Leading SQL comments bypass proxy routing classification

[OskarEichler]

Describe the bug
Rails query-log tags and other leading SQL comments prevent the proxy from recognizing the statement at the start of the SQL string. A tagged SELECT can therefore be sent to the primary, and tagged SET, SET LOCAL, and write statements can be classified incorrectly.

Steps to reproduce

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'

  gem 'activerecord', '8.1.3.1'
  gem 'active_record_proxy_adapters', '0.11.1'
end

require 'active_record_proxy_adapters'

DbConfig = Struct.new(:name)
Pool = Struct.new(:db_config)
Connection = Struct.new(:pool)
connection = Connection.new(Pool.new(DbConfig.new('primary')))
proxy = ActiveRecordProxyAdapters::PrimaryReplicaProxy.new(connection)

sql = '/*application:api*/ SELECT 1'
normalized = proxy.send(:coerce_query_to_string, sql)
p normalized
p proxy.send(:need_primary?, normalized)

No database connection is required to reproduce the classification result.

Expected behavior

Leading whitespace and comments are ignored for routing. The normalized statement is SELECT 1, and need_primary? returns false so the read can use the replica.

Actual behavior

The normalized statement remains /*application:api*/ SELECT 1, and need_primary? returns true because no read matcher recognizes it.

System configuration

Active Record version: 8.1.3.1
Active Record proxy adapters version: 0.11.1
Ruby version: 4.0.6