Handle usage of on_duplicate_key_update in MySQL prepared statements (F…

…ixes jeremyevans#404)

This fixes a general class of bug where columns was called by
the dataset literalization code when using prepared statements.
The columns call would call the prepared statement literalization
to recurse, usually leading to a SystemStackError or a
NoMemoryError.

The fix is fairly simple.  Prepared statements now have a link to
the dataset that created them, and calling columns on a prepared
statement is now delegated to the dataset that prepared it.

lib/sequel/dataset/prepared_statements.rb

@@ -63,6 +63,9 @@ module PreparedStatementMethods
       # The array/hash of bound variable placeholder names.
       attr_accessor :prepared_args
 
+      # The dataset that created this prepared statement.
+      attr_accessor :orig_dataset
+
       # The argument to supply to insert and update, which may use
       # placeholders specified by prepared_args
       attr_accessor :prepared_modify_values
@@ -72,6 +75,12 @@ module PreparedStatementMethods
       def call(bind_vars={}, &block)
         bind(bind_vars).run(&block)
       end
+
+      # Send the columns to the original dataset, as calling it
+      # on the prepared statement can cause problems.
+      def columns
+        orig_dataset.columns
+      end
 
       # Returns the SQL for the prepared statement, depending on
       # the type of the statement and the prepared_modify_values.
@@ -244,6 +253,7 @@ def prepare(type, name=nil, *values)
     def to_prepared_statement(type, values=nil)
       ps = bind
       ps.extend(PreparedStatementMethods)
+      ps.orig_dataset = self
       ps.prepared_type = type
       ps.prepared_modify_values = values
       ps

spec/adapters/mysql_spec.rb

@@ -247,6 +247,16 @@ def logger.method_missing(m, msg)
 
     @d.first[:name].should == ':\\'
   end
+
+  specify "should handle prepared statements with on_duplicate_key_update" do
+    @d.db.add_index :items, :value, :unique=>true
+    ds = @d.on_duplicate_key_update
+    ps = ds.prepare(:insert, :insert_user_id_feature_name, :value => :$v, :name => :$n)
+    ps.call(:v => 1, :n => 'a')
+    ds.all.should == [{:value=>1, :name=>'a'}]
+    ps.call(:v => 1, :n => 'b')
+    ds.all.should == [{:value=>1, :name=>'b'}]
+  end
 end
 
 describe "MySQL datasets" do

spec/core/dataset_spec.rb

@@ -3066,6 +3066,13 @@ class ::InspectDataset < Sequel::Dataset; end
     @db.sqls.should == ['SELECT * FROM items WHERE (num = 1)']
   end
 
+  specify "should handle columns on prepared statements correctly" do
+    @db.columns = [:num]
+    @ds.meta_def(:select_where_sql){|sql| super(sql); sql << " OR #{columns.first} = 1" if opts[:where]}
+    @ds.filter(:num=>:$n).prepare(:select, :sn).sql.should == 'SELECT * FROM items WHERE (num = $n) OR num = 1'
+    @db.sqls.should == ['SELECT * FROM items LIMIT 1']
+  end
+
   specify "should handle datasets using static sql and placeholders" do
     @db["SELECT * FROM items WHERE (num = ?)", :$n].call(:select, :n=>1)
     @db.sqls.should == ['SELECT * FROM items WHERE (num = 1)']