Opened 14 years ago
Last modified 10 years ago
#13528 new Bug
db_table truncation is applied based on the properties of the default database
Reported by: | Russell Keith-Magee | Owned by: | |
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Component: | Database layer (models, ORM) | Version: | dev |
Severity: | Normal | Keywords: | |
Cc: | loic84 | Triage Stage: | Accepted |
Has patch: | yes | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | yes |
Easy pickings: | no | UI/UX: | no |
Description
Reported by Peter Long in django-dev:
In django/db/models/options.py (line 54), the contribute_to_class method uses the default database connection to get an ops module that is used to truncate the db_table name. The options class isn't in a position to do this truncation, and there's no guarantee that the default database has an appropriate truncation module.
Attachments (1)
Change History (23)
comment:1 by , 14 years ago
Triage Stage: | Unreviewed → Accepted |
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comment:2 by , 14 years ago
milestone: | 1.2 → 1.3 |
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comment:3 by , 14 years ago
Anssi Kaariainen reports that the same problem exists with the validate command.
comment:4 by , 14 years ago
FWIW solving this for the validate command will be a lot easier. Just loop through each DB for each model, check if the model should be synced (with the router) and go from there.
comment:5 by , 14 years ago
Owner: | changed from | to
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Status: | new → assigned |
I'm working on this - my proposed solution is thus:
- Deprecate Options.db_table (PendingDeprecationWarning for 1.3)
- Add Options.get_db_table(using=db_alias)
- Change all the places Django uses db_table to use get_db_table
This should both solve the problem, and allow third-party apps to continue using db_table (as it's still valid if you've only got one database).
comment:7 by , 14 years ago
Update on this ticket: There's several places where the SQL is (imho incorrectly) part of the Query and other classes, so I'm waiting for the second queryset refactor work to get along to the point where the patch can be on top of that, otherwise there's going to be massive conflicts.
comment:8 by , 14 years ago
Severity: | → Normal |
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Type: | → Bug |
comment:13 by , 13 years ago
Ive been thinking that model._meta should contain backend specific sections. This should contain at least quoted db_table name and column names. In addition to solving this problem such an arrangement should speed up SQL generation. Quoting the table and column names can consume a significant amount of time.
So, instead of doing model._meta.db_table you would do something like model._meta[conn].db_table. However, this requires somewhat extensive changes in the sql/query.py and sql/compiler.py, so I guess this has to wait...
comment:14 by , 12 years ago
Has patch: | set |
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Needs tests: | set |
Using router might be a solution, however I don't know if this does negatively affect performance or not.
comment:15 by , 11 years ago
claudep: In the diff you added:
db = router.db_for_read(self.model)
Option object doesn't have an attribute model
comment:17 by , 11 years ago
Owner: | removed |
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Status: | assigned → new |
comment:18 by , 10 years ago
Owner: | set to |
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Status: | new → assigned |
comment:19 by , 10 years ago
Version: | 1.2-beta → master |
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As discussed with Florian on IRC, we should check for minimum length that all available dbs allow and truncate accordingly.
PR: https://github.com/django/django/pull/2765
follow-up: 22 comment:20 by , 10 years ago
Needs tests: | unset |
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Patch needs improvement: | set |
I don't think the approach of the latest PR is good. Let's try implementing what Andrew suggested in comment 5 of this ticket.
comment:21 by , 10 years ago
Cc: | added |
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comment:22 by , 10 years ago
Replying to timo:
I don't think the approach of the latest PR is good. Let's try implementing what Andrew suggested in comment 5 of this ticket.
I tried to implement the above, I think that it is infeasible, atleast at the moment for the following reason:
- There are many places for eg. as in query creation where
db_table
is used but there is no knowledge ofalias
orconnection
in order to callget_db_table
. Even if try to increase the function parameters it would be very hacky to continue all the way up the function calls until analias
is found and pass it down all the way where it is needed. - In the backends there is no alias used so we don't know using the connection to call this function will be correct or not.
- There are many places where still
connection
is used instead ofconnections[alias]
so that might continue to create similar multi-db problems as the above.
I discussed this issue a little with Loic and this is what he suggested that we can note down where and why it is possible to change the suggested behaviour and where all the alias is not used and should be so that we can move on from this and try to fix that bigger problem instead of this one and that might take considerable amount of time.
comment:23 by , 10 years ago
Owner: | removed |
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Status: | assigned → new |
This isn't a trivial thing to fix, and it only affects users that have:
For example, if you have a PostgreSQL default database (max_length=64), and an Oracle secondary database (max_length=30), and you can't keep your table names to under 30 characters, you will be affected by this bug. This is a sufficiently edge case problem that I'm going to bump from 1.2.