Association gives deprecation warning about merging conditions on the same column no longer maintain both conditions

Migrated from Rails 6.0 to 6.1 and stumbled upon this deprecation when is called 'type_documents relation', :

ActionView::Template::Error (DEPRECATION WARNING: Merging ("documents"."type" IN ($1, $2, $3)) and (("documents"."type" = $1 OR "documents"."type" IN ($2, $3) AND "documents"."case_attachment_flag" = $4)) no longer maintain both conditions, and will be replaced by the latter in Rails 6.2. To migrate to Rails 6.2's behavior, use `relation.merge(other, rewhere: true)`. 

I have this relation:

has_many :type_documents,
             lambda {
               where(type: 'Document::Type')
                 .or(
                   where(
                     type: ['Document::Some1', 'Document::Some2'],
                     case_attachment_flag: true
                   )
                 )
             },
             dependent: :destroy,
             as: :record,
             class_name: 'Document::Type'

From 6.0, sql looks like:

Document::Type Load (17.4ms)  SELECT "documents".* FROM "documents" WHERE "documents"."type" IN ($1, $2, $3) AND "documents"."record_id" = $4 AND "documents"."record_type" = $5 AND ("documents"."type" = $6 OR "documents"."type" IN ($7, $8) AND "documents"."case_attachment_flag" = $9)

Found out, that these 2 parts are giving complain:

where(type: 'Document::Type')

and

.or(
  where(
    type: ['Document::Some1', 'Document::Some2'],
    case_attachment_flag: true
  )
)

And can't figure out how to rewrite it without using SQL.

Note: 'type_documents' is like document section, where are shown documents in view if in db under column 'type' document has one of these types: 'Document::Type' or 'Document::Some1' and 'Document::Some2', also last two should have that boolean flag check.
All conditions are from the same table.

Maybe you are just misunderstanding what the warning is telling you:

> DEPRECATION WARNING: Merging ("documents"."type" IN ($1, $2, $3)) and (("documents"."type" = $1 OR "documents"."type" IN ($2, $3) AND "documents"."case_attachment_flag" = $4)) no longer maintain both conditions, and will be replaced by the latter in Rails 6.2. To migrate to Rails 6.2's behavior, use `relation.merge(other, rewhere: true)

What this is actually saying is that the query can be simplified and rails will be doing that for you in the future (or now if you opt in). This does not guarantee the simplification will be the desired result as Rails will, it appears based on the warning, just assume the second condition is the intended condition.

Right now the query is:

"documents"."record_id" = $4` AND `"documents"."record_type" = $5

(these are fine)

Then you also have this condition

"documents"."type" IN ($1, $2, $3)`

This condition has no impact whatsoever (other than making the query less efficient) because "documents.type" is already further constrained by:

("documents"."type" = $6 OR 
"documents"."type" IN ($7, $8) 
AND "documents"."case_attachment_flag" = $9)

This means that:

• the documents.type must be equal to $6 (condition 1); OR
• it must be in the list of ($7, $8) AND have a case_attachment_flag equal to $9 (condition 2)

So as you can see whether or not it is in types ($1, $2, $3) does not matter it because it must pass 1 of the 2 tests above.

Rails has recognized the [possibly] contradictory conditions and is now telling you it will forfeit the first for the second going forward.

Solution was to change:

class_name: 'Document::Typed' to class_name: 'Document::Base'

then sql was what is defined in scope:

"documents"."type" = $1 OR "documents"."type" IN ($2, $3) AND "documents"."case_attachment_flag" = $4