DOC: show a more informative query performance plot

Corrects the plot to show a larger range of numbers of rows to see where the
Python and NumExpr lines intersect.

Author: cpcloud

bench/bench_with_subset.py

@@ -112,5 +112,5 @@ def plot_perf(df, engines, title, filename=None):
 
     plot_perf(ev[ev.size <= 50000], engines, 'DataFrame.eval()',
               filename=join('eval-perf-small.png'))
-    plot_perf(qu[qu.size <= 100000], engines, 'DataFrame.query()',
+    plot_perf(qu[qu.size <= 500000], engines, 'DataFrame.query()',
               filename=join('query-perf-small.png'))

doc/source/_static/query-perf-small.png

@@ -969,7 +969,7 @@ large frames
 .. note::
 
    You will only see the performance benefits of using the ``numexpr`` engine
-   with ``DataFrame.query()`` if your frame has more than approximately 50,000
+   with ``DataFrame.query()`` if your frame has more than approximately 200,000
    rows
 
       .. image:: _static/query-perf-small.png