Github user njayaram2 commented on a diff in the pull request:
https://github.com/apache/incubator-madlib/pull/80#discussion_r92718644
--- Diff: src/ports/postgres/modules/knn/knn.sql_in ---
@@ -0,0 +1,126 @@
+/* -----------------------------------------------------------------------
*//**
+ *
+ * @file knn.sql_in
+ *
+ * @brief Set of functions for k-nearest neighbors.
+ *
+ *
+ *//*
----------------------------------------------------------------------- */
+
+m4_include(`SQLCommon.m4')
+
+DROP TYPE IF EXISTS MADLIB_SCHEMA.knn_result CASCADE;
+CREATE TYPE MADLIB_SCHEMA.knn_result AS (
+ prediction float
+);
+DROP TYPE IF EXISTS MADLIB_SCHEMA.test_table_spec CASCADE;
+CREATE TYPE MADLIB_SCHEMA.test_table_spec AS (
+ id integer,
+ vector DOUBLE PRECISION[]
+);
+
+CREATE OR REPLACE FUNCTION MADLIB_SCHEMA.__knn_validate_src(
+rel_source VARCHAR
+) RETURNS VOID AS $$
+ PythonFunction(knn, knn, knn_validate_src)
+$$ LANGUAGE plpythonu
+m4_ifdef(`__HAS_FUNCTION_PROPERTIES__', `READS SQL DATA', `');
+
--- End diff --
I believe this is just the first version of this code. But
it is a good idea to have some documentation that
would be helpful for users. Try to include a function
that would show the help messages when the user just
calls `select madlib.knn()` or `select madlib.knn('help')`.
It'll also be awesome to include some small example data
that can be used. For instance, include a small train and
test tables. Functions that display these help messages
are typically written in python. Check out other modules
to get some ideas for the same.
Fyi, I created the following train and test tables locally
when I tried to run this code:
```sql
drop table if exists knn_train_data;
create table knn_train_data (
id integer,
data integer[],
label float);
copy knn_train_data (id, data, label) from stdin delimiter '|';
1|{1,1}|1.0
2|{2,2}|1.0
3|{3,3}|1.0
4|{4,4}|1.0
5|{4,5}|1.0
6|{20,50}|0.0
7|{10,31}|0.0
8|{81,13}|0.0
9|{1,111}|0.0
\.
drop table if exists knn_test_data;
create table knn_test_data (
id integer,
data integer[]);
copy knn_test_data (id, data) from stdin delimiter '|';
1|{2,1}
2|{2,6}
3|{15,40}
4|{12,1}
5|{2,90}
6|{50,45}
\.
```
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