Add self reference for macro (#163)

Co-authored-by: Lasse Benninga <lassebenninga@gmail.com>

macros/plugins/spark/get_external_build_plan.sql

@@ -19,8 +19,8 @@
         {% set build_plan = build_plan + dbt_external_tables.refresh_external_table(source_node) %}
     {% endif %}
 
-    {% set recover_partitions = spark__recover_partitions(source_node) %}
-    {% if recover_partitions|length > 0 %}
+    {% set recover_partitions = dbt_external_tables.recover_partitions(source_node) %}
+    {% if recover_partitions %}
     {% set build_plan = build_plan + [
         recover_partitions
     ] %}

macros/plugins/spark/helpers/recover_partitions.sql

@@ -1,12 +1,27 @@
 {% macro spark__recover_partitions(source_node) %}
     {# https://docs.databricks.com/sql/language-manual/sql-ref-syntax-ddl-alter-table.html #}
 
-    {% set ddl %}
     {%- if source_node.external.partitions and source_node.external.using and source_node.external.using|lower != 'delta' -%}
-        ALTER TABLE {{ source(source_node.source_name, source_node.name) }} RECOVER PARTITIONS
+        {% set ddl %}
+            ALTER TABLE {{ source(source_node.source_name, source_node.name) }} RECOVER PARTITIONS
+        {% endset %}
+    {%- else -%}
+        {% set ddl = none %}
     {%- endif -%}
-    {% endset %}
 
     {{return(ddl)}}
 
 {% endmacro %}
+
+{% macro recover_partitions(source_node) %}
+    {{ return(adapter.dispatch('recover_partitions', 'dbt_external_tables')(source_node)) }}
+{% endmacro %}
+
+{% macro default__recover_partitions(source_node) %}
+    /*{# 
+        We're dispatching this macro so that users can override it if required on other adapters
+        but this will work for spark/databricks. 
+    #}*/
+
+    {{ exceptions.raise_not_implemented('recover_partitions macro not implemented for adapter ' + adapter.type()) }}
+{% endmacro %}