Now I'm trying to follow the example given in this wiki: https://www.monetdb.org/wiki/TPCH_Example and https://www.monetdb.org/Documentation/Manuals/SQLreference/Explain.
I tried to perform in the mclient the following query, where with the first statement I try to initialize the sql module.
mal>s := sql.start();
mal>_2 := sql.mvc();
but after the second command, the client hangs and does not me allow to perform the query.
Is there any way to overcome this problem? Thanks again.
________________________________
Da: users-list [users-list-bounces+giacomo.bergami2=unibo.it@monetdb.org] per conto di Lefteris [lsidir@gmail.com]
Inviato: mercoledì 16 dicembre 2015 17.20
A: Communication channel for MonetDB users
Oggetto: Re: Performing a direct access to MonetDB's BAT tables via MAL
Hi,
in the MAL level the fastest and best access to a BAT is still subselect if you are looking for a value and fetch if you are interested in the value to a specific position (aka oid).
Lefteris
On Wed, Dec 16, 2015 at 4:45 PM, Giacomo Bergami mailto:giacomo.bergami2@unibo.it> wrote:
Good Morning/Evening everyone.
My aim is to direcly access to the BAT column store representation of MonetDB through the standard libraries (MAPI/JDBC) - if possible. I know that each SQL query gets rewrited into a BAT algebra expression, but in my case I want to access to a single value per time (e.g. I want to access to the value stored in the i-th row and in the column labelled "j" of a given table) and maybe in this case the direct access is quicker than performing the whole SQL query.
I've already tried to use the mclient with the MAL language and read the documentation, and I tried to use the client with something like this:
mdb.start();
bbp.open();
bbp.prelude();
a := bbp.bind("fx", "size");
where "fx" should be the name of the table and "size" one of its attributes. But unfortunately I do not know how to search for a specific row-key and to get the correspondant value, and AFAIK i have to get the id of the column "size".
Thanks in advance,
Giacomo Bergami
____________________________
Giacomo Bergami, Ph.D Student
University of Bologna
https://www.unibo.it/sitoweb/giacomo.bergami2
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