Re: Autocounter/Sequqnce-Numbers

2011-05-23 Thread Matt Pouttu-Clarke 
Tim,

Does H2 allow multiple concurrent threads to update the database?  I'm not
sure it's fair to compare a single threaded database to a multi-threaded
database with a single threaded workload.

I have done benchmarks that show that Derby is much faster than H2 with a
multi-threaded workload in embedded mode.

Cheers,
Matt


On 5/21/11 3:56 AM, Tim Dudgeon tdudg...@informaticsmatters.com wrote:

 There are some other things here that might deserve some comment:
 http://www.h2database.com/html/features.html#comparison
 
 e.g. performance of embeded derby is slow!
 
 Tiim
 
 
 On 18/05/2011 16:05,
 malte.kem...@de.equens.com wrote:
 Hi to all,
 
 in http://www.h2database.com/html/features.html#feature_list I found
 this particular statement to above topic:
 
 *Sequence*and autoincrement columns, computed columns (can be used for
 function based indexes)
 
 Later on is a matrix that shows some RDBMs in releation to some features
 where it is denied that Derby supports sequences.
 
 So what is actually the case? And if Derby supports running numbers (in
 Oracle they are called /sequences/, in Microsoft DBs the are often
 called /auto counters/) how are they to be used.
 
 Thanks in advance for any hint
 
 Malte
 
 
 


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Performance Optimization for In-Memory ReadOnly Database

2011-05-23 Thread Stefan Bühlmann 
Hi together,

I'm using derby for a dataprocessing application.
SYSCS_UTIL.SYSCS_IMPORT_TABLE is used to import CSV data (around 100mb).
The tables contain huge amount of rows (~100k) with some CLOB (max 60mb)
columns.

The table data is never altered (after the CSV import).

Currently I'm using a in-memory database with pageCacheSize of 2000.

Are there any other tricks to make querying the data more efficient?

Kind Regards

Stefan

Question on automatic statistics feature in 10.8.2.1

2011-05-23 Thread Bergquist, Brett 
I have been testing with the new automatic statistics feature in 10.8.2.1 and 
turned on the logging and see it being triggered as I make changes to my 
database.  So this appears to be working.  What I am surprised at however, is 
that I have tables in my database that have out of date statistics (none) as 
reported by this query:

select schemaname,
tablename || ' (' || CONGLOMERATENAME || ')' as Table (Index),
CASE WHEN CAST
(
   creationtimestamp AS varchar(24)
)
IS NULL THEN 'Recreate Index to Initialize' ELSE CAST
(
   creationtimestamp AS varchar(24)
)
END
from sys.systables t
join sys.sysconglomerates c on t.tableid = c.tableid
JOIN sys.SYSSCHEMAS x on t.SCHEMAID = x.SCHEMAID
LEFT OUTER JOIN sys.sysstatistics s ON c.conglomerateid = s.referenceid
where t.tableid = c.tableid
and c.isindex = true
and t.tabletype = 'T';

The tables start empty but with indexes and then data gets added later.  I 
thought that probably the new automatic statistics feature would be triggered 
on a query of these tables but it does not seem to be.  If the table already 
has statistics they seem to be updated.   I could be wrong however and maybe my 
query is not sufficient to trigger statistics update but I did do a query for a 
specific value of primary key and saw nothing in derby.log.

So do I still need to prime these statistics myself with a call to 
syscs_util.update_statistics?

Thanks for any information.

Brett