Add materialization macro for materialized view (#207)

* Add materialization macro for materialized view

* fix isort issues in materialized view test

dbt/include/clickhouse/macros/materializations/materialized_view.sql

@@ -0,0 +1,120 @@
+{#-
+  Create or update a materialized view in ClickHouse.
+  This involves creating both the materialized view itself and a
+  target table that the materialized view writes to.
+-#}
+{%- materialization materialized_view, adapter='clickhouse' -%}
+
+  {%- set target_relation = this.incorporate(type='table') -%}
+  {%- set mv_name = target_relation.name + '_mv' -%}
+  {%- set target_mv = api.Relation.create(identifier=mv_name, schema=schema, database=database, type='materializedview') -%}
+  {%- set cluster_clause = on_cluster_clause(target_relation) -%}
+
+  {# look for an existing relation for the target table and create backup relations if necessary #}
+  {%- set existing_relation = load_cached_relation(this) -%}
+  {%- set backup_relation = none -%}
+  {%- set preexisting_backup_relation = none -%}
+  {%- set preexisting_intermediate_relation = none -%}
+  {% if existing_relation is not none %}
+    {%- set backup_relation_type = existing_relation.type -%}
+    {%- set backup_relation = make_backup_relation(target_relation, backup_relation_type) -%}
+    {%- set preexisting_backup_relation = load_cached_relation(backup_relation) -%}
+    {% if not existing_relation.can_exchange %}
+      {%- set intermediate_relation =  make_intermediate_relation(target_relation) -%}
+      {%- set preexisting_intermediate_relation = load_cached_relation(intermediate_relation) -%}
+    {% endif %}
+  {% endif %}
+
+  {% set grant_config = config.get('grants') %}
+
+  {{ run_hooks(pre_hooks, inside_transaction=False) }}
+
+  -- drop the temp relations if they exist already in the database
+  {{ drop_relation_if_exists(preexisting_intermediate_relation) }}
+  {{ drop_relation_if_exists(preexisting_backup_relation) }}
+
+  -- `BEGIN` happens here:
+  {{ run_hooks(pre_hooks, inside_transaction=True) }}
+
+  {% if backup_relation is none %}
+    {{ log('Creating new materialized view ' + target_relation.name )}}
+    {% call statement('main') -%}
+      {{ clickhouse__get_create_materialized_view_as_sql(target_relation, sql) }}
+    {%- endcall %}
+  {% elif existing_relation.can_exchange %}
+    {{ log('Replacing existing materialized view' + target_relation.name) }}
+    {% call statement('drop existing materialized view') %}
+      drop view if exists {{ mv_name }} {{ cluster_clause }}
+    {% endcall %}
+    {% call statement('main') -%}
+      {{ get_create_table_as_sql(False, backup_relation, sql) }}
+    {%- endcall %}
+    {% do exchange_tables_atomic(backup_relation, existing_relation) %}
+    {% call statement('create new materialized view') %}
+      {{ clickhouse__create_mv_sql(mv_name, existing_relation.name, cluster_clause, sql) }}
+    {% endcall %}
+  {% else %}
+    {{ log('Replacing existing materialized view' + target_relation.name) }}
+    {{ clickhouse__replace_mv(target_relation, existing_relation, intermediate_relation, backup_relation, sql) }}
+  {% endif %}
+
+  -- cleanup
+  {% set should_revoke = should_revoke(existing_relation, full_refresh_mode=True) %}
+  {% do apply_grants(target_relation, grant_config, should_revoke=should_revoke) %}
+
+  {% do persist_docs(target_relation, model) %}
+
+  {{ run_hooks(post_hooks, inside_transaction=True) }}
+
+  {{ adapter.commit() }}
+
+  {{ drop_relation_if_exists(backup_relation) }}
+
+  {{ run_hooks(post_hooks, inside_transaction=False) }}
+
+  {{ return({'relations': [target_relation, target_mv]}) }}
+
+{%- endmaterialization -%}
+
+
+{#
+  There are two steps to creating a materialized view:
+  1. Create a new table based on the SQL in the model
+  2. Create a materialized view using the SQL in the model that inserts
+  data into the table creating during step 1
+#}
+{% macro clickhouse__get_create_materialized_view_as_sql(relation, sql) -%}
+  {% call statement('create_target_table') %}
+    {{ get_create_table_as_sql(False, relation, sql) }}
+  {% endcall %}
+  {%- set cluster_clause = on_cluster_clause(relation) -%}
+  {%- set mv_name = relation.name + '_mv' -%}
+  {{ clickhouse__create_mv_sql(mv_name, relation.name, cluster_clause, sql) }}
+{%- endmacro %}
+
+
+{% macro clickhouse__create_mv_sql(relation_name, target_table, cluster_clause, sql)  -%}
+  create materialized view if not exists {{ relation_name }} {{ cluster_clause }}
+  to {{ target_table }}
+  as {{ sql }}
+{%- endmacro %}
+
+
+{% macro clickhouse__replace_mv(target_relation, existing_relation, intermediate_relation, backup_relation, sql) %}
+  {# drop existing materialized view while we recreate the target table #}
+  {%- set cluster_clause = on_cluster_clause(target_relation) -%}
+  {%- set mv_name = target_relation.name + '_mv' -%}
+  {% call statement('drop existing mv') -%}
+    drop view if exists {{ mv_name }} {{ cluster_clause }}
+  {%- endcall %}
+
+  {# recreate the target table #}
+  {% call statement('main') -%}
+    {{ get_create_table_as_sql(False, intermediate_relation, sql) }}
+  {%- endcall %}
+  {{ adapter.rename_relation(existing_relation, backup_relation) }}
+  {{ adapter.rename_relation(intermediate_relation, target_relation) }}
+
+  {# now that the target table is recreated, we can finally create our new view #}
+  {{ clickhouse__create_mv_sql(mv_name, target_relation.name, cluster_clause, sql) }}
+{% endmacro %}

tests/integration/adapter/test_materialized_view.py

@@ -0,0 +1,164 @@
+"""
+test materialized view creation
+"""
+
+import json
+
+import pytest
+from dbt.tests.util import check_relation_types, run_dbt
+
+PEOPLE_SEED_CSV = """
+id,name,age,department
+1231,Dade,33,engineering
+6666,Ksenia,48,engineering
+8888,Kate,50,engineering
+""".lstrip()
+
+# This model is parameterized, in a way, by the "run_type" dbt project variable
+# This is to be able to switch between different model definitions within
+# the same test run and allow us to test the evolution of a materialized view
+MV_MODEL = """
+{{ config(
+       materialized='materialized_view',
+       engine='MergeTree()',
+       order_by='(id)',
+) }}
+
+{% if var('run_type', '') == '' %}
+select
+    id,
+    name,
+    case
+        when name like 'Dade' then 'crash_override'
+        when name like 'Kate' then 'acid burn'
+        else 'N/A'
+    end as hacker_alias
+from {{ source('raw', 'people') }}
+where department = 'engineering'
+
+{% else %}
+
+select
+    id,
+    name,
+    case
+        -- Dade wasn't always known as 'crash override'!
+        when name like 'Dade' and age = 11 then 'zero cool'
+        when name like 'Dade' and age != 11 then 'crash override'
+        when name like 'Kate' then 'acid burn'
+        else 'N/A'
+    end as hacker_alias
+from {{ source('raw', 'people') }}
+where department = 'engineering'
+
+{% endif %}
+"""
+
+
+SEED_SCHEMA_YML = """
+version: 2
+
+sources:
+  - name: raw
+    schema: "{{ target.schema }}"
+    tables:
+      - name: people
+"""
+
+
+class TestBasicMV:
+    @pytest.fixture(scope="class")
+    def seeds(self):
+        """
+        we need a base table to pull from
+        """
+        return {
+            "people.csv": PEOPLE_SEED_CSV,
+            "schema.yml": SEED_SCHEMA_YML,
+        }
+
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "hackers.sql": MV_MODEL,
+        }
+
+    def test_create(self, project):
+        """
+        1. create a base table via dbt seed
+        2. create a model as a materialized view, selecting from the table created in (1)
+        3. insert data into the base table and make sure it's there in the target table created in (2)
+        """
+        results = run_dbt(["seed"])
+        assert len(results) == 1
+        columns = project.run_sql("DESCRIBE TABLE people", fetch="all")
+        assert columns[0][1] == "Int32"
+
+        # create the model
+        results = run_dbt()
+        assert len(results) == 1
+
+        columns = project.run_sql("DESCRIBE TABLE hackers", fetch="all")
+        assert columns[0][1] == "Int32"
+
+        columns = project.run_sql("DESCRIBE hackers_mv", fetch="all")
+        assert columns[0][1] == "Int32"
+
+        check_relation_types(
+            project.adapter,
+            {
+                "hackers_mv": "view",
+                "hackers": "table",
+            },
+        )
+
+        # insert some data and make sure it reaches the target table
+        project.run_sql(
+            f"""
+        insert into {project.test_schema}.people ("id", "name", "age", "department")
+            values (1232,'Dade',16,'engineering'), (9999,'eugene',40,'malware');
+        """
+        )
+
+        result = project.run_sql("select count(*) from hackers", fetch="all")
+        assert result[0][0] == 4
+
+
+class TestUpdateMV:
+    @pytest.fixture(scope="class")
+    def seeds(self):
+        """
+        we need a base table to pull from
+        """
+        return {
+            "people.csv": PEOPLE_SEED_CSV,
+            "schema.yml": SEED_SCHEMA_YML,
+        }
+
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {
+            "hackers.sql": MV_MODEL,
+        }
+
+    def test_update(self, project):
+        # create our initial materialized view
+        run_dbt(["seed"])
+        run_dbt()
+
+        # re-run dbt but this time with the new MV SQL
+        run_vars = {"run_type": "extended_schema"}
+        run_dbt(["run", "--vars", json.dumps(run_vars)])
+
+        project.run_sql(
+            f"""
+        insert into {project.test_schema}.people ("id", "name", "age", "department")
+            values (1232,'Dade',11,'engineering'), (9999,'eugene',40,'malware');
+        """
+        )
+
+        # assert that we now have both of Dade's aliases in our hackers table
+        result = project.run_sql(
+            "select distinct hacker_alias from hackers where name = 'Dade'", fetch="all"
+        )
+        assert len(result) == 2