Python 3.x 如何使用PyOrient确定OrientDB上是否存在类？

如何才能发现类是否存在；这是否允许防止“当前数据库中已存在x类”错误消息

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我已经看到了以下内容，它们用Java和SQL给出了答案。我正在寻找与Python等效的版本。

我在

pyorient

中创建了以下示例：

我的结构：

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() 

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

Class MyClass correctly created

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

Class MyClass already exists into the DB

PyORIENT代码：

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() 

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

Class MyClass correctly created

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

Class MyClass already exists into the DB

首次运行输出：

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() 

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

Class MyClass correctly created

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

Class MyClass already exists into the DB

OrientDB Studio:

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() 

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

Class MyClass correctly created

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

Class MyClass already exists into the DB

第二次运行输出：

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() 

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

Class MyClass correctly created

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

Class MyClass already exists into the DB

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希望对您有所帮助

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.")

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如果这个功能在PyOrient中作为一个单独的功能出现，那就更酷了。我将看一看源代码，目的是将其添加到中。