all of this instead of migrate=False
where you know a table already exist ????? On Thursday, July 26, 2012 5:23:50 PM UTC+2, Chris wrote: > > I've found what seems a simple way to let multiple apps share a DB and > create the same table definitions without conflict. Chris, you may find > this useful and also I'd love to hear from the true experts if there are > problems with this approach. (It works for me but maybe there are other > implications). > > Step 1, be sure that each application is applying the exact same table > definition / structure (by defining in a module that all apps import or > whatnot). There isn't any table-sharing approach that will work right if > two different applications are competing violently to change the schema > over and over. > > Step 2, have all the subsystems share a single directory where the *.table > files are stored. The usual behavior is that each app has its own store of > *.table files in its own app-local ./databases directory. The problem with > conflicting table creates happens, as far as I can tell, when a table > already exists but there is no corresponding table-definition file in the > app's own local ./databases directory. In web2py / gluon / dal.py / > BaseAdapter / create_table(), the logic that determines the location and > name of the table-definition file looks like this (in web2py version > 1.99.7): > > ## at line 697 > dbpath = self.folder > ## e.g. /path/to/web2py/applications/appname/databases > > ## at line 706 > table._dbt = os.path.join(dbpath, '%s_%s.table' % > (table._db._uri_hash,tablename > )) > ## e.g. > /path/to/web2py/applications/appname/databases/51bd584ac1754de09bdf0aac5438df72_tablename.table > > In other words, the path is derived from the app name (and is below the > app directory), and the file name is derived from the DB URI + table name. > > To allow multiple apps to share table-definition files, you could either > change DAL code to point to a different folder that doesn't differ per app > (maybe under web2py or web2py/private), or you could leave DAL alone and > use symbolic links to make all the ./databases folders point to the same > place. > > What I've done is create a web2py / applications / databases folder that > isn't really an app (isn't mentioned in routes.py and so on), then for each > app: > > ## on OSX 10.7.3, may differ on other OS's > ln -s /path/to/web2py/applications/databases /path/to/web2py/applications/ > someapp/databases > > > (Note no trailing "/" on either of the paths.) This allows DAL to > continue as usual, but all apps are reading & writing the same set of table > definition files. > > There are some tradeoffs between doing this in DAL and doing via > symlinks. If you do it via DAL, then there are no additional steps to > configuring your app other than deploying the right source files, and you > don't rely on having an OS that supports symlinks -- although that's a > smaller issue than it used to be now that Windows Vista supports symlinks; > however this approach does mean a source code change, that you would need > to keep track of over web2py releases, and might obligate you to publish > the code and so on for licensing reasons. Also if you do it via DAL, if > you want different subsets of apps in a single web2py instance to share > DBs differently (i.e. it's not all-or-none), you would have to add logica > saying which shared directories are for which apps, via a configuration > file or whatever. If you do it via symlinks, then you don't have to change > source code, you can decide which apps share table definitions or not by > which app directories you point to which shared directories -- but you have > to know how to make these changes as you move code between machines, > changing deployment from a "drop the files in" approach to "... then run > these scripts", which is probably a matter of taste. > > In any case, once I have apps sharing a folder for table-definition files, > this problem goes away. > > > > On Monday, June 27, 2011 2:22:57 PM UTC-4, Christopher Baron wrote: >> >> Hi web2py users, >> >> Just upgraded to Version 1.97.1 >> >> I checked my code out into the new directory, opened my browser, and >> received and error stating 'auth_cas' already exists. >> >> I removed all files from the databases folder and tried again >> receiving an error that 'auth_user' already exists. >> >> I'm using a private/config file that points to some mysql database on >> another server. >> >> What can I do ? >> >> I'd be happy to share more information needed to help solve the >> problem. >> >> Thanks in advance, >> >> Chris > > --
