Description

Follow-up to #18092. It requires a signature change in the BaseRelationField::existsQueryCondition() method, hence targeting 5.9.

PR #18092 resolves an issue with querying an instance of the same field in a single field layout.
This PR takes that further and improves querying an instance of the same field (with the same handle) across multiple field layouts.

Steps to reproduce:

• follow the steps from multi-instance relation fields; empty/notempty querying #18092, but add a second entry type to the section; the entry type should pull in the assets field (don’t override the handle)
• add an entry using this second entry type and fill out the field
• query assets field for :empty:
  • on 5.x branch, only entry 5 is returned
  • on bugfix/multi-instance-relation-field-empty-notempty-querying branch, entries 3, 5, 6 are returned
  • correct result (result with this PR): entries 3, 5 returned
• now query for :notempty:
  • on 5.x branch, entries 1, 2, 3, 4, 6 are returned
  • on bugfix/multi-instance-relation-field-empty-notempty-querying branch, entries 1, 2, 4 are returned
  • correct result (result with this PR): entries 1, 2, 4, 6 returned

Related issues

n/a