fix: alter table description without full_refresh

[kiwamizamurai]

resolves #1138
docs dbt-labs/docs.getdbt.com/#

Problem

when materialization is incremental, table description does not be updated.

Solution

I implemented the method that alters the table description without table recreation.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX

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[kiwamizamurai]

@cla-bot
cla has been signed

[kiwamizamurai]

@colin-rogers-dbt
hello. this is my frist pr. please help me.
is there anything else i should do?

[kiwamizamurai]

Changelog file might be required?

[dataders]

see #1138 (comment)

[kiwamizamurai]

@dataders

Could you review my PR?
I have verified in my local environment with the same step.

• [Feature] Support the updating of incremental model description after initial creation #1138 (comment)

[dataders]

currently this is within the if that has to do with column comments.

perhaps there needs to be a new if that is something like the below. that said, I'm very confused about the purpose of for_relation and for_columns

Suggested change

	{% do adapter.update_table_description(relation, model.description) %}
	{% if for_relation and config.persist_relation_docs() and model.description %}
	{% do adapter.update_table_description(relation, model.description) %}
	{% endif %}

Actually it looks like the seed materialization is already doing something very similar.

dbt-bigquery/dbt/include/bigquery/macros/materializations/seed.sql

Lines 20 to 23 in 978a1ae

	{% if config.persist_relation_docs() and 'description' in model %}
	{{ adapter.update_table_description(model['database'], model['schema'], model['alias'], model['description']) }}
	{% endif %}

[kiwamizamurai]

@dataders
Thank you for your comment.

I modified the implementation to use an existing method in the seed materialization.

• ac75ff2

[kiwamizamurai]

@dataders
let me remind you
In my local environment, I checked that the code works fine.

However, I'm not sure how to write the test, could you please help me?

import pytest
from dbt.tests.util import relation_from_name, get_connection, run_dbt

from dbt.adapters.bigquery import BigQueryRelation

_TABLE_DESCRIPTION_MODEL = """{{
  config(
    materialized='incremental',
    persist_docs={ 'relation': true }
  )
}}

select 1 as first_col
from unnest([struct(1 as dual)]) as dual

{% if is_incremental() %}
    where 1=1
{% endif %}
"""
_TABLE_DESCRIPTION_MODEL_NAME = "table_description_model"
_TABLE_DESCRIPTION = "this is not a field"
_TABLE_DESCRIPTION_MODEL_YML = """
version: 2

models:
- name: table_description_model
  description: '{{ var("table_description") }}'
"""


class TestBigqueryUpdateTableDescription:
    @pytest.fixture(scope="class")
    def project_config_update(self):
        return {"config-version": 2, "vars": {"table_description": _TABLE_DESCRIPTION}}

    @pytest.fixture(scope="class")
    def models(self):
        return {
            f"{_TABLE_DESCRIPTION_MODEL_NAME}.sql": _TABLE_DESCRIPTION_MODEL,
            "schema.yml": _TABLE_DESCRIPTION_MODEL_YML,
        }

    def test_bigquery_update_table_description(self, project):
        results = run_dbt(["run"])
        assert len(results) == 1

        # TODO update docs
        results = run_dbt(["run"])
        assert len(results) == 1
        relation: BigQueryRelation = relation_from_name(
            project.adapter, _TABLE_DESCRIPTION_MODEL_NAME
        )
        adapter = project.adapter
        with get_connection(project.adapter) as conn:
            table = conn.handle.get_table(
                adapter.connections.get_bq_table(
                    relation.database, relation.schema, relation.table
                )
            )
            assert table.description == _TABLE_DESCRIPTION

[martinazapletalova]

Hi @kiwamizamurai any updates on this PR?

[kiwamizamurai]

@colin-rogers-dbt
@dataders
could you review this pr?