On 04/25/2016 07:26 AM, Babak Alipour wrote:
That is correct. The function I've written only works when the two
tables are named table_train and table_test; is it possible to
generalize that to take in any two tables?
I'm heading out the door and off the top of my head:
1) Get tables names as text.
2) Get the row conditions as text.
3) Use EXECUTE to build a query string:
http://www.postgresql.org/docs/9.5/interactive/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN
In particular:
"A cleaner approach is to use format()'s %I specification for table or
column names (strings separated by a newline are concatenated):"
http://www.postgresql.org/docs/9.5/static/functions-string.html#FUNCTIONS-STRING-FORMAT
4) SELECT the result INTO a record variable:
http://www.postgresql.org/docs/9.5/interactive/plpgsql-declarations.html#PLPGSQL-DECLARATION-RECORDS
5) Do your calculations
6) Not considered, validating that number of table columns are the same
and the types are compatible.
Thanks in advance.
Babak
On Mon, Apr 25, 2016 at 10:24 AM, Adrian Klaver
<adrian.kla...@aklaver.com <mailto:adrian.kla...@aklaver.com>> wrote:
On 04/25/2016 07:07 AM, Babak Alipour wrote:
Greetings everyone,
I'm a novice plpgsql user.
For an application, I'm trying to write a user-defined function that
takes a row of some table (let's say with k fields) and takes
another
row from another table (again with k fields); then calculate the
Euclidean, Manhattan or generally Minkowski distance (with some
p) and
then return an integer.
I've written this:
CREATE FUNCTION euclidean_distance(row1 table_train, row2
table_test,
OUT distance DOUBLE PRECISION) AS $$
DECLARE
tmp DOUBLE PRECISION;
BEGIN
FOR col IN SELECT column_name FROM information_schema.columns WHERE
table_name=table_train LOOP
tmp := (row1.col - row2.col);
distance += tmp*tmp;
END LOOP;
distance := sqrt(distance);
END;
$$ LANGUAGE plpgsql;
Could anyone please help me fix this function so that I can pass
any two
rows of two tables (with same number of columns) and have their
distance
returned.
You are already doing that, so do you mean any two rows of any two
tables?
Best regards,
Babak Alipour
--
*/Babak Alipour ,/*
*/University of Florida/*
--
Adrian Klaver
adrian.kla...@aklaver.com <mailto:adrian.kla...@aklaver.com>
--
*/Babak Alipour ,/*
*/University of Florida/*
--
Adrian Klaver
adrian.kla...@aklaver.com
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