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

8 Feb 2008

      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.

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.

~Yuva

On 08/02/2008, Yuvaraj Athur Raghuvir  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
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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;