ADAP-473: Table materialization not properly dropping existing relati…

…on on refresh (#724) (#727)

* update `drop_relation()` to drop `target_relation` instead of `old_relation`; these should be the same anyway, but `old_relation` doesn't always get populated

* add in old relation type in cases where the relation type changes

(cherry picked from commit 44b10f9)

Co-authored-by: Mike Alfare <[email protected]>

.changes/unreleased/Fixes-20230420-214433.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: Fixed issue where table materialization was not always properly refreshing for non-admin users on Databricks
+time: 2023-04-20T21:44:33.343598-04:00
+custom:
+  Author: mikealfare
+  Issue: "725"

dbt/include/spark/macros/materializations/table.sql

@@ -14,16 +14,22 @@
   -- setup: if the target relation already exists, drop it
   -- in case if the existing and future table is delta or iceberg, we want to do a
   -- create or replace table instead of dropping, so we don't have the table unavailable
-  {% if old_relation and not (old_relation.is_delta and config.get('file_format', validator=validation.any[basestring]) == 'delta') -%}
-    {{ adapter.drop_relation(old_relation) }}
-  {%- endif %}
-
-  {% if old_relation and not (old_relation.is_iceberg and config.get('file_format', validator=validation.any[basestring]) == 'iceberg') -%}
-    {{ adapter.drop_relation(old_relation) }}
-  {%- endif %}
+  {% if old_relation is not none %}
+    {% set is_delta = (old_relation.is_delta and config.get('file_format', validator=validation.any[basestring]) == 'delta') %}
+    {% set is_iceberg = (old_relation.is_iceberg and config.get('file_format', validator=validation.any[basestring]) == 'iceberg') %}
+    {% set old_relation_type = old_relation.type %}
+  {% else %}
+    {% set is_delta = false %}
+    {% set is_iceberg = false %}
+    {% set old_relation_type = target_relation.type %}
+  {% endif %}
+
+  {% if not is_delta and not is_iceberg %}
+    {% set existing_relation = target_relation %}
+    {{ adapter.drop_relation(existing_relation.incorporate(type=old_relation_type)) }}
+  {% endif %}
 
   -- build model
-
   {%- call statement('main', language=language) -%}
     {{ create_table_as(False, target_relation, compiled_code, language) }}
   {%- endcall -%}