Ability to support using index fields as ranking factor

[scruel]

Proposal:

This can give users more freedom to change the rankings result, otherwise, we may have to do the re-ranking by multiple query results with other programming languages.

Checklist:

^{To be completed by the assignee. Check off tasks that have been completed or are not applicable.}

• Task estimated
• Specification created, reviewed and approved
• Implementation completed
• Tests developed
• Documentation updated
• Documentation proofread
• Changelog updated
• OpenAPI YAML updated and issue created to rebuild clients

[sanikolaev]

currently, I have to do two queries to achieve this, one for less than, one for gather than

Pls provide an example. I don't quite understand what you mean.

[scruel]

Sorry, what I really need first is let manticoresearch support custom ranking by field values, consider this haven't yet been supported, then this issue is unnecessary, I've changed description.
BTW, if you can implment this feature, then abs function is useful as follows:

SELECT ... OPTION ranker=<score>-abs(<id>-10)+sph04;

<score> and id are not built-in ranking factors, they are index fields, which can give users more freedom to change rankings, the above will add score and 'whether <id> is close to 10' in to ranking consideration.

[sanikolaev]

need first is let manticoresearch support custom ranking by field values, consider this haven't yet been supported

It is supported to some extent, e.g.:

➜  ~ mysql -P9306 -h0 -e "drop table if exists t; create table t(f text, a int); insert into t(f, a) values('a', 1),('a a', 5); select *, weight() from t where match('a') option ranker=expr('a*2+5');"
+---------------------+------+------+----------+
| id                  | f    | a    | weight() |
+---------------------+------+------+----------+
| 1515860105357164700 | a a  |    5 |       15 |
| 1515860105357164699 | a    |    1 |        7 |
+---------------------+------+------+----------+

Please experiment with it and elaborate more on the task.