Drop checkout_some, simpler pool_prepared statement

src/db/pool.cr

@@ -158,27 +158,6 @@ module DB
       end
     end
 
-    # ```
-    # selected, is_candidate = pool.checkout_some(candidates)
-    # ```
-    # `selected` be a resource from the `candidates` list and `is_candidate` == `true`
-    # or `selected` will be a new resource and `is_candidate` == `false`
-    def checkout_some(candidates : Enumerable(WeakRef(T))) : {T, Bool}
-      sync do
-        candidates.each do |ref|
-          resource = ref.value
-          if resource && is_available?(resource)
-            @idle.delete resource
-            resource.before_checkout
-            return {resource, true}
-          end
-        end
-      end
-
-      resource = checkout
-      {resource, candidates.any? { |ref| ref.value == resource }}
-    end
-
     def release(resource : T) : Nil
       idle_pushed = false
 

src/db/pool_prepared_statement.cr

@@ -5,74 +5,22 @@ module DB
   #
   # See `PoolStatement`
   class PoolPreparedStatement < PoolStatement
-    # connections where the statement was prepared
-    @connections = Set(WeakRef(Connection)).new
-    @mutex = Mutex.new
-
     def initialize(db : Database, query : String)
       super
-      # Prepares a statement on some connection
-      # otherwise the preparation is delayed until the first execution.
-      # After the first initialization the connection must be released
-      # it will be checked out when executing it.
-
-      # This only happens if the db is configured to use prepared statements cache.
-      # Without that there is no reference to the already prepared statement we can
-      # take advantage of.
-      if db.prepared_statements_cache?
-        statement_with_retry &.release_connection
-      end
-
-      # TODO use a round-robin selection in the pool so multiple sequentially
-      #      initialized statements are assigned to different connections.
     end
 
     protected def do_close
-      @mutex.synchronize do
-        # TODO close all statements on all connections.
-        # currently statements are closed when the connection is closed.
-
-        # WHAT-IF the connection is busy? Should each statement be able to
-        # deallocate itself when the connection is free.
-        @connections.clear
-      end
     end
 
     # builds a statement over a real connection
-    # the connection is registered in `@connections`
     private def build_statement : Statement
-      clean_connections
-
-      conn, existing = @mutex.synchronize do
-        @db.checkout_some(@connections)
-      end
-
+      conn = @db.pool.checkout
       begin
-        stmt = conn.prepared.build(@query)
+        conn.prepared.build(@query)
       rescue ex
         conn.release
         raise ex
       end
-      if !existing && @db.prepared_statements_cache?
-        @mutex.synchronize do
-          @connections << WeakRef.new(conn)
-        end
-      end
-      stmt
-    end
-
-    private def clean_connections
-      return unless @db.prepared_statements_cache?
-
-      @mutex.synchronize do
-        # remove disposed or closed connections
-        @connections.each do |ref|
-          conn = ref.value
-          if !conn || conn.closed?
-            @connections.delete ref
-          end
-        end
-      end
     end
   end
 end