Re: Adding a bulk_save method to models

[Tom Forbes]

Thank you all for the feedback, I’ve changed the method to be bulk_update()
as this seems to be the most liked option. Naming things is hard, and while
bulk_update() isn’t perfect I think it’s a bit better than
bulk_update_fields() or just update_fields().




On 16 September 2018 at 10:19:40, Tobias Kunze (r...@rixx.de) wrote:

On 18-09-15 23:15:10, Adam Johnson wrote:
>> I agree bulk_save() maybe is not the best name as people might expect
>> signals to be sent, but are there any suggestions other than
bulk_update()?
>> Maybe something more accurate, like bulk_update_fields()? Or
>> bulk_save_fields()?
>
>bulk_update_fields also sounds good, the longer method name is probably
>balanced by the lower frequency of use.

bulk_update_fields() sounds fine to me, as it makes clearer what
happens. With bulk_update() alone, I'd expect the exact analogous
action to update() to occur, since we're already used to that pattern
from create() vs bulk_create().

update_fields() alone may also work. Upside: it's shorter. Downside:
it's not immediately clear that it takes an iterable and not an
instance. I'd be happy with both options.

Best regards,
Tobias

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Re: Adding a bulk_save method to models

[Tobias Kunze]

On 18-09-15 23:15:10, Adam Johnson wrote:
>> I agree bulk_save() maybe is not the best name as people might expect
>> signals to be sent, but are there any suggestions other than bulk_update()?
>> Maybe something more accurate, like bulk_update_fields()? Or
>> bulk_save_fields()?
>
>bulk_update_fields also sounds good, the longer method name is probably
>balanced by the lower frequency of use.

bulk_update_fields() sounds fine to me, as it makes clearer what
happens. With bulk_update() alone, I'd expect the exact analogous
action to update() to occur, since we're already used to that pattern
from create() vs bulk_create().

update_fields() alone may also work. Upside: it's shorter. Downside:
it's not immediately clear that it takes an iterable and not an
instance. I'd be happy with both options.

Best regards,
Tobias

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Re: Adding a bulk_save method to models

[charettes]

I also dislike bulk_save() for the same reasons.

I feel like bulk_update makes the most of sense given it has a signature 
similar to bulk_create where an iterable of model instances must be passed 
we're really just performing an update.

To the bulk_update and update is the natural analogous to what bulk_create 
is to create; bulk_update_fields feels too verbose and breaks the symmetry 
of bulk_create/create for update.

Cheers,
Simon

Le samedi 15 septembre 2018 18:15:39 UTC-4, Adam Johnson a écrit :
>
> Bikeshed time.
>
> I'm also against bulk_save for the same reason that it implies save().
>
> bulk_update sounds okay to me, update() is indeed already a 'bulk' 
> operation but it could be claimed this is doing a 'bulk' amount of update 
> operations.
>
> bulk_update_fields also sounds good, the longer method name is probably 
> balanced by the lower frequency of use.
>
>
> On Sat, 15 Sep 2018 at 15:01, Tom Forbes > 
> wrote:
>
>> My original reasoning was that Queryset.update() already bulk updates 
>> rows, so the bulk prefix seems a bit redundant here (how do you bulk 
>> something that already does something in bulk?). .save() however 
>> operates on a single object, so the bulk prefix seems more appropriate and 
>> easier to understand.
>>
>> I agree bulk_save() maybe is not the best name as people might expect 
>> signals to be sent, but are there any suggestions other than 
>> bulk_update()? Maybe something more accurate, like bulk_update_fields()? 
>> Or bulk_save_fields()?
>>
>>
>>
>>
>> On 14 September 2018 at 16:32:05, Raphael Michel (ma...@raphaelmichel.de 
>> ) wrote:
>>
>> Hi, 
>>
>> I'd be very careful about calling it bulk_save(), since calling 
>> it something with save() very strongly suggests that it calls pre_save 
>> or post_save signals. 
>>
>> Best 
>> Raphael 
>>
>>
>> Am Fri, 14 Sep 2018 07:56:38 -0700 (PDT) 
>> schrieb Tim Graham >: 
>>
>> > 
>> > 
>> > I wanted to ask about naming of the new method. Currently the 
>> > proposed name is "QuerySet.bulk_save()" but I think it's a bit 
>> > confusing since it uses QuerySet.update(), not Model.save(). It works 
>> > similarly to QuerySet.bulk_update() from 
>> > https://github.com/aykut/django-bulk-update but the arguments are a 
>> > bit different. 
>> > 
>> > 
>> > Josh's comment on the PR: "Since this only works for instances with 
>> > an pk, do you think that bulk_update would be a better name? The 
>> > regular save() method can either create or update depending on pk 
>> > status which may confuse users here." 
>> > 
>> > And Tom's reply: "I considered this, but queryset.update() is the 
>> > best 'bulk update' method. I didn't want to confuse the two, this is 
>> > more about saving multiple model fields with multiple differing 
>> > values, gene bulk_save. Open to changing it though." 
>> > 
>> > 
>> > On Tuesday, January 23, 2018 at 7:38:18 AM UTC-5, Neal Todd wrote: 
>> > > 
>> > > Hi Tom, 
>> > > 
>> > > That's great, should be a helpful addition to core. Will follow the 
>> > > ticket and PR. 
>> > > 
>> > > Neal 
>> > > 
>> > > (Apologies - I hadn't spotted that you'd already referenced 
>> > > django-bulk-update in your ticket when I left my drive-by comment!) 
>> > > 
>> > > On Monday, January 22, 2018 at 7:41:11 PM UTC, Tom Forbes wrote: 
>> > >> 
>> > >> Hey Neal, 
>> > >> 
>> > >> Thank you very much for pointing that out, I actually found out 
>> > >> about this package as I was researching the ticket - I wish I had 
>> > >> known about this a couple of years ago as it would have saved me a 
>> > >> fair bit of CPU and brain time! 
>> > >> 
>> > >> I think that module is a good starting point and proves that it’s 
>> > >> possible, however I think the implementation can be improved upon 
>> > >> if we bring it inside core. I worked on a small PR to add this 
>> > >> <
>> https://github.com/django/django/pull/9606/files#diff-5b0dda5eb9a242c15879dc9cd2121379R473>
>>  
>>
>> > >> and the implementation was refreshingly simple. It still needs 
>> > >> docs, a couple more tests and to fix a strange error with sqlite 
>> > >> on Windows, but overall it seems like a lot of gain for a small 
>> > >> amount of code. 
>> > >> 
>> > >> Tom 
>> > >> 
>> > >> 
>> > >> On 22 January 2018 at 15:10:53, Neal Todd (ne...@torchbox.com) 
>> > >> wrote: 
>> > >> 
>> > >> Hi Tom, 
>> > >> 
>> > >> A built-in bulk save that's more flexible than update would 
>> > >> certainly be nice. Just in case you haven't come across it though, 
>> > >> there is a package called django-bulk-update: 
>> > >> 
>> > >> https://github.com/aykut/django-bulk-update 
>> > >> 
>> > >> I've found it very useful on a number of occassions where update 
>> > >> isn't quite enough but the loop-edit-save pattern is too slow to 
>> > >> be convenient. 
>> > >> 
>> > >> Probably some useful things in there when considering the API and 
>> > >> approach. 
>> > >> 
>> > >> Cheers, Neal 
>> > >> 
>> > >> On Friday, January 19, 2018 at 5:49:48 PM UTC, Tom Forbes 

Re: Adding a bulk_save method to models

[Adam Johnson]

Bikeshed time.

I'm also against bulk_save for the same reason that it implies save().

bulk_update sounds okay to me, update() is indeed already a 'bulk'
operation but it could be claimed this is doing a 'bulk' amount of update
operations.

bulk_update_fields also sounds good, the longer method name is probably
balanced by the lower frequency of use.


On Sat, 15 Sep 2018 at 15:01, Tom Forbes  wrote:

> My original reasoning was that Queryset.update() already bulk updates
> rows, so the bulk prefix seems a bit redundant here (how do you bulk
> something that already does something in bulk?). .save() however operates
> on a single object, so the bulk prefix seems more appropriate and easier to
> understand.
>
> I agree bulk_save() maybe is not the best name as people might expect
> signals to be sent, but are there any suggestions other than bulk_update()?
> Maybe something more accurate, like bulk_update_fields()? Or
> bulk_save_fields()?
>
>
>
>
> On 14 September 2018 at 16:32:05, Raphael Michel (m...@raphaelmichel.de)
> wrote:
>
> Hi,
>
> I'd be very careful about calling it bulk_save(), since calling
> it something with save() very strongly suggests that it calls pre_save
> or post_save signals.
>
> Best
> Raphael
>
>
> Am Fri, 14 Sep 2018 07:56:38 -0700 (PDT)
> schrieb Tim Graham :
>
> >
> >
> > I wanted to ask about naming of the new method. Currently the
> > proposed name is "QuerySet.bulk_save()" but I think it's a bit
> > confusing since it uses QuerySet.update(), not Model.save(). It works
> > similarly to QuerySet.bulk_update() from
> > https://github.com/aykut/django-bulk-update but the arguments are a
> > bit different.
> >
> >
> > Josh's comment on the PR: "Since this only works for instances with
> > an pk, do you think that bulk_update would be a better name? The
> > regular save() method can either create or update depending on pk
> > status which may confuse users here."
> >
> > And Tom's reply: "I considered this, but queryset.update() is the
> > best 'bulk update' method. I didn't want to confuse the two, this is
> > more about saving multiple model fields with multiple differing
> > values, gene bulk_save. Open to changing it though."
> >
> >
> > On Tuesday, January 23, 2018 at 7:38:18 AM UTC-5, Neal Todd wrote:
> > >
> > > Hi Tom,
> > >
> > > That's great, should be a helpful addition to core. Will follow the
> > > ticket and PR.
> > >
> > > Neal
> > >
> > > (Apologies - I hadn't spotted that you'd already referenced
> > > django-bulk-update in your ticket when I left my drive-by comment!)
> > >
> > > On Monday, January 22, 2018 at 7:41:11 PM UTC, Tom Forbes wrote:
> > >>
> > >> Hey Neal,
> > >>
> > >> Thank you very much for pointing that out, I actually found out
> > >> about this package as I was researching the ticket - I wish I had
> > >> known about this a couple of years ago as it would have saved me a
> > >> fair bit of CPU and brain time!
> > >>
> > >> I think that module is a good starting point and proves that it’s
> > >> possible, however I think the implementation can be improved upon
> > >> if we bring it inside core. I worked on a small PR to add this
> > >> <
> https://github.com/django/django/pull/9606/files#diff-5b0dda5eb9a242c15879dc9cd2121379R473>
>
> > >> and the implementation was refreshingly simple. It still needs
> > >> docs, a couple more tests and to fix a strange error with sqlite
> > >> on Windows, but overall it seems like a lot of gain for a small
> > >> amount of code.
> > >>
> > >> Tom
> > >>
> > >>
> > >> On 22 January 2018 at 15:10:53, Neal Todd (ne...@torchbox.com)
> > >> wrote:
> > >>
> > >> Hi Tom,
> > >>
> > >> A built-in bulk save that's more flexible than update would
> > >> certainly be nice. Just in case you haven't come across it though,
> > >> there is a package called django-bulk-update:
> > >>
> > >> https://github.com/aykut/django-bulk-update
> > >>
> > >> I've found it very useful on a number of occassions where update
> > >> isn't quite enough but the loop-edit-save pattern is too slow to
> > >> be convenient.
> > >>
> > >> Probably some useful things in there when considering the API and
> > >> approach.
> > >>
> > >> Cheers, Neal
> > >>
> > >> On Friday, January 19, 2018 at 5:49:48 PM UTC, Tom Forbes wrote:
> > >>>
> > >>> Hello all,
> > >>>
> > >>> I’d love for some feedback on an idea I’ve been mulling around
> > >>> lately, namely adding a bulk_save method to Dango.
> > >>>
> > >>> A somewhat common pattern for some applications is to loop over a
> > >>> list of models, set an attribute and call save on them. This
> > >>> unfortunately can issue a lot of database queries which can be a
> > >>> significant slowdown. You can work around this by using
> > >>> ‘.update()’ in some cases, but not all.
> > >>>
> > >>> It seems it would be possible to use a CASE statement in SQL to
> > >>> handle bulk-updating many rows with differing values. For example:
> > >>>
> > >>> SomeModel.object.filter(id__in=[1,2]).update(
> > >>> 

Re: Adding a bulk_save method to models

[Tom Forbes]

My original reasoning was that Queryset.update() already bulk updates rows,
so the bulk prefix seems a bit redundant here (how do you bulk something
that already does something in bulk?). .save() however operates on a single
object, so the bulk prefix seems more appropriate and easier to understand.

I agree bulk_save() maybe is not the best name as people might expect
signals to be sent, but are there any suggestions other than bulk_update()?
Maybe something more accurate, like bulk_update_fields()? Or
bulk_save_fields()?




On 14 September 2018 at 16:32:05, Raphael Michel (m...@raphaelmichel.de)
wrote:

Hi,

I'd be very careful about calling it bulk_save(), since calling
it something with save() very strongly suggests that it calls pre_save
or post_save signals.

Best
Raphael


Am Fri, 14 Sep 2018 07:56:38 -0700 (PDT)
schrieb Tim Graham :

>
>
> I wanted to ask about naming of the new method. Currently the
> proposed name is "QuerySet.bulk_save()" but I think it's a bit
> confusing since it uses QuerySet.update(), not Model.save(). It works
> similarly to QuerySet.bulk_update() from
> https://github.com/aykut/django-bulk-update but the arguments are a
> bit different.
>
>
> Josh's comment on the PR: "Since this only works for instances with
> an pk, do you think that bulk_update would be a better name? The
> regular save() method can either create or update depending on pk
> status which may confuse users here."
>
> And Tom's reply: "I considered this, but queryset.update() is the
> best 'bulk update' method. I didn't want to confuse the two, this is
> more about saving multiple model fields with multiple differing
> values, gene bulk_save. Open to changing it though."
>
>
> On Tuesday, January 23, 2018 at 7:38:18 AM UTC-5, Neal Todd wrote:
> >
> > Hi Tom,
> >
> > That's great, should be a helpful addition to core. Will follow the
> > ticket and PR.
> >
> > Neal
> >
> > (Apologies - I hadn't spotted that you'd already referenced
> > django-bulk-update in your ticket when I left my drive-by comment!)
> >
> > On Monday, January 22, 2018 at 7:41:11 PM UTC, Tom Forbes wrote:
> >>
> >> Hey Neal,
> >>
> >> Thank you very much for pointing that out, I actually found out
> >> about this package as I was researching the ticket - I wish I had
> >> known about this a couple of years ago as it would have saved me a
> >> fair bit of CPU and brain time!
> >>
> >> I think that module is a good starting point and proves that it’s
> >> possible, however I think the implementation can be improved upon
> >> if we bring it inside core. I worked on a small PR to add this
> >> <
https://github.com/django/django/pull/9606/files#diff-5b0dda5eb9a242c15879dc9cd2121379R473>

> >> and the implementation was refreshingly simple. It still needs
> >> docs, a couple more tests and to fix a strange error with sqlite
> >> on Windows, but overall it seems like a lot of gain for a small
> >> amount of code.
> >>
> >> Tom
> >>
> >>
> >> On 22 January 2018 at 15:10:53, Neal Todd (ne...@torchbox.com)
> >> wrote:
> >>
> >> Hi Tom,
> >>
> >> A built-in bulk save that's more flexible than update would
> >> certainly be nice. Just in case you haven't come across it though,
> >> there is a package called django-bulk-update:
> >>
> >> https://github.com/aykut/django-bulk-update
> >>
> >> I've found it very useful on a number of occassions where update
> >> isn't quite enough but the loop-edit-save pattern is too slow to
> >> be convenient.
> >>
> >> Probably some useful things in there when considering the API and
> >> approach.
> >>
> >> Cheers, Neal
> >>
> >> On Friday, January 19, 2018 at 5:49:48 PM UTC, Tom Forbes wrote:
> >>>
> >>> Hello all,
> >>>
> >>> I’d love for some feedback on an idea I’ve been mulling around
> >>> lately, namely adding a bulk_save method to Dango.
> >>>
> >>> A somewhat common pattern for some applications is to loop over a
> >>> list of models, set an attribute and call save on them. This
> >>> unfortunately can issue a lot of database queries which can be a
> >>> significant slowdown. You can work around this by using
> >>> ‘.update()’ in some cases, but not all.
> >>>
> >>> It seems it would be possible to use a CASE statement in SQL to
> >>> handle bulk-updating many rows with differing values. For example:
> >>>
> >>> SomeModel.object.filter(id__in=[1,2]).update(
> >>> some_field=Case(
> >>> When(id=1, then=Value('Field value for ID=1')),
> >>> When(id=2, then=Value('Field value for ID=2'))
> >>> )
> >>> )
> >>>
> >>> I’ve made a ticket for this here:
> >>> https://code.djangoproject.com/ticket/29037
> >>>
> >>> I managed to get a 70x performance increase using this technique
> >>> on a fairly large table, and it seems it could be applicable to
> >>> many projects just like bulk_create.
> >>>
> >>> The downsides to this is that it can produce very large SQL
> >>> statements when updating many rows (I had MySQL complain about a
> >>> 10MB statement once), but this can be overcome with batching and
> >>> other 

Re: Adding a bulk_save method to models

[Raphael Michel]

Hi,

I'd be very careful about calling it bulk_save(), since calling
it something with save() very strongly suggests that it calls pre_save
or post_save signals.

Best
Raphael


Am Fri, 14 Sep 2018 07:56:38 -0700 (PDT)
schrieb Tim Graham :

>  
> 
> I wanted to ask about naming of the new method. Currently the
> proposed name is "QuerySet.bulk_save()" but I think it's a bit
> confusing since it uses QuerySet.update(), not Model.save(). It works
> similarly to QuerySet.bulk_update() from
> https://github.com/aykut/django-bulk-update but the arguments are a
> bit different.
> 
> 
> Josh's comment on the PR: "Since this only works for instances with
> an pk, do you think that bulk_update would be a better name? The
> regular save() method can either create or update depending on pk
> status which may confuse users here."
> 
> And Tom's reply: "I considered this, but queryset.update() is the
> best 'bulk update' method. I didn't want to confuse the two, this is
> more about saving multiple model fields with multiple differing
> values, gene bulk_save. Open to changing it though."
> 
> 
> On Tuesday, January 23, 2018 at 7:38:18 AM UTC-5, Neal Todd wrote:
> >
> > Hi Tom,
> >
> > That's great, should be a helpful addition to core. Will follow the
> > ticket and PR.
> >
> > Neal
> >
> > (Apologies - I hadn't spotted that you'd already referenced 
> > django-bulk-update in your ticket when I left my drive-by comment!)
> >
> > On Monday, January 22, 2018 at 7:41:11 PM UTC, Tom Forbes wrote:  
> >>
> >> Hey Neal,
> >>
> >> Thank you very much for pointing that out, I actually found out
> >> about this package as I was researching the ticket - I wish I had
> >> known about this a couple of years ago as it would have saved me a
> >> fair bit of CPU and brain time!
> >>
> >> I think that module is a good starting point and proves that it’s 
> >> possible, however I think the implementation can be improved upon
> >> if we bring it inside core. I worked on a small PR to add this 
> >> 
> >>  
> >> and the implementation was refreshingly simple. It still needs
> >> docs, a couple more tests and to fix a strange error with sqlite
> >> on Windows, but overall it seems like a lot of gain for a small
> >> amount of code.
> >>
> >> Tom 
> >>
> >>
> >> On 22 January 2018 at 15:10:53, Neal Todd (ne...@torchbox.com)
> >> wrote:
> >>
> >> Hi Tom,
> >>
> >> A built-in bulk save that's more flexible than update would
> >> certainly be nice. Just in case you haven't come across it though,
> >> there is a package called django-bulk-update:
> >>
> >> https://github.com/aykut/django-bulk-update
> >>
> >> I've found it very useful on a number of occassions where update
> >> isn't quite enough but the loop-edit-save pattern is too slow to
> >> be convenient.
> >>
> >> Probably some useful things in there when considering the API and 
> >> approach.
> >>
> >> Cheers, Neal 
> >>
> >> On Friday, January 19, 2018 at 5:49:48 PM UTC, Tom Forbes wrote:   
> >>>
> >>> Hello all,
> >>>
> >>> I’d love for some feedback on an idea I’ve been mulling around
> >>> lately, namely adding a bulk_save method to Dango.
> >>>
> >>> A somewhat common pattern for some applications is to loop over a
> >>> list of models, set an attribute and call save on them. This
> >>> unfortunately can issue a lot of database queries which can be a
> >>> significant slowdown. You can work around this by using
> >>> ‘.update()’ in some cases, but not all.
> >>>
> >>> It seems it would be possible to use a CASE statement in SQL to
> >>> handle bulk-updating many rows with differing values. For example:
> >>>
> >>> SomeModel.object.filter(id__in=[1,2]).update(
> >>> some_field=Case(
> >>> When(id=1, then=Value('Field value for ID=1')),
> >>> When(id=2, then=Value('Field value for ID=2'))
> >>> )
> >>> )
> >>>
> >>> I’ve made a ticket for this here: 
> >>> https://code.djangoproject.com/ticket/29037
> >>>
> >>> I managed to get a 70x performance increase using this technique
> >>> on a fairly large table, and it seems it could be applicable to
> >>> many projects just like bulk_create.
> >>>
> >>> The downsides to this is that it can produce very large SQL
> >>> statements when updating many rows (I had MySQL complain about a
> >>> 10MB statement once), but this can be overcome with batching and
> >>> other optimisations (i.e the same values can use WHEN id IN (x,
> >>> y, z) rather than 3 individual WHEN statements).
> >>>
> >>> I’m imagining an API very similar to bulk_create, but spend any
> >>> time on a patch I thought I would ask if anyone have any feedback
> >>> on this suggestion. Would this be a good addition to Dango?
> >>>
> >>>
> >>> --  
> >> You received this message because you are subscribed to the Google
> >> Groups "Django developers (Contributions to Django itself)" group.
> >> To unsubscribe from this group and stop receiving emails from it,
> 

Re: Adding a bulk_save method to models

[Tim Graham]

 

I wanted to ask about naming of the new method. Currently the proposed name 
is "QuerySet.bulk_save()" but I think it's a bit confusing since it uses 
QuerySet.update(), not Model.save(). It works similarly to 
QuerySet.bulk_update() from https://github.com/aykut/django-bulk-update but 
the arguments are a bit different.


Josh's comment on the PR: "Since this only works for instances with an pk, 
do you think that bulk_update would be a better name? The regular save() 
method can either create or update depending on pk status which may confuse 
users here."

And Tom's reply: "I considered this, but queryset.update() is the best 
'bulk update' method. I didn't want to confuse the two, this is more about 
saving multiple model fields with multiple differing values, gene bulk_save. 
Open to changing it though."


On Tuesday, January 23, 2018 at 7:38:18 AM UTC-5, Neal Todd wrote:
>
> Hi Tom,
>
> That's great, should be a helpful addition to core. Will follow the ticket 
> and PR.
>
> Neal
>
> (Apologies - I hadn't spotted that you'd already referenced 
> django-bulk-update in your ticket when I left my drive-by comment!)
>
> On Monday, January 22, 2018 at 7:41:11 PM UTC, Tom Forbes wrote:
>>
>> Hey Neal,
>>
>> Thank you very much for pointing that out, I actually found out about 
>> this package as I was researching the ticket - I wish I had known about 
>> this a couple of years ago as it would have saved me a fair bit of CPU and 
>> brain time!
>>
>> I think that module is a good starting point and proves that it’s 
>> possible, however I think the implementation can be improved upon if we 
>> bring it inside core. I worked on a small PR to add this 
>> 
>>  
>> and the implementation was refreshingly simple. It still needs docs, a 
>> couple more tests and to fix a strange error with sqlite on Windows, but 
>> overall it seems like a lot of gain for a small amount of code.
>>
>> Tom 
>>
>>
>> On 22 January 2018 at 15:10:53, Neal Todd (ne...@torchbox.com) wrote:
>>
>> Hi Tom,
>>
>> A built-in bulk save that's more flexible than update would certainly be 
>> nice. Just in case you haven't come across it though, there is a package 
>> called django-bulk-update:
>>
>> https://github.com/aykut/django-bulk-update
>>
>> I've found it very useful on a number of occassions where update isn't 
>> quite enough but the loop-edit-save pattern is too slow to be convenient.
>>
>> Probably some useful things in there when considering the API and 
>> approach.
>>
>> Cheers, Neal 
>>
>> On Friday, January 19, 2018 at 5:49:48 PM UTC, Tom Forbes wrote: 
>>>
>>> Hello all,
>>>
>>> I’d love for some feedback on an idea I’ve been mulling around lately, 
>>> namely adding a bulk_save method to Dango.
>>>
>>> A somewhat common pattern for some applications is to loop over a list 
>>> of models, set an attribute and call save on them. This unfortunately can 
>>> issue a lot of database queries which can be a significant slowdown. You 
>>> can work around this by using ‘.update()’ in some cases, but not all.
>>>
>>> It seems it would be possible to use a CASE statement in SQL to handle 
>>> bulk-updating many rows with differing values. For example:
>>>
>>> SomeModel.object.filter(id__in=[1,2]).update(
>>> some_field=Case(
>>> When(id=1, then=Value('Field value for ID=1')),
>>> When(id=2, then=Value('Field value for ID=2'))
>>> )
>>> )
>>>
>>> I’ve made a ticket for this here: 
>>> https://code.djangoproject.com/ticket/29037
>>>
>>> I managed to get a 70x performance increase using this technique on a 
>>> fairly large table, and it seems it could be applicable to many projects 
>>> just like bulk_create.
>>>
>>> The downsides to this is that it can produce very large SQL statements 
>>> when updating many rows (I had MySQL complain about a 10MB statement once), 
>>> but this can be overcome with batching and other optimisations (i.e the 
>>> same values can use WHEN id IN (x, y, z) rather than 3 individual WHEN 
>>> statements).
>>>
>>> I’m imagining an API very similar to bulk_create, but spend any time on 
>>> a patch I thought I would ask if anyone have any feedback on this 
>>> suggestion. Would this be a good addition to Dango?
>>>
>>>
>>> --
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>> To unsubscribe from this group and stop receiving emails from it, send an 
>> email to django-develop...@googlegroups.com.
>> To post to this group, send email to django-d...@googlegroups.com.
>> Visit this group at https://groups.google.com/group/django-developers.
>> To view this discussion on the web visit 
>> https://groups.google.com/d/msgid/django-developers/5988d579-7843-4c42-a6f9-1e389c58ece6%40googlegroups.com
>>  
>> 

Re: Adding a bulk_save method to models

[Neal Todd]

Hi Tom,

That's great, should be a helpful addition to core. Will follow the ticket 
and PR.

Neal

(Apologies - I hadn't spotted that you'd already referenced 
django-bulk-update in your ticket when I left my drive-by comment!)

On Monday, January 22, 2018 at 7:41:11 PM UTC, Tom Forbes wrote:
>
> Hey Neal,
>
> Thank you very much for pointing that out, I actually found out about this 
> package as I was researching the ticket - I wish I had known about this a 
> couple of years ago as it would have saved me a fair bit of CPU and brain 
> time!
>
> I think that module is a good starting point and proves that it’s 
> possible, however I think the implementation can be improved upon if we 
> bring it inside core. I worked on a small PR to add this 
> 
>  
> and the implementation was refreshingly simple. It still needs docs, a 
> couple more tests and to fix a strange error with sqlite on Windows, but 
> overall it seems like a lot of gain for a small amount of code.
>
> Tom 
>
>
> On 22 January 2018 at 15:10:53, Neal Todd (ne...@torchbox.com 
> ) wrote:
>
> Hi Tom,
>
> A built-in bulk save that's more flexible than update would certainly be 
> nice. Just in case you haven't come across it though, there is a package 
> called django-bulk-update:
>
> https://github.com/aykut/django-bulk-update
>
> I've found it very useful on a number of occassions where update isn't 
> quite enough but the loop-edit-save pattern is too slow to be convenient.
>
> Probably some useful things in there when considering the API and approach.
>
> Cheers, Neal 
>
> On Friday, January 19, 2018 at 5:49:48 PM UTC, Tom Forbes wrote: 
>>
>> Hello all,
>>
>> I’d love for some feedback on an idea I’ve been mulling around lately, 
>> namely adding a bulk_save method to Dango.
>>
>> A somewhat common pattern for some applications is to loop over a list of 
>> models, set an attribute and call save on them. This unfortunately can 
>> issue a lot of database queries which can be a significant slowdown. You 
>> can work around this by using ‘.update()’ in some cases, but not all.
>>
>> It seems it would be possible to use a CASE statement in SQL to handle 
>> bulk-updating many rows with differing values. For example:
>>
>> SomeModel.object.filter(id__in=[1,2]).update(
>> some_field=Case(
>> When(id=1, then=Value('Field value for ID=1')),
>> When(id=2, then=Value('Field value for ID=2'))
>> )
>> )
>>
>> I’ve made a ticket for this here: 
>> https://code.djangoproject.com/ticket/29037
>>
>> I managed to get a 70x performance increase using this technique on a 
>> fairly large table, and it seems it could be applicable to many projects 
>> just like bulk_create.
>>
>> The downsides to this is that it can produce very large SQL statements 
>> when updating many rows (I had MySQL complain about a 10MB statement once), 
>> but this can be overcome with batching and other optimisations (i.e the 
>> same values can use WHEN id IN (x, y, z) rather than 3 individual WHEN 
>> statements).
>>
>> I’m imagining an API very similar to bulk_create, but spend any time on a 
>> patch I thought I would ask if anyone have any feedback on this suggestion. 
>> Would this be a good addition to Dango?
>>
>>
>> --
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> "Django developers (Contributions to Django itself)" group.
> To unsubscribe from this group and stop receiving emails from it, send an 
> email to django-develop...@googlegroups.com .
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> .
> Visit this group at https://groups.google.com/group/django-developers.
> To view this discussion on the web visit 
> https://groups.google.com/d/msgid/django-developers/5988d579-7843-4c42-a6f9-1e389c58ece6%40googlegroups.com
>  
> 
> .
> For more options, visit https://groups.google.com/d/optout.
>
>

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Re: Adding a bulk_save method to models

[Tom Forbes]

Hey Neal,

Thank you very much for pointing that out, I actually found out about this
package as I was researching the ticket - I wish I had known about this a
couple of years ago as it would have saved me a fair bit of CPU and brain
time!

I think that module is a good starting point and proves that it’s possible,
however I think the implementation can be improved upon if we bring it
inside core. I worked on a small PR to add this

and the implementation was refreshingly simple. It still needs docs, a
couple more tests and to fix a strange error with sqlite on Windows, but
overall it seems like a lot of gain for a small amount of code.

Tom


On 22 January 2018 at 15:10:53, Neal Todd (n...@torchbox.com) wrote:

Hi Tom,

A built-in bulk save that's more flexible than update would certainly be
nice. Just in case you haven't come across it though, there is a package
called django-bulk-update:

https://github.com/aykut/django-bulk-update

I've found it very useful on a number of occassions where update isn't
quite enough but the loop-edit-save pattern is too slow to be convenient.

Probably some useful things in there when considering the API and approach.

Cheers, Neal

On Friday, January 19, 2018 at 5:49:48 PM UTC, Tom Forbes wrote:
>
> Hello all,
>
> I’d love for some feedback on an idea I’ve been mulling around lately,
> namely adding a bulk_save method to Dango.
>
> A somewhat common pattern for some applications is to loop over a list of
> models, set an attribute and call save on them. This unfortunately can
> issue a lot of database queries which can be a significant slowdown. You
> can work around this by using ‘.update()’ in some cases, but not all.
>
> It seems it would be possible to use a CASE statement in SQL to handle
> bulk-updating many rows with differing values. For example:
>
> SomeModel.object.filter(id__in=[1,2]).update(
> some_field=Case(
> When(id=1, then=Value('Field value for ID=1')),
> When(id=2, then=Value('Field value for ID=2'))
> )
> )
>
> I’ve made a ticket for this here: https://code.djangoproject.
> com/ticket/29037
>
> I managed to get a 70x performance increase using this technique on a
> fairly large table, and it seems it could be applicable to many projects
> just like bulk_create.
>
> The downsides to this is that it can produce very large SQL statements
> when updating many rows (I had MySQL complain about a 10MB statement once),
> but this can be overcome with batching and other optimisations (i.e the
> same values can use WHEN id IN (x, y, z) rather than 3 individual WHEN
> statements).
>
> I’m imagining an API very similar to bulk_create, but spend any time on a
> patch I thought I would ask if anyone have any feedback on this suggestion.
> Would this be a good addition to Dango?
>
>
> --
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Re: Adding a bulk_save method to models

[Neal Todd]

Hi Tom,

A built-in bulk save that's more flexible than update would certainly be 
nice. Just in case you haven't come across it though, there is a package 
called django-bulk-update:

https://github.com/aykut/django-bulk-update

I've found it very useful on a number of occassions where update isn't 
quite enough but the loop-edit-save pattern is too slow to be convenient.

Probably some useful things in there when considering the API and approach.

Cheers, Neal  

On Friday, January 19, 2018 at 5:49:48 PM UTC, Tom Forbes wrote:
>
> Hello all,
>
> I’d love for some feedback on an idea I’ve been mulling around lately, 
> namely adding a bulk_save method to Dango.
>
> A somewhat common pattern for some applications is to loop over a list of 
> models, set an attribute and call save on them. This unfortunately can 
> issue a lot of database queries which can be a significant slowdown. You 
> can work around this by using ‘.update()’ in some cases, but not all.
>
> It seems it would be possible to use a CASE statement in SQL to handle 
> bulk-updating many rows with differing values. For example:
>
> SomeModel.object.filter(id__in=[1,2]).update(
> some_field=Case(
> When(id=1, then=Value('Field value for ID=1')),
> When(id=2, then=Value('Field value for ID=2'))
> )
> )
>
> I’ve made a ticket for this here: 
> https://code.djangoproject.com/ticket/29037
>
> I managed to get a 70x performance increase using this technique on a 
> fairly large table, and it seems it could be applicable to many projects 
> just like bulk_create.
>
> The downsides to this is that it can produce very large SQL statements 
> when updating many rows (I had MySQL complain about a 10MB statement once), 
> but this can be overcome with batching and other optimisations (i.e the 
> same values can use WHEN id IN (x, y, z) rather than 3 individual WHEN 
> statements).
>
> I’m imagining an API very similar to bulk_create, but spend any time on a 
> patch I thought I would ask if anyone have any feedback on this suggestion. 
> Would this be a good addition to Dango?
>
>
>
>

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