#125 - ENH: Add support for query returning a List of single Attribute type

src/main/java/com/avaje/ebean/EbeanServer.java

@@ -988,6 +988,40 @@ public interface EbeanServer {
    */
   <T> Map<?, T> findMap(Query<T> query, Transaction transaction);
 
+  /**
+   * Execute the query returning a list of values for a single property.
+   *
+   * <h3>Example 1:</h3>
+   * <pre>{@code
+   *
+   *  List<String> names =
+   *    Ebean.find(Customer.class)
+   *      .select("name")
+   *      .orderBy().asc("name")
+   *      .findSingleAttributeList();
+   *
+   * }</pre>
+   *
+   * <h3>Example 2:</h3>
+   * <pre>{@code
+   *
+   *  List<String> names =
+   *    Ebean.find(Customer.class)
+   *      .setDistinct(true)
+   *      .select("name")
+   *      .where().eq("status", Customer.Status.NEW)
+   *      .orderBy().asc("name")
+   *      .setMaxRows(100)
+   *      .findSingleAttributeList();
+   *
+   * }</pre>
+   *
+   * @return the list of values for the selected property
+   *
+   * @see Query#findSingleAttributeList()
+   */
+  <A> List<A> findSingleAttributeList(Query<?> query, Transaction transaction);
+
   /**
    * Execute the query returning at most one entity bean or null (if no matching
    * bean is found).

src/main/java/com/avaje/ebean/ExpressionList.java

@@ -31,7 +31,7 @@ import java.util.Set;
  * more methods than you would initially expect (the ones duplicated from
  * Query).
  * </p>
- * 
+ *
  * @see Query#where()
  */
 public interface ExpressionList<T> {
@@ -83,14 +83,14 @@ public interface ExpressionList<T> {
 
   /**
    * Add an orderBy clause to the query.
-   * 
+   *
    * @see Query#orderBy(String)
    */
   Query<T> orderBy(String orderBy);
 
   /**
    * Add an orderBy clause to the query.
-   * 
+   *
    * @see Query#orderBy(String)
    */
   Query<T> setOrderBy(String orderBy);
@@ -164,14 +164,14 @@ public interface ExpressionList<T> {
 
   /**
    * Execute the query returning a list.
-   * 
+   *
    * @see Query#findList()
    */
   List<T> findList();
 
   /**
    * Execute the query returning the list of Id's.
-   * 
+   *
    * @see Query#findIds()
    */
   List<Object> findIds();
@@ -193,14 +193,14 @@ public interface ExpressionList<T> {
 
   /**
    * Execute the query returning a set.
-   * 
+   *
    * @see Query#findSet()
    */
   Set<T> findSet();
 
   /**
    * Execute the query returning a map.
-   * 
+   *
    * @see Query#findMap()
    */
   Map<?, T> findMap();
@@ -210,6 +210,38 @@ public interface ExpressionList<T> {
    */
   <K> Map<K, T> findMap(String keyProperty, Class<K> keyType);
 
+  /**
+   * Execute the query returning a list of values for a single property.
+   *
+   * <h3>Example 1:</h3>
+   * <pre>{@code
+   *
+   *  List<String> names =
+   *    Ebean.find(Customer.class)
+   *      .select("name")
+   *      .orderBy().asc("name")
+   *      .findSingleAttributeList();
+   *
+   * }</pre>
+   *
+   * <h3>Example 2:</h3>
+   * <pre>{@code
+   *
+   *  List<String> names =
+   *    Ebean.find(Customer.class)
+   *      .setDistinct(true)
+   *      .select("name")
+   *      .where().eq("status", Customer.Status.NEW)
+   *      .orderBy().asc("name")
+   *      .setMaxRows(100)
+   *      .findSingleAttributeList();
+   *
+   * }</pre>
+   *
+   * @return the list of values for the selected property
+   */
+  <A> List<A> findSingleAttributeList();
+
   /**
    * Execute the query returning a single bean or null (if no matching
    * bean is found).
@@ -232,7 +264,7 @@ public interface ExpressionList<T> {
    * execution status (isDone etc) and get the value (with or without a
    * timeout).
    * </p>
-   * 
+   *
    * @return a Future object for the row count query
    */
   FutureRowCount<T> findFutureCount();
@@ -251,7 +283,7 @@ public interface ExpressionList<T> {
    * execution status (isDone etc) and get the value (with or without a
    * timeout).
    * </p>
-   * 
+   *
    * @return a Future object for the list of Id's
    */
   FutureIds<T> findFutureIds();
@@ -263,7 +295,7 @@ public interface ExpressionList<T> {
    * execution status (isDone etc) and get the value (with or without a
    * timeout).
    * </p>
-   * 
+   *
    * @return a Future object for the list result of the query
    */
   FutureList<T> findFutureList();
@@ -326,7 +358,7 @@ public interface ExpressionList<T> {
   /**
    * Specify specific properties to fetch on the main/root bean (aka partial
    * object).
-   * 
+   *
    * @see Query#select(String)
    */
   Query<T> select(String properties);
@@ -351,28 +383,28 @@ public interface ExpressionList<T> {
 
   /**
    * Set the first row to fetch.
-   * 
+   *
    * @see Query#setFirstRow(int)
    */
   Query<T> setFirstRow(int firstRow);
 
   /**
    * Set the maximum number of rows to fetch.
-   * 
+   *
    * @see Query#setMaxRows(int)
    */
   Query<T> setMaxRows(int maxRows);
 
   /**
    * Set the name of the property which values become the key of a map.
-   * 
+   *
    * @see Query#setMapKey(String)
    */
   Query<T> setMapKey(String mapKey);
 
   /**
    * Set to true to use the query for executing this query.
-   * 
+   *
    * @see Query#setUseCache(boolean)
    */
   Query<T> setUseCache(boolean useCache);
@@ -633,7 +665,7 @@ public interface ExpressionList<T> {
    * To get control over the options you can create an ExampleExpression and set
    * those options such as case insensitive etc.
    * </p>
-   * 
+   *
    * <pre>{@code
    *
    * // create an example bean and set the properties
@@ -641,26 +673,26 @@ public interface ExpressionList<T> {
    * Customer example = new Customer();
    * example.setName("Rob%");
    * example.setNotes("%something%");
-   * 
+   *
    * List&lt;Customer&gt; list = Ebean.find(Customer.class).where()
    *     // pass the bean into the where() clause
    *     .exampleLike(example)
    *     // you can add other expressions to the same query
    *     .gt("id", 2).findList();
-   * 
+   *
    * }</pre>
-   * 
+   *
    * Similarly you can create an ExampleExpression
-   * 
+   *
    * <pre>{@code
    *
    * Customer example = new Customer();
    * example.setName("Rob%");
    * example.setNotes("%something%");
-   * 
+   *
    * // create a ExampleExpression with more control
    * ExampleExpression qbe = new ExampleExpression(example, true, LikeType.EQUAL_TO).includeZeros();
-   * 
+   *
    * List<Customer> list = Ebean.find(Customer.class).where().add(qbe).findList();
    *
    * }</pre>
@@ -762,7 +794,7 @@ public interface ExpressionList<T> {
    * Exists expression
    */
   ExpressionList<T> exists(Query<?> subQuery);
-  
+
   /**
    * Not exists expression
    */
@@ -789,7 +821,7 @@ public interface ExpressionList<T> {
    * Expression where all the property names in the map are equal to the
    * corresponding value.
    * </p>
-   * 
+   *
    * @param propertyMap
    *          a map keyed by property names.
    */

src/main/java/com/avaje/ebean/Query.java

@@ -677,6 +677,38 @@ public interface Query<T> {
    */
   <K> Map<K, T> findMap(String keyProperty, Class<K> keyType);
 
+  /**
+   * Execute the query returning a list of values for a single property.
+   *
+   * <h3>Example 1:</h3>
+   * <pre>{@code
+   *
+   *  List<String> names =
+   *    Ebean.find(Customer.class)
+   *      .select("name")
+   *      .orderBy().asc("name")
+   *      .findSingleAttributeList();
+   *
+   * }</pre>
+   *
+   * <h3>Example 2:</h3>
+   * <pre>{@code
+   *
+   *  List<String> names =
+   *    Ebean.find(Customer.class)
+   *      .setDistinct(true)
+   *      .select("name")
+   *      .where().eq("status", Customer.Status.NEW)
+   *      .orderBy().asc("name")
+   *      .setMaxRows(100)
+   *      .findSingleAttributeList();
+   *
+   * }</pre>
+   *
+   * @return the list of values for the selected property
+   */
+  <A> List<A> findSingleAttributeList();
+
   /**
    * Execute the query returning either a single bean or null (if no matching
    * bean is found).

src/main/java/com/avaje/ebeaninternal/api/SpiQuery.java

@@ -78,6 +78,11 @@ public interface SpiQuery<T> extends Query<T> {
      */
     ID_LIST,
 
+    /**
+     * Find single attribute.
+     */
+    ATTRIBUTE,
+
     /**
      * Find rowCount.
      */
@@ -341,6 +346,24 @@ public interface SpiQuery<T> extends Query<T> {
    */
   void setSelectId();
 
+  /**
+   * Mark the query as selecting a single attribute.
+   */
+  void setSingleAttribute();
+
+  /**
+   * Return true if this is singleAttribute query.
+   */
+  boolean isSingleAttribute();
+
+  /**
+   * Return true if the query should include the Id property.
+   * <p>
+   * distinct and single attribute queries exclude the Id property.
+   * </p>
+   */
+  boolean isWithId();
+
   /**
    * Set a filter to a join path.
    */

src/main/java/com/avaje/ebeaninternal/server/core/DefaultServer.java

@@ -1152,6 +1152,23 @@ public final class DefaultServer implements SpiServer, SpiEbeanServer {
     }
   }
 
+  @Override
+  public <A> List<A> findSingleAttributeList(Query<?> query, Transaction t) {
+
+    SpiOrmQueryRequest request = createQueryRequest(Type.ATTRIBUTE, query, t);
+    Object result = request.getFromQueryCache();
+    if (result != null) {
+      return (List<A>) result;
+    }
+    try {
+      request.initTransIfRequired();
+      return (List<A>) request.findSingleAttributeList();
+
+    } finally {
+      request.endTransIfRequired();
+    }
+  }
+
   public <T> int findCount(Query<T> query, Transaction t) {
 
     SpiQuery<T> copy = ((SpiQuery<T>) query).copy();

src/main/java/com/avaje/ebeaninternal/server/core/OrmQueryEngine.java

@@ -21,6 +21,14 @@ public interface OrmQueryEngine {
    */
   <T> BeanCollection<T> findMany(OrmQueryRequest<T> request);
 
+  /**
+   * Execute the findSingleAttributeList query.
+   */
+  <A> List<A> findSingleAttributeList(OrmQueryRequest<?> request);
+
+  /**
+   * Execute the findVersions query.
+   */
   <T> List<Version<T>> findVersions(OrmQueryRequest<T> request);
 
   /**

src/main/java/com/avaje/ebeaninternal/server/core/OrmQueryRequest.java

@@ -373,6 +373,14 @@ public final class OrmQueryRequest<T> extends BeanRequest implements BeanQueryRe
     return (Map<?, ?>) queryEngine.findMany(this);
   }
 
+  /**
+   * Execute the findSingleAttributeList query.
+   */
+  @Override
+  public <A> List<A> findSingleAttributeList() {
+    return queryEngine.findSingleAttributeList(this);
+  }
+
   /**
    * Return a bean specific finder if one has been set.
    */

src/main/java/com/avaje/ebeaninternal/server/core/SpiOrmQueryRequest.java

@@ -107,6 +107,11 @@ public interface SpiOrmQueryRequest<T> extends DocQueryRequest<T> {
    */
   Map<?, ?> findMap();
 
+  /**
+   * Execute the findSingleAttributeList query.
+   */
+  <A> List<A> findSingleAttributeList();
+
   /**
    * Try to get the query result from the query cache.
    */

src/main/java/com/avaje/ebeaninternal/server/expression/DefaultExpressionList.java

@@ -388,6 +388,11 @@ public class DefaultExpressionList<T> implements SpiExpressionList<T> {
     return query.findMap(keyProperty, keyType);
   }
 
+  @Override
+  public <A> List<A> findSingleAttributeList() {
+    return query.findSingleAttributeList();
+  }
+
   @Override
   public T findUnique() {
     return query.findUnique();

src/main/java/com/avaje/ebeaninternal/server/expression/JunctionExpression.java

@@ -400,6 +400,11 @@ class JunctionExpression<T> implements SpiJunction<T>, SpiExpression, Expression
     return exprList.findMap(keyProperty, keyType);
   }
 
+  @Override
+  public <A> List<A> findSingleAttributeList() {
+    return exprList.findSingleAttributeList();
+  }
+
   @Override
   public PagedList<T> findPagedList() {
     return exprList.findPagedList();

src/main/java/com/avaje/ebeaninternal/server/query/CQueryBuilder.java

@@ -165,13 +165,35 @@ public class CQueryBuilder {
     return StringHelper.replaceString(sql, "${RTA}", replaceWith);
   }
 
+  public CQueryFetchSingleAttribute buildFetchAttributeQuery(OrmQueryRequest<?> request) {
+
+    SpiQuery<?> query = request.getQuery();
+    query.setSingleAttribute();
+
+    CQueryPredicates predicates = new CQueryPredicates(binder, request);
+    CQueryPlan queryPlan = request.getQueryPlan();
+    if (queryPlan != null) {
+      predicates.prepare(false);
+      return new CQueryFetchSingleAttribute(request, predicates, queryPlan);
+    }
+
+    // use RawSql or generated Sql
+    predicates.prepare(true);
+
+    SqlTree sqlTree = createSqlTree(request, predicates, getHistorySupport(query), getDraftSupport(query));
+    SqlLimitResponse s = buildSql(null, request, predicates, sqlTree);
+
+    queryPlan = new CQueryPlan(request, s.getSql(), sqlTree, false, s.isIncludesRowNumberColumn(), predicates.getLogWhereSql());
+    request.putQueryPlan(queryPlan);
+    return new CQueryFetchSingleAttribute(request, predicates, queryPlan);
+  }
+
   /**
    * Build the row count query.
    */
   public <T> CQueryFetchIds buildFetchIdsQuery(OrmQueryRequest<T> request) {
 
     SpiQuery<T> query = request.getQuery();
-
     query.setSelectId();
 
     CQueryPredicates predicates = new CQueryPredicates(binder, request);
@@ -179,8 +201,7 @@ public class CQueryBuilder {
     if (queryPlan != null) {
       // skip building the SqlTree and Sql string
       predicates.prepare(false);
-      String sql = queryPlan.getSql();
-      return new CQueryFetchIds(request, predicates, sql);
+      return new CQueryFetchIds(request, predicates, queryPlan.getSql());
     }
 
     // use RawSql or generated Sql
@@ -450,8 +471,8 @@ public class CQueryBuilder {
       }
 
       sb.append(select.getSelectSql());
-      if (query.isDistinctQuery() && dbOrderBy != null) {
-        // add the orderby columns to the select clause (due to distinct)
+      if (query.isDistinctQuery() && dbOrderBy != null && !query.isSingleAttribute()) {
+        // add the orderBy columns to the select clause (due to distinct)
         sb.append(", ").append(convertDbOrderByForSelect(dbOrderBy));
       }
     }

src/main/java/com/avaje/ebeaninternal/server/query/CQueryEngine.java

@@ -88,6 +88,27 @@ public class CQueryEngine {
     }
   }
 
+  /**
+   * Build and execute the findSingleAttributeList query.
+   */
+  public <A> List<A> findSingleAttributeList(OrmQueryRequest<?> request) {
+
+    CQueryFetchSingleAttribute rcQuery = queryBuilder.buildFetchAttributeQuery(request);
+    try {
+      List list = rcQuery.findList();
+      if (request.isLogSql()) {
+        logGeneratedSql(request, rcQuery.getGeneratedSql(), rcQuery.getBindLog());
+      }
+      if (request.isLogSummary()) {
+        request.getTransaction().logSummary(rcQuery.getSummary());
+      }
+      return list;
+
+    } catch (SQLException e) {
+      throw CQuery.createPersistenceException(e, request.getTransaction(), rcQuery.getBindLog(), rcQuery.getGeneratedSql());
+    }
+  }
+
   /**
    * Build and execute the find Id's query.
    */
@@ -97,15 +118,12 @@ public class CQueryEngine {
     try {
 
       BeanIdList list = rcQuery.findIds();
-
       if (request.isLogSql()) {
         logGeneratedSql(request, rcQuery.getGeneratedSql(), rcQuery.getBindLog());
       }
-
       if (request.isLogSummary()) {
         request.getTransaction().logSummary(rcQuery.getSummary());
       }
-
       if (request.getQuery().isFutureFetch()) {
         // end the transaction for futureFindIds (it had it's own one)
         logger.debug("Future findIds completed!");

src/main/java/com/avaje/ebeaninternal/server/query/CQueryFetchBase.java

@@ -0,0 +1,208 @@
+package com.avaje.ebeaninternal.server.query;
+
+import com.avaje.ebean.bean.BeanCollection;
+import com.avaje.ebean.bean.EntityBean;
+import com.avaje.ebean.bean.EntityBeanIntercept;
+import com.avaje.ebean.bean.PersistenceContext;
+import com.avaje.ebeaninternal.api.SpiQuery;
+import com.avaje.ebeaninternal.api.SpiQuery.Mode;
+import com.avaje.ebeaninternal.api.SpiTransaction;
+import com.avaje.ebeaninternal.server.core.OrmQueryRequest;
+import com.avaje.ebeaninternal.server.deploy.BeanDescriptor;
+import com.avaje.ebeaninternal.server.deploy.BeanPropertyAssocMany;
+import com.avaje.ebeaninternal.server.deploy.DbReadContext;
+import com.avaje.ebeaninternal.server.type.DataReader;
+import com.avaje.ebeaninternal.server.type.RsetDataReader;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.Map;
+
+/**
+ * Base compiled query request for single attribute queries.
+ */
+public abstract class CQueryFetchBase {
+
+  private static final Logger logger = LoggerFactory.getLogger(CQueryFetchBase.class);
+
+  /**
+   * The overall find request wrapper object.
+   */
+  protected final OrmQueryRequest<?> request;
+
+  protected final BeanDescriptor<?> desc;
+
+  protected final SpiQuery<?> query;
+
+  /**
+   * Where clause predicates.
+   */
+  protected final CQueryPredicates predicates;
+
+  /**
+   * The final sql that is generated.
+   */
+  protected final String sql;
+
+  protected RsetDataReader dataReader;
+
+  /**
+   * The statement used to create the resultSet.
+   */
+  protected PreparedStatement pstmt;
+
+  protected String bindLog;
+
+  protected int executionTimeMicros;
+
+  protected int rowCount;
+
+  protected final int maxRows;
+
+  /**
+   * Create the Sql select based on the request.
+   */
+  public CQueryFetchBase(OrmQueryRequest<?> request, CQueryPredicates predicates, String sql) {
+
+    this.request = request;
+    this.query = request.getQuery();
+    this.sql = sql;
+    this.maxRows = query.getMaxRows();
+
+    query.setGeneratedSql(sql);
+
+    this.desc = request.getBeanDescriptor();
+    this.predicates = predicates;
+  }
+
+  /**
+   * Return the bind log.
+   */
+  public String getBindLog() {
+    return bindLog;
+  }
+
+  /**
+   * Return the generated sql.
+   */
+  public String getGeneratedSql() {
+    return sql;
+  }
+
+  protected ResultSet prepareExecute() throws SQLException {
+
+    SpiTransaction t = request.getTransaction();
+    Connection conn = t.getInternalConnection();
+    pstmt = conn.prepareStatement(sql);
+
+    if (query.getBufferFetchSizeHint() > 0) {
+      pstmt.setFetchSize(query.getBufferFetchSizeHint());
+    }
+    if (query.getTimeout() > 0) {
+      pstmt.setQueryTimeout(query.getTimeout());
+    }
+
+    bindLog = predicates.bind(pstmt, conn);
+
+    ResultSet rset = pstmt.executeQuery();
+    dataReader = new RsetDataReader(request.getDataTimeZone(), rset);
+    return rset;
+  }
+
+  /**
+   * Close the resources.
+   * <p>
+   * The jdbc resultSet and statement need to be closed. Its important that
+   * this method is called.
+   * </p>
+   */
+  protected void close() {
+    try {
+      if (dataReader != null) {
+        dataReader.close();
+        dataReader = null;
+      }
+    } catch (SQLException e) {
+      logger.error("Error closing DataReader", e);
+    }
+    try {
+      if (pstmt != null) {
+        pstmt.close();
+        pstmt = null;
+      }
+    } catch (SQLException e) {
+      logger.error("Error closing PreparedStatement", e);
+    }
+  }
+
+
+  protected class DbContext implements DbReadContext {
+
+    public void propagateState(Object e) {
+      throw new RuntimeException("Not Called");
+    }
+
+    public Mode getQueryMode() {
+      return Mode.NORMAL;
+    }
+
+    public DataReader getDataReader() {
+      return dataReader;
+    }
+
+    public Boolean isReadOnly() {
+      return Boolean.FALSE;
+    }
+
+    @Override
+    public boolean isDisableLazyLoading() {
+      return false;
+    }
+
+    public boolean isRawSql() {
+      return false;
+    }
+
+    public void register(String path, EntityBeanIntercept ebi) {
+    }
+
+    public void register(String path, BeanCollection<?> bc) {
+    }
+
+    public BeanPropertyAssocMany<?> getManyProperty() {
+      // always null
+      return null;
+    }
+
+    public PersistenceContext getPersistenceContext() {
+      // always null
+      return null;
+    }
+
+    public boolean isAutoTuneProfiling() {
+      return false;
+    }
+
+    public void profileBean(EntityBeanIntercept ebi, String prefix) {
+      // no-op
+    }
+
+    public void setCurrentPrefix(String currentPrefix, Map<String, String> pathMap) {
+      // no-op
+    }
+
+    public void setLazyLoadedChildBean(EntityBean loadedBean, Object lazyLoadParentId) {
+      // no-op
+    }
+
+    @Override
+    public boolean isDraftQuery() {
+      return false;
+    }
+  }
+
+}

src/main/java/com/avaje/ebeaninternal/server/query/CQueryFetchIds.java

@@ -1,86 +1,25 @@
 package com.avaje.ebeaninternal.server.query;
 
-import com.avaje.ebean.bean.BeanCollection;
-import com.avaje.ebean.bean.EntityBean;
-import com.avaje.ebean.bean.EntityBeanIntercept;
-import com.avaje.ebean.bean.PersistenceContext;
 import com.avaje.ebeaninternal.api.BeanIdList;
-import com.avaje.ebeaninternal.api.SpiQuery;
-import com.avaje.ebeaninternal.api.SpiQuery.Mode;
-import com.avaje.ebeaninternal.api.SpiTransaction;
 import com.avaje.ebeaninternal.server.core.OrmQueryRequest;
-import com.avaje.ebeaninternal.server.deploy.BeanDescriptor;
-import com.avaje.ebeaninternal.server.deploy.BeanPropertyAssocMany;
 import com.avaje.ebeaninternal.server.deploy.DbReadContext;
-import com.avaje.ebeaninternal.server.type.DataReader;
-import com.avaje.ebeaninternal.server.type.RsetDataReader;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
-import java.sql.Connection;
-import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
-import java.util.Map;
 
 /**
  * Executes the select row count query.
  */
-public class CQueryFetchIds {
-
-  private static final Logger logger = LoggerFactory.getLogger(CQueryFetchIds.class);
-
-  /**
-   * The overall find request wrapper object.
-   */
-  private final OrmQueryRequest<?> request;
-
-  private final BeanDescriptor<?> desc;
-
-  private final SpiQuery<?> query;
-
-  /**
-   * Where clause predicates.
-   */
-  private final CQueryPredicates predicates;
-
-  /**
-   * The final sql that is generated.
-   */
-  private final String sql;
-
-  private RsetDataReader dataReader;
-
-  /**
-   * The statement used to create the resultSet.
-   */
-  private PreparedStatement pstmt;
-
-  private String bindLog;
-
-  private int executionTimeMicros;
-
-  private int rowCount;
-
-  private final int maxRows;
+public class CQueryFetchIds extends CQueryFetchBase {
 
   /**
    * Create the Sql select based on the request.
    */
   public CQueryFetchIds(OrmQueryRequest<?> request, CQueryPredicates predicates, String sql) {
-
-    this.request = request;
-    this.query = request.getQuery();
-    this.sql = sql;
-    this.maxRows = query.getMaxRows();
-
-    query.setGeneratedSql(sql);
-
-    this.desc = request.getBeanDescriptor();
-    this.predicates = predicates;
+    super(request, predicates, sql);
   }
 
   /**
@@ -97,20 +36,6 @@ public class CQueryFetchIds {
     return sb.toString();
   }
 
-  /**
-   * Return the bind log.
-   */
-  public String getBindLog() {
-    return bindLog;
-  }
-
-  /**
-   * Return the generated sql.
-   */
-  public String getGeneratedSql() {
-    return sql;
-  }
-
   /**
    * Execute the query returning the row count.
    */
@@ -131,22 +56,7 @@ public class CQueryFetchIds {
 
       BeanIdList result = new BeanIdList(idList);
 
-      SpiTransaction t = request.getTransaction();
-      Connection conn = t.getInternalConnection();
-      pstmt = conn.prepareStatement(sql);
-
-      if (query.getBufferFetchSizeHint() > 0) {
-        pstmt.setFetchSize(query.getBufferFetchSizeHint());
-      }
-
-      if (query.getTimeout() > 0) {
-        pstmt.setQueryTimeout(query.getTimeout());
-      }
-
-      bindLog = predicates.bind(pstmt, conn);
-
-      ResultSet rset = pstmt.executeQuery();
-      dataReader = new RsetDataReader(request.getDataTimeZone(), rset);
+      ResultSet rset = prepareExecute();
 
       boolean hitMaxRows = false;
       boolean hasMoreRows = false;
@@ -183,96 +93,4 @@ public class CQueryFetchIds {
     }
   }
 
-  /**
-   * Close the resources.
-   * <p>
-   * The jdbc resultSet and statement need to be closed. Its important that
-   * this method is called.
-   * </p>
-   */
-  private void close() {
-    try {
-      if (dataReader != null) {
-        dataReader.close();
-        dataReader = null;
-      }
-    } catch (SQLException e) {
-      logger.error("Error closing DataReader", e);
-    }
-    try {
-      if (pstmt != null) {
-        pstmt.close();
-        pstmt = null;
-      }
-    } catch (SQLException e) {
-      logger.error("Error closing PreparedStatement", e);
-    }
-  }
-
-
-  class DbContext implements DbReadContext {
-
-    public void propagateState(Object e) {
-      throw new RuntimeException("Not Called");
-    }
-
-    public Mode getQueryMode() {
-      return Mode.NORMAL;
-    }
-
-    public DataReader getDataReader() {
-      return dataReader;
-    }
-
-    public Boolean isReadOnly() {
-      return Boolean.FALSE;
-    }
-
-    @Override
-    public boolean isDisableLazyLoading() {
-      return false;
-    }
-
-    public boolean isRawSql() {
-      return false;
-    }
-
-    public void register(String path, EntityBeanIntercept ebi) {
-    }
-
-    public void register(String path, BeanCollection<?> bc) {
-    }
-
-    public BeanPropertyAssocMany<?> getManyProperty() {
-      // always null
-      return null;
-    }
-
-    public PersistenceContext getPersistenceContext() {
-      // always null
-      return null;
-    }
-
-    public boolean isAutoTuneProfiling() {
-      return false;
-    }
-
-    public void profileBean(EntityBeanIntercept ebi, String prefix) {
-      // no-op
-    }
-
-    public void setCurrentPrefix(String currentPrefix, Map<String, String> pathMap) {
-      // no-op
-    }
-
-    public void setLazyLoadedChildBean(EntityBean loadedBean, Object lazyLoadParentId) {
-      // no-op
-    }
-
-    @Override
-    public boolean isDraftQuery() {
-      return false;
-    }
-  }
-
 }

src/main/java/com/avaje/ebeaninternal/server/query/CQueryFetchSingleAttribute.java

@@ -0,0 +1,71 @@
+package com.avaje.ebeaninternal.server.query;
+
+import com.avaje.ebeaninternal.server.core.OrmQueryRequest;
+import com.avaje.ebeaninternal.server.deploy.BeanProperty;
+import com.avaje.ebeaninternal.server.type.ScalarType;
+
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Executes the select row count query.
+ */
+public class CQueryFetchSingleAttribute extends CQueryFetchBase {
+
+  private final BeanProperty property;
+
+  private final ScalarType<Object> scalarType;
+
+  /**
+   * Create the Sql select based on the request.
+   */
+  public CQueryFetchSingleAttribute(OrmQueryRequest<?> request, CQueryPredicates predicates, CQueryPlan plan) {
+    super(request, predicates, plan.getSql());
+    this.property = plan.getSingleProperty();
+    this.scalarType = property.getScalarType();
+  }
+
+  /**
+   * Return a summary description of this query.
+   */
+  public String getSummary() {
+    StringBuilder sb = new StringBuilder(80);
+    sb.append("FindAttr exeMicros[").append(executionTimeMicros)
+        .append("] rows[").append(rowCount)
+        .append("] type[").append(desc.getName())
+        .append("] predicates[").append(predicates.getLogWhereSql())
+        .append("] bind[").append(bindLog).append("]");
+
+    return sb.toString();
+  }
+
+  /**
+   * Execute the query returning the row count.
+   */
+  public List<Object> findList() throws SQLException {
+
+    long startNano = System.nanoTime();
+    try {
+
+      List<Object> result = new ArrayList<Object>();
+
+      ResultSet rset = prepareExecute();
+      while (rset.next()) {
+        result.add(scalarType.read(dataReader));
+        dataReader.resetColumnPosition();
+        rowCount++;
+      }
+
+      long exeNano = System.nanoTime() - startNano;
+      executionTimeMicros = (int) exeNano / 1000;
+
+      return result;
+
+    } finally {
+      close();
+    }
+  }
+
+}

src/main/java/com/avaje/ebeaninternal/server/query/CQueryPlan.java

@@ -266,4 +266,7 @@ public class CQueryPlan {
     return stats.getLastQueryTime();
   }
 
+  public BeanProperty getSingleProperty() {
+    return sqlTree.getRootNode().getSingleProperty();
+  }
 }

src/main/java/com/avaje/ebeaninternal/server/query/DefaultOrmQueryEngine.java

@@ -71,6 +71,12 @@ public class DefaultOrmQueryEngine implements OrmQueryEngine {
     return queryEngine.findIds(request);
   }
 
+  @Override
+  public <A> List<A> findSingleAttributeList(OrmQueryRequest<?> request) {
+    flushJdbcBatchOnQuery(request);
+    return queryEngine.findSingleAttributeList(request);
+  }
+
   public <T> QueryIterator<T> findIterate(OrmQueryRequest<T> request) {
 
     // LIMITATION: You can not use QueryIterator to load bean cache

src/main/java/com/avaje/ebeaninternal/server/query/SqlTreeBuilder.java

@@ -260,7 +260,7 @@ public class SqlTreeBuilder {
 
       // Optional many property for lazy loading query
       BeanPropertyAssocMany<?> lazyLoadMany = (query == null) ? null : query.getLazyLoadMany();
-      boolean withId = !rawNoId && !subQuery && (query == null || !query.isDistinct());
+      boolean withId = !rawNoId && !subQuery && (query == null || query.isWithId());
       return new SqlTreeNodeRoot(desc, props, myList, withId, includeJoin, lazyLoadMany, SpiQuery.TemporalMode.of(query), disableLazyLoad);
 
     } else if (prop instanceof BeanPropertyAssocMany<?>) {

src/main/java/com/avaje/ebeaninternal/server/query/SqlTreeNode.java

@@ -3,6 +3,7 @@ package com.avaje.ebeaninternal.server.query;
 import com.avaje.ebean.Version;
 import com.avaje.ebean.bean.EntityBean;
 import com.avaje.ebeaninternal.api.SpiQuery;
+import com.avaje.ebeaninternal.server.deploy.BeanProperty;
 import com.avaje.ebeaninternal.server.deploy.DbReadContext;
 import com.avaje.ebeaninternal.server.deploy.DbSqlContext;
 
@@ -62,4 +63,10 @@ public interface SqlTreeNode {
    * Return true if the query has a many join.
    */
   boolean hasMany();
+
+  /**
+   * Return the property for singleAttribute query.
+   */
+  BeanProperty getSingleProperty();
+
 }

src/main/java/com/avaje/ebeaninternal/server/query/SqlTreeNodeBean.java

@@ -137,6 +137,11 @@ public class SqlTreeNodeBean implements SqlTreeNode {
     pathMap = createPathMap(prefix, desc);
   }
 
+  @Override
+  public BeanProperty getSingleProperty() {
+    return properties[0];
+  }
+
   private Map<String, String> createPathMap(String prefix, BeanDescriptor<?> desc) {
 
     BeanPropertyAssocMany<?>[] manys = desc.propertiesMany();

src/main/java/com/avaje/ebeaninternal/server/query/SqlTreeNodeExtraJoin.java

@@ -3,6 +3,7 @@ package com.avaje.ebeaninternal.server.query;
 import com.avaje.ebean.Version;
 import com.avaje.ebean.bean.EntityBean;
 import com.avaje.ebeaninternal.api.SpiQuery;
+import com.avaje.ebeaninternal.server.deploy.BeanProperty;
 import com.avaje.ebeaninternal.server.deploy.BeanPropertyAssoc;
 import com.avaje.ebeaninternal.server.deploy.BeanPropertyAssocMany;
 import com.avaje.ebeaninternal.server.deploy.DbReadContext;
@@ -55,6 +56,11 @@ public class SqlTreeNodeExtraJoin implements SqlTreeNode {
     // nothing to do here
   }
 
+  @Override
+  public BeanProperty getSingleProperty() {
+    throw new IllegalStateException("No expected");
+  }
+
   /**
    * Return true if the extra join is a many join.
    * <p>

src/main/java/com/avaje/ebeaninternal/server/query/SqlTreeNodeManyWhereJoin.java

@@ -3,6 +3,7 @@ package com.avaje.ebeaninternal.server.query;
 import com.avaje.ebean.Version;
 import com.avaje.ebean.bean.EntityBean;
 import com.avaje.ebeaninternal.api.SpiQuery;
+import com.avaje.ebeaninternal.server.deploy.BeanProperty;
 import com.avaje.ebeaninternal.server.deploy.BeanPropertyAssoc;
 import com.avaje.ebeaninternal.server.deploy.BeanPropertyAssocMany;
 import com.avaje.ebeaninternal.server.deploy.BeanPropertyAssocOne;
@@ -39,6 +40,11 @@ public class SqlTreeNodeManyWhereJoin implements SqlTreeNode {
     this.parentPrefix = split[0];
   }
 
+  @Override
+  public BeanProperty getSingleProperty() {
+    throw new IllegalStateException("No expected");
+  }
+
   @Override
   public void addAsOfTableAlias(SpiQuery<?> query) {
     // do nothing here ...

src/main/java/com/avaje/ebeaninternal/server/querydefn/DefaultOrmQuery.java

@@ -192,6 +192,8 @@ public class DefaultOrmQuery<T> implements SpiQuery<T> {
    */
   private boolean forUpdate;
 
+  private boolean singleAttribute;
+
   /**
    * Set to true if this query has been tuned by autoTune.
    */
@@ -534,6 +536,26 @@ public class DefaultOrmQuery<T> implements SpiQuery<T> {
     select(beanDescriptor.getIdBinder().getIdProperty());
   }
 
+  @Override
+  public void setSingleAttribute() {
+    this.singleAttribute = true;
+  }
+
+  /**
+   * Return true if this is a single attribute query.
+   */
+  public boolean isSingleAttribute() {
+    return singleAttribute;
+  }
+
+  /**
+   * Return true if the Id should be included in the query.
+   */
+  @Override
+  public boolean isWithId() {
+    return !distinct && !singleAttribute;
+  }
+
   @Override
   public NaturalKeyBindParam getNaturalKeyBindParam() {
     NaturalKeyBindParam namedBind = null;
@@ -1133,6 +1155,11 @@ public class DefaultOrmQuery<T> implements SpiQuery<T> {
     return (Map<K, T>) findMap();
   }
 
+  @Override
+  public <A> List<A> findSingleAttributeList() {
+    return (List<A>)server.findSingleAttributeList(this, null);
+  }
+
   @Override
   public T findUnique() {
     return server.findUnique(this, null);