Wow. Must have completely missing this in the docs. Thank you for the sample, it definitely has helped.
I was looking through the source code and noticed internally many of the DDL elements inherit from _CreateDropBase versus DDLElement. It looks like in these cases, the element object is something like a Table object, etc. being passed in versus something like a table name. Would you say its best practice to always subclass DDLElement? I didn't know about configure_mappers() but that is good to know. Is that strictly something to be aware of if I am fully using the ORM? I ran the example using the declarative style just to build the table query (executing with an engine, not session) and it seemed to function as exactly as I had intended, but I'm not very familiar the Session object/ORM. On Wednesday, November 1, 2017 at 8:03:51 AM UTC-7, Mike Bayer wrote: > > you can use a hook like __declare_first__ to make this happen: > > class AuditMixin(object): > """created_at, updated_at, table audit mixin.""" > > @classmethod > def __declare_first__(cls): > table = getattr(cls, '__table__', None) > > if table is not None: > event.listen( > table, 'after_create', > CreateUpdateAtTrigger(table.name)) > > event.listen( > table, 'before_drop', > DropUpdateAtTrigger(table.name)) > > created_at = Column( > TIMESTAMP(timezone=True), server_default=utcnow(), nullable=False > ) > updated_at = Column( > TIMESTAMP(timezone=True), server_default=utcnow(), > server_onupdate=FetchedValue(for_update=True), nullable=False > ) > > > > however, don't go insane like I just did, and remember to call > configure_mappers() before you try to create tables, which will > trigger hooks like __declare_first__(). > > There are a lot of other hooks to set these triggers up but since you > are linking to a mixin, __declare_first__ is the simplest, but needs > the configure_mappers() step to happen for it to be called. > > also your function recipe needs a @compiles, I'm assuming you got that > from the documentation example. > > > > > On Tue, Oct 31, 2017 at 10:49 PM, Philip Martin > <[email protected] <javascript:>> wrote: > > I was trying to embed the reference code, but here is the link to the > gist I > > have so far. > > > > On Tuesday, October 31, 2017 at 7:46:30 PM UTC-7, Philip Martin wrote: > >> > >> > >> I am attempting to create an audit mixin object that would use a server > >> side column trigger to set the updated_at timestamp. Ideally, whenever > a > >> class inherits from a declarative base and this mixin class, the > trigger > >> statement would be created after the table is created and dropped prior > to > >> the table being dropped. > >> > >> So far, I have my column mixin class, AuditMixin, and I also have added > >> classes CreateUpdateAtTrigger and DropUpdateAtTrigger to compile the > trigger > >> DDL create and drop statements. From here, I am a bit unsure how to > proceed > >> to mount an event to any table's that use this mixin. Any help for > specific > >> reference examples would be appreciated. Thanks. > >> > >> > >> <script > >> src=" > https://gist.github.com/pmart123/b6681e9d9c6ddc92582143e13c1c6941.js";></script> > > > > > > -- > > SQLAlchemy - > > The Python SQL Toolkit and Object Relational Mapper > > > > http://www.sqlalchemy.org/ > > > > To post example code, please provide an MCVE: Minimal, Complete, and > > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > > description. > > --- > > 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 [email protected] <javascript:>. > > To post to this group, send email to [email protected] > <javascript:>. > > Visit this group at https://groups.google.com/group/sqlalchemy. > > For more options, visit https://groups.google.com/d/optout. > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
