From d2d5ba66c9b0d905286c5a4bc8fef2eb527c2daf Mon Sep 17 00:00:00 2001
From: Sam Debruyn <sam@debruyn.dev>
Date: Tue, 19 May 2026 10:53:21 +0200
Subject: [PATCH] Use intermediate-and-swap pattern in full-refresh incremental
 path
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The full-refresh branch of fabric__incremental dropped the existing
target before re-creating it. If the subsequent CREATE TABLE AS SELECT
failed for any reason — transient Fabric error, query timeout, broken
model SQL, capacity throttling, OOM, network hiccup — the user was left
with no target table at all.

Build the new table into an intermediate relation first, then rename the
existing target to a backup, rename the intermediate to the target, and
drop the backup. If the build fails, the existing target stays in place.
This is the same pattern dbt-postgres, dbt-snowflake, and dbt-spark use.
---
 .../models/incremental/incremental.sql        | 24 +++++++++++++++----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/dbt/include/fabric/macros/materializations/models/incremental/incremental.sql b/dbt/include/fabric/macros/materializations/models/incremental/incremental.sql
index f4c3e9fc..d7bfd098 100644
--- a/dbt/include/fabric/macros/materializations/models/incremental/incremental.sql
+++ b/dbt/include/fabric/macros/materializations/models/incremental/incremental.sql
@@ -24,19 +24,33 @@
 
   {% if existing_relation is none or full_refresh_mode or existing_relation.is_view %}
 
-    {% set tmp_vw_relation = target_relation.incorporate(path={"identifier": target_relation.identifier ~ '__dbt_tmp_vw'}, type='view')-%}
-    -- Dropping temp view relation if it exists
+    {%- set intermediate_relation = make_intermediate_relation(target_relation) -%}
+    {%- set backup_relation = make_backup_relation(target_relation, 'table') -%}
+    {% set tmp_vw_relation = intermediate_relation.incorporate(path={"identifier": intermediate_relation.identifier ~ '__dbt_tmp_vw'}, type='view')-%}
+
+    -- Dropping any leftover intermediate / backup / temp view relations from a previous failed run
+    {{ adapter.drop_relation(intermediate_relation) }}
+    {{ adapter.drop_relation(backup_relation) }}
     {{ adapter.drop_relation(tmp_vw_relation) }}
-    -- Dropping target relation if exists
-    {{ adapter.drop_relation(target_relation) }}
 
+    -- Build into an intermediate relation. If this fails, the existing target is untouched.
     {%- call statement('main') -%}
-      {{ get_create_table_as_sql(False, target_relation, sql)}}
+      {{ get_create_table_as_sql(False, intermediate_relation, sql)}}
     {%- endcall -%}
 
     -- Dropping temp view relation
     {{ adapter.drop_relation(tmp_vw_relation) }}
 
+    -- Atomic swap: rename existing target to backup (if any), intermediate to target, then drop backup
+    {%- set target_existing = load_cached_relation(target_relation) -%}
+    {% if target_existing is not none %}
+      {{ adapter.rename_relation(target_existing, backup_relation) }}
+    {% endif %}
+    {{ adapter.rename_relation(intermediate_relation, target_relation) }}
+    {% if target_existing is not none %}
+      {{ adapter.drop_relation(backup_relation) }}
+    {% endif %}
+
     -- Add constraints including FK relation.
     {{ build_model_constraints(target_relation) }}