From fd3b927771e649c67aff43aff6e47a20dfd1df70 Mon Sep 17 00:00:00 2001
From: Mike Dirolf <mike@10gen.com>
Date: Fri, 21 Aug 2009 14:11:59 -0400
Subject: [PATCH] API CHANGE no longer save internal array for to_a - means you
 can't call each or to_a after calling to_a already, doc updates

---
 lib/mongo/cursor.rb | 53 ++++++++++++++-------------------------------
 lib/mongo/errors.rb |  3 +++
 test/test_db_api.rb | 17 +++++----------
 3 files changed, 24 insertions(+), 49 deletions(-)

diff --git a/lib/mongo/cursor.rb b/lib/mongo/cursor.rb
index ca55b3b..d3c9683 100644
--- a/lib/mongo/cursor.rb
+++ b/lib/mongo/cursor.rb
@@ -35,9 +35,7 @@ module Mongo
       @num_to_return = @query.number_to_return || 0
       @cache = []
       @closed = false
-      @can_call_to_a = true
       @query_run = false
-      @rows = nil
     end
 
     # Return the next object or nil if there are no more. Raises an error
@@ -75,53 +73,34 @@ module Mongo
       raise OperationFailure, "Count failed: #{response['errmsg']}"
     end
 
-    # Iterate over each object, yielding it to the given block. At most
-    # @num_to_return records are returned (or all of them, if
-    # @num_to_return is 0).
+    # Iterate over each document in this cursor, yielding it to the given
+    # block.
     #
-    # If #to_a has already been called then this method uses the array
-    # that we store internally. In that case, #each can be called multiple
-    # times because it re-uses that array.
-    #
-    # You can call #each after calling #to_a (multiple times even, because
-    # it will use the internally-stored array), but you can't call #to_a
-    # after calling #each unless you also called it before calling #each.
-    # If you try to do that, an error will be raised.
+    # Iterating over an entire cursor will close it.
     def each
-      if @rows              # Already turned into an array
-        @rows.each { |row| yield row }
-      else
-        num_returned = 0
-        while more? && (@num_to_return <= 0 || num_returned < @num_to_return)
-          yield next_object()
-          num_returned += 1
-        end
-        @can_call_to_a = false
+      num_returned = 0
+      while more? && (@num_to_return <= 0 || num_returned < @num_to_return)
+        yield next_object()
+        num_returned += 1
       end
     end
 
-    # Return all of the rows (up to the +num_to_return+ value specified in
-    # #new) as an array. Calling this multiple times will work fine; it
-    # always returns the same array.
+    # Return all of the documents in this cursor as an array of hashes.
     #
-    # Don't use this if you're expecting large amounts of data, of course.
-    # All of the returned rows are kept in an array stored in this object
-    # so it can be reused.
+    # Raises InvalidOperation if this cursor has already been used (including
+    # any previous calls to this method).
     #
-    # You can call #each after calling #to_a (multiple times even, because
-    # it will use the internally-stored array), but you can't call #to_a
-    # after calling #each unless you also called it before calling #each.
-    # If you try to do that, an error will be raised.
+    # Use of this method is discouraged - iterating over a cursor is much
+    # more efficient in most cases.
     def to_a
-      return @rows if @rows
-      raise "can't call Cursor#to_a after calling Cursor#each" unless @can_call_to_a
-      @rows = []
+      raise InvalidOperation, "can't call Cursor#to_a on a used cursor" if @query_run
+      rows = []
       num_returned = 0
       while more? && (@num_to_return <= 0 || num_returned < @num_to_return)
-        @rows << next_object()
+        rows << next_object()
         num_returned += 1
       end
-      @rows
+      rows
     end
 
     # Returns an explain plan record for this cursor.
diff --git a/lib/mongo/errors.rb b/lib/mongo/errors.rb
index 5e73312..60bd370 100644
--- a/lib/mongo/errors.rb
+++ b/lib/mongo/errors.rb
@@ -18,6 +18,9 @@ module Mongo
   # Raised when a database operation fails.
   class OperationFailure < RuntimeError; end
 
+  # Raised when a client attempts to perform an invalid operation.
+  class InvalidOperation < RuntimeError; end
+
   # Raised when an invalid name is used.
   class InvalidName < RuntimeError; end
 end
diff --git a/test/test_db_api.rb b/test/test_db_api.rb
index 7dd5bae..37e5932 100644
--- a/test/test_db_api.rb
+++ b/test/test_db_api.rb
@@ -500,25 +500,18 @@ class DBAPITest < Test::Unit::TestCase
     cursor = @@coll.find()
     rows = cursor.to_a
 
-    # Make sure we get back exactly the same array the next time we ask
-    rows2 = cursor.to_a
-    assert_same rows, rows2
+    assert_raise InvalidOperation do
+      cursor.to_a
+    end
 
-    # Make sure we can still iterate after calling to_a
-    rows_with_each = cursor.collect{|row| row}
-    assert_equal rows, rows_with_each
-
-    # Make sure we can iterate more than once after calling to_a
+    cursor.each { |doc| fail "should be no docs in each now" }
   end
 
   def test_to_a_after_each
     cursor = @@coll.find
     cursor.each { |row| row }
-    begin
+    assert_raise InvalidOperation do
       cursor.to_a
-      fail "expected \"can't call\" error"
-    rescue => ex
-      assert_equal "can't call Cursor#to_a after calling Cursor#each", ex.to_s
     end
   end