Add support for incremental models

The incremental strategy supported is to insert new records into target table,
without updating or overwriting.

Resolves: #1

README.md

@@ -83,7 +83,6 @@ on your Trino instance.
 Due to the nature of Trino, not all core `dbt` functionality is supported.
 The following features of dbt are not implemented in `dbt-trino`:
 - Snapshot
-- Incremental models
 
 Also, note that upper or mixed case schema names will cause catalog queries to fail. 
 Please only use lower case schema names with this adapter.
@@ -100,6 +99,17 @@ hive.allow-drop-table=true
 hive.allow-rename-table=true
 ```
 
+#### Incremental models
+
+The incremental strategy currently supported by this adapter is to append new records
+without updating/overwriting any existing data from the target model.
+
+```
+{{
+    config(materialized = 'incremental')
+}}
+```
+
 #### Use table properties to configure connector specifics
 
 Trino connectors use table properties to configure connector specifics.

dbt/include/trino/macros/materializations/incremental.sql

@@ -1,6 +1,42 @@
+{% macro dbt_trino_get_append_sql(tmp_relation, target_relation) %}
+
+    {%- set dest_columns = adapter.get_columns_in_relation(target_relation) -%}
+    {%- set dest_cols_csv = dest_columns | map(attribute='quoted') | join(', ') -%}
+    insert into {{ target_relation }}
+    select {{dest_cols_csv}} from {{ tmp_relation.include(database=false, schema=false) }};
+
+    drop table if exists {{ tmp_relation }};
+
+{% endmacro %}
 
 {% materialization incremental, adapter='trino' -%}
-  {{ exceptions.raise_not_implemented(
-    'incremental materialization not implemented for '+adapter.type())
-  }}
-{% endmaterialization %}
+
+  {%- set full_refresh_mode = (flags.FULL_REFRESH == True) -%}
+
+  {% set target_relation = this %}
+  {% set existing_relation = load_relation(this) %}
+  {% set tmp_relation = make_temp_relation(this) %}
+
+  {{ run_hooks(pre_hooks) }}
+
+  {% if existing_relation is none %}
+    {% set build_sql = create_table_as(False, target_relation, sql) %}
+  {% elif existing_relation.is_view or full_refresh_mode %}
+    {% do adapter.drop_relation(existing_relation) %}
+    {% set build_sql = create_table_as(False, target_relation, sql) %}
+  {% else %}
+    {% set drop_tmp_relation_sql = "drop table if exists " ~  tmp_relation %}
+    {% do run_query(drop_tmp_relation_sql) %}
+    {% do run_query(create_table_as(True, tmp_relation, sql)) %}
+    {% set build_sql = dbt_trino_get_append_sql(tmp_relation, target_relation) %}
+  {% endif %}
+
+  {%- call statement('main') -%}
+    {{ build_sql }}
+  {%- endcall -%}
+
+  {{ run_hooks(post_hooks) }}
+
+  {{ return({'relations': [target_relation]}) }}
+
+{%- endmaterialization %}

docker/dbt/jaffle_shop/models/marts/core/dim_order_dates.sql

@@ -0,0 +1,17 @@
+{{
+    config(materialized = 'incremental')
+}}
+
+with orders as (
+
+    select * from {{ ref('stg_orders') }}
+
+)
+
+select distinct order_date
+from orders
+
+{% if is_incremental() %}
+    -- this filter will only be applied on an incremental run
+    where order_date > (select max(order_date) from {{ this }})
+{% endif %}

docker/dbt/jaffle_shop/models/marts/core/schema.yml

@@ -32,6 +32,16 @@ models:
       - name: total_order_amount
         description: Total value (AUD) of a customer's orders
 
+  - name: dim_order_dates
+    description: This table is built in an incremental fashion and contains all the dates on which orders have been placed.
+
+    columns:
+      - name: order_date
+        description: A unique order date
+        tests:
+          - unique
+          - not_null
+
   - name: fct_orders
     description: This table has basic information about orders, as well as some derived facts based on payments
 

docker/run_tests.bash

@@ -4,8 +4,13 @@
 cd "$(dirname "${BASH_SOURCE[0]}")"
 
 set -exo pipefail
+# run the dim_order_dates model two times in order to test incremental functionality
 docker run \
     --network="dbt-net" \
     -v $PWD/dbt:/root/.dbt \
     dbt-trino \
-    "cd /jaffle_shop && dbt seed && dbt run && dbt test"
+    "cd /jaffle_shop \
+        && dbt seed \
+        && dbt run \
+        && dbt run --model dim_order_dates \
+        && dbt test"

test/integration/trino.dbtspec

@@ -21,8 +21,8 @@ sequences:
   test_dbt_empty: empty
   test_dbt_base: base
   test_dbt_ephemeral: ephemeral
-  # no incrementals, no snapshots
-  # test_dbt_incremental: incremental
+  test_dbt_incremental: incremental
+  # no snapshots
   # test_dbt_snapshot_strategy_timestamp: snapshot_strategy_timestamp
   # test_dbt_snapshot_strategy_check_cols: snapshot_strategy_check_cols
   test_dbt_data_test: data_test