Added warning comment to alter macro

dbt-labs · Jun 16, 2020 · 769e4d5 · 769e4d5
1 parent a7a73df
commit 769e4d5
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/plugins/bigquery/dbt/include/bigquery/macros/adapters.sql b/plugins/bigquery/dbt/include/bigquery/macros/adapters.sql
@@ -129,6 +129,12 @@
 {% endmacro %}
 
 {% macro bigquery__alter_column_type(relation, column_name, new_column_type) -%}
+ {#
+ Changing a column's data type using a query requires you to scan the entire table.
+ The query charges can be significant if the table is very large.
+
+ https://cloud.google.com/bigquery/docs/manually-changing-schemas#changing_a_columns_data_type
+ #}
  {% set relation_columns = get_columns_in_relation(relation) %}
 
  {% set sql %}