Fix: column comparison logic for check-strategy snapshots

[jtcohen6]

resolves #5222
resolves dbt-labs/dbt-snowflake#154

Description

The logic in snapshot_check_all_get_existing_columns added by #4893 doesn't account for cases where the user-configured check_cols doesn't match the database's column quoting/casing.

This is almost always true on Snowflake, which is where we've been seeing test failures. The snapshot doesn't fail explicitly, but it always considers the column schema to have changed, so it adds new records every single time it runs.

I added a new test case, on top of the one added in #4893. It fails without the changes to the macro in this PR, and passes with them.

For a longer-term resolution, and to ensure this doesn't happen again, let's:

• Move tests/functional/simple_snapshot into the "adapter zone" and get it running on Snowflake
• Create a mechanism to proactively test dbt-core changes against one/all adapter(s): [CT-449] Make it easy to run integration tests in an adapter plugin against a dbt-core PR #4988

That's out of scope for the current PR, which is just trying to fix the nightly tests in dbt-snowflake, and preclude an unintended regression in v1.2.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• 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
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[leahwicz]

@jtcohen6 this is what is causing the failed scheduled test runs for us?

[jtcohen6]

@leahwicz I believe so. I'll kick off a dbt-snowflake PR to run against this branch to confirm.

Update: All checks passing in dbt-labs/dbt-snowflake#159 (CI)

[ueshin]

Hi @jtcohen6, seems like this commit broke dbt-databrick's integration tests and I guess dbt-spark's, too.

[gw0] [100%] FAILED tests/functional/adapter/test_basic.py::TestSnapshotCheckColsDatabricks::test_snapshot_check_cols

==================================================================================================== FAILURES =====================================================================================================
____________________________________________________________________________ TestSnapshotCheckColsDatabricks.test_snapshot_check_cols _____________________________________________________________________________
[gw0] darwin -- Python 3.9.11 /.../bin/python

self = <test_basic.TestSnapshotCheckColsDatabricks object at 0x7fbb684f9e20>, project = <dbt.tests.fixtures.project.TestProjInfo object at 0x7fbbb8a081f0>

    def test_snapshot_check_cols(self, project):
        # seed command
        results = run_dbt(["seed"])
        assert len(results) == 2

        # snapshot command
        results = run_dbt(["snapshot"])
        for result in results:
            assert result.status == "success"

        # check rowcounts for all snapshots
        check_relation_rows(project, "cc_all_snapshot", 10)
        check_relation_rows(project, "cc_name_snapshot", 10)
        check_relation_rows(project, "cc_date_snapshot", 10)

        relation = relation_from_name(project.adapter, "cc_all_snapshot")
        result = project.run_sql(f"select * from {relation}", fetch="all")

        # point at the "added" seed so the snapshot sees 10 new rows
        results = run_dbt(["--no-partial-parse", "snapshot", "--vars", "seed_name: added"])
        for result in results:
            assert result.status == "success"

        # check rowcounts for all snapshots
>       check_relation_rows(project, "cc_all_snapshot", 20)

/.../dbt-core/tests/adapter/dbt/tests/adapter/basic/test_snapshot_check_cols.py:62:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

project = <dbt.tests.fixtures.project.TestProjInfo object at 0x7fbbb8a081f0>, snapshot_name = 'cc_all_snapshot', count = 20

    def check_relation_rows(project, snapshot_name, count):
        relation = relation_from_name(project.adapter, snapshot_name)
        result = project.run_sql(f"select count(*) as num_rows from {relation}", fetch="one")
>       assert result[0] == count
E       assert 30 == 20

/.../dbt-core/tests/adapter/dbt/tests/adapter/basic/test_snapshot_check_cols.py:15: AssertionError

[jtcohen6]

@ueshin You're totally right. I'm digging in now.