Yes indeed, that does the trick. Thank you! I would kindly suggest referencing this capability from higher up on that page. It seems relevant for the section discussing that sequences associated with a table will be created/destroyed with the table, but this is the key piece of information that makes it clear *how* to achieve this association.
On Wed, Jan 27, 2016 at 11:49 AM, Simon King <si...@simonking.org.uk> wrote: > > > On 27 Jan 2016, at 18:59, Chris Macklin <chris.mack...@gmail.com> wrote: > > > > If I declare a Sequence at the class level in a model class declaration > using declarative (SQLAlchemy 0.9.10 on postgres), the sequence is not > created by create_all unless the sequence is explicitly associated with a > Column. My use case is a column which stores a URI; if a row is inserted > which already has a URI, it is passed in. If an insert doesn't come with a > URI, we need to mint a new one, and thus call a default function which > retrieves the next value of a sequence that is exclusively used for minting > these URIs, and appends it to a namespace before adding that value to the > column. Thus, the sequence isn't actually associated with a column, but > should still be table-level and created/destroyed when the table is added > or dropped. > > > > All of the workarounds I've found so far are somewhat distasteful: > > - creating a dummy table, associating the sequence with a column in that > table, and never inserting into it (not great as the sequence is detached > from the table it is logically associated with, plus the chaff of a totally > meaningless table sitting in my db) > > - manually calling create on the sequence with the engine; this doesn't > really work, as all of this code is sitting in a larger framework in which > sqlalchemy is executing and it would require significant alterations to the > framework to pass these sequences all the way out to the top level where > create_all is called. > > > > Any suggestions? Am I missing something obvious here? > > According to: > > > http://docs.sqlalchemy.org/en/rel_1_0/core/defaults.html#sqlalchemy.schema.Sequence.params.metadata > > “”” > Additionally, the appropriate CREATE SEQUENCE/ DROP SEQUENCE DDL commands > will be emitted corresponding to this Sequence when MetaData.create_all() > andMetaData.drop_all() are invoked. > “”” > > For this to work, the Sequence needs to be attached to the Metadata, which > you can access as Base.metadata. > > Does that make any difference? > > Simon > > -- > You received this message because you are subscribed to a topic in the > Google Groups "sqlalchemy" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/sqlalchemy/zwz1grNHNio/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > sqlalchemy+unsubscr...@googlegroups.com. > To post to this group, send email to sqlalchemy@googlegroups.com. > Visit this group at https://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
