An ActiveRecord::ActiveRecordError is raised if a selected row contains the string 'DB::Exception'

[kyrylo]

My issue is with a table that has a name column. When I insert a string containing DB::Exception into the name column and select the row, I get an ActiveRecord::ActiveRecordError.

The raw ClickHouse query works fine, but selecting via the adapter triggers the error. The buggy code is here: https://github.com/PNixx/clickhouse-activerecord/blob/ddfa259bbec88aefa3eaf2942392b8473a477601/lib/active_record/connection_adapters/clickhouse/schema_statements.rb#L185-L187

It assumes that DB::Exception only appears during a real ClickHouse exception.

Thank you for the gem! It makes the impossible possible :)

[PNixx]

Please, write example request.

[kyrylo]

How to reproduce:

1. Create a table:

   CREATE TABLE things
   (
       name String,
   )
   ENGINE = MergeTree
   ORDER BY name;

2. Insert a record with the string DB::Exception:

   INSERT INTO things (name) VALUES ('DB::Exception');

3. Create a model for this in the Rails app

   class Thing < ApplicationRecord
     establish_connection :clickhouse
   end

4. Run any query that selects the inserted row:

irb(main):002> Thing.first
  Clickhouse Thing Load (4.1ms)  SELECT things.* FROM things ORDER BY things.name ASC LIMIT 1
(irb):2:in `<main>': Response code: 200: (ActiveRecord::ActiveRecordError)
["name"]
["String"]
["DB::Exception"]

Query: SELECT things.* FROM things ORDER BY things.name ASC LIMIT 1

[kyrylo]

This is the commit that introduced the bug: https://github.com/PNixx/clickhouse-activerecord/commit/df61a892da5fe13b685ae38cdcda91ecc4efd27b

Not sure why a DB::Exception happens when the response is 200. I couldn't find any relevant info online.

[kyrylo]

I created a PR with the possible fix. https://github.com/PNixx/clickhouse-activerecord/pull/165