
     List<String> colA_NotDistinct = DB
       .find(EColAB.class)
       .setUseQueryCache(true)
@@ -89,15 +92,39 @@ public class TestQueryCache extends BaseTestCase {
     // ensure that findCount & findSingleAttribute use different
     // slots in cache. If not a "Cannot cast List to int" should happen.
     int count = DB
-        .find(EColAB.class)
-        .setUseQueryCache(true)
-        .select("columnA")
-        .where()
-        .eq("columnB", "SingleAttribute")
-        .findCount();
+      .find(EColAB.class)
+      .setUseQueryCache(true)
+      .select("columnA")
+      .where()
+      .eq("columnB", "SingleAttribute")
+      .findCount();
     assertThat(count).isEqualTo(2);
   }
 
+  @Test
+  public void findSingleAttributeSet() {
+
+    DB.find(EColAB.class).delete();
+    new EColAB("03", "SingleAttribute").save();
+    new EColAB("03", "SingleAttribute").save();
+    ExpressionList<EColAB> query = DB
+      .find(EColAB.class)
+      .setUseQueryCache(true)
+      .select("columnA")
+      .where()
+      .eq("columnB", "SingleAttribute");
+    Set<String> colA_first = query.findSingleAttributeSet();
+
+    Set<String> colA_Second = query.findSingleAttributeSet();
+
+    assertThat(colA_Second).isSameAs(colA_first).hasSize(1);
+    assertThatThrownBy(colA_first::clear).isInstanceOf(UnsupportedOperationException.class);
+    // ensure, that we do not have cache collisions on same query
+    query.findSingleAttributeList();
+    query.findSingleAttribute();
+    query.findCount();
+  }
+
   @Test
   public void findCount() {
 
@@ -279,7 +306,7 @@ public class TestQueryCache extends BaseTestCase {
     assertSame(list, list2B);
 
     List<Customer> list3 = DB.find(Customer.class).setUseQueryCache(true).setReadOnly(false).where()
-        .ilike("name", "Rob").findList();
+      .ilike("name", "Rob").findList();
 
     assertNotSame(list, list3);
     BeanCollection<Customer> bc3 = (BeanCollection<Customer>) list3;
@@ -323,10 +350,10 @@ public class TestQueryCache extends BaseTestCase {
     // and now, ensure that we hit the database
     LoggedSql.start();
     colA_second = DB.find(EColAB.class)
-        .setUseQueryCache(CacheMode.PUT)
-        .where()
-        .eq("columnB", "someId")
-        .findIds();
+      .setUseQueryCache(CacheMode.PUT)
+      .where()
+      .eq("columnB", "someId")
+      .findIds();
     sql = LoggedSql.stop();
 
     assertThat(sql).hasSize(1);
@@ -335,15 +362,15 @@ public class TestQueryCache extends BaseTestCase {
   @Test
   public void findCountDifferentQueriesBit() {
     DB.getDefault().pluginApi().cacheManager().clearAll();
-    differentFindCount(q->q.bitwiseAny("id",1), q->q.bitwiseAny("id",0));
-    differentFindCount(q->q.bitwiseAll("id",1), q->q.bitwiseAll("id",0));
+    differentFindCount(q -> q.bitwiseAny("id", 1), q -> q.bitwiseAny("id", 0));
+    differentFindCount(q -> q.bitwiseAll("id", 1), q -> q.bitwiseAll("id", 0));
     // differentFindCount(q->q.bitwiseNot("id",1), q->q.bitwiseNot("id",0)); NOT 1 == AND 1 = 0
-    differentFindCount(q->q.bitwiseAnd("id",1, 0), q->q.bitwiseAnd("id",1, 1));
+    differentFindCount(q -> q.bitwiseAnd("id", 1, 0), q -> q.bitwiseAnd("id", 1, 1));
 
-    differentFindCount(q->q.bitwiseAnd("id",2, 0), q->q.bitwiseAnd("id",4, 0));
-    differentFindCount(q->q.bitwiseAnd("id",2, 1), q->q.bitwiseAnd("id",4, 1));
+    differentFindCount(q -> q.bitwiseAnd("id", 2, 0), q -> q.bitwiseAnd("id", 4, 0));
+    differentFindCount(q -> q.bitwiseAnd("id", 2, 1), q -> q.bitwiseAnd("id", 4, 1));
     // Will produce hash collision
-    differentFindCount(q->q.bitwiseAnd("id",10, 0), q->q.bitwiseAnd("id",0, 928210));
+    differentFindCount(q -> q.bitwiseAnd("id", 10, 0), q -> q.bitwiseAnd("id", 0, 928210));
 
   }