UnboundLocalError Returned for dataframe filters that have no results

[blaklaybul]

If the query returns no results, the following Exception is thrown. This should result in returning an empty dataframe.

eland

>>> df2 = ed.read_es('localhost:9200', 'ecommerce')
>>> df2[df2['currency']=='USD']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/michael/projects/eland/eland/dataframe.py", line 273, in __repr__
    line_width=width, show_dimensions=show_dimensions)
  File "/Users/michael/projects/eland/eland/dataframe.py", line 662, in to_string
    line_width=line_width)
  File "/Users/michael/projects/eland/venv/lib/python3.7/site-packages/pandas/core/frame.py", line 759, in to_string
    line_width=line_width,
  File "/Users/michael/projects/eland/venv/lib/python3.7/site-packages/pandas/io/formats/format.py", line 502, in __init__
    self._chk_truncate()
  File "/Users/michael/projects/eland/venv/lib/python3.7/site-packages/pandas/io/formats/format.py", line 525, in _chk_truncate
    n_add_rows = self.header + dot_row + show_dimension_rows + prompt_row
UnboundLocalError: local variable 'show_dimension_rows' referenced before assignment

pandas

>>> pdf = ed.eland_to_pandas(df2)
>>> pdf[pdf['currency']=='USD']
Empty DataFrame
Columns: [category, currency, customer_birth_date, customer_first_name, customer_full_name, customer_gender, customer_id, customer_last_name, customer_phone, day_of_week, day_of_week_i, email, geoip.city_name, geoip.continent_name, geoip.country_iso_code, geoip.location, geoip.region_name, manufacturer, order_date, order_id, products._id, products.base_price, products.base_unit_price, products.category, products.created_on, products.discount_amount, products.discount_percentage, products.manufacturer, products.min_price, products.price, products.product_id, products.product_name, products.quantity, products.sku, products.tax_amount, products.taxful_price, products.taxless_price, products.unit_discount_amount, sku, taxful_total_price, taxless_total_price, total_quantity, total_unique_products, type, user]
Index: []

[blaklaybul]

this is a nasty bug that results from https://github.com/pandas-dev/pandas/blob/547f128eff607479c0fcda4b363595303b6272c8/pandas/io/formats/format.py#L620.

Essentially, when we encounter an empty dataframe, we pass max_rows=0 over to pandas formatting. Since we handle printing dimensions in eland, we also initially pass show_dimensions=False. This combination results in unexpected behavior in pandas.