Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+-
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:  duplicate
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+-
Changes (by timgraham):

 * resolution:  fixed => duplicate


--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.a2e932cc49d5400a1737fef72f3806cd%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:  fixed
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+

Comment (by Tim Graham ):

 In [changeset:"d7b32d31205834262758ca5f48e5fe3a453f7ad3"]:
 {{{
 #!CommitTicketReference repository=""
 revision="d7b32d31205834262758ca5f48e5fe3a453f7ad3"
 [1.7.x] Revert "Fixed #23474 -- Prevented migrating backwards from
 unapplying the wrong migrations."

 Backport of d7ab2cefb7 from master
 }}}

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.3543594a6bbf6e6d30d90c29b804a2b4%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:  fixed
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+
Changes (by Tim Graham ):

 * status:  new => closed
 * resolution:   => fixed


Comment:

 In [changeset:"d7ab2cefb7ec94bf45d37a02c79b6703ea2880e5"]:
 {{{
 #!CommitTicketReference repository=""
 revision="d7ab2cefb7ec94bf45d37a02c79b6703ea2880e5"
 Revert "Fixed #23474 -- Prevented migrating backwards from unapplying the
 wrong migrations."

 This reverts commit abcf28a07695a45cb5fb15b81bffc97bea5e0be3.
 }}}

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.aa050463a68fb9abf5dba468961badda%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+

Comment (by carljm):

 After discussion with MarkusH and looking at the patch here more closely,
 I agree with him that this particular implementation is problematic and
 should be rolled back.

 I still favor a change in behavior as described in my comment above, but
 it needs a better implementation. That discussion can happen on the
 mailing list and/or #23410.

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.142f91522eb4173f4df6ab35f9a03601%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+

Comment (by Markush2010):

 With the patch [abcf28a076] being applied I cannot rollback to a previous
 migration if. Furthermore the detection of the "next_migration" is wrong
 and depends on a leading number in the migration name which is not
 required. Dependencies are defined explicitly and not implicit by their
 name.

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.a097a5c042485d7f617a80ef79fe2f7d%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+

Comment (by carljm):

 I think akaariai's idea of requiring more explicit intent to rollback
 migrations is worth consideration, but entirely apart from that it still
 seems to me that the previous behaviour was bad and this PR made it
 better.

 In #23410 I see that Andrew stated that the previous behavior was
 intentional, to wit: "the contract is that backwards migrations roll back
 to just after the application of the named migration, and all its
 dependencies are unapplied."

 I don't see any clear reasoning provided there as to _why_ that contract
 is more desirable than the alternatives. Based on the following paragraph,
 it _seems_ that the reasoning is that a "graph node specification" such as
 "appname 0001" should always precisely specify a single state, regardless
 of whether you are rolling backwards or forwards to that state.

 I don't find that convincing. Although I see the purity argument, I think
 that in practice a much more useful (and intuitive, and less likely to
 result in data loss) contract is that "migrate appname 0001" will ensure
 that appname-0001 is applied and appname-0002 is not applied, and will
 otherwise apply or unapply as few migrations as possible.

 I also don't see a backwards-compatibility issue with switching to that
 contract in 1.7.1. This is code that runs interactively and tells you
 exactly what it is doing as it is doing it.

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.f66d8825738d6fe3603e1fbb90797703%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+

Comment (by akaariai):

 I think the problem is that the user never asked for backwards migration.
 Having "./manage.py migrate a 0001" unapply dependencies is a dangerous
 API. Either add --backwards flag to migrate or at least ask the user if
 they want to unapply the dependent migrations.

 Also, I think --noinput should *not* assume that the user wants to unapply
 dependencies. Unapply should only happen if the user explicitly tells
 Django to do so. For this reason the --backwards flag seems better - it is
 much harder to unapply migrations accidently, and there is no problem for
 --noinput interpretation (what if the user wants to unapply dependencies,
 and wants to use --noinput?)

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.8f96e2b9ba14a85ebeb851833531b913%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+

Comment (by Naddiseo):

 My understanding of the PR was that it stopped the unapplication of
 migrations that weren't applied to begin with; rolling back a no-op should
 still be a no-op.

 The issue I was facing was that m.0001 is already applied (and along with
 it some other that it depends on) then I try to migrate it again. Since
 it's already applied, the operation shouldn't touch the database, but
 instead it rolls back its dependencies.

 Perhaps @andrewgodwin can shed some light on this since he wrote it -> is
 the outcome of the use case I provided in my second comment the expected
 behaviour?

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.5a5c47faf3aae1649c904716c1ac45d6%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+
Changes (by Markush2010):

 * cc: info+coding@… (added)


--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.2bb036eaf4c8844103da47241c643d5b%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  0|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  0
Easy pickings:  0|UI/UX:  0
-+
Changes (by timgraham):

 * status:  closed => new
 * needs_better_patch:  1 => 0
 * has_patch:  1 => 0
 * resolution:  fixed =>


Comment:

 We might have to revert this change as apparently the current behavior is
 considered correct (see #23410). Maybe a solution to prevent inadvertent
 data loss would be to add a confirmation step that shows what migrations
 will be unapplied (see #23359 for a general display mechanism).

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.69fcb10362a5be764ae2ee1719694132%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:  fixed
 Keywords:   | Triage Stage:  Accepted
Has patch:  1|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  1
Easy pickings:  0|UI/UX:  0
-+

Comment (by Tim Graham ):

 In [changeset:"563eaf04998da3ef88de4553f54eccd900a12805"]:
 {{{
 #!CommitTicketReference repository=""
 revision="563eaf04998da3ef88de4553f54eccd900a12805"
 [1.7.x] Fixed #23474 -- Prevented migrating backwards from unapplying the
 wrong migrations.

 Backport of abcf28a076 from master
 }}}

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.9f521b53da0408f962089e446054f899%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  closed
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:  fixed
 Keywords:   | Triage Stage:  Accepted
Has patch:  1|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  1
Easy pickings:  0|UI/UX:  0
-+
Changes (by Tim Graham ):

 * status:  new => closed
 * resolution:   => fixed


Comment:

 In [changeset:"abcf28a07695a45cb5fb15b81bffc97bea5e0be3"]:
 {{{
 #!CommitTicketReference repository=""
 revision="abcf28a07695a45cb5fb15b81bffc97bea5e0be3"
 Fixed #23474 -- Prevented migrating backwards from unapplying the wrong
 migrations.
 }}}

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.cce0a551deb2274cf771a5fff174e83e%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
-+
 Reporter:  Naddiseo |Owner:  nobody
 Type:  Bug  |   Status:  new
Component:  Migrations   |  Version:  1.7
 Severity:  Release blocker  |   Resolution:
 Keywords:   | Triage Stage:  Accepted
Has patch:  1|  Needs documentation:  0
  Needs tests:  0|  Patch needs improvement:  1
Easy pickings:  0|UI/UX:  0
-+
Changes (by timgraham):

 * needs_better_patch:  0 => 1
 * severity:  Normal => Release blocker
 * stage:  Unreviewed => Accepted


Comment:

 Left some minor comments for improvement on the PR.

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.43315629b649a2f95a85c8273a2e7b48%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
+--
 Reporter:  Naddiseo|Owner:  nobody
 Type:  Bug |   Status:  new
Component:  Migrations  |  Version:  1.7
 Severity:  Normal  |   Resolution:
 Keywords:  | Triage Stage:  Unreviewed
Has patch:  1   |  Needs documentation:  0
  Needs tests:  0   |  Patch needs improvement:  0
Easy pickings:  0   |UI/UX:  0
+--
Changes (by valtron):

 * cc: valtron (added)
 * has_patch:  0 => 1
 * type:  Uncategorized => Bug


--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.63381c45ee59463aa9f294419544c200%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
---+--
 Reporter:  Naddiseo   |Owner:  nobody
 Type:  Uncategorized  |   Status:  new
Component:  Migrations |  Version:  1.7
 Severity:  Normal |   Resolution:
 Keywords: | Triage Stage:  Unreviewed
Has patch:  0  |  Needs documentation:  0
  Needs tests:  0  |  Patch needs improvement:  0
Easy pickings:  0  |UI/UX:  0
---+--

Comment (by valtron):

 The bug is in
 
https://github.com/django/django/blob/master/django/db/migrations/executor.py#L39-L43.

 The code should be (I think)

 {{{#!python
 next_migration = get_next_migration_in_same_app(target)
 # If `target` is the most recent one in its app, there is nothing to do.
 if next_migration:
 backwards_plan = self.loader.graph.backwards_plan(next_migration)
 }}}

 The reasoning: forwards migrations to app.000X are inclusive; backwards
 migrations to app.000X are exclusive (app.000X isn't actually unapplied).
 The not-unapplying of app.000X is currently handled by the `[:-1]` in line
 39; however, the dependents of app.000X are still unapplied.

 I'll submit a pull request as soon as I figure out how to implement
 `get_next_migration_in_same_app`.

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.3a40447f778b0120b30d593cf812b777%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

Re: [Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
---+--
 Reporter:  Naddiseo   |Owner:  nobody
 Type:  Uncategorized  |   Status:  new
Component:  Migrations |  Version:  1.7
 Severity:  Normal |   Resolution:
 Keywords: | Triage Stage:  Unreviewed
Has patch:  0  |  Needs documentation:  0
  Needs tests:  0  |  Patch needs improvement:  0
Easy pickings:  0  |UI/UX:  0
---+--
Changes (by Naddiseo):

 * needs_better_patch:   => 0
 * needs_tests:   => 0
 * needs_docs:   => 0


Comment:

 Here a more relevant use-case. I'm moving my project to django 1.7 and
 already have data, so I create the initial migrations, then fake them.
 Next I migrate the first migration of another app (maybe by accident I
 forget the `--fake`), and voila, my data is gone.

 {{{#!bash

 $ unzip unapp.zip
 $ cd unapp/
 $ sqlite3 db.sqlite3 ".tables"
 B_b
 $ manage migrate --fake B
 Operations to perform:
   Apply all migrations: B
 Running migrations:
   Applying A.0001_initial... FAKED
   Applying B.0001_initial... FAKED
   Applying B.0002_b... FAKED
 $ sqlite3 db.sqlite3 ".tables"
 B_bdjango_migrations
 $ manage migrate A  0001
 Operations to perform:
   Target specific migration: 0001_initial, from A
 Running migrations:
   Unapplying B.0002_b... OK
   Unapplying B.0001_initial... OK
 $ sqlite3 db.sqlite3 ".tables"
 django_migrations
 }}}

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/066.579aca00be57de0b992616de69f5a382%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.

[Django] #23474: Schema migrations can inadvertently destroy data

[Django]

#23474: Schema migrations can inadvertently destroy data
---+
 Reporter:  Naddiseo   |  Owner:  nobody
 Type:  Uncategorized  | Status:  new
Component:  Migrations |Version:  1.7
 Severity:  Normal |   Keywords:
 Triage Stage:  Unreviewed |  Has patch:  0
Easy pickings:  0  |  UI/UX:  0
---+
 I attached a sample project that will show that migrations can destroy
 data.

 There are two apps, `A` and `B`, both of which have two migrations. Both
 of app `B`s migrations depend on `A`'s first migration. Both of app `A`'s
 migrations are empty noops. Migrating `B` first should apply migrations
 A.0001, B.0001, B.0002, which will leave the database with the B.B table
 creating via B.0001.

 If you then explicitly migrate A.0001 again, it will unapply B.0001 and
 B.0002 which removes the B.B table causing data loss. A.0001 should be a
 noop since it's already been applied.

 Interestingly, this bug only occurs if A.0002 exists.

 Here are the steps to reproduce:

 {{{#!bash

 $ unzip destructive-example.zip
 $ cd foo
 $ sqlite3 db.sqlite3 ".tables";
 django_migrations
 # Create the "B" table. Both, b migrations depend on a.0001
 $ ./manage.py migrate b
 Operations to perform:
   Apply all migrations: b
 Running migrations:
   Applying b.0001_initial... OK
   Applying b.0002_b... OK
 $ sqlite3 db.sqlite3 ".tables";
 b_bdjango_migrations
 $ ./manage.py migrate a 0001
 Operations to perform:
   Target specific migration: 0001_initial, from a
 Running migrations:
   Unapplying b.0002_b... OK
   Unapplying b.0001_initial... OK
 $ sqlite3 db.sqlite3 ".tables";
 django_migrations

 }}}

--
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

-- 
You received this message because you are subscribed to the Google Groups 
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to django-updates+unsubscr...@googlegroups.com.
To post to this group, send email to django-updates@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/django-updates/051.8b078fbcf3980cc8b2726e10091c7667%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.