Hello Guys,
historically concat_ws() UDF was added in the scope of
https://issues.apache.org/jira/browse/HIVE-682 ticket. I have a simple
question about its implementation. According to above ticket's description
it should have behavior like MySQL implementation (
http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_concat-ws).
MySQL documentation says:
"CONCAT_WS()<http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_concat-ws>
does
not skip empty strings. However, it does skip any NULL values after the
separator argument.". I have performed a simple test:
> create table test (col1 string);
> select concat_ws(',', '10', NULL, '4', '', 'a') from test limit 1;
as a result I have got:
> 10,4,,a
which looks good for me.
But in tests (
https://github.com/apache/hive/blob/trunk/ql/src/test/results/clientpositive/udf_concat_ws.q.out
:
78 line) I see the following lines:
POSTHOOK: query: SELECT concat_ws(dest1.c1, dest1.c2, dest1.c3),
> concat_ws(',', dest1.c1, dest1.c2, dest1.c3),
> concat_ws(NULL, dest1.c1, dest1.c2, dest1.c3),
> concat_ws('**', dest1.c1, *NULL*, dest1.c3) FROM dest1
> POSTHOOK: type: QUERY
> POSTHOOK: Input: default@dest1
> #### A masked pattern was here ####
> POSTHOOK: Lineage: dest1.c1 SIMPLE []
> POSTHOOK: Lineage: dest1.c2 SIMPLE []
> POSTHOOK: Lineage: dest1.c3 SIMPLE []
> xyzabc8675309 abc,xyz,8675309 NULL abc****8675309
which looks like NULLs are not skipped.
What have I missed?
Thanks, Alexey.
