no DBAPI I've tested does it, at most it would only be possible for PG, SQL Server dialects.
On Mar 27, 2014, at 2:30 AM, Cosmia Luna <cosm...@gmail.com> wrote: > Wow, I didn't know that... is it a bug? > > But, the RETURNING clause will work though :) > > stmt = P.__table__.insert(returning=[P.id], values=[{"val": 1}, {"val": 2}]) > with engine.connect() as conn: > result = conn.execute(stmt) > # do something with result > > hmm, maybe perfomance suffers from huge-size-SQL...... well, which I didn't > test > > Cosmia > > On Monday, March 24, 2014 9:39:51 PM UTC+8, Michael Bayer wrote: > RETURNING doesn't work with DBAPI's "executemany" style of execution, > however, which is what conn.execute(stmt, [list of parameter sets]) calls. > > > > On Mar 24, 2014, at 5:33 AM, Cosmia Luna <cos...@gmail.com> wrote: > >> INSERT statement of postgresql supports RETURNING, read this >> http://docs.sqlalchemy.org/en/rel_0_8/core/dml.html#sqlalchemy.sql.expression.Insert.returning >> >> On Monday, March 24, 2014 2:43:46 PM UTC+8, James Meneghello wrote: >> Oops, I should add - the reason I can't use an itertools counter to >> pre-assign IDs is because the table is potentially being dumped to by >> multiple scripts, which is why I have to commit the parts prior to the >> segments (since engine.execute can't return multiple insert_ids). >> >> On Monday, 24 March 2014 14:40:52 UTC+8, James Meneghello wrote: >> Thanks for the quick reply! >> >> This seems to work pretty well. I took out the batching (as it's already >> batched at a higher level) and modified it to suit the insertion of children >> as well (and reducded the unique to a single field) , and it appears to work. >> >> with db_session() as db: >> existing_entries = dict( >> ((entry.subject, entry) for entry in >> >> db.query(Entry).filter(Entry.subject.in_(entries.keys())).options(subqueryload('segments')).all() >> ) >> ) >> >> segment_inserts = [] >> for subject, entry in entries.items(): >> existing_entry = existing_entries.get(subject, None) >> if existing_entry: >> segments = dict(((s.segment, s) for s in >> existing_entry.segments)) >> for segment_number, segment in entry['segments'].items(): >> if int(segment_number) not in segments: >> segment['entry_id'] = existing_entry.id >> segment_inserts.append(segment) >> else: >> entry_id = engine.execute(Entry.__table__.insert(), >> entry).inserted_primary_key >> for segment in entry['segments'].values(): >> segment['entry_id'] = entry_id[0] >> segment_inserts.append(segment) >> >> engine.execute(Segment.__table__.insert(), segment_inserts) >> >> For 20,000 segments, this ends up being about 45 seconds and 1650 queries - >> 2 to select all the entries and segments, 1 to insert the segments and the >> rest to insert parts. From here, however, I rewrote it a bit: >> >> with db_session() as db: >> existing_entries = dict( >> ((entry.subject, entry) for entry in >> >> db.query(Entry).filter(Entry.subject.in_(entries.keys())).all() >> ) >> ) >> >> entry_inserts = [] >> for subject, entry in entries.items(): >> existing_entry = existing_entries.get(subject, None) >> if not existing_entry: >> entry_inserts.append(entry) >> >> engine.execute(Entry.__table__.insert(), entry_inserts) >> >> existing_entries = dict( >> ((entry.subject, entry) for entry in >> >> db.query(Entry).filter(Entry.subject.in_(entries.keys())).options(subqueryload('segments')).all() >> ) >> ) >> >> segment_inserts = [] >> for subject, entry in entries.items(): >> existing_entry = existing_entries.get(subject, None) >> if existing_entry: >> segments = dict(((s.segment, s) for s in >> existing_entry.segments)) >> for segment_number, segment in entry['segments'].items(): >> if int(segment_number) not in segments: >> segment['entry_id'] = existing_entry.id >> segment_inserts.append(segment) >> else: >> log.error('i\'ve made a huge mistake') >> >> engine.execute(Segment.__table__.insert(), segment_inserts) >> >> This ends up being about 19 seconds, 6 queries for a clean dump, and a bit >> less if the table is already populated. Removing the unique indexes on both >> the entries and segments tables and replacing them with standard indexes >> saves about a second in a full dump, and about 6 seconds for an update. I'm >> pretty happy with where it is now, and I suspect most of the time (aside >> from the two insert calls) is being spent in Python. That said, if you have >> any tips for improvements I'd be all ears. >> >> Thanks for the help! >> >> On Monday, 24 March 2014 09:19:25 UTC+8, Michael Bayer wrote: >> >> On Mar 23, 2014, at 11:33 AM, James Meneghello <muro...@gmail.com> wrote: >> >>> I'm having a few issues with unique constraints and bulk inserts. The >>> software I'm writing takes data from an external source (a lot of it, >>> anywhere from 1,000 rows per minute to 100-200k+), crunches it down into >>> its hierarchy and saves it to the DB, to be aggregated in the background. >>> The function handling the initial DB save is designed to work with about >>> 20-50k rows at a time - very little modification takes place, it's pretty >>> much just grabbed and thrown into the table. Obviously the amount of data >>> being saved somewhat excludes the use of the ORM in this particular table, >>> but there are a number of other tables that benefit from using the ORM. >>> Hence, the small stuff uses the ORM and the big stuff uses the Core. >>> >>> The main problem I'm having is with the initial save. The data comes in >>> unordered and sometimes contains duplicates, so there's a UniqueConstraint >>> on Entry on sub, division, created. Unfortunately, this hampers the bulk >>> insert - if there's a duplicate, it rolls back the entire insert and hence >>> the entries aren't available to be referenced by the segments later. >>> Obviously, capturing it in a try/catch would skip the whole block as well. >>> Both Entry and Segment have the same problem - there are often duplicate >>> segments. Since there's a large amount of data being pushed through it, I >>> assume it's impractical to insert the elements individually - while there's >>> only 100-200 entries per block, there's usually 20-50k segments. >>> >>> Is there any way of forcing the engine to skip over duplicates and not >>> rollback the transaction on exception? Code's below. Using Postgres, with >>> psycopg2 as the driver. >>> >>> >>> engine.execute(Entry.__table__.insert(), entries) >>> >>> segment_list = [] >>> for sub, entry in entry.items(): >>> segments = entry.pop('segments') >>> >>> e = db.query(Entry)\ >>> .filter(Entry.sub==entry['sub'])\ >>> .filter(Entry.division==entry['division'])\ >>> .filter(Entry.created==entry['created']).first() >>> >>> for segment in segments: >>> segment['entry_id'] = e.id >>> segment_list.append(segment) >>> >>> engine.execute(Segment.__table__.insert(), segment_list) >> >> >>> >>> In addition, is there some way to pre-fetch data? Rather than query for >>> each Entry, it'd be nice to pre-load all entries and save a couple hundred >>> queries. >> >> you have all the entries in segment_list. Seems like you'd just want to >> dedupe entries as they enter that list, that's a pretty simple thing to do >> with a dictionary. but additionally you're also emitting a SELECT for >> every item individually so whatever time you're saving on that INSERT is >> just being expended with that huge number of SELECT statements anyway. >> >> so yes you certainly want to pre-load everything, since the criteria here is >> three different things you can use a tuple-based IN clause. >> >> below is an example that uses this and also batches so that it won't run out >> of memory under any circumstances, it starts with 50K rows in the database >> and then adds another 50K with 20K overlapping. the whole thing runs in >> about 28 seconds on my mac. >> >> from sqlalchemy import * >> from sqlalchemy.orm import * >> from sqlalchemy.ext.declarative import declarative_base >> import random >> import itertools >> >> Base = declarative_base() >> >> class Entry(Base): >> __tablename__ = 'a' >> >> id = Column(Integer, primary_key=True) >> sub = Column(Integer) >> division = Column(Integer) >> created = Column(Integer) >> __table_args__ = (UniqueConstraint('sub', 'division', 'created'), ) >> >> e = create_engine("postgresql://scott:tiger@localhost/test", echo=True) >> Base.metadata.drop_all(e) >> Base.metadata.create_all(e) >> >> >> a_bunch_of_fake_unique_entries = list(set( >> (random.randint(1, 100000), random.randint(1, 100000), random.randint(1, >> 100000)) >> for i in range(100000) >> )) >> >> entries_we_will_start_with = a_bunch_of_fake_unique_entries[0:50000] >> entries_we_will_merge = a_bunch_of_fake_unique_entries[30000:100000] >> >> sess = Session(e) >> >> counter = itertools.count(1) >> sess.add_all([Entry(id=next(counter), sub=sub, division=division, >> created=created) >> for sub, division, created in >> entries_we_will_start_with]) >> sess.commit() >> >> # here's where your example begins... This will also batch it >> # to ensure it can scale arbitrarily >> >> while entries_we_will_merge: >> batch = entries_we_will_merge[0:1000] >> entries_we_will_merge = entries_we_will_merge[1000:] >> >> existing_entries = dict( >> ((entry.sub, entry.division, entry.created), entry) >> for entry in sess.query(Entry).filter( >> tuple_(Entry.sub, Entry.division, >> Entry.created).in_([ >> tuple_(sub, division, created) >> for sub, division, created in >> batch >> ]) >> ) >> ) >> >> inserts = [] >> for entry_to_merge in batch: >> existing_entry = existing_entries.get(entry_to_merge, None) >> if existing_entry: >> # do whatever to update existing >> pass >> else: >> inserts.append( >> dict( >> id=next(counter), >> sub=entry_to_merge[0], >> division=entry_to_merge[1], >> create_engine=entry_to_merge[2] >> ) >> ) >> if inserts: >> sess.execute(Entry.__table__.insert(), params=inserts) >> >> >> >> >> >> >> >> >> >> >>> >>> Thanks! >>> >>> -- >>> 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+...@googlegroups.com. >>> To post to this group, send email to sqlal...@googlegroups.com. >>> Visit this group at http://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+...@googlegroups.com. >> To post to this group, send email to sqlal...@googlegroups.com. >> Visit this group at http://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 http://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. 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