Hi, Richa! On Mar 13, Richa Sehgal wrote:
Dear mentors,
I am currently pursuing Master's in University of Illinois at Urbana Champaign, USA and completed by B.Tech from Indian Institute of Technology - Delhi (IIT- Delhi)
This is regarding GSoC 2015. I am really interested in databases, and I was very excited to see all these projects listed here. The exciting part was that some of the projects are really “hard” as in they have challenged the database community since a long time, and thus it would be very interesting to solve some of these challenges as part of GSoC.
I want to discuss 2 projects:
A. Indexes on virtual columns
Materialization gives us two things:
1. A name to the column which we can use in queries
Not quite. Even non-materialized columns always have names. See https://mariadb.com/kb/en/mariadb/virtual-computed-columns/
2. A formal "regular" column which is stored and indexed in the regular fashion - Disadvantage: Extra memory requirements for the materialized column.
Exactly.
My initial thoughts on this project are the following:
We do need the name of the column which can be used to query. So maybe we can expose a command such as:
create virtual_index <name> on <column_name> <expression>
What this would do would run a regular query which evaluates expressions (like in WHERE clause) and the feed the result into the indexer. This index can then be stored in the regular fashion.
Yes, in a sense. The update_virtual_fields() function calculates values of virtual columns (e.g. if one does SELECT * from table_with_virtual columns). In MyISAM, _mi_make_key() creates a key from the row image. Pure virtual columns are not in the row image, so they cannot be indexed that way. So, in a very simplified way, this project is about calling update_virtual_fields() from _mi_make_key().
B. Having UDFs returning an array/set
There are three approaches that I can think of: ... I would like to discuss these and then decide on one of them. Am I approaching this in the right direction? Can you please point me to the next steps?
I'm afraid, the project was badly formulated. I've rewritten it now to highlight what it is really about. It is not about arrays, the important part is a "result set". See MDEV-5199 Regards, Sergei