web2py auto_import vs define_table

Question

The documentation we can use auto_import if we "need access to the data but not to he web2py table attributes", but this code seems to use the table attributes just fine.

from gluon import DAL, Field

db = DAL('sqlite://storage.sqlite', auto_import=True)
for row in db(db.person).select():
    print row.name

The table was defined in a previous run.

db = DAL('sqlite://storage.sqlite', auto_import=True)
db.define_table('person',
                Field('name'))
db.person[0] = {'name' : 'dave'}
db.commit()

Doing both auto_import=True and the define_table gives an error about "invalid table name". Doing neither gives an error if I try to access db.table.

Answer 1

With auto_import=True, web2py will get the field names and types directly from the *.table files in the application's "databases" folder. When the documentation refers to "web2py table attributes" that will not be available, it is referring to attributes that are defined in the model (i.e., using db.define_table()) but not stored in the database or *.table files, such as "requires", "widget", "represent", etc. Those attributes are defined only in web2py code and therefore cannot be determined merely by reading the *.table files. Note, the *.table files are used for database migrations, so they only store metadata directly relevant to the database (i.e., field names and types, and database-level contraints, such as "notnull" and "unique"). Attributes like "requires" and "represent" are only used by web2py and have no effect on the database, so are not recorded in the *.table files.