Hi,
We have been happily using h2 for a number of years now for our development
teams where our final deployment is on an Oracle or DB2 database - thank you!
What we have recently noticed is some performance issues with JUnit testing
against H2 versus Oracle so over the last few days I have spent some time
investigating this and would like to report the problem.
We use the same JDBC access across all the databases that our product supports
and the recent performance issues come down to some testing using large Blobs.
The code that we use to retrieve Blobs from the database does not use what may
be the typical getBinaryStream but instead uses Blob.getBytes(1, blob.length()).
The reason we do this is that the Blob getBytes and Clob.getSubString is the
most performing on DB2 and Oracle and we share the code across all databases.
H2's performance here was nearly twice as slow as Oracle's with either an
embedded or server scenario.
I looked into the code of H2 and in particular the JDBCBlob class getBytes
method and found that if a byteBuffer is used to read from the Inputstream
here, performance improves by 400%.
The code I used was below to read the full blob back from the stream but you
may wish to reduce this to some other BufferSize like the length() method in
the same class.
public byte[] getBytes(final long pos, final int length) throws SQLException {
try {
debugCode("getBytes(" + pos + ", " + length + ");");
checkClosed();
final ByteArrayOutputStream out = new ByteArrayOutputStream();
final InputStream in = value.getInputStream();
try {
IOUtils.skipFully(in, pos - 1);
final byte[] buf = new byte[length];
in.read(buf);
out.write(buf, 0, buf.length);
} finally {
in.close();
}
return out.toByteArray();
} catch (Exception e) {
throw logAndConvert(e);
}
}
I'd believe the JDBCClob method getSubString could benefit from the same
consideration for a buffered Reader read.
I appreciate any consideration given to inclusion of this in the future release.
Thanks,
Ronan
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