我有一个数百万的记录SQL表,我打算使用pyarrow库写出文件夹中的许多镶木地板文件 . 数据内容似乎太大而无法存储在单个拼花文件中 .
但是,我似乎无法找到pyarrow库的API或参数,允许我指定类似的东西:
file_scheme="hive"
由fastparquet python库支持 .
这是我的示例代码:
#!/usr/bin/python
import pyodbc
import pandas as pd
import pyarrow as pa
import pyarrow.parquet as pq
conn_str = 'UID=username;PWD=passwordHere;' +
'DRIVER=FreeTDS;SERVERNAME=myConfig;DATABASE=myDB'
#----> Query the SQL database into a Pandas dataframe
conn = pyodbc.connect( conn_str, autocommit=False)
sql = "SELECT * FROM ClientAccount (NOLOCK)"
df = pd.io.sql.read_sql(sql, conn)
#----> Convert the dataframe to a pyarrow table and write it out
table = pa.Table.from_pandas(df)
pq.write_table(table, './clients/' )
这会引发错误:
File "/usr/local/lib/python2.7/dist-packages/pyarrow/parquet.py", line 912, in write_table
os.remove(where)
OSError: [Errno 21] Is a directory: './clients/'
如果我用以下内容替换最后一行,它可以正常工作,但只写一个大文件:
pq.write_table(table, './clients.parquet' )
有什么想法我怎么能用pyarrow做多文件输出的东西?
1 回答
试试
pyarrow.parquet.write_to_dataset
https://github.com/apache/arrow/blob/master/python/pyarrow/parquet.py#L938 .我打开https://issues.apache.org/jira/browse/ARROW-1858关于添加更多关于此的文档 .
我建议在邮件列表dev@arrow.apache.org上寻求对Apache Arrow的支持 . 谢谢!