Incremental models with a contract don't need their columns modified

.changes/unreleased/Fixes-20240728-221421.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: Do not update varchar column definitions if a contract exists
+time: 2024-07-28T22:14:21.67712-04:00
+custom:
+  Author: gshank
+  Issue: "10362"

dev-requirements.txt

@@ -1,4 +1,4 @@
-git+https://github.com/dbt-labs/dbt-adapters.git@main
+git+https://github.com/dbt-labs/dbt-adapters.git@incremental_contract_varchar
 git+https://github.com/dbt-labs/dbt-adapters.git@main#subdirectory=dbt-tests-adapter
 git+https://github.com/dbt-labs/dbt-common.git@main
 git+https://github.com/dbt-labs/dbt-postgres.git@main

tests/functional/materializations/test_incremental_with_contract.py

@@ -0,0 +1,131 @@
+import pytest
+
+from dbt.tests.util import (
+    check_relations_equal,
+    get_relation_columns,
+    relation_from_name,
+    run_dbt,
+)
+
+seeds_base_csv = """
+id,name_xxx,some_date
+1,Easton,1981-05-20T06:46:51
+2,Lillian,1978-09-03T18:10:33
+3,Jeremiah,1982-03-11T03:59:51
+4,Nolan,1976-05-06T20:21:35
+5,Hannah,1982-06-23T05:41:26
+6,Eleanor,1991-08-10T23:12:21
+7,Lily,1971-03-29T14:58:02
+8,Jonathan,1988-02-26T02:55:24
+9,Adrian,1994-02-09T13:14:23
+10,Nora,1976-03-01T16:51:39
+""".lstrip()
+
+
+seeds_added_csv = (
+    seeds_base_csv
+    + """
+11,Mateo,2014-09-07T17:04:27
+12,Julian,2000-02-04T11:48:30
+13,Gabriel,2001-07-10T07:32:52
+14,Isaac,2002-11-24T03:22:28
+15,Levi,2009-11-15T11:57:15
+16,Elizabeth,2005-04-09T03:50:11
+17,Grayson,2019-08-06T19:28:17
+18,Dylan,2014-03-01T11:50:41
+19,Jayden,2009-06-06T07:12:49
+20,Luke,2003-12-05T21:42:18
+""".lstrip()
+)
+
+incremental_not_schema_change_sql = """
+{{ config(materialized="incremental", unique_key="user_id_current_time",on_schema_change="sync_all_columns") }}
+select
+    1 || '-' || current_timestamp as user_id_current_time,
+    {% if is_incremental() %}
+        'thisis18characters' as platform
+    {% else %}
+        'okthisis20characters' as platform
+    {% endif %}
+"""
+
+incremental_sql = """
+  {{ config(materialized="incremental") }}
+  select * from {{ source('raw', 'seed') }}
+  {% if is_incremental() %}
+  where id > (select max(id) from {{ this }})
+  {% endif %}
+"""
+
+schema_base_yml = """
+sources:
+  - name: raw
+    schema: "{{ target.schema }}"
+    tables:
+      - name: seed
+        identifier: "{{ var('seed_name', 'base') }}"
+
+models:
+  - name: incremental
+    config:
+      contract:
+        enforced: true
+      on_schema_change: append_new_columns
+    columns:
+      - name: id
+        data_type: int
+      - name: name_xxx
+        data_type: character varying(10)
+      - name: some_date
+        data_type: timestamp
+"""
+
+
+class TestIncremental:
+    @pytest.fixture(scope="class")
+    def project_config_update(self):
+        return {"name": "incremental"}
+
+    @pytest.fixture(scope="class")
+    def models(self):
+        return {"incremental.sql": incremental_sql, "schema.yml": schema_base_yml}
+
+    @pytest.fixture(scope="class")
+    def seeds(self):
+        return {"base.csv": seeds_base_csv, "added.csv": seeds_added_csv}
+
+    def test_incremental(self, project):
+        # seed command
+        results = run_dbt(["seed"])
+        assert len(results) == 2
+
+        # base table rowcount
+        relation = relation_from_name(project.adapter, "base")
+        result = project.run_sql(f"select count(*) as num_rows from {relation}", fetch="one")
+        assert result[0] == 10
+
+        # added table rowcount
+        relation = relation_from_name(project.adapter, "added")
+        result = project.run_sql(f"select count(*) as num_rows from {relation}", fetch="one")
+        assert result[0] == 20
+
+        # run command
+        # the "seed_name" var changes the seed identifier in the schema file
+        results = run_dbt(["run", "--vars", "seed_name: base"])
+        assert len(results) == 1
+
+        # check relations equal
+        check_relations_equal(project.adapter, ["base", "incremental"])
+
+        # change seed_name var
+        # the "seed_name" var changes the seed identifier in the schema file
+        results = run_dbt(["run", "--debug", "--vars", "seed_name: added"])
+        assert len(results) == 1
+
+        # Error before fix:  Changing col type from character varying(10) to character varying(256) in table:
+        #  "dbt"."test<...>_test_incremental_with_contract"."incremental"
+        columns = get_relation_columns(project.adapter, "incremental")
+        # [('id', 'integer', None), ('name_xxx', 'character varying', 10), ('some_date', 'timestamp without time zone', None)]
+        for column in columns:
+            if column[0] == "name_xxx":
+                assert column[2] == 10