Strange behaviour when using morphology_skip_fields

General Discussions - English
1

Hi,

I have noticed a weird problem / bug when using morphology_skip_fields with morphology=‘libstemmer_ro’

Here is how the problem can be reproduced

mysql> drop table if exists test;
Query OK, 0 rows affected (0.00 sec)

mysql> create table test (id bigint, title text, title_extras text) charset_table=‘non_cjk’ dict=‘keywords’ index_exact_words=‘1’ min_word_len=‘1’ min_infix_len=‘1’ min_stemming_len=‘5’ morphology=‘libstemmer_ro’ morphology_skip_fields=‘title_extras’;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> insert into test (title, title_extras) values (‘abc def’, ‘xyz’);
Query OK, 1 row affected (0.00 sec)

mysql> SELECT * from test WHERE MATCH(‘+xyz’);
Empty set (0.00 sec)

If I drop the morphology_skip_fields it will be working just fine.

Is there somehting obvious that I am missing?

Thank you

2

you could issue

SELECT * from test WHERE MATCH(‘+xyz’);
show meta;

to make sure about the search

or

set profiling=1;
SELECT * from test WHERE MATCH(‘+xyz’);
show plan;

to check for search tree

3

mysql> SELECT * from test WHERE MATCH(‘+xyz’);
Empty set (0.00 sec)

mysql> show meta;
±---------------±------+
| Variable_name | Value |
±---------------±------+
| total | 0 |
| total_found | 0 |
| total_relation | eq |
| time | 0.000 |
| keyword[0] | xyz |
| docs[0] | 0 |
| hits[0] | 0 |
±---------------±------+
7 rows in set (0.00 sec)

mysql> set profiling=1;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT * from test WHERE MATCH(‘+xyz’);
Empty set (0.01 sec)

mysql> show plan;
±-----------------±------------------------------+
| Variable | Value |
±-----------------±------------------------------+
| transformed_tree | AND(KEYWORD(xyz, querypos=1)) |
±-----------------±------------------------------+
1 row in set (0.00 sec)

4

you need to issue

SELECT * from test WHERE MATCH(‘=xyz’);

as morphology_skip_fields indexes terms as term with the exact modifier
or use expand_keywords index or query option
or use the last daemon version and query exact that field and daemon will do such expansion on its own

you could read the ticket with the explanation strange behavior with morphology_skip_fields · Issue #560 · manticoresoftware/manticoresearch · GitHub

5

It makes sense, thank you!