perf regression in vbench timeseries_slice_minutely  0.11.0rc1
![ts_slice_minutely](https://f.cloud.github.com/assets/1820866/377777/e061a602-a4eb-11e2-9807-bcc42fa01b4f.png)

7c51d54    0.096846
bf543f7    0.097370
0033f0a    0.106812
19d15a3    0.107574
1de6536    0.107765
