Description of problem:

By default work_mem is 1MB or 2 in postgres. When computing baselines, it can happen with much data, that this uses more than this work_mem and thus postgres is using temporary files to "swap", which very much limits performance - up to the point where the computation runs into transaction timeouts.

It coule be possible to globally increase work_mem, but this new value would be for every connection (50 configured) and may have other bad effects.

It is possible to set the work_mem per connection in postgres:

rhq=> set work_mem=32768;
SET
rhq=> show work_mem;
 work_mem 
----------
 32MB
(1 row)

So we should in the case of postgres increase the work_mem before starting the computation:

MeasurementBaselineManagerBean - around line 210:
            conn = dataSource.getConnection();
            DatabaseType dbType = DatabaseTypeFactory.getDatabaseType(conn);

            if (dbType instanceof PostgresqlDatabaseType || dbType instanceof H2DatabaseType) {

+                Statement stm = conn.createStatement();
+                stm.execute("set work_mem=32768");
+                stm.close();


                insertQuery = conn.prepareStatement(MeasurementBaseline.NATIVE_QUERY_CALC_FIRST_AUTOBASELINE_POSTGRES);
                insertQuery.setLong(1, computeTime);


If it is only this one connection, we could even up this to 64MB