#1331 - ENH: Support Aggregation formula with findSingleAttribute() ... max, min, avg, count and count(distinct ..)

src/main/java/io/ebeaninternal/server/deploy/BeanDescriptor.java

@@ -62,11 +62,13 @@ import io.ebeaninternal.server.el.ElPropertyValue;
 import io.ebeaninternal.server.persist.DmlUtil;
 import io.ebeaninternal.server.query.CQueryPlan;
 import io.ebeaninternal.server.query.CQueryPlanStatsCollector;
+import io.ebeaninternal.server.query.SqlTreeProperty;
 import io.ebeaninternal.server.querydefn.OrmQueryDetail;
 import io.ebeaninternal.server.rawsql.SpiRawSql;
 import io.ebeaninternal.server.text.json.ReadJson;
 import io.ebeaninternal.server.text.json.SpiJsonWriter;
 import io.ebeaninternal.server.type.DataBind;
+import io.ebeaninternal.server.type.ScalarType;
 import io.ebeaninternal.util.SortByClause;
 import io.ebeaninternal.util.SortByClauseParser;
 import io.ebeanservice.docstore.api.DocStoreBeanAdapter;
@@ -112,6 +114,8 @@ public class BeanDescriptor<T> implements BeanType<T> {
 
   private final ConcurrentHashMap<String, ElComparator<T>> comparatorCache = new ConcurrentHashMap<>();
 
+  private final ConcurrentHashMap<String, SqlTreeProperty> dynamicProperty = new ConcurrentHashMap<>();
+
   private final Map<String, SpiRawSql> namedRawSql;
 
   private final Map<String, String> namedQuery;
@@ -1055,6 +1059,13 @@ public class BeanDescriptor<T> implements BeanType<T> {
     return owner.getEncryptKey(tableName, columnName);
   }
 
+  /**
+   * Return the Scalar type for the given JDBC type.
+   */
+  public ScalarType<?> getScalarType(int jdbcType) {
+    return owner.getScalarType(jdbcType);
+  }
+
   /**
    * Return true if this bean type has a default select clause that is not
    * simply select all properties.
@@ -2437,6 +2448,37 @@ public class BeanDescriptor<T> implements BeanType<T> {
     return null;
   }
 
+  /**
+   * Return a 'dynamic property' used to read a formula.
+   */
+  private SqlTreeProperty findSqlTreeFormula(String formulaExpression) {
+
+    return dynamicProperty.computeIfAbsent(formulaExpression, (formula) -> {
+      FormulaPropertyPath propertyFormula = new FormulaPropertyPath(formula);
+      if (!propertyFormula.isFormula()) {
+        throw new IllegalStateException("unable to parse formula [" + formula + "} on bean type " + fullName);
+      }
+      String baseName = propertyFormula.basePropertyName();
+      BeanProperty base = _findBeanProperty(baseName);
+      if (base == null) {
+        throw new IllegalStateException("unable to find property [" + baseName + "] from formula [" + formula + "} on bean type " + fullName);
+      }
+      return propertyFormula.formulaProperty(base);
+    });
+  }
+
+  /**
+   * Return a property that is part of the SQL tree.
+   *
+   * The property can be a dynamic formula or a well known bean property.
+   */
+  public SqlTreeProperty findSqlTreeProperty(String propName) {
+    if (propName.indexOf('(') > -1) {
+      return findSqlTreeFormula(propName);
+    }
+    return _findBeanProperty(propName);
+  }
+
   /**
    * Find a BeanProperty including searching the inheritance hierarchy.
    * <p>

src/main/java/io/ebeaninternal/server/deploy/BeanDescriptorManager.java

@@ -52,7 +52,9 @@ import io.ebeaninternal.server.properties.BeanPropertiesReader;
 import io.ebeaninternal.server.properties.BeanPropertyAccess;
 import io.ebeaninternal.server.properties.EnhanceBeanPropertyAccess;
 import io.ebeaninternal.server.query.CQueryPlan;
+import io.ebeaninternal.server.type.ScalarType;
 import io.ebeaninternal.server.type.ScalarTypeInteger;
+import io.ebeaninternal.server.type.TypeManager;
 import io.ebeaninternal.xmlmapping.XmlMappingReader;
 import io.ebeaninternal.xmlmapping.model.XmAliasMapping;
 import io.ebeaninternal.xmlmapping.model.XmColumnMapping;
@@ -139,6 +141,8 @@ public class BeanDescriptorManager implements BeanDescriptorMap {
 
   private final MultiValueBind multiValueBind;
 
+  private final TypeManager typeManager;
+
   private int entityBeanCount;
 
   private final boolean updateChangesOnly;
@@ -222,6 +226,7 @@ public class BeanDescriptorManager implements BeanDescriptorMap {
     this.dbIdentity = config.getDatabasePlatform().getDbIdentity();
     this.deplyInherit = config.getDeployInherit();
     this.deployUtil = config.getDeployUtil();
+    this.typeManager = deployUtil.getTypeManager();
 
     this.beanManagerFactory = new BeanManagerFactory(config.getDatabasePlatform());
 
@@ -260,6 +265,11 @@ public class BeanDescriptorManager implements BeanDescriptorMap {
     }
   }
 
+  @Override
+  public ScalarType<?> getScalarType(int jdbcType) {
+    return typeManager.getScalarType(jdbcType);
+  }
+
   /**
    * Return the AsOfViewSuffix based on the DbHistorySupport.
    */
@@ -1463,7 +1473,7 @@ public class BeanDescriptorManager implements BeanDescriptorMap {
         prop.setGetter(beanPropertyAccess.getGetter(propertyIndex));
         prop.setSetter(beanPropertyAccess.getSetter(propertyIndex));
         if (prop.isAggregation()) {
-          prop.setAggregationPrefix(DetermineAggPath.manyPath(prop.getAggregation(), desc));
+          prop.setAggregationPrefix(DetermineAggPath.manyPath(prop.getRawAggregation(), desc));
         }
       }
     }

src/main/java/io/ebeaninternal/server/deploy/BeanDescriptorMap.java

@@ -6,6 +6,7 @@ import io.ebean.config.ServerConfig;
 import io.ebeaninternal.server.cache.SpiCacheManager;
 import io.ebeaninternal.server.deploy.id.IdBinder;
 import io.ebeaninternal.server.deploy.meta.DeployBeanDescriptor;
+import io.ebeaninternal.server.type.ScalarType;
 import io.ebeanservice.docstore.api.DocStoreBeanAdapter;
 
 /**
@@ -60,4 +61,9 @@ public interface BeanDescriptorMap {
    * Create a doc store specific adapter for this bean type.
    */
   <T> DocStoreBeanAdapter<T> createDocStoreBeanAdapter(BeanDescriptor<T> descriptor, DeployBeanDescriptor<T> deploy);
+
+  /**
+   * Return the scalarType for the given JDBC type.
+   */
+  ScalarType<?> getScalarType(int jdbcType);
 }

src/main/java/io/ebeaninternal/server/deploy/BeanProperty.java

@@ -24,6 +24,7 @@ import io.ebeaninternal.server.properties.BeanPropertyGetter;
 import io.ebeaninternal.server.properties.BeanPropertySetter;
 import io.ebeaninternal.server.query.SqlBeanLoad;
 import io.ebeaninternal.server.query.SqlJoinType;
+import io.ebeaninternal.server.query.SqlTreeProperty;
 import io.ebeaninternal.server.text.json.ReadJson;
 import io.ebeaninternal.server.text.json.SpiJsonWriter;
 import io.ebeaninternal.server.type.DataBind;
@@ -55,7 +56,7 @@ import java.util.Set;
  * Description of a property of a bean. Includes its deployment information such
  * as database column mapping information.
  */
-public class BeanProperty implements ElPropertyValue, Property {
+public class BeanProperty implements ElPropertyValue, Property, SqlTreeProperty {
 
   private static final Logger logger = LoggerFactory.getLogger(BeanProperty.class);
 
@@ -321,7 +322,7 @@ public class BeanProperty implements ElPropertyValue, Property {
 
     this.dbColumn = tableAliasIntern(descriptor, deploy.getDbColumn(), false, null);
     this.dbComment = deploy.getDbComment();
-    this.aggregation = deploy.getAggregation();
+    this.aggregation = deploy.parseAggregation();
     this.sqlFormulaJoin = InternString.intern(deploy.getSqlFormulaJoin());
     this.sqlFormulaSelect = InternString.intern(deploy.getSqlFormulaSelect());
     this.formula = sqlFormulaSelect != null;
@@ -575,8 +576,7 @@ public class BeanProperty implements ElPropertyValue, Property {
   public void appendSelect(DbSqlContext ctx, boolean subQuery) {
 
     if (aggregation != null) {
-      ctx.appendRawColumn(aggregation);
-
+      ctx.appendFormulaSelect(aggregation);
     } else if (formula) {
       ctx.appendFormulaSelect(sqlFormulaSelect);
 

src/main/java/io/ebeaninternal/server/deploy/DbSqlContext.java

@@ -64,6 +64,11 @@ public interface DbSqlContext {
    */
   void appendColumn(String column);
 
+  /**
+   * Parse and add formula with standard table alias replacement.
+   */
+  void appendParseSelect(String parseSelect);
+
   /**
    * Append a Sql Formula select. This converts the "${ta}" keyword to the
    * current table alias.

src/main/java/io/ebeaninternal/server/deploy/DeployParser.java

@@ -27,6 +27,8 @@ public abstract class DeployParser {
    */
   protected static final char PERIOD = '.';
 
+  protected static final char OPEN_BRACKET = '(';
+
   protected boolean encrypted;
 
   protected String source;
@@ -43,6 +45,8 @@ public abstract class DeployParser {
 
   protected char wordTerminator;
 
+  private StringBuilder wordBuffer;
+
   protected abstract String convertWord();
 
   public abstract String getDeployWord(String expression);
@@ -77,7 +81,9 @@ public abstract class DeployParser {
         priorWord = deployWord;
       }
       if (pos < sourceLength) {
-        sb.append(wordTerminator);
+        if (wordTerminator != OPEN_BRACKET) {
+          sb.append(wordTerminator);
+        }
         if (wordTerminator == SINGLE_QUOTE) {
           readLiteral();
         }
@@ -97,7 +103,7 @@ public abstract class DeployParser {
       return false;
     }
 
-    StringBuilder wordBuffer = new StringBuilder();
+    wordBuffer = new StringBuilder();
     wordBuffer.append(source.charAt(pos));
     while (++pos < sourceLength) {
       char ch = source.charAt(pos);
@@ -172,6 +178,11 @@ public abstract class DeployParser {
    * return true if the char is a letter, digit or underscore.
    */
   private boolean isWordPart(char ch) {
+    if (ch == OPEN_BRACKET) {
+      // include in the 'word' such that "count(" formula doesn't clash with property "count"
+      wordBuffer.append(ch);
+      return false;
+    }
     return Character.isLetterOrDigit(ch) || ch == UNDERSCORE || ch == PERIOD;
   }
 

src/main/java/io/ebeaninternal/server/deploy/DeployPropertyParserMap.java

@@ -7,7 +7,7 @@ import java.util.Set;
 /**
  * Converts logical property names to database columns using a Map.
  */
-public final class DeployPropertyParserMap extends DeployParser {
+public class DeployPropertyParserMap extends DeployParser {
 
   private final Map<String, String> map;
 

src/main/java/io/ebeaninternal/server/deploy/DetermineAggPath.java

@@ -12,6 +12,10 @@ class DetermineAggPath {
    */
   static String manyPath(String aggregation, DeployBeanDescriptor<?> desc) {
     DetermineAggPath.Path path = paths(aggregation);
+    if (path.length() == 1) {
+      // a top level aggregation (so here we need to exclude Id property)
+      return null;
+    }
     return path.getManyPath(0, desc);
   }
 

src/main/java/io/ebeaninternal/server/deploy/DynamicPropertyAggregationFormula.java

@@ -0,0 +1,52 @@
+package io.ebeaninternal.server.deploy;
+
+import io.ebeaninternal.server.query.SqlBeanLoad;
+import io.ebeaninternal.server.type.ScalarType;
+
+import javax.persistence.PersistenceException;
+
+/**
+ * Dynamic property based on aggregation (max, min, avg, count).
+ */
+class DynamicPropertyAggregationFormula extends DynamicPropertyBase {
+
+  private final String parsedAggregation;
+
+  private final BeanProperty asTarget;
+
+  DynamicPropertyAggregationFormula(String name, ScalarType<?> scalarType, String parsedAggregation, BeanProperty asTarget) {
+    super(name, name, null, scalarType);
+    this.parsedAggregation = parsedAggregation;
+    this.asTarget = asTarget;
+  }
+
+  @Override
+  public String toString() {
+    return "DynamicPropertyFormula[" + parsedAggregation + "]";
+  }
+
+  @Override
+  public boolean isAggregation() {
+    return true;
+  }
+
+  @Override
+  public void load(SqlBeanLoad sqlBeanLoad) {
+
+    try {
+      Object value = scalarType.read(sqlBeanLoad.ctx().getDataReader());
+      if (asTarget != null) {
+        sqlBeanLoad.load(asTarget, value);
+      }
+
+    } catch (Exception e) {
+      throw new PersistenceException("Error loading on " + fullName, e);
+    }
+  }
+
+  @Override
+  public void appendSelect(DbSqlContext ctx, boolean subQuery) {
+    ctx.appendParseSelect(parsedAggregation);
+  }
+
+}

src/main/java/io/ebeaninternal/server/deploy/DynamicPropertyBase.java

@@ -0,0 +1,70 @@
+package io.ebeaninternal.server.deploy;
+
+import io.ebeaninternal.server.query.SqlJoinType;
+import io.ebeaninternal.server.query.SqlTreeProperty;
+import io.ebeaninternal.server.type.ScalarType;
+
+import java.util.List;
+
+/**
+ * Abstract base for dynamic properties.
+ */
+abstract class DynamicPropertyBase implements SqlTreeProperty {
+
+  final String name;
+  final String fullName;
+  final String elPrefix;
+  final ScalarType<?> scalarType;
+
+  public DynamicPropertyBase(String name, String fullName, String elPrefix, ScalarType<?> scalarType) {
+    this.name = name;
+    this.fullName = fullName;
+    this.elPrefix = elPrefix;
+    this.scalarType = scalarType;
+  }
+
+  @Override
+  public String getName() {
+    return name;
+  }
+
+  @Override
+  public String getFullBeanName() {
+    return fullName;
+  }
+
+  @Override
+  public boolean isId() {
+    return false;
+  }
+
+  @Override
+  public boolean isEmbedded() {
+    return false;
+  }
+
+  @Override
+  public String getElPrefix() {
+    return elPrefix;
+  }
+
+  @Override
+  public ScalarType<?> getScalarType() {
+    return scalarType;
+  }
+
+  @Override
+  public void buildRawSqlSelectChain(String prefix, List<String> selectChain) {
+    // do nothing, only for RawSql
+  }
+
+  @Override
+  public void loadIgnore(DbReadContext ctx) {
+    scalarType.loadIgnore(ctx.getDataReader());
+  }
+
+  @Override
+  public void appendFrom(DbSqlContext ctx, SqlJoinType joinType) {
+    // do not add to from usually
+  }
+}

src/main/java/io/ebeaninternal/server/deploy/FormulaPropertyPath.java

@@ -0,0 +1,89 @@
+package io.ebeaninternal.server.deploy;
+
+import io.ebeaninternal.server.query.SqlTreeProperty;
+import io.ebeaninternal.server.type.ScalarType;
+
+import java.sql.Types;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+class FormulaPropertyPath {
+
+  private static final Pattern pattern = Pattern.compile("(max|min|avg|count)\\((.*)\\)");
+
+  private static final String DISTINCT_ = "distinct ";
+
+  private final String aggType;
+
+  private final String baseName;
+
+  private boolean countDistinct;
+
+  FormulaPropertyPath(String propName) {
+
+    Matcher matcher = pattern.matcher(propName);
+    if (matcher.find()) {
+      aggType = matcher.group(1);
+      baseName = trimDistinct(matcher.group(2));
+
+    } else {
+      aggType = null;
+      baseName = null;
+    }
+  }
+
+  private String trimDistinct(String propertyName) {
+    if (propertyName.startsWith(DISTINCT_)){
+      countDistinct = true;
+      return propertyName.substring(DISTINCT_.length());
+    } else {
+      return propertyName;
+    }
+  }
+
+  boolean isFormula() {
+    return aggType != null;
+  }
+
+  String aggType() {
+    return aggType;
+  }
+
+  String basePropertyName() {
+    return baseName;
+  }
+
+  /**
+   * Create a bean property dynamically for the formula in the select clause.
+   */
+  SqlTreeProperty formulaProperty(BeanProperty base) {
+
+    String parsedAggregation = buildFormula(base);
+    String name = logicalName();
+
+    ScalarType<?> scalarType = base.getScalarType();
+    if (isCount()) {
+      // count maps to Long / BIGINT
+      scalarType = base.getBeanDescriptor().getScalarType(Types.BIGINT);
+    }
+
+    return new DynamicPropertyAggregationFormula(name, scalarType, parsedAggregation, null);
+  }
+
+  private String buildFormula(BeanProperty base) {
+    if (countDistinct) {
+      return "count(distinct ${}"+base.getDbColumn()+")";
+    } else {
+      return aggType+"(${}"+base.getDbColumn()+")";
+    }
+  }
+
+  private boolean isCount() {
+    return aggType.equals("count");
+  }
+
+  private String logicalName() {
+    return aggType+Character.toUpperCase(baseName.charAt(0))+baseName.substring(1);
+  }
+
+}

src/main/java/io/ebeaninternal/server/deploy/meta/DeployBeanDescriptor.java

@@ -25,6 +25,7 @@ import io.ebeaninternal.server.deploy.ChainedBeanPersistListener;
 import io.ebeaninternal.server.deploy.ChainedBeanPostConstructListener;
 import io.ebeaninternal.server.deploy.ChainedBeanPostLoad;
 import io.ebeaninternal.server.deploy.ChainedBeanQueryAdapter;
+import io.ebeaninternal.server.deploy.DeployPropertyParserMap;
 import io.ebeaninternal.server.deploy.IndexDefinition;
 import io.ebeaninternal.server.deploy.InheritInfo;
 import io.ebeaninternal.server.deploy.TableJoin;
@@ -849,18 +850,18 @@ public class DeployBeanDescriptor<T> {
     this.idGeneratorName = PlatformIdGenerator.AUTO_UUID;
 
     switch (serverConfig.getUuidVersion()) {
-    case VERSION1:
-      this.idGenerator = UuidV1IdGenerator.getInstance(serverConfig.getUuidStateFile());
-      break;
+      case VERSION1:
+        this.idGenerator = UuidV1IdGenerator.getInstance(serverConfig.getUuidStateFile());
+        break;
 
-    case VERSION1RND:
-      this.idGenerator = UuidV1RndIdGenerator.INSTANCE;
-      break;
+      case VERSION1RND:
+        this.idGenerator = UuidV1RndIdGenerator.INSTANCE;
+        break;
 
-    case VERSION4:
-    default:
-      this.idGenerator = UuidV4IdGenerator.INSTANCE;
-      break;
+      case VERSION4:
+      default:
+        this.idGenerator = UuidV4IdGenerator.INSTANCE;
+        break;
     }
   }
 
@@ -1168,4 +1169,38 @@ public class DeployBeanDescriptor<T> {
     }
     namedRawSql.put(name, rawSql);
   }
+
+  /**
+   * Parse the aggregation formula into expressions with table alias placeholders.
+   */
+  public String parse(String aggregation) {
+    return new Parser(this).parse(aggregation);
+  }
+
+  /**
+   * Parser for top level properties into EL expressions (table alias placeholders).
+   */
+  private static class Parser extends DeployPropertyParserMap {
+
+    private final DeployBeanDescriptor<?> descriptor;
+
+    Parser(DeployBeanDescriptor<?> descriptor) {
+      super(null);
+      this.descriptor = descriptor;
+    }
+
+    public String getDeployWord(String expression) {
+      return descriptor.getDeployWord(expression);
+    }
+  }
+
+  private String getDeployWord(String expression) {
+    if (expression.charAt(expression.length() - 1) == '(') {
+      return null;
+    }
+    // use 'current' table alias - refer BeanProperty appendSelect() for aggregation
+    DeployBeanProperty property = propMap.get(expression);
+    return (property == null) ? null : "${ta}." + property.getDbColumn();
+  }
+
 }

src/main/java/io/ebeaninternal/server/deploy/meta/DeployBeanProperty.java

@@ -175,6 +175,7 @@ public class DeployBeanProperty {
 
   private String aggregationPrefix;
   private String aggregation;
+  private String aggregationParsed;
 
   private String sqlFormulaSelect;
   private String sqlFormulaJoin;
@@ -615,10 +616,23 @@ public class DeployBeanProperty {
     return aggregation != null;
   }
 
-  public String getAggregation() {
+  /**
+   * Get the raw/logical aggregation formula.
+   */
+  public String getRawAggregation() {
     return aggregation;
   }
 
+  /**
+   * Get the parsed aggregation formula with table alias placeholders.
+   */
+  public String parseAggregation() {
+    if (aggregation != null) {
+      aggregationParsed = desc.parse(aggregation);
+    }
+    return aggregationParsed;
+  }
+
   public void setAggregation(String aggregation) {
     this.aggregation = aggregation;
     this.dbRead = true;
@@ -629,9 +643,9 @@ public class DeployBeanProperty {
   /**
    * Set the path to the aggregation.
    */
-  public void setAggregationPrefix(String aggregationPrefix) {
-    this.aggregationPrefix = aggregationPrefix;
-    this.aggregation = aggregation.replace(aggregationPrefix, "u1");
+  public void setAggregationPrefix(String prefix) {
+    this.aggregationPrefix = prefix;
+    this.aggregation = (prefix == null) ? aggregation : aggregation.replace(aggregationPrefix, "u1");
   }
 
   public String getElPrefix() {
@@ -644,7 +658,7 @@ public class DeployBeanProperty {
 
   public String getElPlaceHolder() {
     if (aggregation != null) {
-      return aggregation;
+      return aggregationParsed;
     } else if (sqlFormulaSelect != null) {
       return sqlFormulaSelect;
     } else {

src/main/java/io/ebeaninternal/server/query/DefaultDbSqlContext.java

@@ -273,13 +273,19 @@ class DefaultDbSqlContext implements DbSqlContext {
     sb.append(" ");
   }
 
+  @Override
+  public void appendParseSelect(String parseSelect) {
+    String converted = alias.parse(parseSelect);
+    sb.append(COMMA);
+    sb.append(converted);
+    appendColumnAlias();
+  }
+
   @Override
   public void appendFormulaSelect(String sqlFormulaSelect) {
 
     String tableAlias = tableAliasStack.peek();
-    String converted = StringHelper.replaceString(sqlFormulaSelect, tableAliasPlaceHolder,
-      tableAlias);
-
+    String converted = StringHelper.replaceString(sqlFormulaSelect, tableAliasPlaceHolder, tableAlias);
     sb.append(COMMA);
     sb.append(converted);
 

src/main/java/io/ebeaninternal/server/query/SqlBeanLoad.java

@@ -44,6 +44,13 @@ public class SqlBeanLoad {
     return lazyLoading;
   }
 
+  /**
+   * Return the DB read context.
+   */
+  public DbReadContext ctx() {
+    return ctx;
+  }
+
   /**
    * Increment the resultSet index 1.
    */
@@ -86,4 +93,14 @@ public class SqlBeanLoad {
     }
   }
 
+  /**
+   * Load the given value into the property.
+   */
+  public void load(BeanProperty target, Object dbVal) {
+    if (!refreshLoading) {
+      target.setValue(bean, dbVal);
+    } else {
+      target.setValueIntercept(bean, dbVal);
+    }
+  }
 }

src/main/java/io/ebeaninternal/server/query/SqlTreeBuilder.java

@@ -418,7 +418,7 @@ public final class SqlTreeBuilder {
 
       // make sure we only included the base/embedded bean once
       if (!selectProps.containsProperty(baseName)) {
-        BeanProperty p = desc.findBeanProperty(baseName);
+        SqlTreeProperty p = desc.findSqlTreeProperty(baseName);
         if (p == null) {
           logger.error("property [" + propName + "] not found on " + desc + " for query - excluding it.");
 
@@ -436,7 +436,7 @@ public final class SqlTreeBuilder {
     } else {
       // find the property including searching the
       // sub class hierarchy if required
-      BeanProperty p = desc.findBeanProperty(propName);
+      SqlTreeProperty p = desc.findSqlTreeProperty(propName);
       if (p == null) {
         logger.error("property [" + propName + "] not found on " + desc + " for query - excluding it.");
         p = desc.findBeanProperty("id");

src/main/java/io/ebeaninternal/server/query/SqlTreeNodeBean.java

@@ -48,7 +48,7 @@ class SqlTreeNodeBean implements SqlTreeNode {
    */
   private final boolean partialObject;
 
-  protected final BeanProperty[] properties;
+  protected final SqlTreeProperty[] properties;
 
   /**
    * Extra where clause added by Where annotation on associated many.
@@ -87,6 +87,7 @@ class SqlTreeNodeBean implements SqlTreeNode {
   private boolean intersectionAsOfTableAlias;
 
   private final boolean aggregation;
+  private final boolean aggregationRoot;
 
   /**
    * Construct for leaf node.
@@ -124,13 +125,15 @@ class SqlTreeNodeBean implements SqlTreeNode {
     this.nodeBeanProp = beanProp;
     this.extraWhere = (beanProp == null) ? null : beanProp.getExtraWhere();
 
+    this.aggregation = props.isAggregation();
+    this.aggregationRoot = props.isAggregationRoot();
+
     // the bean has an Id property and we want to use it
-    this.readId = withId && (desc.getIdProperty() != null);
+    this.readId = !aggregationRoot && withId && (desc.getIdProperty() != null);
     this.disableLazyLoad = disableLazyLoad || !readId || desc.isRawSqlBased() || temporalVersions;
 
     this.partialObject = props.isPartialObject();
     this.properties = props.getProps();
-    this.aggregation = props.isAggregation();
     this.children = myChildren == null ? NO_CHILDREN : myChildren.toArray(new SqlTreeNode[myChildren.size()]);
 
     pathMap = createPathMap(prefix, desc);
@@ -186,7 +189,7 @@ class SqlTreeNodeBean implements SqlTreeNode {
       }
       idBinder.buildRawSqlSelectChain(prefix, selectChain);
     }
-    for (BeanProperty property : properties) {
+    for (SqlTreeProperty property : properties) {
       property.buildRawSqlSelectChain(prefix, selectChain);
     }
     // recursively continue reading...
@@ -289,14 +292,14 @@ class SqlTreeNodeBean implements SqlTreeNode {
 
     if (inheritInfo == null) {
       // normal behavior with no inheritance
-      for (BeanProperty property : properties) {
+      for (SqlTreeProperty property : properties) {
         property.load(sqlBeanLoad);
       }
 
     } else {
       // take account of inheritance and due to subclassing approach
       // need to get a 'local' version of the property
-      for (BeanProperty property : properties) {
+      for (SqlTreeProperty property : properties) {
         // get a local version of the BeanProperty
         BeanProperty p = localDesc.getBeanProperty(property.getName());
         if (p != null) {
@@ -416,7 +419,7 @@ class SqlTreeNodeBean implements SqlTreeNode {
     if (readId) {
       appendSelectId(ctx, idBinder.getBeanProperty());
     }
-    for (BeanProperty property : properties) {
+    for (SqlTreeProperty property : properties) {
       if (!property.isAggregation()) {
         property.appendSelect(ctx, subQuery);
       }
@@ -483,9 +486,9 @@ class SqlTreeNodeBean implements SqlTreeNode {
   /**
    * Append the properties to the buffer.
    */
-  private void appendSelect(DbSqlContext ctx, boolean subQuery, BeanProperty[] props) {
+  private void appendSelect(DbSqlContext ctx, boolean subQuery, SqlTreeProperty[] props) {
 
-    for (BeanProperty prop : props) {
+    for (SqlTreeProperty prop : props) {
       prop.appendSelect(ctx, subQuery);
     }
   }
@@ -543,7 +546,7 @@ class SqlTreeNodeBean implements SqlTreeNode {
     // join and return SqlJoinType to use for child joins
     joinType = appendFromBaseTable(ctx, joinType);
 
-    for (BeanProperty property : properties) {
+    for (SqlTreeProperty property : properties) {
       // usually nothing... except for 1-1 Exported
       property.appendFrom(ctx, joinType);
     }

src/main/java/io/ebeaninternal/server/query/SqlTreeProperties.java

@@ -1,7 +1,6 @@
 package io.ebeaninternal.server.query;
 
 import io.ebeaninternal.api.ManyWhereJoins;
-import io.ebeaninternal.server.deploy.BeanProperty;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -21,7 +20,7 @@ public class SqlTreeProperties {
   /**
    * The bean properties in order.
    */
-  private final List<BeanProperty> propsList = new ArrayList<>();
+  private final List<SqlTreeProperty> propsList = new ArrayList<>();
 
   /**
    * Maintain a list of property names to detect embedded bean additions.
@@ -32,6 +31,8 @@ public class SqlTreeProperties {
 
   private boolean aggregation;
 
+  private String aggregationPath;
+
   SqlTreeProperties() {
   }
 
@@ -39,17 +40,17 @@ public class SqlTreeProperties {
     return propNames.contains(propName);
   }
 
-  public void add(BeanProperty[] props) {
+  public void add(SqlTreeProperty[] props) {
     propsList.addAll(Arrays.asList(props));
   }
 
-  public void add(BeanProperty prop) {
+  public void add(SqlTreeProperty prop) {
     propsList.add(prop);
     propNames.add(prop.getName());
   }
 
-  public BeanProperty[] getProps() {
-    return propsList.toArray(new BeanProperty[propsList.size()]);
+  public SqlTreeProperty[] getProps() {
+    return propsList.toArray(new SqlTreeProperty[propsList.size()]);
   }
 
   boolean isPartialObject() {
@@ -77,7 +78,6 @@ public class SqlTreeProperties {
   boolean requireSqlDistinct(ManyWhereJoins manyWhereJoins) {
     String joinProperty = aggregationJoin();
     if (joinProperty != null) {
-      aggregation = true;
       manyWhereJoins.addAggregationJoin(joinProperty);
       return false;
     } else {
@@ -97,12 +97,21 @@ public class SqlTreeProperties {
    */
   private String aggregationJoin() {
     if (!allProperties) {
-      for (BeanProperty beanProperty : propsList) {
+      for (SqlTreeProperty beanProperty : propsList) {
         if (beanProperty.isAggregation()) {
-          return beanProperty.getElPrefix();
+          aggregation = true;
+          aggregationPath = beanProperty.getElPrefix();
+          return aggregationPath;
         }
       }
     }
     return null;
   }
+
+  /**
+   * Return true if a top level aggregation which means the Id property must be excluded.
+   */
+  public boolean isAggregationRoot() {
+    return aggregation && (aggregationPath == null);
+  }
 }

src/main/java/io/ebeaninternal/server/query/SqlTreeProperty.java

@@ -0,0 +1,76 @@
+package io.ebeaninternal.server.query;
+
+import io.ebeaninternal.server.deploy.DbReadContext;
+import io.ebeaninternal.server.deploy.DbSqlContext;
+import io.ebeaninternal.server.type.ScalarType;
+
+import java.util.List;
+
+/**
+ * A property in the SQL Tree.
+ *
+ * A BeanProperty or a dynamically created property based on formula.
+ */
+public interface SqlTreeProperty {
+
+  /**
+   * Return the property name.
+   */
+  String getName();
+
+  /**
+   * Return the full property name (for error messages).
+   */
+  String getFullBeanName();
+
+  /**
+   * Return true if the property is the Id.
+   */
+  boolean isId();
+
+  /**
+   * Return true if the property is an embedded type.
+   */
+  boolean isEmbedded();
+
+  /**
+   * Return true if the property is an aggregation.
+   */
+  boolean isAggregation();
+
+  /**
+   * Return the Expression language prefix (join path).
+   */
+  String getElPrefix();
+
+  /**
+   * Return the underlying scalar type for the property (for findSingleAttribute).
+   */
+  ScalarType<?> getScalarType();
+
+  /**
+   * For RawSql build the select chain.
+   */
+  void buildRawSqlSelectChain(String prefix, List<String> selectChain);
+
+  /**
+   * Load into the bean (from the DataReader/ResultSet).
+   */
+  void load(SqlBeanLoad sqlBeanLoad);
+
+  /**
+   * Ignore the property (moving the column index position without reading).
+   */
+  void loadIgnore(DbReadContext ctx);
+
+  /**
+   * Append to the select clause.
+   */
+  void appendSelect(DbSqlContext ctx, boolean subQuery);
+
+  /**
+   * Append to the from clause.
+   */
+  void appendFrom(DbSqlContext ctx, SqlJoinType joinType);
+
+}