Hello again, I have another problem I've run into maybe someone can help
with.
Let's say I have a table of blog posts and all I want to do is print out
all the titles. I'll make up a really simple example:
MODEL:
db.define_table('myBlog',
Field('title'),
Field('body', 'text'),
Field('created_on', 'datetime', default=request.now))
CONTROLLER:
def index():
titles = db(db.myBlog).select()
return locals()
INDEX VIEW:
{{for title in titles:}}
{{=title.title}}
{{pass}}
Now this works, but isn't it a waste to grab all the body and created_on
fields if I don't plan on using them?
I'm looking at the web2py book and it says in the select section of the DAL:
The select command can take arguments. All unnamed arguments are
interpreted as the names of the fields that you want to fetch. For example,
*you can be explicit on fetching field "id" and field "name"*:
>>> for row in db().select(db.person.id, db.person.name):
print row.name
Alex
Bob
Carl
So if I am understanding this correctly, I should be able to edit the
controller above to say:
def index():
titles = db().select(db.myBlog.title)
return locals()
and titles should now only contain the title fields of myBlog. So if I add
something crazy in the view like this:
VIEW:
{{for title in titles:}}
{{=title.title}}
*{{=title.body}}*
{{pass}}
I am expecting this to break, but this works fine. Shouldn't the
{{=title.body}} part break the view now that I am only grabbing the
titles? Shouldn't title.body not exist?
Why am I still able to print out the title.body, title.created_on date, and
title.id?
Does fetching only the title save me anything in the long run, or will
grabbing the entire table cost the same as far as performance?
What have I misinterpreted with the example taken from the book?
Thanks
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