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

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  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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