James,
We all need to look at this!!! Sorry sorry sorry! I will have a look
ASAP (by early next week, say Tuesday since that's traditionally a "UCR
day" for me, at the latest).
Question - what do you mean by "do we want a scalar or aggregate
version" of the functions? It seems like we don't have a choice, do
we? Aren't they inherently aggregate functions (so the answer would be
the latter)? I think maybe I didn't get the gist of the question. On
the SQL vs. AQL versions - it would be nice to have both versions of
each (aggregate) function, actually - i.e., one version that does what
SQL does in terms of turning a blind eye to nulls, and one version that
does what AQL does, which is to say that if you have a null (a.k.a.
unknown) input then the output must logically be unknown as well (e.g.,
if you add two numbers by either doing "+" or having them appear in a
two-object dataset's numeric column and doing sum( ), you should get the
same answer either way).
More to follow when I look more closely! Sorry we've all been so slow.
(@Others: your take(s)?)
Cheers,
Mike
On 11/18/15 2:06 PM, James Fang wrote:
Just wondering if anyone has a response on this discussion?
Thanks,
James
On Mon, Nov 9, 2015 at 2:11 PM, James Fang <[email protected]> wrote:
The following functions that I am asking about are from
http://www.postgresql.org/docs/9.4/static/functions-aggregate.html
The following google doc contains a spreadsheet of all the current
aggregation functions that exist in AQL and SQL. The colored portions will
be the portions that I wish to discuss. I assumed that AQL returns null if
at least 1 of the results in the aggregation is null while SQL ignores the
tuple if it is null.
https://docs.google.com/document/d/1l9QtRAB7H3yzP3976livpKzJZHVJlPdvDrjlm2YCsM0/edit?usp=sharing
Questions:
1) Do we need array_agg, this function just groups up the results together
into one array as output. If so, do we want a scalar version or aggregate
version?
2) For bitwise-or and bitwise-and, I have implemented a sql aggregate
version. Do we want a AQL aggregate version as well? Do you think that we
should implement this as a scalar or as an aggregation?
3) For boolean-or and boolean and, we current have an existing scalar
version for AQL. Do we need a scalar version for SQL? Should we implement a
aggregate version of these boolean functions?
4) Do we need a json_agg function? I do not think so because all the data
is returned in json format. If you have a different answer, let me know.
5) For string_agg, we currently have a scalar version for AQL known as
string-join. Do we need a SQL version?
