#27834: Add the STRPOS database function
-------------------------------------+-------------------------------------
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 |
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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
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Ticket URL: <https://code.djangoproject.com/ticket/27834>
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