Re: [MonetDB-users] Embedded Use: Persisting and Metadata

11 Feb 2008


      Yuvaraj Athur Raghuvir wrote:
...
...
From a C/C++ code, how do I access the MAL level storage operators? I
to find operators of interest, you may start at the appendix of the manual:
http://monetdb.cwi.nl/projects/monetdb/MonetDB/Documentation/Instruction-Hel...
and perform a grep/find
...
would assume that using the right libraries I should be able to get this 
data into my C/C++ code. Could you please point me to the right 
resources here? Thanks.
Further, I want to know the storage cost on disk for the entire 
database. As I see the data is stored as a "farm". Does this mean that I 
can sum the sizes of all files under the root folder to get the disk 
storage cost?
yes, that is the persistent storage requirement of the database
~Yuva
On Feb 9, 2008 12:10 AM, Martin Kersten mailto:Martin.Kersten@cwi.nl> wrote:
Yuvaraj Athur Raghuvir wrote:
     > Thanks.
     >
     > Regarding db size, I would expect that the storage strategy will have
     > additional overheads due to bookkeeping requirements necessary for
     > reconstruction of the relations between the data elements. Since
    there
     > are no indices (I assume this due to columnar storage) I can discount
     > on the space required for indices.
     >
    Indices are automatically created and dropped as a side effect of
    queries.
    They disappear at the end of a session.
> Are there Mapi calls that I can use to determine the size of the
     > tables? I would like to horizontally partition the data across
     > multiple stores based on table size and growth estimates.
     >
    the SQL level does not open up the kernel information about storage
    requirements.
    At the MAL level several operators are available to assess storage cost.
     > ~Yuva
     >
     >
     > On 08/02/2008, Yuvaraj Athur Raghuvir mailto:yuvaraj.a.r@gmail.com> wrote:
     >
     >> Finally, I have managed to get the Mbeddded example working in
    VC++ 2005
     >> Express Edition on Windows XP ! Thanks to the folks in the
    mailing list.
     >>
     >> Use Case: MonetDB5 , Embedded Mode , SQL
     >>
     >> To move towards the application I intend to experiment on, I
    need some more
     >> information:
     >> 1) How to make data durable?  In the simple example,  I tried
    the following:
     >> a)  First Run: Create table and insert rows. Select to check if
    everything
     >> is ok.
     >> b) Second Run: Only perform selection
     >>
     >>>> I get an error in the second run.
     >>>>
     >> 2) How to get meta data of the database?
     >> a) I want to know the size of the tables and meta tables in the
    data base.
     >> In particular I am interested in seeing the growth of the
    database on
     >> addition of content.
     >> b) Typically, there is a master table in the database that records
     >> information of the schema persisted. What is the name of the
    Master Table
     >> and its schema in MonetDB?
     >> c) SQLite has an independent analyzer tool which dumps the state
    of the
     >> storage from which I can extract most of the data I need. Does
    MonetDB have
     >> a similar mechanism?
     >>
     >> ~Yuva
     >>
     >>
     >>>>>> code snippet >>>>>
     >>>>>>
     >>     dbh = embedded_sql (set, setlen);
     >>     if (dbh == NULL || mapi_error(dbh))
     >>         die(dbh, hdl);
     >>     /* switch off autocommit */
     >>     if (mapi_setAutocommit(dbh, 0) != MOK || mapi_error(dbh))
     >>         die(dbh,NULL);
     >>     if ((hdl = mapi_query(dbh, "create table emp"
     >>     " (name varchar(20),age int)")) == NULL || mapi_error(dbh))
     >>         die(dbh, hdl);
     >>     close_handle(dbh,hdl);
     >>     for(i=0; i< 1000; i++) {
     >>         char query[100];
     >>         _snprintf(query, 100,"insert into emp values(\'user%d\',
    %d)", i, (i
     >> % 82));
     >>         if ((hdl = mapi_query(dbh, query)) == NULL ||
    mapi_error(dbh))
     >>             die(dbh, hdl);
     >>         close_handle(dbh,hdl);
     >>     }
     >>     if ((hdl = mapi_query(dbh, "select * from emp")) == NULL ||
     >> mapi_error(dbh))
     >>         die(dbh, hdl);
     >>     i=0;
     >>     while (mapi_fetch_row(hdl)) {
     >>         char *age = mapi_fetch_field(hdl, 1);
     >>         i= i+ atoi(age);
     >>     }
     >>     if (mapi_error(dbh))
     >>         die(dbh, hdl);
     >>     close_handle(dbh,hdl);
     >>     printf("The sum is %d \n",i);
     >>     mapi_disconnect(dbh);
     >>     return 0;
     >>
     >>
     >
     >
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