Regression: Correctly handle missing relations in get_column_values (d…

…bt-labs#448)

* Create integration test for a dropped relation

* Update get_column_values.sql

* Swap out adapter call for a good old fashioned drop table

integration_tests/data/sql/data_get_column_values_dropped.csv

@@ -0,0 +1,12 @@
+field
+a
+b
+c
+d
+e
+f
+g
+g
+g
+g
+g

integration_tests/dbt_project.yml

@@ -54,6 +54,12 @@ seeds:
     sql:
       data_events_20180103:
         +schema: events
+
+      data_get_column_values_dropped:
+        # TODO: Ideally this would use the adapter, but it gives a "Tried to drop relation, but its type is null" error.
+        #+post-hook: "{% do adapter.drop_relation(this) %}"
+        +post-hook: "drop table {{ this }}"
+
 
     schema_tests:
       data_test_sequential_timestamps:

integration_tests/tests/sql/test_get_column_values_use_default.sql

@@ -0,0 +1,25 @@
+
+{% set column_values = dbt_utils.get_column_values(ref('data_get_column_values_dropped'), 'field', default=['y', 'z'], order_by="field") %}
+
+with expected as (
+    select { dbt_utils.safe_cast('y', dbt_utils.type_string()) }} as expected union all
+    select { dbt_utils.safe_cast('z', dbt_utils.type_string()) }} as expected 
+),
+
+actual as (
+    select 
+        {% for val in column_values %}
+            {{ dbt_utils.safe_cast(val, dbt_utils.type_string()) }} as 'actual'
+            {% if not loop.last %}
+                union all
+            {% endif %}
+        {% endfor %}
+),
+
+failures as (
+    select * from actual
+    except 
+    select * from expected
+)
+
+select * from failures

macros/sql/get_column_values.sql

@@ -13,15 +13,18 @@
     {# TODO: Change the method signature in a future 0.x.0 release #}
     {%- set target_relation = table -%}
 
+    {# adapter.load_relation is a convenience wrapper to avoid building a Relation when we already have one #}
+    {% set relation_exists = (load_relation(target_relation)) is not none %}
+
     {%- call statement('get_column_values', fetch_result=true) %}
 
-        {%- if not target_relation and default is none -%}
+        {%- if not relation_exists and default is none -%}
 
-          {{ exceptions.raise_compiler_error("In get_column_values(): relation " ~ table ~ " does not exist and no default value was provided.") }}
+          {{ exceptions.raise_compiler_error("In get_column_values(): relation " ~ target_relation ~ " does not exist and no default value was provided.") }}
 
-        {%- elif not target_relation and default is not none -%}
+        {%- elif not relation_exists and default is not none -%}
 
-          {{ log("Relation " ~ table ~ " does not exist. Returning the default value: " ~ default) }}
+          {{ log("Relation " ~ target_relation ~ " does not exist. Returning the default value: " ~ default) }}
 
           {{ return(default) }}