Hello, Concerned by the performances of HSQLDB, I've made an audit (using Together 6.0). (see attachment)
I've take a look on the source code of hsqldb and find some easy
improvments which can
speed up hsqldb. In fact, this is some rules to keep in mind while coding:
-1-
int size = Vector.size();
for( int i = 0; i < size; i++ )
{}
is better than
for( int i = 0; i < Vector.size(); i++ )
{}
it's the same for arrays: size = array.length
-2-
Vector is a synchronized object, ArrayList do the same but is not
synchronized.
Although a RDBMS must provide transaction isolation and thus Vector might
be
useful to do that, I think that sometime, hsqldb could use ArrayList
objects instead
of Vector. This remark applies to Hashtable vs HashMap too.
-3-
I've made some performance tests:
Y= 100,000 times and X = 1,000,000 times, remark the different results
between Vector (V) and ArrayList (A)!
(Embedded image moved to file: pic16827.pcx)
-3.1-
Y Creation of Vector: 3345ms
Y Creation of ArrayList: 3234ms
-3.2-
Y addElement (V): 1292ms
Y add (A): 1602ms
-3.3-
Y synchronized addElement (V): 1262ms
Y synchronized add (A): 1552ms
it means:
synchronized( Vector )
{
size = Vector.size();
for ( int i = 0; i < size; i++ )
Vector.addElement( );
}
-3.4-
X elementAt (V): 350ms
-3.5-
X synchronized elementAt (V): 350ms
-3.6-
X get (V): 361ms
X get (A): 291ms
-3.7-
X synchronized get (V): 340ms
X synchronized get (A): 300ms
-3.8-
X Iterator (V): 912ms
X Iterator (A): 792ms
it means:
for( Iterator i = Vector.iterator(); i.hasNext(); )
i.next();
-3.9-
X synchronized Iterator (V): 851ms
X synchronized Iterator (A): 801ms
As you can see, synchronized access to a Vector in a loop is faster but not
for ArrayList
(because it's already synchronized). Iterator must not be used (if it's
possible).
Regards,
Loic Lefevre
(See attached file: hsqldb_1_7_0_AUDIT.zip)
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pic16827.pcx
Description: Binary data
hsqldb_1_7_0_AUDIT.zip
Description: Zip archive
