convert json to highcharts standard multiple series -

i have data db convert json following

[{"name":"partner1","cost":"311328","date":"2013-04-01"}, {"name":"partner1","cost":"363780","date":"2013-04-02"}, {"name":"partner1","cost":"364062","date":"2013-04-03"}, {"name":"partner1","cost":"283128","date":"2013-04-04"}, {"name":"partner1","cost":"322608","date":"2013-04-05"}, {"name":"partner2","cost":"425538","date":"2013-04-01"}, {"name":"partner2","cost":"263670","date":"2013-04-02"}, {"name":"partner2","cost":"213192","date":"2013-04-03"}, {"name":"partner2","cost":"378726","date":"2013-04-04"}, {"name":"partner2","cost":"532698","date":"2013-04-05"}] 

how best wat convert json data highcharta standard multiple series data?

my last resort multiple query db construct data, think comnsume server time resource.

appreciate help.

regards,

ideally you'd transform data this:

{"partner1": [   [date.utc(2013,3,1), 311328],   [date.utc(2013,3,2), 363780], ... 

note month argument javascript's date function starts 0 (january).