From daba363e5722f972abcf2bdb80c4b31665d19397 Mon Sep 17 00:00:00 2001
From: Peter Allen Webb <peter.webb@dbtlabs.com>
Date: Mon, 4 Nov 2024 11:54:13 -0500
Subject: [PATCH] Raise an exception if the user changes the snapshot mode to
 hard_deletes="new_record" from a different mode.

---
 .../materializations/snapshots/helpers.sql       |  2 +-
 .../materializations/snapshots/snapshot.sql      | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/dbt/include/global_project/macros/materializations/snapshots/helpers.sql b/dbt/include/global_project/macros/materializations/snapshots/helpers.sql
index 273a1582..b41a1986 100644
--- a/dbt/include/global_project/macros/materializations/snapshots/helpers.sql
+++ b/dbt/include/global_project/macros/materializations/snapshots/helpers.sql
@@ -119,7 +119,7 @@
             'insert' as dbt_change_type,
             source_data.*
           {%- if strategy.hard_deletes == 'new_record' -%},
-            'False' as {{ columns.dbt_is_deleted }} {# Implies I, II, or III #}
+            'False' as {{ columns.dbt_is_deleted }}
           {%- endif %}
 
         from insertions_source_data as source_data
diff --git a/dbt/include/global_project/macros/materializations/snapshots/snapshot.sql b/dbt/include/global_project/macros/materializations/snapshots/snapshot.sql
index 0c9590b6..0c54ede6 100644
--- a/dbt/include/global_project/macros/materializations/snapshots/snapshot.sql
+++ b/dbt/include/global_project/macros/materializations/snapshots/snapshot.sql
@@ -39,6 +39,22 @@
 
       {{ adapter.valid_snapshot_target(target_relation, columns) }}
 
+      {# Raise an exception if the user has selected the new_record mode for
+         hard deletes, but there is no dbt_is_deleted column in the target,
+         which would indicate it was created in a different mode. #}
+      {% if strategy.hard_deletes == 'new_record' %}
+          {% set target_cols = adapter.get_columns_in_relation(target_relation) %}
+          {% set ns = namespace(found_is_deleted_col = false) %}
+          {% for col in target_cols %}
+              {% if col.column == columns['dbt_is_deleted'] %}
+                {% set ns.found_is_deleted_col = true %}
+              {% endif %}
+          {% endfor %}
+          {% if not ns.found_is_deleted_col %}
+             {% do exceptions.raise_compiler_error('Did not find a dbt_is_deleted column in snapshot target. Changing the snapshot hard_deletes mode is not supported after a snapshot has been created.') %}
+         {% endif %}
+      {% endif %}
+
       {% set build_or_select_sql = snapshot_staging_table(strategy, sql, target_relation) %}
       {% set staging_table = build_snapshot_staging_table(strategy, sql, target_relation) %}