Added pagination features

src/resources.py

@@ -151,10 +151,64 @@ class SampleResource(Resource):
         Get all stored items
         :return:
         """
-        with opentracing.tracer.start_active_span('sqlalchemy.select'):
-            samples = SampleMetadata.query.all()
+        with opentracing.tracer.start_active_span('compileQuery'):
+            query = SampleMetadata.query
 
-        return self.samplemetadataschema.dump(list(samples)), 200
+            ## Compile filters ##
+
+            filters = []
+            try:
+                first = int(request.args.get('first'))
+                filters.append(
+                    SampleMetadata.id >= first
+                )
+            except ValueError:
+                first = None
+
+            try:
+                after = datetime.fromisoformat(request.args.get('after'))
+                filters.append(
+                    SampleMetadata.timestamp > after
+                )
+            except ValueError:
+                after = None
+
+            try:
+                before = datetime.fromisoformat(request.args.get('after'))
+                filters.append(
+                    SampleMetadata.timestamp < before
+                )
+            except ValueError:
+                before = None
+
+            if filters:
+                query = query.filter(db.and_(*filters))
+
+            try:
+                limit = int(request.args.get('limit'))
+                query = query.limit(limit)
+            except ValueError:
+                limit = None
+
+        ## Run query ##
+        count = "count" in request.args.get
+        tags = {
+            "first": first,
+            "limit": limit,
+            "after": after,
+            "before": before
+        }
+
+        if count:
+            with opentracing.tracer.start_active_span('sqlalchemy.count', tags=tags):
+                rows = query.count()
+
+            return {"count": rows}, 200
+        else:
+            with opentracing.tracer.start_active_span('sqlalchemy.select', tags=tags):
+                samples = query.all()
+
+            return self.samplemetadataschema.dump(list(samples)), 200
 
 
 class SampleParameterResource(Resource):