Em 04-07-2012 19:49, Jeremy Evans escreveu:
On Wednesday, July 4, 2012 2:39:11 PM UTC-7, Rodrigo Rosenfeld Rosas
wrote:
There is a critical part in my application where I need to
generate the SQL by myself.
It would be easier to process the results of this generated
dynamic SQL if I could iterate over each row by index.
I mean, instead of having DB[sql].all to return something like
[{tid: 23, tname: 'Some name'}, ...] I'd prefer to get something
like: [[23, "Some name"], [...], ...].
Currently I'm doing something like below, but I'd like to know if
there is some method that already does that and that I'm not aware of:
builder = QueryBuilder.new(params)
json = DB[builder.sql].map do |r|
r = r.map{|k, v| v} # this is the trick I'm currently using
builder.columns.map do |c|
raw = r.shift
case c[:type]
when 'range' then [raw, r.shift]
...
else raw
end
end
You can provide an argument to map:
ds = DB[builder.sql]
ds.map(ds.columns)
Thanks for your support once more, Jeremy.
The problem is that my columns array doesn't contain the alias
information. It is something like [{field_id: 687, type: 'string'},
{field_id: 934, type: 'time-span'}, ...]. Even though all my columns are
aliased in the generated query, they shouldn't be. I don't rely on their
alias for anything but readability. It wouldn't be hard to include the
alias in the columns array but it wouldn't be trivial either. And I'd
need to add more complexity and tests to my QueryBuilder just to work
around a Sequel limitation.
Your current code (r = r.map{|k, v| v}) is not guaranteed to be
portable across adapters (as adapters make no guarantee that hash
entry order is the same as column order), and certainly is unlikely to
work on ruby 1.8 because hashes aren't ordered there.
Yeah, I was aware of that. I'm not worried about 1.8 because I don't use
it for several years now. But I wasn't aware that some adapters wouldn't
fill the hash in the same order of the columns though.
Well, as long as PG does, I won't worry about this for now. After I get
some basic features to work I'll get back to this issue.
Thanks,
Rodrigo.
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