hum i'm thinking about the problem for example if we have an COUNT(*) or a SUM(value) or MAX(value) or MIN(value) or anyother functions shouldn't be more rational allow the 'single thread' query execute and use the GROUP_CONCAT function? ok it's not multi thread, but could the group_concat with limit 'optimize' the shard query or single queries like this?
2015-10-03 0:10 GMT-03:00 Roberto Spadim <[email protected]>: > nice :) > > how it's "rewrite"? > > 2015-10-02 22:25 GMT-03:00 Justin Swanhart <[email protected]>: > >> Hi, >> >> You could use Shard-Query. You don't need to shard the database, you can >> point shard-query at one database. It supports WINDOW functions. >> >> select >> date, >> FIRST_VALUE(value) OVER (ORDER BY value ASC), >> LAST_VALUE(value) OVER (ORDER BY value ASC) >> FROM some_table AS a >> GROUP BY date >> >> --Justin >> >> On Fri, Oct 2, 2015 at 6:12 PM, Roberto Spadim <[email protected]> >> wrote: >> >>> Hi guys >>> I have a problem and a possible solution, that i think is relative easy >>> to develop (i didn't tested but i think the source is easy to change) >>> >>> i have some queries like: >>> >>> >>> SELECT >>> date, >>> (SELECT value FROM some_table WHERE date=a.date ORDER BY date ASC LIMIT >>> 1) AS first, >>> (SELECT value FROM some_table WHERE date=a.date ORDER BY date DESC LIMIT >>> 1) AS last >>> FROM some_table AS a >>> GROUP BY date >>> >>> >>> i want to "convert" the complex sub query, to a agregate function, and i >>> thinking about group concat: >>> from mysql docs: >>> >>> GROUP_CONCAT([DISTINCT] *expr* [,*expr* ...] >>> [ORDER BY {*unsigned_integer* | *col_name* | *expr*} >>> [ASC | DESC] [,*col_name* ...]] >>> [SEPARATOR *str_val*]) >>> >>> >>> we have ORDER BY >>> if we could include a "LIMIT" clause, i could rewrite this query to: >>> >>> SELECT >>> date, >>> GROUP_CONCAT(value ORDER BY date ASC LIMIT 1) AS first, >>> GROUP_CONCAT(value ORDER BY date DESC LIMIT 1) AS last >>> FROM some_table AS a >>> GROUP BY date >>> >>> >>> i know that i could have stats tables / materialized views (with >>> flexview, i already tested :) ), but i want something more "easy to use" >>> and not "very fast", just a "feature" to solve small problems >>> >>> >>> it's a nice idea? does anyone have this "problem" and solve with other >>> solutions? >>> >>> -- >>> Roberto Spadim >>> >>> _______________________________________________ >>> Mailing list: https://launchpad.net/~maria-discuss >>> Post to : [email protected] >>> Unsubscribe : https://launchpad.net/~maria-discuss >>> More help : https://help.launchpad.net/ListHelp >>> >>> >> > > > -- > Roberto Spadim > SPAEmpresarial - Software ERP > Eng. Automação e Controle > -- Roberto Spadim SPAEmpresarial - Software ERP Eng. Automação e Controle
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