add full_refresh control

controlling-full-refresh-config-with-variables/README.md

@@ -0,0 +1,135 @@
+---
+---
+
+## Controlling full refresh config with variables
+
+Some folks want to set the `full_refresh` config dynamically - i.e.
+
+```sql
+-- models/foo.sql
+{{ 
+    config(
+        materialized='incremental',
+        full_refresh='{{ macro_that_runs_some_sql_query_first() }}'
+    ) 
+}}
+...
+```
+
+It is however not possible to set configs based on the outcome of a SQL query: https://github.com/dbt-labs/docs.getdbt.com/discussions/1310.
+
+We can use vars to control whether a model should have it's full_refresh config be set to `true` or `false` like so:
+
+```sql
+-- models/foo.sql
+{{
+    config(
+        materialized="incremental",
+        full_refresh=(this.name in var('allow_full_refresh', [])) 
+    )
+}}
+select 1 id
+
+-- models/bar.sql
+{{
+    config(
+        materialized="incremental",
+        full_refresh=(this.name in var('allow_full_refresh', [])) 
+    )
+}}
+select 1 id
+```
+
+Let's see this in action... first we delete all the existing tables.
+
+```sql
+drop table if exists db.analytics.foo;
+drop table if exists db.analytics.bar;
+```
+
+> Logs below are truncated just to show what is necessary.
+
+Then do our first run:
+
+```sh
+$ dbt run
+
+21:44:20  On model.my_dbt_project.bar: /* {"app": "dbt", "dbt_version": "1.8.5", "profile_name": "all", "target_name": "sf", "node_id": "model.my_dbt_project.bar"} */
+create or replace transient table db.analytics.bar
+         as
+        (
+
+select 1 id
+        );
+
+21:44:23  On model.my_dbt_project.foo: /* {"app": "dbt", "dbt_version": "1.8.5", "profile_name": "all", "target_name": "sf", "node_id": "model.my_dbt_project.foo"} */
+create or replace transient table db.analytics.foo
+         as
+        (
+
+select 1 id
+        );
+```
+
+Table is created from scratch as expected. Now we do a subsequent run:
+
+```sh
+$ dbt run
+
+21:45:32  On model.my_dbt_project.bar: /* {"app": "dbt", "dbt_version": "1.8.5", "profile_name": "all", "target_name": "sf", "node_id": "model.my_dbt_project.bar"} */
+insert into db.analytics.bar ("ID")
+        (
+            select "ID"
+            from db.analytics.bar__dbt_tmp
+        );
+
+21:45:36  On model.my_dbt_project.foo: /* {"app": "dbt", "dbt_version": "1.8.5", "profile_name": "all", "target_name": "sf", "node_id": "model.my_dbt_project.foo"} */
+insert into db.analytics.foo ("ID")
+        (
+            select "ID"
+            from db.analytics.foo__dbt_tmp
+        );
+```
+
+`foo` and `bar` were inserted into as expected of an incremental subsequent run. Let's try to add our `--full-refresh` flag and see:
+
+```sh
+$ dbt run --full-refresh
+
+21:46:56  On model.my_dbt_project.bar: /* {"app": "dbt", "dbt_version": "1.8.5", "profile_name": "all", "target_name": "sf", "node_id": "model.my_dbt_project.bar"} */
+insert into db.analytics.bar ("ID")
+        (
+            select "ID"
+            from db.analytics.bar__dbt_tmp
+        );
+
+21:47:00  On model.my_dbt_project.foo: /* {"app": "dbt", "dbt_version": "1.8.5", "profile_name": "all", "target_name": "sf", "node_id": "model.my_dbt_project.foo"} */
+insert into db.analytics.foo ("ID")
+        (
+            select "ID"
+            from db.analytics.foo__dbt_tmp
+        );
+```
+
+Even with the `--full-refresh` flag, those models were NOT fully refreshed cause their `full_refresh` configs resolved to `false`. Let's set the var so that model `bar` will full refresh but not `foo`:
+
+```sh
+$ dbt run --vars 'allow_full_refresh: ["bar"]'
+
+21:49:18  On model.my_dbt_project.bar: /* {"app": "dbt", "dbt_version": "1.8.5", "profile_name": "all", "target_name": "sf", "node_id": "model.my_dbt_project.bar"} */
+create or replace transient table db.analytics.bar
+         as
+        (
+
+select 1 id
+        );
+
+21:49:23  On model.my_dbt_project.foo: /* {"app": "dbt", "dbt_version": "1.8.5", "profile_name": "all", "target_name": "sf", "node_id": "model.my_dbt_project.foo"} */
+insert into db.analytics.foo ("ID")
+        (
+            select "ID"
+            from db.analytics.foo__dbt_tmp
+        );
+```
+
+By setting the vars accordingly we can prevent or allow models from fully refreshing whenever we run with the `--full-refresh` flag.