Add "fields" filter support on single objects

Change-Id: Iba0401445921f9ea7932628c05590472307ba83a
Closes-Bug: #1718214
Signed-off-by: Xavier Hardy <xavier.hardy@corp.ovh.com>
Co-Authored-By: Oleg Ovcharuk <vgvoleg@gmail.com>
Signed-off-by: Oleg Ovcharuk <vgvoleg@gmail.com>

mistral/api/controllers/resource.py

@@ -51,8 +51,13 @@ class Resource(wtypes.Base):
         return cls.from_tuples(d.items())
 
     @classmethod
-    def from_db_model(cls, db_model):
+    def from_db_model(cls, db_model, fields=()):
-        return cls.from_tuples(db_model.iter_columns())
+        if isinstance(db_model, tuple):
+            db_tuples = zip(fields, db_model)
+        else:
+            db_tuples = db_model.iter_columns(fields=fields)
+
+        return cls.from_tuples(db_tuples)
 
     def __str__(self):
         """WSME based implementation of __str__."""

mistral/api/controllers/v2/action.py

@@ -79,6 +79,9 @@ class ActionsController(rest.RestController, hooks.HookController):
 
         :param identifier: ID or name of the Action to get.
         :param namespace: The namespace of the action.
+        :param fields: Optional. A specified list of fields of the resource to
+                       be returned. 'id' will be included automatically in
+                       fields if it's not provided.
         """
 
         acl.enforce('actions:get', context.ctx())
@@ -251,7 +254,7 @@ class ActionsController(rest.RestController, hooks.HookController):
                           Default: asc.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param name: Optional. Keep only resources with a specific name.
         :param scope: Optional. Keep only resources with a specific scope.

mistral/api/controllers/v2/action_execution.py

@@ -52,25 +52,40 @@ def _load_deferred_output_field(action_ex):
 
 # Use retries to prevent possible failures.
 @rest_utils.rest_retry_on_db_error
-def _get_action_execution(id):
+def _get_action_execution(id, fields=()):
+    if fields and 'id' not in fields:
+        fields.insert(0, 'id')
+
     with db_api.transaction():
-        return _get_action_execution_resource(db_api.get_action_execution(id))
+        return _get_action_execution_resource(
+            db_api.get_action_execution(id),
+            fields=fields
+        )
 
 
-def _get_action_execution_resource(action_ex):
+def _get_action_execution_resource(action_ex, fields=()):
     _load_deferred_output_field(action_ex)
 
-    return _get_action_execution_resource_for_list(action_ex)
+    if fields and 'id' not in fields:
+        fields.insert(0, 'id')
+
+    return _get_action_execution_resource_for_list(action_ex, fields=fields)
 
 
-def _get_action_execution_resource_for_list(action_ex):
+def _get_action_execution_resource_for_list(action_ex, fields=()):
     # TODO(nmakhotkin): Get rid of using dicts for constructing resources.
     # TODO(nmakhotkin): Use db_model for this instead.
-    res = resources.ActionExecution.from_db_model(action_ex)
 
-    task_name = (action_ex.task_execution.name
+    # field_task_name_needed = 'task_name' in fields
-                 if action_ex.task_execution else None)
+    # if field_task_name_needed:
-    setattr(res, 'task_name', task_name)
+    #     fields.remove('task_name')
+
+    res = resources.ActionExecution.from_db_model(action_ex, fields=fields)
+
+    # if not fields or field_task_name_needed:
+    #     task_name = (action_ex.task_execution.name
+    #                  if action_ex.task_execution else None)
+    #     setattr(res, 'task_name', task_name)
 
     return res
 
@@ -95,7 +110,7 @@ def _get_action_executions(task_execution_id=None, marker=None, limit=None,
                       or less than that of sort_keys.
     :param fields: Optional. A specified list of fields of the resource to
                    be returned. 'id' will be included automatically in
-                   fields if it's provided, since it will be used when
+                   fields if it's not provided, since it will be used when
                    constructing 'next' link.
     :param filters: Optional. A list of filters to apply to the result.
     """
@@ -124,17 +139,21 @@ def _get_action_executions(task_execution_id=None, marker=None, limit=None,
 
 class ActionExecutionsController(rest.RestController):
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.ActionExecution, wtypes.text)
+    @wsme_pecan.wsexpose(resources.ActionExecution, wtypes.text,
-    def get(self, id):
+                         types.uniquelist)
+    def get(self, id, fields=None):
         """Return the specified action_execution.
 
         :param id: UUID of action execution to retrieve
+        :param fields: Optional. A specified list of fields of the resource to
+                       be returned. 'id' will be included automatically in
+                       fields if it's not provided.
         """
         acl.enforce('action_executions:get', context.ctx())
 
         LOG.debug("Fetch action_execution [id=%s]", id)
 
-        return _get_action_execution(id)
+        return _get_action_execution(id, fields=fields)
 
     @rest_utils.wrap_wsme_controller_exception
     @wsme_pecan.wsexpose(resources.ActionExecution,
@@ -248,7 +267,7 @@ class ActionExecutionsController(rest.RestController):
                           or less than that of sort_keys.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param name: Optional. Keep only resources with a specific name.
         :param workflow_name: Optional. Keep only resources with a specific
@@ -379,7 +398,7 @@ class TasksActionExecutionController(rest.RestController):
                           or less than that of sort_keys.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param name: Optional. Keep only resources with a specific name.
         :param workflow_name: Optional. Keep only resources with a specific
@@ -444,15 +463,19 @@ class TasksActionExecutionController(rest.RestController):
         )
 
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.ActionExecution, wtypes.text, wtypes.text)
+    @wsme_pecan.wsexpose(resources.ActionExecution, wtypes.text, wtypes.text,
-    def get(self, task_execution_id, action_ex_id):
+                         types.uniquelist)
+    def get(self, task_execution_id, action_ex_id, fields=()):
         """Return the specified action_execution.
 
         :param task_execution_id: Task execution UUID
         :param action_ex_id: Action execution UUID
+        :param fields: Optional. A specified list of fields of the resource to
+                       be returned. 'id' will be included automatically in
+                       fields if it's not provided.
         """
         acl.enforce('action_executions:get', context.ctx())
 
         LOG.debug("Fetch action_execution [id=%s]", action_ex_id)
 
-        return _get_action_execution(action_ex_id)
+        return _get_action_execution(action_ex_id, fields=fields)

mistral/api/controllers/v2/code_source.py

@@ -187,8 +187,9 @@ class CodeSourcesController(rest.RestController, hooks.HookController):
         )
 
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.CodeSource, wtypes.text, wtypes.text)
+    @wsme_pecan.wsexpose(resources.CodeSource, wtypes.text,
-    def get(self, identifier, namespace=''):
+                         wtypes.text, types.uniquelist)
+    def get(self, identifier, namespace='', fields=''):
         """Return a code source.
 
         :param identifier: Name or UUID of the code source to retrieve.
@@ -202,13 +203,17 @@ class CodeSourcesController(rest.RestController, hooks.HookController):
             identifier,
             namespace
         )
+        if fields and 'id' not in fields:
+            fields.insert(0, 'id')
 
         db_model = rest_utils.rest_retry_on_db_error(
             db_api.get_code_source)(
             identifier=identifier,
-            namespace=namespace
+            namespace=namespace,
+            fields=fields
         )
-
+        if fields:
+            return resources.CodeSource.from_tuples(zip(fields, db_model))
         return resources.CodeSource.from_db_model(db_model)
 
     @rest_utils.wrap_pecan_controller_exception

mistral/api/controllers/v2/cron_trigger.py

@@ -31,22 +31,30 @@ LOG = logging.getLogger(__name__)
 
 class CronTriggersController(rest.RestController):
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.CronTrigger, wtypes.text)
+    @wsme_pecan.wsexpose(resources.CronTrigger,
-    def get(self, identifier):
+                         wtypes.text, types.uniquelist)
+    def get(self, identifier, fields=''):
         """Returns the named cron_trigger.
 
         :param identifier: Id or name of cron trigger to retrieve
+        :param fields: Optional. A specified list of fields of the resource to
+                       be returned. 'id' will be included automatically in
+                       fields if it's not provided.
         """
         acl.enforce('cron_triggers:get', context.ctx())
 
         LOG.debug('Fetch cron trigger [identifier=%s]', identifier)
 
+        if fields and 'id' not in fields:
+            fields.insert(0, 'id')
+
         # Use retries to prevent possible failures.
         db_model = rest_utils.rest_retry_on_db_error(
             db_api.get_cron_trigger
-        )(identifier)
+        )(identifier, fields=fields)
-
+        if fields:
-        return resources.CronTrigger.from_db_model(db_model)
+            return resources.CronTrigger.from_tuples(zip(fields, db_model))
+        return resources.CronTrigger.from_db_model(db_model, fields=fields)
 
     @rest_utils.wrap_wsme_controller_exception
     @wsme_pecan.wsexpose(
@@ -124,7 +132,7 @@ class CronTriggersController(rest.RestController):
                           or less than that of sort_keys.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param name: Optional. Keep only resources with a specific name.
         :param workflow_name: Optional. Keep only resources with a specific

mistral/api/controllers/v2/dynamic_action.py

@@ -208,8 +208,9 @@ class DynamicActionsController(rest.RestController, hooks.HookController):
         )
 
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.DynamicAction, wtypes.text, wtypes.text)
+    @wsme_pecan.wsexpose(resources.DynamicAction, wtypes.text,
-    def get(self, identifier, namespace=''):
+                         wtypes.text, types.uniquelist)
+    def get(self, identifier, namespace='', fields=''):
         """Return the named action.
 
         :param identifier: Name or UUID of the action to retrieve.
@@ -222,14 +223,19 @@ class DynamicActionsController(rest.RestController, hooks.HookController):
             identifier,
             namespace
         )
+        if fields and 'id' not in fields:
+            fields.insert(0, 'id')
 
         db_model = rest_utils.rest_retry_on_db_error(
             db_api.get_dynamic_action_definition
         )(
             identifier=identifier,
-            namespace=namespace
+            namespace=namespace,
+            fields=fields
         )
 
+        if fields:
+            return resources.DynamicAction.from_tuples(zip(fields, db_model))
         return resources.DynamicAction.from_db_model(db_model)
 
     @rest_utils.wrap_pecan_controller_exception

mistral/api/controllers/v2/environment.py

@@ -59,7 +59,7 @@ class EnvironmentController(rest.RestController):
                           or less than that of sort_keys.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param name: Optional. Keep only resources with a specific name.
         :param description: Optional. Keep only resources with a specific
@@ -101,21 +101,28 @@ class EnvironmentController(rest.RestController):
         )
 
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.Environment, wtypes.text)
+    @wsme_pecan.wsexpose(resources.Environment, wtypes.text, types.uniquelist)
-    def get(self, name):
+    def get(self, name, fields=''):
         """Return the named environment.
 
         :param name: Name of environment to retrieve
+        :param fields: Optional. A specified list of fields of the resource to
+                       be returned. 'id' will be included automatically in
+                       fields if it's not provided.
         """
         acl.enforce('environments:get', context.ctx())
 
         LOG.debug("Fetch environment [name=%s]", name)
 
+        if fields and 'id' not in fields:
+            fields.insert(0, 'id')
+
         # Use retries to prevent possible failures.
         r = rest_utils.create_db_retry_object()
-        db_model = r.call(db_api.get_environment, name)
+        db_model = r.call(db_api.get_environment, name, fields=fields)
-
+        if fields:
-        return resources.Environment.from_db_model(db_model)
+            return resources.Environment.from_tuples(zip(fields, db_model))
+        return resources.Environment.from_db_model(db_model, fields=fields)
 
     @rest_utils.wrap_wsme_controller_exception
     @wsme_pecan.wsexpose(

mistral/api/controllers/v2/event_trigger.py

@@ -34,18 +34,22 @@ CREATE_MANDATORY = set(['exchange', 'topic', 'event', 'workflow_id'])
 
 class EventTriggersController(rest.RestController):
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.EventTrigger, types.uuid)
+    @wsme_pecan.wsexpose(resources.EventTrigger, types.uuid, types.uniquelist)
-    def get(self, id):
+    def get(self, id, fields=''):
         """Returns the specified event_trigger."""
         acl.enforce('event_triggers:get', auth_ctx.ctx())
 
         LOG.debug('Fetch event trigger [id=%s]', id)
 
+        if fields and 'id' not in fields:
+            fields.insert(0, 'id')
+
         # Use retries to prevent possible failures.
         r = rest_utils.create_db_retry_object()
-        db_model = r.call(db_api.get_event_trigger, id)
+        db_model = r.call(db_api.get_event_trigger, id, fields=fields)
-
+        if fields:
-        return resources.EventTrigger.from_db_model(db_model)
+            return resources.EventTrigger.from_tuples(zip(fields, db_model))
+        return resources.EventTrigger.from_db_model(db_model, fields=fields)
 
     @rest_utils.wrap_wsme_controller_exception
     @wsme_pecan.wsexpose(resources.EventTrigger, body=resources.EventTrigger,

mistral/api/controllers/v2/execution.py

@@ -68,12 +68,20 @@ def _get_workflow_execution_resource(wf_ex):
 
 # Use retries to prevent possible failures.
 @rest_utils.rest_retry_on_db_error
-def _get_workflow_execution(id, must_exist=True):
+def _get_workflow_execution(id, must_exist=True, fields=None):
+    if fields and 'id' not in fields:
+        fields.insert(0, 'id')
+
+    fields_tuple = rest_utils.fields_list_to_cls_fields_tuple(
+        db_models.WorkflowExecution,
+        fields
+    )
+
     with db_api.transaction():
         if must_exist:
-            wf_ex = db_api.get_workflow_execution(id)
+            wf_ex = db_api.get_workflow_execution(id, fields=fields_tuple)
         else:
-            wf_ex = db_api.load_workflow_execution(id)
+            wf_ex = db_api.load_workflow_execution(id, fields=fields_tuple)
 
         return rest_utils.load_deferred_fields(
             wf_ex,
@@ -90,19 +98,25 @@ class ExecutionsController(rest.RestController):
     executions = sub_execution.SubExecutionsController()
 
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.Execution, wtypes.text)
+    @wsme_pecan.wsexpose(resources.Execution, wtypes.text, types.uniquelist)
-    def get(self, id):
+    def get(self, id, fields=None):
         """Return the specified Execution.
 
         :param id: UUID of execution to retrieve.
+        :param fields: Optional. A specified list of fields of the resource to
+                       be returned. 'id' will be included automatically in
+                       fields if it's not provided.
         """
         acl.enforce("executions:get", context.ctx())
 
         LOG.debug("Fetch execution [id=%s]", id)
 
-        wf_ex = _get_workflow_execution(id)
+        wf_ex = _get_workflow_execution(id, fields=fields)
 
-        resource = resources.Execution.from_db_model(wf_ex)
+        if fields:
+            return resources.Execution.from_tuples(zip(fields, wf_ex))
+
+        resource = resources.Execution.from_db_model(wf_ex, fields=fields)
 
         resource.published_global = (
             data_flow.get_workflow_execution_published_global(wf_ex)
@@ -363,7 +377,7 @@ class ExecutionsController(rest.RestController):
                           or less than that of sort_keys.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param workflow_name: Optional. Keep only resources with a specific
                               workflow name.

mistral/api/controllers/v2/resources.py

@@ -159,8 +159,8 @@ class Workflow(resource.Resource, ScopedResource):
         return obj
 
     @classmethod
-    def from_db_model(cls, db_model):
+    def from_db_model(cls, db_model, fields=()):
-        obj = super(Workflow, cls).from_db_model(db_model)
+        obj = super(Workflow, cls).from_db_model(db_model, fields=fields)
 
         obj.set_attributes_from_spec(db_model.get('spec'))
 

mistral/api/controllers/v2/task.py

@@ -49,19 +49,22 @@ STATE_TYPES = wtypes.Enum(
 )
 
 
-def _get_task_resource_with_result(task_ex):
+def _get_task_resource_with_result(task_ex, fields=()):
-    task = resources.Task.from_db_model(task_ex)
+    task = resources.Task.from_db_model(task_ex, fields=fields)
-
+    if 'result' in fields or not fields:
-    task.result = json.dumps(data_flow.get_task_execution_result(task_ex))
+        task.result = json.dumps(data_flow.get_task_execution_result(task_ex))
 
     return task
 
 
 # Use retries to prevent possible failures.
 @rest_utils.rest_retry_on_db_error
-def _get_task_execution(id):
+def _get_task_execution(id, fields=()):
+    if fields and 'id' not in fields:
+        fields.insert(0, 'id')
+
     with db_api.transaction():
-        task_ex = db_api.get_task_execution(id)
+        task_ex = db_api.get_task_execution(id, fields=fields)
 
         rest_utils.load_deferred_fields(task_ex, ['workflow_execution'])
         rest_utils.load_deferred_fields(
@@ -74,7 +77,7 @@ def _get_task_execution(id):
             ['params']
         )
 
-        return _get_task_resource_with_result(task_ex), task_ex
+        return _get_task_resource_with_result(task_ex, fields), task_ex
 
 
 def get_published_global(task_ex, wf_ex=None):
@@ -141,7 +144,7 @@ class TaskExecutionsController(rest.RestController):
                           or less than that of sort_keys.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param workflow_name: Optional. Keep only resources with a specific
                               workflow name.
@@ -204,18 +207,26 @@ class TasksController(rest.RestController):
     executions = sub_execution.SubExecutionsController()
 
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.Task, wtypes.text)
+    @wsme_pecan.wsexpose(resources.Task, wtypes.text, types.uniquelist)
-    def get(self, id):
+    def get(self, id, fields=''):
         """Return the specified task.
 
         :param id: UUID of task to retrieve
+        :param fields: Optional. A specified list of fields of the resource to
+                       be returned. 'id' will be included automatically in
+                       fields if it's not provided.
         """
         acl.enforce('tasks:get', context.ctx())
         LOG.debug("Fetch task [id=%s]", id)
 
-        task, task_ex = _get_task_execution(id)
+        task, task_ex = _get_task_execution(id, ())
-
+        task = _task_with_published_global(task, task_ex)
-        return _task_with_published_global(task, task_ex)
+        if fields:
+            if 'id' not in fields:
+                fields.insert(0, 'id')
+            task_dict = {field: task.to_dict()[field] for field in fields}
+            task = resources.Task.from_dict(task_dict)
+        return task
 
     @rest_utils.wrap_wsme_controller_exception
     @wsme_pecan.wsexpose(resources.Tasks, types.uuid, int, types.uniquelist,
@@ -249,7 +260,7 @@ class TasksController(rest.RestController):
                           or less than that of sort_keys.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param name: Optional. Keep only resources with a specific name.
         :param workflow_name: Optional. Keep only resources with a specific
@@ -412,7 +423,7 @@ class ExecutionTasksController(rest.RestController):
                           or less than that of sort_keys.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param name: Optional. Keep only resources with a specific name.
         :param workflow_name: Optional. Keep only resources with a specific

mistral/api/controllers/v2/workbook.py

@@ -44,27 +44,36 @@ class WorkbooksController(rest.RestController, hooks.HookController):
     )
 
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.Workbook, wtypes.text, wtypes.text)
+    @wsme_pecan.wsexpose(resources.Workbook, wtypes.text, wtypes.text,
-    def get(self, name, namespace=''):
+                         types.uniquelist)
+    def get(self, name, namespace='', fields=''):
         """Return the named workbook.
 
         :param name: Name of workbook to retrieve.
         :param namespace: Optional. Namespace of workbook to retrieve.
+        :param fields: Optional. A specified list of fields of the resource to
+                       be returned. 'id' will be included automatically in
+                       fields if it's not provided.
         """
         acl.enforce('workbooks:get', context.ctx())
 
         LOG.debug("Fetch workbook [name=%s, namespace=%s]", name, namespace)
 
+        if fields and 'id' not in fields:
+            fields.insert(0, 'id')
+
         # Use retries to prevent possible failures.
         r = rest_utils.create_db_retry_object()
 
         db_model = r.call(
             db_api.get_workbook,
             name,
-            namespace=namespace
+            namespace=namespace,
+            fields=fields
         )
-
+        if fields:
-        return resources.Workbook.from_db_model(db_model)
+            return resources.Workbook.from_tuples(zip(fields, db_model))
+        return resources.Workbook.from_db_model(db_model, fields=fields)
 
     @rest_utils.wrap_pecan_controller_exception
     @pecan.expose(content_type="text/plain")
@@ -171,7 +180,7 @@ class WorkbooksController(rest.RestController, hooks.HookController):
                           Default: asc.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param name: Optional. Keep only resources with a specific name.
         :param definition: Optional. Keep only resources with a specific

mistral/api/controllers/v2/workflow.py

@@ -77,26 +77,36 @@ class WorkflowsController(rest.RestController, hooks.HookController):
         )
 
     @rest_utils.wrap_wsme_controller_exception
-    @wsme_pecan.wsexpose(resources.Workflow, wtypes.text, wtypes.text)
+    @wsme_pecan.wsexpose(resources.Workflow, wtypes.text, wtypes.text,
-    def get(self, identifier, namespace=''):
+                         types.uniquelist)
+    def get(self, identifier, namespace='', fields=''):
         """Return the named workflow.
 
         :param identifier: Name or UUID of the workflow to retrieve.
         :param namespace: Optional. Namespace of the workflow to retrieve.
+        :param fields: Optional. A specified list of fields of the resource to
+                       be returned. 'id' will be included automatically in
+                       fields if it's not provided.
         """
         acl.enforce('workflows:get', context.ctx())
 
         LOG.debug("Fetch workflow [identifier=%s]", identifier)
 
+        if fields and 'id' not in fields:
+            fields.insert(0, 'id')
+
         # Use retries to prevent possible failures.
         r = rest_utils.create_db_retry_object()
         db_model = r.call(
             db_api.get_workflow_definition,
             identifier,
-            namespace=namespace
+            namespace=namespace,
+            fields=fields,
         )
 
-        return resources.Workflow.from_db_model(db_model)
+        if fields:
+            return resources.Workflow.from_tuples(zip(fields, db_model))
+        return resources.Workflow.from_db_model(db_model, fields=fields)
 
     @rest_utils.wrap_pecan_controller_exception
     @pecan.expose(content_type="text/plain")
@@ -240,7 +250,7 @@ class WorkflowsController(rest.RestController, hooks.HookController):
                           Default: asc.
         :param fields: Optional. A specified list of fields of the resource to
                        be returned. 'id' will be included automatically in
-                       fields if it's provided, since it will be used when
+                       fields if it's not provided, since it will be used when
                        constructing 'next' link.
         :param name: Optional. Keep only resources with a specific name.
         :param namespace: Optional. Keep only resources with a specific

mistral/db/sqlalchemy/model_base.py

@@ -87,15 +87,18 @@ class _MistralModelBase(oslo_models.ModelBase, oslo_models.TimestampMixin):
             if col.name not in unloaded and hasattr(self, col.name):
                 yield col.name
 
-    def iter_columns(self):
+    def iter_columns(self, fields=()):
         """Returns an iterator for loaded columns.
 
+        :param fields: names of fields to return
+        :type fields: tuple, list or set
         :return: A generator function that generates
             tuples (column name, column value).
         """
 
         for col_name in self.iter_column_names():
-            yield col_name, getattr(self, col_name)
+            if not fields or col_name in fields:
+                yield col_name, getattr(self, col_name)
 
     def get_clone(self):
         """Clones current object, loads all fields and returns the result."""

mistral/db/v2/api.py

@@ -524,17 +524,17 @@ def get_scheduled_jobs_count(**kwargs):
 
 # Cron triggers.
 
-def get_cron_trigger(identifier):
+def get_cron_trigger(identifier, fields=()):
-    return IMPL.get_cron_trigger(identifier)
+    return IMPL.get_cron_trigger(identifier, fields=fields)
 
 
-def get_cron_trigger_by_id(id):
+def get_cron_trigger_by_id(id, fields=()):
-    return IMPL.get_cron_trigger_by_id(id)
+    return IMPL.get_cron_trigger_by_id(id, fields=fields)
 
 
-def load_cron_trigger(identifier):
+def load_cron_trigger(identifier, fields=()):
     """Unlike get_cron_trigger this method is allowed to return None."""
-    return IMPL.load_cron_trigger(identifier)
+    return IMPL.load_cron_trigger(identifier, fields=fields)
 
 
 def get_cron_triggers(**kwargs):
@@ -593,13 +593,13 @@ def delete_cron_triggers(**kwargs):
 
 # Environments.
 
-def get_environment(name):
+def get_environment(name, fields=()):
-    return IMPL.get_environment(name)
+    return IMPL.get_environment(name, fields=fields)
 
 
-def load_environment(name):
+def load_environment(name, fields=()):
     """Unlike get_environment this method is allowed to return None."""
-    return IMPL.load_environment(name)
+    return IMPL.load_environment(name, fields=fields)
 
 
 def get_environments(limit=None, marker=None, sort_keys=None,
@@ -667,12 +667,12 @@ def delete_resource_members(**kwargs):
 
 # Event triggers.
 
-def get_event_trigger(id, insecure=False):
+def get_event_trigger(id, insecure=False, fields=()):
-    return IMPL.get_event_trigger(id, insecure)
+    return IMPL.get_event_trigger(id, insecure, fields=fields)
 
 
-def load_event_trigger(id, insecure=False):
+def load_event_trigger(id, insecure=False, fields=()):
-    return IMPL.load_event_trigger(id, insecure)
+    return IMPL.load_event_trigger(id, insecure, fields=fields)
 
 
 def get_event_triggers(insecure=False, limit=None, marker=None, sort_keys=None,

mistral/db/v2/sqlalchemy/api.py

@@ -307,6 +307,11 @@ def _get_db_object_by_name(model, name, columns=()):
 
 
 def _get_db_object_by_id(model, id, insecure=False, columns=()):
+    columns = (
+        tuple([getattr(model, f) for f in columns if hasattr(model, f)])
+        if columns and isinstance(columns, list) else columns
+    )
+
     query = (
         b.model_query(model, columns=columns)
         if insecure
@@ -319,6 +324,10 @@ def _get_db_object_by_id(model, id, insecure=False, columns=()):
 def _get_db_object_by_name_and_namespace_or_id(model, identifier,
                                                namespace=None, insecure=False,
                                                columns=()):
+    columns = (
+        tuple([getattr(model, f) for f in columns if hasattr(model, f)])
+        if columns and isinstance(columns, list) else columns
+    )
     query = (
         b.model_query(model, columns=columns)
         if insecure
@@ -1599,13 +1608,14 @@ def _get_completed_root_executions_query(columns):
 
 
 @b.session_aware()
-def get_cron_trigger(identifier, session=None):
+def get_cron_trigger(identifier, session=None, fields=()):
     ctx = context.ctx()
 
     cron_trigger = _get_db_object_by_name_and_namespace_or_id(
         models.CronTrigger,
         identifier,
-        insecure=ctx.is_admin
+        insecure=ctx.is_admin,
+        columns=fields,
     )
 
     if not cron_trigger:
@@ -1617,10 +1627,11 @@ def get_cron_trigger(identifier, session=None):
 
 
 @b.session_aware()
-def get_cron_trigger_by_id(id, session=None):
+def get_cron_trigger_by_id(id, session=None, fields=()):
     ctx = context.ctx()
     cron_trigger = _get_db_object_by_id(models.CronTrigger, id,
-                                        insecure=ctx.is_admin)
+                                        insecure=ctx.is_admin,
+                                        columns=fields)
     if not cron_trigger:
         raise exc.DBEntityNotFoundError(
             "Cron trigger not found [id=%s]" % id
@@ -1630,10 +1641,11 @@ def get_cron_trigger_by_id(id, session=None):
 
 
 @b.session_aware()
-def load_cron_trigger(identifier, session=None):
+def load_cron_trigger(identifier, session=None, fields=()):
     return _get_db_object_by_name_and_namespace_or_id(
         models.CronTrigger,
-        identifier
+        identifier,
+        columns=fields,
     )
 
 
@@ -1744,8 +1756,8 @@ def delete_cron_triggers(session=None, **kwargs):
 # Environments.
 
 @b.session_aware()
-def get_environment(name, session=None):
+def get_environment(name, session=None, fields=()):
-    env = _get_db_object_by_name(models.Environment, name)
+    env = _get_db_object_by_name(models.Environment, name, columns=fields)
 
     if not env:
         raise exc.DBEntityNotFoundError(
@@ -1756,8 +1768,8 @@ def get_environment(name, session=None):
 
 
 @b.session_aware()
-def load_environment(name, session=None):
+def load_environment(name, session=None, fields=()):
-    return _get_db_object_by_name(models.Environment, name)
+    return _get_db_object_by_name(models.Environment, name, columns=fields)
 
 
 @b.session_aware()
@@ -1982,8 +1994,9 @@ def _get_accepted_resources(res_type):
 # Event triggers.
 
 @b.session_aware()
-def get_event_trigger(id, insecure=False, session=None):
+def get_event_trigger(id, insecure=False, session=None, fields=()):
-    event_trigger = _get_db_object_by_id(models.EventTrigger, id, insecure)
+    event_trigger = _get_db_object_by_id(models.EventTrigger, id, insecure,
+                                         columns=fields)
 
     if not event_trigger:
         raise exc.DBEntityNotFoundError(
@@ -1994,8 +2007,9 @@ def get_event_trigger(id, insecure=False, session=None):
 
 
 @b.session_aware()
-def load_event_trigger(id, insecure=False, session=None):
+def load_event_trigger(id, insecure=False, session=None, fields=()):
-    return _get_db_object_by_id(models.EventTrigger, id, insecure)
+    return _get_db_object_by_id(models.EventTrigger, id, insecure,
+                                columns=fields)
 
 
 @b.session_aware()

mistral/tests/unit/api/v2/test_action_executions.py

@@ -226,9 +226,22 @@ class TestActionExecutionsController(base.APITest):
     @mock.patch.object(db_api, 'get_action_execution', MOCK_ACTION)
     def test_get(self):
         resp = self.app.get('/v2/action_executions/123')
+        action_exec = copy.deepcopy(ACTION_EX)
+        del action_exec['task_name']
+        self.assertEqual(200, resp.status_int)
+        self.assertDictEqual(action_exec, resp.json)
+
+    @mock.patch('mistral.db.v2.api.get_action_execution')
+    def test_get_with_fields_filter(self, mocked_get):
+        mocked_get.return_value = (ACTION_EX['id'], ACTION_EX['name'],)
+        resp = self.app.get('/v2/action_executions/123?fields=name')
+        expected = {
+            'id': ACTION_EX['id'],
+            'name': ACTION_EX['name'],
+        }
 
         self.assertEqual(200, resp.status_int)
-        self.assertDictEqual(ACTION_EX, resp.json)
+        self.assertDictEqual(expected, resp.json)
 
     @mock.patch.object(db_api, 'get_action_execution')
     def test_get_operational_error(self, mocked_get):
@@ -239,9 +252,10 @@ class TestActionExecutionsController(base.APITest):
         ]
 
         resp = self.app.get('/v2/action_executions/123')
-
+        action_exec = copy.deepcopy(ACTION_EX)
+        del action_exec['task_name']
         self.assertEqual(200, resp.status_int)
-        self.assertDictEqual(ACTION_EX, resp.json)
+        self.assertDictEqual(action_exec, resp.json)
 
     def test_basic_get(self):
         resp = self.app.get('/v2/action_executions/')
@@ -259,7 +273,7 @@ class TestActionExecutionsController(base.APITest):
         resp = self.app.get('/v2/action_executions/123')
 
         self.assertEqual(200, resp.status_int)
-        self.assertTrue('project_id' in resp.json)
+        self.assertIn('project_id', resp.json)
 
     @mock.patch.object(oslo_client.OsloRPCClient, 'sync_call',
                        mock.MagicMock(side_effect=oslo_exc.MessagingTimeout))
@@ -561,11 +575,12 @@ class TestActionExecutionsController(base.APITest):
     @mock.patch.object(db_api, 'get_action_executions', MOCK_ACTIONS)
     def test_get_all(self):
         resp = self.app.get('/v2/action_executions')
-
+        action_exec = copy.deepcopy(ACTION_EX)
+        del action_exec['task_name']
         self.assertEqual(200, resp.status_int)
 
         self.assertEqual(1, len(resp.json['action_executions']))
-        self.assertDictEqual(ACTION_EX, resp.json['action_executions'][0])
+        self.assertDictEqual(action_exec, resp.json['action_executions'][0])
 
     @mock.patch.object(db_api, 'get_action_executions')
     def test_get_all_operational_error(self, mocked_get_all):
@@ -576,11 +591,13 @@ class TestActionExecutionsController(base.APITest):
         ]
 
         resp = self.app.get('/v2/action_executions')
+        action_exec = copy.deepcopy(ACTION_EX)
+        del action_exec['task_name']
 
         self.assertEqual(200, resp.status_int)
 
         self.assertEqual(1, len(resp.json['action_executions']))
-        self.assertDictEqual(ACTION_EX, resp.json['action_executions'][0])
+        self.assertDictEqual(action_exec, resp.json['action_executions'][0])
 
     @mock.patch.object(rest_utils, 'get_all',
                        return_value=resources.ActionExecutions())

mistral/tests/unit/api/v2/test_cron_triggers.py

@@ -79,6 +79,18 @@ class TestCronTriggerController(base.APITest):
         self.assertEqual(200, resp.status_int)
         self.assertDictEqual(TRIGGER, resp.json)
 
+    @mock.patch('mistral.db.v2.api.get_cron_trigger')
+    def test_get_with_fields_filter(self, mocked_get):
+        mocked_get.return_value = (TRIGGER['id'], TRIGGER['name'],)
+        resp = self.app.get('/v2/cron_triggers/my_cron_trigger?fields=name')
+        expected = {
+            'id': TRIGGER['id'],
+            'name': TRIGGER['name'],
+        }
+
+        self.assertEqual(200, resp.status_int)
+        self.assertDictEqual(expected, resp.json)
+
     @mock.patch.object(db_api, 'get_cron_trigger')
     def test_get_operational_error(self, mocked_get):
         mocked_get.side_effect = [

mistral/tests/unit/api/v2/test_environment.py

@@ -188,6 +188,20 @@ class TestEnvironmentController(base.APITest):
         self.assertEqual(200, resp.status_int)
         self._assert_dict_equal(ENVIRONMENT, resp.json)
 
+    @mock.patch('mistral.db.v2.api.get_environment')
+    def test_get_with_fields_filter(self, mocked_get):
+        mocked_get.return_value = (
+            ENVIRONMENT['id'], ENVIRONMENT['name'],
+        )
+        resp = self.app.get('/v2/environments/123?fields=name')
+        expected = {
+            'id': ENVIRONMENT['id'],
+            'name': ENVIRONMENT['name'],
+        }
+
+        self.assertEqual(200, resp.status_int)
+        self.assertDictEqual(expected, resp.json)
+
     @mock.patch.object(db_api, 'get_environment')
     def test_get_operational_error(self, mocked_get):
         mocked_get.side_effect = [

mistral/tests/unit/api/v2/test_event_trigger.py

@@ -77,6 +77,21 @@ class TestEventTriggerController(base.APITest):
         self.assertEqual(200, resp.status_int)
         self.assertDictEqual(TRIGGER, resp.json)
 
+    @mock.patch('mistral.db.v2.api.get_event_trigger')
+    def test_get_with_fields_filter(self, mocked_get):
+        mocked_get.return_value = (TRIGGER['id'], TRIGGER['name'],)
+        resp = self.app.get(
+            '/v2/event_triggers/09cc56a9-d15e-4494-a6e2-c4ec8bdaacae'
+            '?fields=name'
+        )
+        expected = {
+            'id': TRIGGER['id'],
+            'name': TRIGGER['name'],
+        }
+
+        self.assertEqual(200, resp.status_int)
+        self.assertDictEqual(expected, resp.json)
+
     @mock.patch.object(db_api, 'get_event_trigger')
     def test_get_operational_error(self, mocked_get):
         mocked_get.side_effect = [

mistral/tests/unit/api/v2/test_executions.py

@@ -169,6 +169,20 @@ class TestExecutionsController(base.APITest):
 
         self.assertDictEqual(expected, resp.json)
 
+    @mock.patch('mistral.db.v2.api.get_workflow_execution')
+    def test_get_with_fields_filter(self, mocked_get):
+        mocked_get.return_value = (
+            WF_EX_JSON_WITH_DESC['id'], WF_EX_JSON_WITH_DESC['description'],
+        )
+        resp = self.app.get('/v2/executions/123?fields=description')
+        expected = {
+            'id': WF_EX_JSON_WITH_DESC['id'],
+            'description': WF_EX_JSON_WITH_DESC['description'],
+        }
+
+        self.assertEqual(200, resp.status_int)
+        self.assertDictEqual(expected, resp.json)
+
     @mock.patch.object(db_api, 'get_workflow_execution')
     def test_get_operational_error(self, mocked_get):
         mocked_get.side_effect = [
@@ -564,7 +578,8 @@ class TestExecutionsController(base.APITest):
         self.assertEqual(201, resp.status_int)
         self.assertDictEqual(expected_json, resp.json)
 
-        load_wf_ex_func.assert_called_once_with(expected_json['id'])
+        load_wf_ex_func.assert_called_once_with(expected_json['id'],
+                                                fields=())
 
         kwargs = json.loads(expected_json['params'])
         kwargs['description'] = expected_json['description']
@@ -600,7 +615,8 @@ class TestExecutionsController(base.APITest):
         self.assertEqual(201, resp.status_int)
         self.assertDictEqual(expected_json, resp.json)
 
-        load_wf_ex_func.assert_called_once_with(expected_json['id'])
+        load_wf_ex_func.assert_called_once_with(expected_json['id'],
+                                                fields=())
 
         # Note that "start_workflow" method on engine API should not be called
         # in this case because we passed execution ID to the endpoint and the

mistral/tests/unit/api/v2/test_tasks.py

@@ -171,6 +171,18 @@ class TestTasksController(base.APITest):
         self.assertEqual(200, resp.status_int)
         self.assertDictEqual(TASK, resp.json)
 
+    @mock.patch('mistral.db.v2.api.get_task_execution')
+    def test_get_with_fields_filter(self, mocked_get):
+        mocked_get.return_value = TASK_EX
+        resp = self.app.get('/v2/tasks/123?fields=name')
+        expected = {
+            'id': TASK['id'],
+            'name': TASK['name'],
+        }
+
+        self.assertEqual(200, resp.status_int)
+        self.assertDictEqual(expected, resp.json)
+
     @mock.patch.object(db_api, 'get_task_execution')
     def test_get_operational_error(self, mocked_get):
         mocked_get.side_effect = [

mistral/tests/unit/api/v2/test_workbooks.py

@@ -169,6 +169,18 @@ class TestWorkbooksController(base.APITest):
         self.assertEqual(200, resp.status_int)
         self.assertDictEqual(WORKBOOK, resp.json)
 
+    @mock.patch('mistral.db.v2.api.get_workbook')
+    def test_get_with_fields_filter(self, mocked_get):
+        mocked_get.return_value = (WORKBOOK['id'], WORKBOOK['name'],)
+        resp = self.app.get('/v2/workbooks/123?fields=name')
+        expected = {
+            'id': WORKBOOK['id'],
+            'name': WORKBOOK['name'],
+        }
+
+        self.assertEqual(200, resp.status_int)
+        self.assertDictEqual(expected, resp.json)
+
     @mock.patch.object(db_api, "get_workbook", MOCK_WB_WITH_NAMESPACE)
     def test_get_with_namespace(self):
         resp = self.app.get('/v2/workbooks/123?namespace=xyz')

mistral/tests/unit/api/v2/test_workflows.py

@@ -264,6 +264,18 @@ class TestWorkflowsController(base.APITest):
         self.assertEqual(200, resp.status_int)
         self.assertDictEqual(WF, resp_json)
 
+    @mock.patch('mistral.db.v2.api.get_workflow_definition')
+    def test_get_with_fields_filter(self, mocked_get):
+        mocked_get.return_value = (WF['id'], WF['name'],)
+        resp = self.app.get('/v2/workflows/123?fields=name')
+        expected = {
+            'id': WF['id'],
+            'name': WF['name'],
+        }
+
+        self.assertEqual(200, resp.status_int)
+        self.assertDictEqual(expected, resp.json)
+
     @mock.patch.object(db_api, 'get_workflow_definition')
     def test_get_operational_error(self, mocked_get):
         mocked_get.side_effect = [
@@ -886,4 +898,4 @@ class TestWorkflowsController(base.APITest):
         resp = self.app.get(
             '/v2/workflows/123e4567-e89b-12d3-a456-426655440000')
         self.assertEqual(200, resp.status_int)
-        self.assertTrue('project_id' in resp.json)
+        self.assertIn('project_id', resp.json)

mistral/utils/rest_utils.py

@@ -121,6 +121,14 @@ def validate_fields(fields, object_fields):
         )
 
 
+def fields_list_to_cls_fields_tuple(model, f):
+    if not f:
+        return ()
+    return tuple(
+        [getattr(model, str(field)) for field in f]
+    )
+
+
 def filters_to_dict(**kwargs):
     """Return only non-null values
 
@@ -157,7 +165,7 @@ def get_all(list_cls, cls, get_all_function, get_function,
                       Default: ['asc'].
     :param fields: Optional. A specified list of fields of the resource to
                    be returned. 'id' will be included automatically in
-                   fields if it's provided, since it will be used when
+                   fields if it's not provided, since it will be used when
                    constructing 'next' link.
     :param filters: Optional. A specified dictionary of filters to match.
     :param all_projects: Optional. Get resources of all projects.