maria-developers team mailing list archive

[Roberto Spadim <roberto@xxxxxxxxxxxxx>]

well, i'm not a expert , and it's not comment about storage engine plugin,
but i will give one example with information schema plugin, there's
parameters to know what you could optimize with where clausule, maybe this
can help:

http://dev.mysql.com/doc/refman/5.7/en/writing-information-schema-plugins.html

static int simple_fill_table(THD *thd, TABLE_LIST *tables, Item *cond)


http://dev.mysql.com/tech-resources/articles/mysql_i_s_plugins_part2.html
The TABLE_LIST *tables argument provides the handle to the information
schema table that is being filled, and the COND *cond argument represents
the WHERE condition of the SQL statement that is currently being handled,
allowing the fill_table function to directly filter rows (instead of
relying on the query execution engine to do that). As such, these arguments
are occupied with the actual delivery of rows of data to the server.


2015-02-06 14:08 GMT-02:00 Andras Szabo <andrei.hu@xxxxxxxxx>:

> Hi Folks,
>
>  A new question has risen during the development of our storage engine.
>
>  In short the engine is providing a read-only view to the server
> filesystem.
>
>  One can issue (implemented via assisted discovery):
>
> CREATE TABLE etc ENGINE=fsview ROOT=‘/etc’;
>
>  Then it’s possible to tell:
>
> SELECT name, fsize FROM etc ORDER BY fsize DESC LIMIT 10
>
> resulting in:
>
> +-----------------+--------+
> | name            | fsize  |
> +-----------------+--------+
> | ld.so.cache     | 129417 |
> | mailcap         |  44732 |
> | fb.modes        |  24501 |
> | mime.types      |  24066 |
> | brltty.conf     |  22478 |
> | services        |  19558 |
> | devscripts.conf |  18037 |
> | ltrace.conf     |  14867 |
> | login.defs      |  10551 |
> | sensors3.conf   |  10344 |
> +-----------------+--------+
>
> So far so good (the listing is not recursive).
>
> An additional feature is to access subdirectories of the root (this is
> working via automated discovery):
>
> SELECT name, fsize FROM `etc/init.d`
>
> This is not terribly wrong, but we’re thinking about the possiblity of
> improving it somehow that:
>
> SELECT name, fsize FROM etc WHERE path = “init.d”;
>
> However we’re in a bit of trouble how we could improve the storage engine
> to be able to handle this.
>
> Of course we would not like to do a "deep enumeration" of the root
> directory (full table scan) . So somehow we would like to access/use the
> information from the where clause.
>
> Can anybody recommend a way to solve that?
>
>
> --
> Andras Szabo
> Sent with Airmail
>
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-- 
Roberto Spadim
SPAEmpresarial - Software ERP
Eng. Automação e Controle