尝试以下代码
alerts = df.read_sql_table('alerts', db_url, index_col='id', npartitions=16)
我收到以下错误：
TypeError Traceback (most recent call last)
<ipython-input-67-d14f44b5a2c5> in <module>()
----> 1 alerts = df.read_sql_table('alerts', db_url, index_col='id', npartitions=16)
/home/avlach/virtualenvs/dask/local/lib/python2.7/site-packages/dask/dataframe/io/sql.pyc in read_sql_table(table, uri, index_col, divisions, npartitions, limits, columns, bytes_per_chunk, **kwargs)
121 divisions[-1] = maxi
122 else:
--> 123 divisions = np.linspace(mini, maxi, npartitions + 1).tolist()
124
125 parts = []
/home/avlach/virtualenvs/dask/local/lib/python2.7/site-packages/numpy/core/function_base.pyc in linspace(start, stop, num, endpoint, retstep, dtype)
106 # Convert float/complex array scalars to float, gh-3504
107 # and make sure one can use variables that have an __array_interface__, gh-6634
--> 108 start = asanyarray(start) * 1.0
109 stop = asanyarray(stop) * 1.0
110
TypeError: unsupported operand type(s) for *: 'NoneType' and 'float'
数据库架构如下：
describe alerts;
+-------------------+----------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------------+----------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| description | text | NO | | NULL | |
| channel_id | int(11) | NO | MUL | NULL | |
| score | float | NO | | NULL | |
| raised_at | datetime | YES | | NULL | |
| updated_at | datetime | YES | | NULL | |
| activity_earliest | datetime | NO | | NULL | |
| activity_latest | datetime | NO | | NULL | |
+-------------------+----------+------+-----+---------+----------------+
8 rows in set (0,00 sec)
我无法理解错误。表现在是空的。