PG::SyntaxError: ERROR: Error decoding result: failed to decode Protobuf message

[mhenrixon]

I originally posted this to ankane/pghero#527 but after going through the code I only had one reference to google-protobuf and that was from pg_query.

PgHero.databases[:primary].sequences

(wm):12:in '<main>': PG::SyntaxError: ERROR:  Error decoding result: failed to decode Protobuf message: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: Node.node: RawStmt.stmt: ParseResult.stmts: recursion limit reached (ActiveRecord::StatementInvalid)
/usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/postgresql/database_statements.rb:160:in 'PG::Connection#exec': ERROR:  Error decoding result: failed to decode Protobuf message: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: SelectStmt.larg: Node.node: RawStmt.stmt: ParseResult.stmts: recursion limit reached (PG::SyntaxError)
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/postgresql/database_statements.rb:160:in 'ActiveRecord::ConnectionAdapters::PostgreSQL::DatabaseStatements#perform_query'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:556:in 'block (2 levels) in ActiveRecord::ConnectionAdapters::DatabaseStatements#raw_execute'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract_adapter.rb:1015:in 'block in ActiveRecord::ConnectionAdapters::AbstractAdapter#with_raw_connection'
	from /usr/local/bundle/ruby/3.4.0/gems/activesupport-8.0.2/lib/active_support/concurrency/null_lock.rb:9:in 'ActiveSupport::Concurrency::NullLock#synchronize'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract_adapter.rb:984:in 'ActiveRecord::ConnectionAdapters::AbstractAdapter#with_raw_connection'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:555:in 'block in ActiveRecord::ConnectionAdapters::DatabaseStatements#raw_execute'
	from /usr/local/bundle/ruby/3.4.0/gems/activesupport-8.0.2/lib/active_support/notifications/instrumenter.rb:58:in 'ActiveSupport::Notifications::Instrumenter#instrument'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract_adapter.rb:1135:in 'ActiveRecord::ConnectionAdapters::AbstractAdapter#log'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:554:in 'ActiveRecord::ConnectionAdapters::DatabaseStatements#raw_execute'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:591:in 'ActiveRecord::ConnectionAdapters::DatabaseStatements#internal_execute'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:547:in 'ActiveRecord::ConnectionAdapters::DatabaseStatements#internal_exec_query'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:693:in 'ActiveRecord::ConnectionAdapters::DatabaseStatements#select'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract/database_statements.rb:73:in 'ActiveRecord::ConnectionAdapters::DatabaseStatements#select_all'
	from /usr/local/bundle/ruby/3.4.0/gems/activerecord-8.0.2/lib/active_record/connection_adapters/abstract/query_cache.rb:251:in 'ActiveRecord::ConnectionAdapters::QueryCache#select_all'
	from /usr/local/bundle/ruby/3.4.0/gems/pghero-3.7.0/lib/pghero/methods/basic.rb:49:in 'PgHero::Methods::Basic#select_all_leased'
	from /usr/local/bundle/ruby/3.4.0/gems/pghero-3.7.0/lib/pghero/methods/basic.rb:41:in 'block in PgHero::Methods::Basic#select_all'
	... 39 levels...

For some queries, pghero crashes with this error message. The one I looked into was sequences, but it seems that removing sequence handling on staging didn't help in production, so I am guessing it's something different.

All and any help debugging this would be greatly appreciated.

[lfittl]

This is likely caused by a query that has a deeply nested syntax tree. If the protobuf version is sufficiently new, the limit should be 1000 entries deep (see source), which I've never seen exceeded personally - so it seems very unlikely that's what you're running into.

It seems more likely that the google-protobuf Ruby library that pghero is using (which pg_query depends on) is outdated, so I would check that first.

For further debugging we'd need an isolated test case (i.e. reproducer that we can run without running pghero itself on your database). The basic format of that should be PgQuery.parse("SELECT 1 /* long query here */").