Here is the test case.
It fails with java.lang.OutOfMemoryError: Java heap space exception.
Increasing value of N will kill any increase in -Xmx parameter. It
seems that the intermediate results are accumulated in memory
instead of creating a temporary table.
@Test
public void memory() throws Exception {
int N = 1000;
Class.forName("org.h2.Driver");
ca = DriverManager.getConnection("jdbc:h2:c:\\temp\\h2");
Statement statement = ca.createStatement();
statement.execute("DROP TABLE one if exists");
statement.execute("DROP TABLE two if exists");
statement.execute("DROP TABLE three if exists");
statement.execute("CREATE TABLE one(id INT )");
PreparedStatement ins = ca.prepareStatement("insert into one
values(?)");
for (int i = 0; i < N; i++) {
for (int j = 0; j < 1000; j++) {
ins.setInt(1, i * 1000 + j);
ins.addBatch();
}
ins.executeBatch();
}
String sql = "create table two as select id from one group by
id";
boolean success = statement.execute(sql);
sql = "create table three as select id from one group by id
order by id";
statement.execute(sql);
}
PS. The last select clause "order by" does not make sense for standard
H2 tables but it is important for our own customized extension of the
class RegularTable.
Sincerely,
Pavel
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