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nexedi
gitlab-ce
Commits
b1fe8180
Commit
b1fe8180
authored
Jun 08, 2021
by
Alex Ives
Committed by
Russell Dickenson
Jun 08, 2021
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Docs single table inheritance in migrations
parent
a6460069
Changes
3
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3 changed files
with
44 additions
and
12 deletions
+44
-12
doc/development/background_migrations.md
doc/development/background_migrations.md
+2
-12
doc/development/migration_style_guide.md
doc/development/migration_style_guide.md
+3
-0
doc/development/single_table_inheritance.md
doc/development/single_table_inheritance.md
+39
-0
No files found.
doc/development/background_migrations.md
View file @
b1fe8180
...
...
@@ -255,12 +255,8 @@ batches instead of doing this one by one:
class
ScheduleExtractServicesUrl
<
ActiveRecord
::
Migration
[
4.2
]
disable_ddl_transaction!
class
Service
<
ActiveRecord
::
Base
self
.
table_name
=
'services'
end
def
up
Service
.
select
(
:id
).
in_batches
do
|
relation
|
define_batchable_model
(
'services'
)
.
select
(
:id
).
in_batches
do
|
relation
|
jobs
=
relation
.
pluck
(
:id
).
map
do
|
id
|
[
'ExtractServicesUrl'
,
[
id
]]
end
...
...
@@ -286,18 +282,12 @@ this:
class
ConsumeRemainingExtractServicesUrlJobs
<
ActiveRecord
::
Migration
[
4.2
]
disable_ddl_transaction!
class
Service
<
ActiveRecord
::
Base
include
::
EachBatch
self
.
table_name
=
'services'
end
def
up
# This must be included
Gitlab
::
BackgroundMigration
.
steal
(
'ExtractServicesUrl'
)
# This should be included, but can be skipped - see below
Service
.
where
(
url:
nil
).
each_batch
(
of:
50
)
do
|
batch
|
define_batchable_model
(
'services'
)
.
where
(
url:
nil
).
each_batch
(
of:
50
)
do
|
batch
|
range
=
batch
.
pluck
(
'MIN(id)'
,
'MAX(id)'
).
first
Gitlab
::
BackgroundMigration
::
ExtractServicesUrl
.
new
.
perform
(
*
range
)
...
...
doc/development/migration_style_guide.md
View file @
b1fe8180
...
...
@@ -976,6 +976,9 @@ If using a model in the migrations, you should first
[
clear the column cache
](
https://api.rubyonrails.org/classes/ActiveRecord/ModelSchema/ClassMethods.html#method-i-reset_column_information
)
using
`reset_column_information`
.
If using a model that leverages single table inheritance (STI), there are
[
special
considerations
](
single_table_inheritance.md#in-migrations
)
.
This avoids problems where a column that you are using was altered and cached
in a previous migration.
...
...
doc/development/single_table_inheritance.md
View file @
b1fe8180
...
...
@@ -22,3 +22,42 @@ The solution is very simple: just use a separate table for every type you'd
otherwise store in the same table. For example, instead of having a
`keys`
table
with
`type`
set to either
`Key`
or
`DeployKey`
you'd have two separate tables:
`keys`
and
`deploy_keys`
.
## In migrations
Whenever a model is used in a migration, single table inheritance should be disabled.
Due to the way Rails loads associations (even in migrations), failing to disable STI
could result in loading unexpected code or associations which may cause unintended
side effects or failures during upgrades.
```
ruby
class
SomeMigration
<
ActiveRecord
::
Migration
[
6.0
]
class
Services
<
ActiveRecord
::
Base
self
.
table_name
=
'services'
self
.
inheritance_column
=
:_type_disabled
end
def
up
...
```
If nothing needs to be added to the model other than disabling STI or
`EachBatch`
,
use the helper
`define_batchable_model`
instead of defining the class.
This ensures that the migration loads the columns for the migration in isolation,
and the helper disables STI by default.
```
ruby
class
EnqueueSomeBackgroundMigration
<
ActiveRecord
::
Migration
[
6.0
]
disable_ddl_transaction!
def
up
define_batchable_model
(
'services'
).
select
(
:id
).
in_batches
do
|
relation
|
jobs
=
relation
.
pluck
(
:id
).
map
do
|
id
|
[
'ExtractServicesUrl'
,
[
id
]]
end
BackgroundMigrationWorker
.
bulk_perform_async
(
jobs
)
end
end
...
```
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