Wednesday 30 January 2019

using python to execute bcp to export query from remote server to local drive

I have the below python group of statements. I am using dynamic built sql statements using python. the resulting SELECT statement is then used as teh queryout statement in a bcp.

My problem is that the query itself is too large, and BCP is failing to operate it. I have confirmed that bcp works using:

BCP "Select * from <<DATABASE.dbo.TABLE>>" queryout "D:\data\test.csv" -t^ -r '0x0A' 
    -U <<USER>> -P <<PASSWORD>> -S "LIVE" -c -C65001

but if the select statement is large, the statement fails. How can I counter this? The table is large (over 100m records) and all I want to do is use the dynamic SQL to export it from a remote server to a local table.

Python Script:

def getRoster(self):
    self.conn = pyodbc.connect(self.ConnStr)
    sql = r'SELECT * FROM <<DB>>.dbo.TableConfiguration'
    self.roster = pd.read_sql(sql,self.conn)

def GenerateSQL(self, table):
    exportsql = 'select '

    columnsql = """select
                    'CASE WHEN ISNULL('+COLUMN_NAME+', '''') = '''' THEN '''' ELSE '+COLUMN_NAME+' END AS '+UPPER(COLUMN_NAME)
                    from <<DB>>.INFORMATION_SCHEMA.COLUMNS
                    where TABLE_NAME = '%s'
                    order by ORDINAL_POSITION""" % table.tablename
    self.conn = pyodbc.connect(self.ConnStr)
    cursor = self.conn.cursor()
    cursor.execute(columnsql)
    exportsql += ', '.join([field[0] for field in cursor])
    exportsql += ' from {}.dbo.{}'.format(table.dbname, table.tablename)
    exportsql += ' {}'.format(table.Clause)
    return (exportsql)

def ExportTables(self):
    now = datetime.now()
    self.getRoster()
    for row in self.roster.itertuples():
         SQL = self.GenerateSQL(row)
         self.filename = '{}_{}.csv'.format(row.tablename, now.strftime("%Y-%m-%d"))
         command = 'BCP \"{}\" queryout \"{}\" -t|| -U "<<USER>>" -P <<PASSWORD>> -S "LIVE" -T -r 0x0a -c -C65001'.format(SQL, os.path.join(self.path, self.filename))
         print (command)
         subprocess.run(command)



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