Feature request #130: add element reference operator #[] to Mysql2::Result using mysql_data_seek.

Author: sodabrew

ext/mysql2/result.c

@@ -475,6 +475,51 @@ static void rb_mysql_row_query_options(VALUE opts, ID *db_timezone, ID *app_time
   }
 }
 
+static VALUE rb_mysql_result_element(VALUE self, VALUE seek) {
+  VALUE row, opts;
+  ID db_timezone, app_timezone;
+  long offset;
+  int symbolizeKeys, asArray, castBool, cacheRows, cast;
+  mysql2_result_wrapper * wrapper;
+
+  GetMysql2Result(self, wrapper);
+
+  offset = NUM2LONG(seek);
+
+  if (!wrapper->numberOfRows) {
+    wrapper->numberOfRows = mysql_num_rows(wrapper->result);
+  }
+
+  opts = rb_iv_get(self, "@query_options");
+  rb_mysql_row_query_options(opts, &db_timezone, &app_timezone, &symbolizeKeys, &asArray, &castBool, &cast, &cacheRows);
+
+  if (wrapper->is_streaming) {
+    rb_raise(cMysql2Error, "Element reference operator #[] cannot be used in streaming mode.");
+  }
+
+  /* count back from the end if passed a negative number */
+  if (offset < 0) {
+    offset = wrapper->numberOfRows + offset;
+  }
+
+  /* negative offset was too big */
+  if (offset < 0) {
+    return Qnil;
+    /* rb_raise(cMysql2Error, "Out of range: offset %ld is beyond %lu rows (offset begins at 0).", offset, wrapper->numberOfRows); */
+  }
+
+  if (wrapper->numberOfRows <= (unsigned long)offset) {
+    return Qnil;
+    /* rb_raise(cMysql2Error, "Out of range: offset %ld is beyond %lu rows (offset begins at 0).", offset, wrapper->numberOfRows); */
+  }
+
+  mysql_data_seek(wrapper->result, offset);
+
+  row = rb_mysql_result_fetch_row(self, db_timezone, app_timezone, symbolizeKeys, asArray, castBool, cast);
+
+  return row;
+}
+
 static VALUE rb_mysql_result_each(int argc, VALUE * argv, VALUE self) {
   VALUE defaults, opts, block;
   ID db_timezone, app_timezone;
@@ -634,6 +679,7 @@ void init_mysql2_result() {
   cDateTime = rb_const_get(rb_cObject, rb_intern("DateTime"));
 
   cMysql2Result = rb_define_class_under(mMysql2, "Result", rb_cObject);
+  rb_define_method(cMysql2Result, "[]", rb_mysql_result_element, 1);
   rb_define_method(cMysql2Result, "each", rb_mysql_result_each, -1);
   rb_define_method(cMysql2Result, "fields", rb_mysql_result_fetch_fields, 0);
   rb_define_method(cMysql2Result, "count", rb_mysql_result_count, 0);

spec/mysql2/result_spec.rb

@@ -90,6 +90,37 @@
     end
   end
 
+  context "#[]" do
+    it "should return results when accessed by [offset]" do
+      result = @client.query "SELECT 1 UNION SELECT 2"
+      result[1][result.fields.first].should eql(2)
+      result[0][result.fields.first].should eql(1)
+    end
+
+    it "should return results when accessed by negative [offset]" do
+      result = @client.query "SELECT 1 UNION SELECT 2"
+      result[-1][result.fields.first].should eql(2)
+      result[-2][result.fields.first].should eql(1)
+    end
+
+    it "should return nil if we use too large [offset]" do
+      result = @client.query "SELECT 1 UNION SELECT 2"
+      result[2].should be_nil
+      result[200].should be_nil
+    end
+
+    it "should return nil if we use too negative [offset]" do
+      result = @client.query "SELECT 1 UNION SELECT 2"
+      result[-3].should be_nil
+      result[-300].should be_nil
+    end
+
+    it "should throw an exception if we use an [offset] in streaming mode" do
+      result = @client.query "SELECT 1 UNION SELECT 2", :stream => true
+      expect { result[0] }.to raise_exception(Mysql2::Error)
+    end
+  end
+
   context "#fields" do
     before(:each) do
       @test_result = @client.query("SELECT * FROM mysql2_test ORDER BY id DESC LIMIT 1")