Switch default connection pool to timed_queue on Ruby 3.2+

The timed_queue connection pool was already the default on Ruby
3.4+.  However, recent discussions have shown that it is much
better than the threaded connection pool, at least in cases where
a sampling profiler is used.

This should be a drop-in replacement for most applications. However,
the timed_queue connection pool does not support the
available_connections and allocated accessors that the threaded
connection pool supports.  Those accessors are planned for removal
in Sequel 6, but are not formally deprecated yet.  Applications
that are using those accessors should either stop, or specify
pool_class: :threaded to continue using the threaded connection
pool.

CHANGELOG

@@ -1,3 +1,7 @@
+=== master
+
+* Switch default connection pool to timed_queue on Ruby 3.2+ (jeremyevans)
+
 === 5.84.0 (2024-09-01)
 
 * Support creating VIRTUAL tables on SQLite via the create_table :using option (jeremyevans)

lib/sequel/connection_pool.rb

@@ -70,13 +70,13 @@ def connection_pool_class(opts)
       else
         pc = if opts[:single_threaded]
           opts[:servers] ? :sharded_single : :single
-        # :nocov:
-        elsif RUBY_VERSION >= '3.4' # SEQUEL6 or maybe earlier switch to 3.2
+        elsif RUBY_VERSION >= '3.2'
           opts[:servers] ? :sharded_timed_queue : :timed_queue
         # :nocov:
         else
           opts[:servers] ? :sharded_threaded : :threaded
         end
+        # :nocov:
 
         connection_pool_class(:pool_class=>pc)
       end

spec/core/connection_pool_spec.rb

@@ -1271,12 +1271,12 @@ def @pool.acquire(_,_=nil) raise Sequel::DatabaseDisconnectError; end
     Sequel::ConnectionPool.send(:get_pool, db, :single_threaded=>true, :servers=>{}).pool_type.must_equal :sharded_single
   end
 
-  it "should default to :single without :single_threaded or :servers" do
-    Sequel::ConnectionPool.send(:get_pool, db, {}).pool_type.must_equal(RUBY_VERSION >= '3.4' ? :timed_queue : :threaded)
+  it "should default to :timed_queue/:threaded without :single_threaded or :servers" do
+    Sequel::ConnectionPool.send(:get_pool, db, {}).pool_type.must_equal(RUBY_VERSION >= '3.2' ? :timed_queue : :threaded)
   end
 
-  it "should default to :single without :single_threaded with :servers" do
-    Sequel::ConnectionPool.send(:get_pool, db, :servers=>{}).pool_type.must_equal(RUBY_VERSION >= '3.4' ? :sharded_timed_queue : :sharded_threaded)
+  it "should default to :sharded_timed_queue/:sharded_threaded without :single_threaded with :servers" do
+    Sequel::ConnectionPool.send(:get_pool, db, :servers=>{}).pool_type.must_equal(RUBY_VERSION >= '3.2' ? :sharded_timed_queue : :sharded_threaded)
   end
 end unless ENV['SEQUEL_DEFAULT_CONNECTION_POOL']