如何使用PyOrient查找OrientDB上是否存在类？

Question

怎么可能找出一个类是否存在;这允许防止'class x已经存在于当前数据库'错误消息中？

我看过以下Question，它给出了Java和SQL的答案。我正在寻找Python的等价物。

Answer 1

我创建在pyorient以下示例：

MY结构：

PyORIENT CODE：

import pyorient 

db_name = 'Stack37277880' 

print("Connecting to the server...") 
client = pyorient.OrientDB("localhost",2424) 
session_id = client.connect("root","root") 
print("OK - sessionID: ",session_id,"\n") 

if client.db_exists(db_name, pyorient.STORAGE_TYPE_PLOCAL): 
    client.db_open(db_name, "root", "root") 
    dbClasses = client.command("SELECT name FROM (SELECT expand(classes) FROM metadata:schema)") 
    newClass = "MyClass" 
    classFound = False 
    for idx, val in enumerate(dbClasses): 
     if (val.name == newClass): 
      classFound = True 
      break 
    if (classFound != True): 
     client.command("CREATE CLASS " + newClass) 
     print("Class " + newClass + " correctly created") 
    else: 
     print("Class " + newClass + " already exists into the DB") 

client.db_close() 

首次运行输出：

Connecting to the server... 
OK - sessionID: 70 

Class MyClass correctly created 

OrientDB演播室：

第二次运行输出：

Connecting to the server... 
OK - sessionID: 74 

Class MyClass already exists into the DB 

希望它可以帮助

Answer 2

您可以使用与Java示例中相同的查询。

import pyorient 

className = "MyClass" 

database = pyorient.OrientDB("localhost", 2424) 
database.db_open(
"DB_name", 
"user", 
"password" 
) 

if not database.command("SELECT FROM (SELECT expand(classes) FROM metadata:schema) WHERE name = '%s'" % className): 
    print("Create class %s" % className) 
    database.command("CREATE CLASS %s EXTENDS V" % className) 
else: 
    print("Class already exist.")