“check” snapshot strategy fails if columns need to be quoted

Describe the bug

If you use the “check” snapshot strategy (default) on data which contains columns with special characters in it and do one initial run and then a subsequent insert run. The second run will fail due to a syntax error (see “Screenshots and log output below”).

Steps To Reproduce

{% snapshot fake_snapshot2 %}
{{
    config(
      target_database='analytics',
      target_schema='dbt_claire',
      unique_key='id',
      strategy='check',
      check_cols='all'
    )
}}
select
    1 as id,
    1 as "unnamed: 0",
    current_timestamp() as created_at
{% endsnapshot %}

(stolen from slack discussion: https://getdbt.slack.com/archives/CBSQTAPLG/p1608759471264100?thread_ts=1608758278.258300&cid=CBSQTAPLG)

Expected behavior

I expect the snapshot to not fail on columns containing special characters. Special characters should work as long as you enclose it with ".

Screenshots and log output

2020-12-23 21:00:59.335996 (MainThread):   syntax error at or near ":"
2020-12-23 21:00:59.339215 (MainThread):   LINE 81: ..._data._dbt_id is null) or snapshotted_data.Unnamed: 0 != sou...

System information

Which database are you using dbt with?

• postgres
• redshift
• bigquery
• snowflake
• other (specify: ____________)

The output of dbt --version:

installed version: 0.18.1
   latest version: 0.18.1

Up to date!

Plugins:
  - postgres: 0.18.1
  - snowflake: 0.18.1
  - bigquery: 0.18.1
  - redshift: 0.18.1

The operating system you’re using: MacOS Catalina Version 10.15.7 with Docker for Mac 3.0.3

The output of python --version: Python 3.8.6

cc @clrcrl

[sou-joshi]

I would like to pick this.

[clrcrl]

I’m pretty sure it’s this line here (or the related function — we don’t seem to be quoting the column names) https://github.com/fishtown-analytics/dbt/blob/dev/kiyoshi-kuromiya/core/dbt/include/global_project/macros/materializations/snapshot/strategies.sql#L167