Not necessarily.
If you export and reimport them with the option
db.import_from_csv_file(...,id_map={}) and if the db is empty when
reimporting, everything works fine.
If you want to be able to import data in a database already populated, you
must have the UUID field. This is because web2py cannot tell if two records
are the same my simply looking at the id. In fact the database could have
been exported on a different instance with a different numbering system.
On Saturday, 14 July 2012 11:33:50 UTC-5, Alexei Vinidiktov wrote:
>
>
>
> On Monday, May 14, 2012 7:58:57 PM UTC+7, Ross Peoples wrote:
>>
>> Some databases allow you to temporarily turn off auto-generating IDs so
>> that you can import a table keeping its original IDs intact. I wrote a
>> database abstraction layer a few years back for another project that
>> specifically allowed you to make an identical copy of a database from a
>> MySQL database to a PostgreSQL database on a different machine and
>> preserving the IDs was something I needed to figure out. Here is how you do
>> it with MSSQL, MySQL, and PostgreSQL. Maybe Massimo can add this as an
>> option to the DAL's import method:
>>
>> First, import your records, then run these on your database engine:
>>
>> MSSQL:
>> db.executesql('SET IDENTITY_INSERT dbo.mytable OFF');
>> db.executesql('DBCC CHECKIDENT (mytable)');
>>
>> MySQL:
>> count = db.executesql('SELECT MAX(id) FROM mytable;')
>> count += 1
>> db.executesql('ALTER TABLE mytable AUTO_INCREMENT=%s;' % count)
>>
>> PostgreSQL:
>> count = db.executesql('SELECT MAX(id) FROM mytable;')
>> count += 1
>> db.executesql('ALTER SEQUENCE mytable_sequence RESTART WITH %s;' % count)
>>
>> For all 3 database engines, this sets the auto-increment counter to the
>> max ID it finds in the table (AFTER the import) +1 so that new rows will
>> have the proper IDs.
>>
>
> Do I understand correctly that without this addition it is impossible to
> maintain referential integrity of a database when exporting its tables as
> csv files and then importing them back?
>
