Naming of columns

[dantownsend]

Discussed in #206

Allow Table columns to map to database columns with different names.

For example:

class MyTable(Table):
    name = Varchar(name="person_name")

In the example above, when doing queries, you will use MyTable.name, but the actual column in the database is called person_name.

This is useful when using Piccolo on legacy databases with non-ideal column names.

[gmos]

Would be nice to have this. I have an existing database with a column name called 'class'. So named the field 'class_' in the definition. But then obviously table accesses fail. So needed a workaround.

Already wanted to make a view in the database to change the offending name. But then looked into the code and found this workaround:

class LoraKey(Table, tablename="copy_lora_key", db=DB):
    # ...
    class_ = Varchar(null=False, length=1)

LoraKey.class_._meta._name = 'class'

Seems to do the job nicely, albeit a bit of a hack.

[gmos]

Seems to do the job nicely, albeit a bit of a hack.

Alas, while fetching and updating works, creating and initializing a new instance doesn't.

t1 = LoraKey( class_="A", other=42 )  # doesn't find the field and vs-code gives a warning
t2 = LoraKey( class="A", other=42 )   # obviously gives a syntax error.
# Need to do it in steps for this to work...
t3 = LoraKey( other=42 )
t3['class'] = "A"

[dantownsend]

@gmos I had a quick go at fixing this issue - still need to write some more tests, but hopefully should be able to release it soon.

[dantownsend]

The most problematic thing is passing it into the constructor - so in your example LoraKey( class="A", other=42 ).

There's a related issue, where a dictionary of arguments can be passed in. This is one potential fix:

#268

I think it's cleaner than letting a user pass in either class or class_. I'll have a think.

[dantownsend]

@gmos There's a new version on PyPI which supports this feature now. Hopefully it solves your issue.

This should now work:

class LoraKey(Table, tablename="copy_lora_key", db=DB):
    class_ = Varchar(null=False, length=1, db_column_name='class')

[dantownsend]

There's also this approach for anyone coming across this in the future:

piccolo/piccolo/table.py

Line 955 in 6938913

def create_table_class(

So it's:

from piccolo.table import create_table_class

LoraKey = create_table_class(
    class_kwargs={'tablename': 'copy_lora_key', 'db': DB},
    class_members={'class': Varchar(null=False, length=1)}
)

A bit harder to read, but useful in a pinch.

[gmos]

Just installed the new version. Works perfectly. Thnx.