#32858: Syntax error when using an index transform on an ArrayField in an
ExclusionConstraint
-------------------------------------+-------------------------------------
Reporter: Lucidiot | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 3.2
(models, ORM) |
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
-------------------------------------+-------------------------------------
Description changed by Lucidiot:
Old description:
> I am trying to create a GIST exclusion constraint on a PostgreSQL 12
> database. One of the fields is an ArrayField, and I want to apply the
> constraint on its first item using `my_array__0`. When doing so, I get a
> syntax error from Postgres.
>
> {{{#!python
> from django.db import models
> from django.contrib.postgres.constraints import ExclusionConstraint
> from django.contrib.postgres.fields import ArrayField, RangeOperators
>
> class MyModel(models.Model):
>
> my_array = models.ArrayField()
>
> class Meta:
> constraints = (
> ExclusionConstraint(
> name='foo',
> expressions=[
> ('my_array__0', RangeOperators.EQUAL),
> ]
> )
> )
> }}}
>
> {{{
> django.db.utils.ProgrammingError: syntax error at or near "WITH"
> LINE 1: ..." ADD CONSTRAINT "foo" EXCLUDE USING GIST ("my_array"[1] WITH
> =)
> ^
> }}}
>
> It seems a similar issue had occurred with casts (#32392). The
> [https://www.postgresql.org/docs/current/sql-altertable.html docs for
> ALTER TABLE] mention this syntax for expressions in an EXCLUDE
> constraint:
>
> {{{
> exclude_element in an EXCLUDE constraint is:
>
> { column_name | ( expression ) } [ opclass ] [ ASC | DESC ] [ NULLS {
> FIRST | LAST } ]
> }}}
>
> This implies that parentheses around anything that is not a column name
> are mandatory. Maybe a more generic fix could be made to detect if
> something is only a column name, or just to add parentheses all the time?
> `EXCLUDE USING GIST (("my_array"[1]) WITH =)` works without any trouble.
New description:
I am trying to create a GIST exclusion constraint on a PostgreSQL 12
database. One of the fields is an ArrayField, and I want to apply the
constraint on its first item using `my_array__0`. When doing so, I get a
syntax error from Postgres.
{{{#!python
from django.db import models
from django.contrib.postgres.constraints import ExclusionConstraint
from django.contrib.postgres.fields import ArrayField, RangeOperators
class MyModel(models.Model):
my_array = ArrayField()
class Meta:
constraints = (
ExclusionConstraint(
name='foo',
expressions=[
('my_array__0', RangeOperators.EQUAL),
]
)
)
}}}
{{{
django.db.utils.ProgrammingError: syntax error at or near "WITH"
LINE 1: ..." ADD CONSTRAINT "foo" EXCLUDE USING GIST ("my_array"[1] WITH
=)
^
}}}
It seems a similar issue had occurred with casts (#32392). The
[https://www.postgresql.org/docs/current/sql-altertable.html docs for
ALTER TABLE] mention this syntax for expressions in an EXCLUDE constraint:
{{{
exclude_element in an EXCLUDE constraint is:
{ column_name | ( expression ) } [ opclass ] [ ASC | DESC ] [ NULLS {
FIRST | LAST } ]
}}}
This implies that parentheses around anything that is not a column name
are mandatory. Maybe a more generic fix could be made to detect if
something is only a column name, or just to add parentheses all the time?
`EXCLUDE USING GIST (("my_array"[1]) WITH =)` works without any trouble.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/32858#comment:1>
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