Use subtypes in select queries

Select queries would originally only select the returned properties by their names and would check if a property is a subtype of a selected property. This has changed now and select queries will also return subtypes of selected properties.

CHANGELOG.md

@@ -23,6 +23,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+* Select queries would originally only select the returned properties by their
+  names and would not check if a property is a subtype of a selected property. This
+  has changed now and select queries will also return subtypes of selected
+  properties.
+
 ### Deprecated
 
 * `SERVER_SIDE_SCRIPTING_BIN_DIR` property is deprecated.

src/doc/CaosDB-Query-Language.md

@@ -351,6 +351,33 @@ Any result set can be filtered by logically combining POV filters or back refere
 *  REFERENCE:: This one is tricky: `REFERENCE TO` expresses a the state of _having_ a reference property. `REFERENCED BY` expresses the state of _being_ referenced by another entity.
 *  COUNT:: `COUNT` works like `FIND` but doesn't return the entities.
 
+
+## Select Queries
+
+In contrast to `FIND` queries, which always return the complete entity, there are `SELECT` queries which only return the entity with only those properties which are specified in the query. The syntax is very similar to `FIND` queries - just replace the `FIND` by `SELECT <comma separated list of selectors> FROM`:
+
+`SELECT p1, p2, p3 FROM Record ename`
+
+However, the `SELECT` query can also return properties of referenced entities and thereby are a means of joining entities together and return a custom view or projection:
+
+`SELECT Conductor.Last Name FROM Experiment`
+
+would return the conductor's last name, when `Conductor` is a reference property of `Experiment` and `Last Name` is a property of the `Conductor` records.
+
+### Selectors
+
+Selectors are strings of entity names which are separated by `.` (dot). E.g. `Conductor.Last Name` or `Conductor.Address` or even `Experiment.Conductor.Last name`. Selectors in a `SELECT` queries are separated by `,` (comma). E.g. `Conductor.First Name, Conductor.Last Name`.
+
+### Evaluation of Selectors
+
+The query will return all those properties which have the same name as
+specified by the selector (case-insensitive). However, `SELECT` queries are
+also capable of subtyping in the selectors:
+
+`SELECT Person FROM Experiment` would return all `Person` properties but all `Conductors` as well, if `Conductor` is a child of `Person`.
+
+Note: When a property `responsible` with data type `Person` exists, the above `SELECT` statement would not include records that use this property (since `responsible` is not a child of Person).
+
 ## Versioning
 
 Since Caosdb 0.2 entities are optionally version controlled. The query language will be extended to include versioning in the future. A current minimal implementation introduces the `ANY VERSION OF` modifier which can be used to return all matching versions in the results of `COUNT`, `FIND`, and `SELECT` queries.

src/main/java/org/caosdb/server/database/backend/transaction/IsSubType.java

@@ -29,19 +29,36 @@ import org.caosdb.server.database.exceptions.TransactionException;
 public class IsSubType extends BackendTransaction {
 
   private final Integer child;
-  private final Integer parent;
+  private Integer parent = null;
+  private String parentName = null;
 
   public IsSubType(final Integer child, final Integer parent) {
     this.child = child;
     this.parent = parent;
   }
 
-  private boolean isSubType;
+  public IsSubType(Integer child, String parent) {
+    this.parentName = parent;
+    this.child = child;
+  }
+
+  private Boolean isSubType = null;
 
   @Override
   public void execute() throws TransactionException {
     final IsSubTypeImpl t = getImplementation(IsSubTypeImpl.class);
-    this.isSubType = t.execute(this.child, this.parent);
+
+    if (this.parent == null) {
+      this.isSubType = false;
+      for (Integer parent : execute(new GetIDByName(parentName, false)).getList()) {
+        this.isSubType = t.execute(this.child, parent);
+        if (this.isSubType) {
+          return;
+        }
+      }
+    } else {
+      this.isSubType = t.execute(this.child, this.parent);
+    }
   }
 
   public boolean isSubType() {

src/main/java/org/caosdb/server/database/backend/transaction/RetrieveFullEntity.java

 /*
- * ** header v3.0
- * This file is a part of the CaosDB Project.
+ * ** header v3.0 This file is a part of the CaosDB Project.
  *
- * Copyright (C) 2018 Research Group Biomedical Physics,
- * Max-Planck-Institute for Dynamics and Self-Organization Göttingen
- * Copyright (C) 2020 Timm Fitschen <t.fitschen@indiscale.com>
- * Copyright (C) 2020 IndiScale GmbH <info@indiscale.com>
+ * Copyright (C) 2018 Research Group Biomedical Physics, Max-Planck-Institute for Dynamics and
+ * Self-Organization Göttingen Copyright (C) 2020 Timm Fitschen <t.fitschen@indiscale.com> Copyright
+ * (C) 2020 IndiScale GmbH <info@indiscale.com>
  *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License as
- * published by the Free Software Foundation, either version 3 of the
- * License, or (at your option) any later version.
+ * This program is free software: you can redistribute it and/or modify it under the terms of the
+ * GNU Affero General Public License as published by the Free Software Foundation, either version 3
+ * of the License, or (at your option) any later version.
  *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Affero General Public License for more details.
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
+ * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Affero General Public License for more details.
  *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ * You should have received a copy of the GNU Affero General Public License along with this program.
+ * If not, see <https://www.gnu.org/licenses/>.
  *
  * ** end header
  */
@@ -27,6 +23,7 @@ package org.caosdb.server.database.backend.transaction;
 import java.util.LinkedList;
 import java.util.List;
 import org.caosdb.server.database.BackendTransaction;
+import org.caosdb.server.database.exceptions.EntityDoesNotExistException;
 import org.caosdb.server.datatype.ReferenceDatatype;
 import org.caosdb.server.datatype.ReferenceValue;
 import org.caosdb.server.entity.EntityInterface;
@@ -124,10 +121,9 @@ public class RetrieveFullEntity extends BackendTransaction {
    */
   public void retrieveSubEntities(EntityInterface e, List<Selection> selections) {
     for (final Selection s : selections) {
+      String propertyName = s.getSelector();
       if (s.getSubselection() != null) {
 
-        String propertyName = s.getSelector();
-
         // Find matching (i.e. referencing) Properties
         for (Property p : e.getProperties()) {
           // get reference properties by name.
@@ -142,10 +138,47 @@ public class RetrieveFullEntity extends BackendTransaction {
 
               ReferenceValue value = (ReferenceValue) p.getValue();
               RetrieveEntity ref = new RetrieveEntity(value.getId());
-              // recursion!  (Only for the matching selections)
+              // recursion! (Only for the matching selections)
               retrieveFullEntity(ref, getSubSelects(selections, propertyName));
               value.setEntity(ref, true);
             }
+            continue;
+          }
+          try {
+            boolean isSubtype = execute(new IsSubType(p.getId(), propertyName)).isSubType();
+            if (isSubtype) {
+              if (p.getValue() != null) {
+                if (p.getDatatype() instanceof ReferenceDatatype) {
+                  try {
+                    p.parseValue();
+                  } catch (Message m) {
+                    p.addError(m);
+                  }
+
+                  ReferenceValue value = (ReferenceValue) p.getValue();
+                  RetrieveEntity ref = new RetrieveEntity(value.getId());
+                  // recursion! (Only for the matching selections)
+                  retrieveFullEntity(ref, getSubSelects(selections, propertyName));
+                  value.setEntity(ref, true);
+                  p.setName(propertyName);
+                }
+              }
+            }
+          } catch (EntityDoesNotExistException exc) {
+            // unknown parent name.
+          }
+        }
+      } else {
+        for (Property p : e.getProperties()) {
+          if (!propertyName.equalsIgnoreCase(p.getName())) {
+            try {
+              boolean isSubtype = execute(new IsSubType(p.getId(), propertyName)).isSubType();
+              if (isSubtype) {
+                p.setName(propertyName);
+              }
+            } catch (EntityDoesNotExistException exc) {
+              // unknown parent name.
+            }
           }
         }
       }

src/main/java/org/caosdb/server/jobs/Job.java

@@ -57,12 +57,10 @@ import org.caosdb.server.utils.Observer;
 import org.caosdb.server.utils.ServerMessages;
 import org.reflections.Reflections;
 
-
 /**
  * This is a Job.
  *
  * @todo Describe me.
- *
  */
 public abstract class Job extends AbstractObservable implements Observer {
   private Transaction<? extends TransactionContainer> transaction = null;