rails: can't add a new key into hash during iteration lib/active_record/connection_adapters/abstract/query_cache.rb

Steps to reproduce

Since it is caching problem, it is tricky to reproduce

Expected behavior

No error

Actual behavior

backlog from the first case:

gems/activerecord-6.1.0.rc1/lib/active_record/connection_adapters/abstract/query_cache.rb:54:in `block in initialize': can't add a new key into hash during iteration (RuntimeError)
    from gems/activerecord-6.1.0.rc1/lib/active_record/connection_adapters/abstract/query_cache.rb:111:in `block in cache_sql'
    from gems/activesupport-6.1.0.rc1/lib/active_support/concurrency/load_interlock_aware_monitor.rb:26:in `block (2 levels) in synchronize'
    from gems/activesupport-6.1.0.rc1/lib/active_support/concurrency/load_interlock_aware_monitor.rb:25:in `handle_interrupt'
    from gems/activesupport-6.1.0.rc1/lib/active_support/concurrency/load_interlock_aware_monitor.rb:25:in `block in synchronize'
    from gems/activesupport-6.1.0.rc1/lib/active_support/concurrency/load_interlock_aware_monitor.rb:21:in `handle_interrupt'
    from gems/activesupport-6.1.0.rc1/lib/active_support/concurrency/load_interlock_aware_monitor.rb:21:in `synchronize'
    from gems/activerecord-6.1.0.rc1/lib/active_record/connection_adapters/abstract/query_cache.rb:109:in `cache_sql'
    from gems/activerecord-6.1.0.rc1/lib/active_record/connection_adapters/abstract/query_cache.rb:101:in `select_all'
    from gems/activerecord-6.1.0.rc1/lib/active_record/connection_adapters/mysql/database_statements.rb:12:in `select_all'
    from gems/activerecord-6.1.0.rc1/lib/active_record/relation/calculations.rb:200:in `block in pluck'
    from gems/activerecord-6.1.0.rc1/lib/active_record/relation.rb:868:in `skip_query_cache_if_necessary'
    from gems/activerecord-6.1.0.rc1/lib/active_record/relation/calculations.rb:196:in `pluck'

yet another one:

gems/activerecord-6.1.0.rc1/lib/active_record/connection_adapters/abstract/query_cache.rb:54:in `block in initialize': can't add a new key into hash during iteration (RuntimeError)
    from gems/activerecord-6.1.0.rc1/lib/active_record/connection_adapters/abstract/query_cache.rb:111:in `block in cache_sql'
    from gems/activesupport-6.1.0.rc1/lib/active_support/concurrency/load_interlock_aware_monitor.rb:26:in `block (2 levels) in synchronize'
    from gems/activesupport-6.1.0.rc1/lib/active_support/concurrency/load_interlock_aware_monitor.rb:25:in `handle_interrupt'
    from gems/activesupport-6.1.0.rc1/lib/active_support/concurrency/load_interlock_aware_monitor.rb:25:in `block in synchronize'
    from gems/activesupport-6.1.0.rc1/lib/active_support/concurrency/load_interlock_aware_monitor.rb:21:in `handle_interrupt'
    from gems/activesupport-6.1.0.rc1/lib/active_support/concurrency/load_interlock_aware_monitor.rb:21:in `synchronize'
    from gems/activerecord-6.1.0.rc1/lib/active_record/connection_adapters/abstract/query_cache.rb:109:in `cache_sql'
    from gems/activerecord-6.1.0.rc1/lib/active_record/connection_adapters/abstract/query_cache.rb:101:in `select_all'
    from gems/activerecord-6.1.0.rc1/lib/active_record/connection_adapters/mysql/database_statements.rb:12:in `select_all'
    from gems/activerecord-6.1.0.rc1/lib/active_record/querying.rb:47:in `find_by_sql'
    from gems/activerecord-6.1.0.rc1/lib/active_record/statement_cache.rb:150:in `execute'
    from gems/activerecord-6.1.0.rc1/lib/active_record/associations/association.rb:227:in `find_target'
    from gems/activerecord-6.1.0.rc1/lib/active_record/associations/collection_association.rb:274:in `load_target'
    from gems/activerecord-6.1.0.rc1/lib/active_record/associations/collection_proxy.rb:43:in `load_target'
    from gems/activerecord-6.1.0.rc1/lib/active_record/associations/collection_proxy.rb:1002:in `records'
    from gems/activerecord-6.1.0.rc1/lib/active_record/relation/delegation.rb:88:in `each'

System configuration

Rails version: 6.1.0.rc1

Ruby version: 2.5.8

Connect replaygaming/replaypoker#4860 Connect #24627