multiple ephemeral refs should share a cte (#316)

* multiple ephemeral refs should share a cte
* update changelog

CHANGELOG.md

@@ -7,6 +7,7 @@
 ### Changes
 
 - Graph refactor: fix common issues with load order ([#292](https://github.com/fishtown-analytics/dbt/pull/292))
+- Graph refactor: multiple references to an ephemeral models should share a CTE ([#316](https://github.com/fishtown-analytics/dbt/pull/316))
 - Refactor: factor out jinja interactions ([#309](https://github.com/fishtown-analytics/dbt/pull/309))
 - Speedup: detect cycles at the end of compilation ([#307](https://github.com/fishtown-analytics/dbt/pull/307))
 - Speedup: write graph file with gpickle instead of yaml ([#306](https://github.com/fishtown-analytics/dbt/pull/306))

dbt/compilation.py

@@ -206,10 +206,12 @@ def do_ref(*args):
 
             target_model_id = target_model.get('unique_id')
 
-            model['depends_on'].append(target_model_id)
+            if target_model_id not in model['depends_on']:
+                model['depends_on'].append(target_model_id)
 
             if get_materialization(target_model) == 'ephemeral':
-                model['extra_cte_ids'].append(target_model_id)
+                if target_model_id not in model['extra_cte_ids']:
+                    model['extra_cte_ids'].append(target_model_id)
                 return '__dbt__CTE__{}'.format(target_model.get('name'))
             else:
                 return '"{}"."{}"'.format(schema, target_model.get('name'))

test/integration/020_ephemeral_test/models/dependent.sql

@@ -1 +1,5 @@
-select * from {{ref('base')}}
+
+-- multiple ephemeral refs should share a cte
+select * from {{ref('base')}} where gender = 'Male'
+union all
+select * from {{ref('base')}} where gender = 'Female'