[sqlalchemy] How to (quick) check if a table exists in schema?

2012-04-25 Thread Massi
Hi everyone,

in my script I have to deal with a huge database with thousands of
tables. Given a table name (a python string) I would have to now if
such a table exists or not. Up to now I have written this function:

def DBGetTableByName(table_name) :
metadata = MetaData(engine)
try :
table = Table(table_name, metadata, autoload=True)
return table
except NoSuchTableError :
return None

I use its return value to check if the table exists, but the problem
is that it is too slow. Since I have to repeat this operation several
times I wonder if there is a faster (and smarter) way to perform this
control.
Any hints?
Thanks in advance!

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Re: [sqlalchemy] How to (quick) check if a table exists in schema?

2012-04-25 Thread Wichert Akkerman

On 04/25/2012 03:57 PM, Massi wrote:

Hi everyone,

in my script I have to deal with a huge database with thousands of
tables. Given a table name (a python string) I would have to now if
such a table exists or not. Up to now I have written this function:

def DBGetTableByName(table_name) :
 metadata = MetaData(engine)
 try :
 table = Table(table_name, metadata, autoload=True)
 return table
 except NoSuchTableError :
 return None

I use its return value to check if the table exists, but the problem
is that it is too slow. Since I have to repeat this operation several
times I wonder if there is a faster (and smarter) way to perform this
control.
Any hints?


Use the inspector:

from sqlalchemy.engine.reflection import Inspector

inspector = Inspector.from_engine(engine)
print table_name in inspector.get_table_names()

You can find the documentation here: 
http://docs.sqlalchemy.org/en/rel_0_7/core/schema.html?highlight=inspector#sqlalchemy.engine.reflection.Inspector


Wichert.

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