[Django] #27834: Add the STRPOS database function
Django
-------------------------------------+-------------------------------------
Reporter: Baptiste | Owner: nobody
Mispelon |
Type: New | Status: new
feature |
Component: Database | Version: 1.10
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 1
UI/UX: 0 |
-------------------------------------+-------------------------------------
Django currently ships with a dozen or so database functions [1].
I recently had the need for what postgres calls `STRPOS(string,
substring)` to find the position of a string inside a substring and was
surprised to find it was not included in the list of builtins.
I'm not sure if there's an official criteria for deciding which functions
get implemented in core, but I did some quick research and found that this
`STRPOS()` functionality at least seems to be present in all 4 officially
supported databases:
* **Postgres**: `STRPOS(string, substring)` [2]
* **Sqlite**: `INSTR(string, substring)` [3]
* **MySQL**: `LOCATE(substring, string)` [4]
* **Oracle**: `INSTR(string, substring)` [5]
The names and order of arguments are somewhat inconsistent but the
behavior and return value of the function seems well-defined: it returns a
positive integer corresponding to the (1-indexed) position of the
substring inside the string; if the substring is not found, 0 is returned.
I'm marking this as "easy pickings" because other than the inconsistent
naming and argument order, the actual implementation of the `Func`
shouldn't be too complex.
[1] https://docs.djangoproject.com/en/dev/ref/models/database-functions/
[2] https://www.postgresql.org/docs/current/static/functions-string.html
[3] https://www.sqlite.org/lang_corefunc.html#instr
[4] https://dev.mysql.com/doc/refman/5.7/en/string-
functions.html#function_locate
[5]
https://docs.oracle.com/cd/B19306_01/server.102/b14200/functions068.htm
--
Ticket URL: <https://code.djangoproject.com/ticket/27834>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
Django
-------------------------------------+-------------------------------------
Type: New feature | Status: new
Component: Database layer | Version: 1.10
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
* stage: Unreviewed => Accepted
Comment:
This seems valid to me maybe it could be called something like `Indexstr`
to be in keeping with `'asdf'.index('s')`?
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:1>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: 1.10
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
* owner: nobody => Brad Melin
* status: new => assigned
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:2>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
(models, ORM) |
Severity: Normal | Resolution:
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
* cc: josh.smeaton@… (added)
* keywords: => expressions
* version: 1.10 => master
Comment:
> I'm not sure if there's an official criteria for deciding which
functions get implemented in core
Nope, there's no official criteria. As you noted there's support in all 4
official backends, and it's a commonly used function, which makes this a
good candidate for inclusion. For anyone reading this in the future, I'm
wary about including obscure functions that don't enjoy support for all
(or most) backends, and would probably like to see a library spring up to
support those use cases.
Thanks for doing the investigation Baptiste.
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:3>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: expressions | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by vikram):
Hello,
I have some experience using django for developing web apps/rest api's. I
want to get to know about the internal of django, how the thing works.
I had read the contributing docs and completed with setup of django code.
Can you guide me how can I kickstart implementing `Add the STRPOS
database function` feature
Thanks
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:4>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: expressions | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Tim Graham):
Brad has already assigned the ticket three days ago. If there's no
activity or update from after after some weeks it's fine to reassign,
otherwise it's not polite to reassign the ticket so quickly. In choosing a
ticket, try to find something that you some idea of how to begin.
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:5>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: expressions | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Josh Smeaton):
Vikram, as Tim already mentioned this particular ticket has been picked up
by someone else. That doesn't mean you can't hunt around for another
database function to implement that meets the criteria of "widely used"
and "works on mysql, postgres, oracle, and sqlite". Be sure to open a
ticket if you find such a one.
> Can you guide me how can I kickstart implementing X Database Function
First you should check out the docs for this existing functions:
https://docs.djangoproject.com/en/1.10/ref/models/database-functions/
Then you should read up on the Expressions API:
https://docs.djangoproject.com/en/1.10/ref/models/expressions/
You can have a look at how some of the current functions are implemented
here:
https://github.com/django/django/blob/1f7ca858664491589ba400419a491dd0a9af5dff/django/db/models/functions/base.py
Read the various parts of the expressions API as you're looking into how
the other functions are implemented. Generally get familiar with the
following files:
django/db/models/functions/*
django/db/models/expressions.py
They're all reasonably self contained, and don't venture too far into the
rest of the ORM.
Once you've got some code to make a function work, then you'd write some
tests in
https://github.com/django/django/blob/1f7ca858664491589ba400419a491dd0a9af5dff/tests/db_functions/tests.py
and write some docs in
https://github.com/django/django/blob/1f7ca858664491589ba400419a491dd0a9af5dff/docs/ref/models
/database-functions.txt
For testing, you can use https://github.com/django/django-box to run tests
on all databases except for Oracle.
Of course, this assumes you've read the previous contributing to django
documentation. If you haven't, you should definitely start there.
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:6>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: expressions | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Brad Melin):
Would this patch be considered non-trivial? I.e. should I discuss it in
django-developers?
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:7>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: expressions | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Josh Smeaton):
No, no need. Just make a start, open a PR, and we'll review there. If you
need some help feel free to reply here or #django-dev on IRC
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:8>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: expressions | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
* needs_docs: 0 => 1
* has_patch: 0 => 1
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:9>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: expressions | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
* needs_docs: 1 => 0
Comment:
Turns out that MySQL also has the INSTR function that uses the same
argument order as the other backends. Using that instead.
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:10>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
| checkin
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
-------------------------------------+-------------------------------------
* stage: Accepted => Ready for checkin
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:11>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 1
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Tim Graham):
* needs_better_patch: 0 => 1
* easy: 1 => 0
* stage: Ready for checkin => Accepted
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:12>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: assigned
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: expressions | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
-------------------------------------+-------------------------------------
* needs_better_patch: 1 => 0
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:13>
Django
-------------------------------------+-------------------------------------
| Melin
Component: Database layer | Version: master
(models, ORM) |
Keywords: expressions | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
-------------------------------------+-------------------------------------
* status: assigned => closed
* resolution: => fixed
Comment:
In [changeset:"b625907a79bb1336cbc54231bdf7cace25fecaf7" b625907a]:
{{{
#!CommitTicketReference repository=""
revision="b625907a79bb1336cbc54231bdf7cace25fecaf7"
Fixed #27834 -- Added StrIndex database function.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:14>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: closed
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution: fixed
Keywords: expressions | Triage Stage: Accepted
Needs tests: 0 | Patch needs improvement: 0
-------------------------------------+-------------------------------------
Comment (by Tim Graham <timograham@…>):
In [changeset:"7f8a924b45906a66aa3f562489550eacf2a622ed" 7f8a924]:
{{{
#!CommitTicketReference repository=""
revision="7f8a924b45906a66aa3f562489550eacf2a622ed"
Refs #27834 -- Removed Value wrapping from StrIndex's substring param.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:15>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: closed
Severity: Normal | Resolution: fixed
Keywords: expressions | Triage Stage: Accepted
-------------------------------------+-------------------------------------
In [changeset:"020e5799ad74cfafd469f032cd05767c9d670a16" 020e579]:
{{{#!CommitTicketReference repository=""
revision="020e5799ad74cfafd469f032cd05767c9d670a16"
Refs #27834 -- Restored "expression" in StrIndex's docs signature.
Documentation regression in 20dbf19fc505f0383e96b323905953c863817fe4.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:16>
Django
-------------------------------------+-------------------------------------
| Melin
Type: New feature | Status: closed
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution: fixed
Keywords: expressions | Triage Stage: Accepted
-------------------------------------+-------------------------------------
In [changeset:"bdd06c5457bada41ecca742c451b90770250bc4e" bdd06c5]:
{{{#!CommitTicketReference repository=""
revision="bdd06c5457bada41ecca742c451b90770250bc4e"
[6.0.x] Refs #27834 -- Restored "expression" in StrIndex's docs signature.
Documentation regression in 20dbf19fc505f0383e96b323905953c863817fe4.
Backport of 020e5799ad74cfafd469f032cd05767c9d670a16 from main.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/27834#comment:17>