Bug in models.functions.ConcatPair for sqlite

[jerch]

Concat is not working for me due to this line in models.functions.ConcatPair.coalesce:

Coalesce(expression, Value('')) for expression in c.get_source_expressions()

With a minor change it works as intended:

Coalesce(expression, Value('""')) for expression in c.get_source_expressions()

Tested with Django 1.8.12 under Ubuntu with sqlite 3.8.2-1ubuntu2.1.

[Shai Berger]

When you say "not working for me" -- what did you give as inputs, what did you expect to happen and what happened instead?

[jerch]

I tried to concat two db fields into one output column like this:

expr = Concat(models.F('field1'), models.Value('"-"'), models.F('field2'), output_field=models.CharField())

Expected output: 'value_from_field_1-value_from_field_2'

Instead I just got an invalid syntax sql error:

django.db.utils.OperationalError: near ")": syntax error

Problem is that the empty Value('') creates something like this for sqlite:

COALESCE("A", )

which is not valid for sqlite:

sqlite> SELECT COALESCE("A", );
Error: near ")": syntax error
sqlite> SELECT COALESCE("A", "");
A

while the second with an empty string with string delimiters is.

[Josh Smeaton]

I can't reproduce:

In [6]: from django.db import connection

In [7]: connection.vendor
Out[7]: u'sqlite'

In [8]: concat = Concat(F('name'), Value('-'), F('motto'), output_field=CharField())

In [9]: Company.objects.annotate(concat=concat).first().concat
Out[9]: u'HI-'

In [10]: concat = Concat(F('name'), Value('"-"'), F('motto'), output_field=CharField())

In [11]: Company.objects.annotate(concat=concat).first().concat
Out[11]: u'HI"-"'

In [12]: import django

In [13]: django.get_version()
Out[13]: '1.10.dev20160401110429'

Note that I tried both Value('"-"') and Value('-'). You shouldn't be injecting quotes into Value, it'll take care of itself.

Can you please post the full queryset you're running that generates the error, and also print the underlying query of the queryset, like this:

qs = Model.objects.whatever()
print(qs.query)

Also, what version of Django are you using? Can you reproduce on master?

[Josh Smeaton]

Can't reproduce on stable 1.8 or 1.9 either.

[Simon Charette]

Please reopen if you can provide more details about your Django, Python and SQLite3 version (import sqlite3; sqlite3.version).