Python查询oracle数据库速度慢的解决方案

conn = cx_oracle.connect('username/passWord@ip:port/servername')
cur = conn.cursor()
cur.execute('SELECT * FROM "db"."table"')

Mysql-python
    mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>
 
pymysql
    mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]
 
MySQL-Connector
    mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>
 
cx_Oracle
    oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...]

create_engine('oracle+cx_oracle://{a}:{b}@{c}:{d}/?service_name={e}'.fORMat(a,b,c,d,e))
create_engine('mysql+pymysql://%(user)s:%(password)s@%(host)s/%(database)s?charset=utf8' % laoshifu_info)
 
df = pd.read_sql_table(table_name="table_name", con=engine)  
（the function to_sql is case-sensitive，Found the root cause from DBMS (mysql) autoconvert the table name to lowercase.）
df = pd.read_sql_query(sql=sql,con=engine)  # 很慢
ordf = pd.read_sql("SELECT * FROM db.table ",engine,chunksize=50000)
dflist = []
for chunk in ordf:
    dflist.append(chunk)
df = pd.concat(dflist)

    {
        fields : [
            {name : "project_id", type : "string"},
            {name : "project_name", type : "string"}
        ],
        
        sql : "select t.project_id, t.project_name from dp_project t"
    }

    def makedict(self, cursor):
        cols = [d[0] for d in cursor.description]     
        def createrow(*args):
            return dict(zip(cols, args))     
        return createrow

   [
   ('PROJECT_ID', <;type 'cx_Oracle.STRING'>, 40, 40, 0, 0, 0), 
   ('PROJECT_NAME', <;type 'cx_Oracle.STRING'>, 50, 50, 0, 0, 1)
   ]

 cursor.rowfactory = self.makedict(cursor)

    def outtypehandler(self, cursor, name, dtype, size, p, s):
        if dtype in (oracle.STRING, oracle.FIXED_CHAR):
            return cursor.var(unicode, size, cursor.arraysize)

   connection = oracle.connect(self.constr)
   connection.outputtypehandler = self.outtypehandler