dbt Constraints / model contracts

.changes/unreleased/Features-20230130-125855.yaml

@@ -0,0 +1,8 @@
+kind: Features
+body: 'Support for data types constraints in Spark following the dbt Core feature
+  #6271'
+time: 2023-01-30T12:58:55.972992+01:00
+custom:
+  Author: b-per
+  Issue: "558"
+  PR: "574"

dbt/include/spark/macros/adapters.sql

@@ -138,6 +138,9 @@
       {% else %}
         create table {{ relation }}
       {% endif %}
+      {% if config.get('constraints_enabled', False) %}
+        {{ get_assert_columns_equivalent(sql) }}
+      {% endif %}
       {{ file_format_clause() }}
       {{ options_clause() }}
       {{ partition_cols(label="partitioned by") }}
@@ -160,6 +163,55 @@
 {%- endmacro -%}
 
 
+{% macro persist_constraints(relation, model) %}
+  {{ return(adapter.dispatch('persist_constraints', 'dbt')(relation, model)) }}
+{% endmacro %}
+
+{% macro spark__persist_constraints(relation, model) %}
+  {% if config.get('constraints_enabled', False) and config.get('file_format', 'delta') == 'delta' %}
+    {% do alter_table_add_constraints(relation, model.columns) %}
+    {% do alter_column_set_constraints(relation, model.columns) %}
+  {% endif %}
+{% endmacro %}
+
+{% macro alter_table_add_constraints(relation, constraints) %}
+  {{ return(adapter.dispatch('alter_table_add_constraints', 'dbt')(relation, constraints)) }}
+{% endmacro %}
+
+{% macro spark__alter_table_add_constraints(relation, column_dict) %}
+
+  {% for column_name in column_dict %}
+    {% set constraints_check = column_dict[column_name]['constraints_check'] %}
+    {% if constraints_check and not is_incremental() %}
+      {%- set constraint_hash = local_md5(column_name ~ ";" ~ constraint_check) -%}
+      {% call statement() %}
+        alter table {{ relation }} add constraint {{ constraint_hash }} check {{ constraints_check }};
+      {% endcall %}
+    {% endif %}
+  {% endfor %}
+{% endmacro %}
+
+{% macro alter_column_set_constraints(relation, column_dict) %}
+  {{ return(adapter.dispatch('alter_column_set_constraints', 'dbt')(relation, column_dict)) }}
+{% endmacro %}
+
+{% macro spark__alter_column_set_constraints(relation, column_dict) %}
+  {% for column_name in column_dict %}
+    {% set constraints = column_dict[column_name]['constraints'] %}
+    {% for constraint in constraints %}
+      {% if constraint != 'not null' %}
+        {{ exceptions.warn('Invalid constraint for column ' ~ column_name ~ '. Only `not null` is supported.') }}
+      {% else %}
+        {% set quoted_name = adapter.quote(column_name) if column_dict[column_name]['quote'] else column_name %}
+        {% call statement() %}
+          alter table {{ relation }} change column {{ quoted_name }} set {{ constraint }};
+        {% endcall %}
+      {% endif %}
+    {% endfor %}
+  {% endfor %}
+{% endmacro %}
+
+
 {% macro spark__create_view_as(relation, sql) -%}
   create or replace view {{ relation }}
   {{ comment_clause() }}

dbt/include/spark/macros/materializations/table.sql

@@ -29,6 +29,8 @@
 
   {% do persist_docs(target_relation, model) %}
 
+  {% do persist_constraints(target_relation, model) %}
+
   {{ run_hooks(post_hooks) }}
 
   {{ return({'relations': [target_relation]})}}

tests/functional/adapter/test_constraints.py

@@ -0,0 +1,58 @@
+import pytest
+from dbt.tests.util import relation_from_name
+from dbt.tests.adapter.constraints.test_constraints import (
+    BaseConstraintsColumnsEqual,
+    BaseConstraintsRuntimeEnforcement
+)
+
+# constraints are enforced via 'alter' statements that run after table creation
+_expected_sql_spark = """
+create or replace table {0}  
+    using delta
+    as
+
+select
+    1 as id,
+    'blue' as color,
+    cast('2019-01-01' as date) as date_day
+"""
+
+@pytest.mark.skip_profile('spark_session', 'apache_spark')
+class TestSparkConstraintsColumnsEqual(BaseConstraintsColumnsEqual):
+    pass
+
+@pytest.mark.skip_profile('spark_session', 'apache_spark')
+class TestSparkConstraintsRuntimeEnforcement(BaseConstraintsRuntimeEnforcement):
+    @pytest.fixture(scope="class")
+    def project_config_update(self):
+        return {
+            "models": {
+                "+file_format": "delta",
+            }
+        }
+
+    @pytest.fixture(scope="class")
+    def expected_sql(self, project):
+        relation = relation_from_name(project.adapter, "my_model")
+        return _expected_sql_spark.format(relation)
+
+    # On Spark/Databricks, constraints are applied *after* the table is replaced.
+    # We don't have any way to "rollback" the table to its previous happy state.
+    # So the 'color' column will be updated to 'red', instead of 'blue'.
+    @pytest.fixture(scope="class")
+    def expected_color(self):
+        return "red"
+
+    @pytest.fixture(scope="class")
+    def expected_error_messages(self):
+        return [
+            "violate the new CHECK constraint",
+            "DELTA_NEW_CHECK_CONSTRAINT_VIOLATION",
+            "violate the new NOT NULL constraint",
+        ]
+
+    def assert_expected_error_messages(self, error_message, expected_error_messages):
+        # This needs to be ANY instead of ALL
+        # The CHECK constraint is added before the NOT NULL constraint
+        # and different connection types display/truncate the error message in different ways...
+        assert any(msg in error_message for msg in expected_error_messages)