Re: simultaneously-created tables not generating

i guess i don't understand OCC as well as i should. there are cases [1] where i get a massive speed improvement when i COPY INTO multiple (separate) tables at once.. [1] https://www.monetdb.org/bugzilla/show_bug.cgi?id=3963 On Tue, Mar 29, 2016 at 8:14 AM, Pierre-Adrien Coustillas < pcoustillas@1g6.biz> wrote:

Hi,

No,there will also be transaction conflict Update, insert, copy into, create table, can not be executed simultaneously. An update or delete query with a "select" query will also be a conflict.

Reading performance has a significant cost to the constraints writings

In my company we are considering developing a query scheduler to avoid conflicts

Pierre

------------------------------ *De: *"Anthony Damico" *À: *"Communication channel for MonetDB users" *Envoyé: *Mardi 29 Mars 2016 12:57:07 *Objet: *Re: simultaneously-created tables not generating

so the trick would be to create each empty table individually and then INSERT INTO or COPY INTO each separate table simultaneously? thanks!

On Tue, Mar 29, 2016 at 5:00 AM, Pierre-Adrien Coustillas < pcoustillas@1g6.biz> wrote:

...

Hi,

It is not possible to create multiple tables simultaneously, because this causes a transaction conflict on the table sys.tables.

If you log the error messages you see !40000!COMMIT: transaction is aborted because of concurrency conflicts, will ROLLBACK instead

Pierre

------------------------------ *De: *"Anthony Damico" *À: *"Communication channel for MonetDB users" *Envoyé: *Vendredi 25 Mars 2016 17:28:49 *Objet: *simultaneously-created tables not generating

i have three clients connected to one mserver. they are simultaneously running these three commands, which share table `z` but not the x or y tables--

CREATE TABLE y1 AS SELECT x1.* FROM x1 LEFT JOIN SELECT col FROM Z ON x1.id = z.id WITH DATA ;

CREATE TABLE y2 AS SELECT x2.* FROM x2 LEFT JOIN SELECT col FROM Z ON x2.id = z.id WITH DATA ;

CREATE TABLE y3 AS SELECT x3.* FROM x3 LEFT JOIN SELECT col FROM Z ON x3.id = z.id WITH DATA ;

when all three commands complete, tables y2 and y3 do not exist

if i run the commands sequentially, everything works.

am i making a mistake in how sql transactions should behave, or is this potentially a bug that i should figure out how to reproduce for bugzilla?

thanks!

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