Python 数据库连接：值错误：<cx_Oracle.LOB object at 0x000001CB4819E5A0> 不是 unicode 或序列

Question

Hey I am pulling a date field from Oracle DB using the cx_Oracle module. The redacted query and connection module are:

def getInitialData():   
    print("Gathering... ")     
    dsn_tns = cx_Oracle.makedsn('xyz.com', '1234', service_name='DB')
    conn = cx_Oracle.connect(user=r'me', password='password', dsn=dsn_tns) 
    SQLquery = ("""
SELECT REPORTDATE, 

FROM LONGDESCRIPTION 
WHERE 
       REPORTDATE > TO_DATE('01/01/2015 0:00:00', 'MM/DD/YYYY HH24:MI:SS'))""") 
    datai = pd.read_sql(SQLquery, conn)
    datai['REPORTDATE'] = pd.to_datetime(datai['REPORTDATE'], format='%m-%d-%Y')
    print("Data Retrieved")
    return datai

However, when I try to manipulate this later via:

writer = index.writer()
print("Adding Data, this may take a moment... ")
for i in range(len(initialData)):      
    writer.add_document(docId=initialData.iloc[i]['CONTENTUID'], \
                        content=initialData.iloc[i]['LOWER(LDTEXT)'], \
                        date=initialData.iloc[i]['REPORTDATE'])
writer.commit()

I get:

ValueError: <cx_Oracle.LOB object at 0x000001CB4819E5A0> is not unicode or sequence

Has anyone seen this error? Nothing in documentation/Google about it. How does it happen? It is weird to me because I am able to get this to work using a different datefield. Both show dtype of datetime64[ns]

Answer 1

Since this is a data conversion issue, knowing the character sets in use would have been useful info.

Some thoughts:

1. Set the character set when you connect. Use the appropriate character set for your data.:

    connection = cx_Oracle.connect(connectString, encoding="UTF-8", nencoding="UTF-8")

   You only need to use nencoding if you have NCHAR / NVARCHAR / NCLOB columns.

2. For 'small' LOBs (that are < 1GB and fit in cx_Oracle memory), you probably want to fetch them directly as strings , since this is faster. Add a type handler:

    def OutputTypeHandler(cursor, name, defaultType, size, precision, scale): if defaultType == cx_Oracle.CLOB: return cursor.var(cx_Oracle.LONG_STRING, arraysize=cursor.arraysize) if defaultType == cx_Oracle.BLOB: return cursor.var(cx_Oracle.LONG_BINARY, arraysize=cursor.arraysize)

3. Check if you have corrupted data that can't be handled in the character sets.