Re: [Engine-devel] Opimizing Postgres Stored Procedures

From: "Eli Mesika" <emesika(a)redhat.com&gt; To: "Laszlo Hornyak" <lhornyak(a)redhat.com&gt; Cc: "engine-devel" <engine-devel(a)ovirt.org&gt; Sent: Sunday, September 1, 2013 10:35:43 AM Subject: Re: [Engine-devel] Opimizing Postgres Stored Procedures ----- Original Message ----- > From: "Laszlo Hornyak" <lhornyak(a)redhat.com&gt; > To: "Eli Mesika" <emesika(a)redhat.com&gt; > Cc: "engine-devel" <engine-devel(a)ovirt.org&gt; > Sent: Friday, August 30, 2013 7:17:32 PM > Subject: Re: [Engine-devel] Opimizing Postgres Stored Procedures > > Hi Eli, > > I wrote a quick benchmark to see if there is any difference when using > STABLE > modifier on functions running queries the way the engine does it (calling > it > from JDBC, one function in a single statement) > > with a stable function: > create function getKakukk(_id int) returns VARCHAR STABLE as 'select val > from > kakukk where id = $1' language sql; > and one not marked as stable > create function getKakukk_(_id int) returns VARCHAR as 'select val from > kakukk where id = $1' language sql; > the table is this simple: > create table kakukk(id int primary key, val varchar); > and the only content is: > insert into kakukk (id, val) values (1, 'bla bla bla'); > > Now the benchmark code: > > package com.foobar; > > import java.sql.Connection; > import java.sql.DriverManager; > import java.sql.PreparedStatement; > import java.sql.ResultSet; > import java.sql.SQLException; > > import org.junit.After; > import org.junit.Before; > import org.junit.Test; > > public class SpeedTest { > > Connection connection; > > @Before > public void connect() throws SQLException { > connection = > DriverManager.getConnection("jdbc:postgresql://localhost/stabletest", > "engine", "engine"); > } > > @After > public void disconnect() throws SQLException { > connection.close(); > } > > private long measure(Runnable runnable, int times) { > final long start = System.currentTimeMillis(); > for (int i = 0; i < times; i++) { > runnable.run(); > } > final long end = System.currentTimeMillis(); > return end - start; > } > > public static class Select implements Runnable { > > public Select(PreparedStatement preparedStatement) { > super(); > this.preparedStatement = preparedStatement; > } > > final PreparedStatement preparedStatement; > > public void run() { > try ( > ResultSet resultSet = > preparedStatement.executeQuery();) > { > while (resultSet.next()) { > // nothing, just next > } > } catch (SQLException e) { > // TODO Auto-generated catch block > e.printStackTrace(); > } > } > } > > @Test > public void performTest() throws SQLException { > for (int i = 0; i < 10; i++) { > try ( > PreparedStatement stable = > connection.prepareStatement("select getKakukk(1)"); > PreparedStatement notStable = > connection.prepareStatement("select getKakukk_(1)");) { > System.out.println("STABLE: " + measure(new Select(stable), > 100000)); > System.out.println("not STABLE: " + measure(new > Select(notStable), 100000)); > System.out.println("---"); > > } > } > } > } > > > -- > > The results are very similar, seemingly no difference at all. > Therefore, it seems we do not need those STABLE markers for performance > reasons. Please refer to http://www.postgresql.org/docs/8.3/static/xfunc-volatility.html It says : "For best optimization results, you should label your functions with the strictest volatility category that is valid for them."

So , using STABLE , IMMUTABLE , STRICT is mandatory from now on. Thanks Eli > > Thank you, > Laszlo > > ----- Original Message ----- > > From: "Laszlo Hornyak" <lhornyak(a)redhat.com&gt; > > To: "Eli Mesika" <emesika(a)redhat.com&gt; > > Cc: "engine-devel" <engine-devel(a)ovirt.org&gt; > > Sent: Wednesday, August 28, 2013 1:02:18 PM > > Subject: Re: [Engine-devel] Opimizing Postgres Stored Procedures > > > > > > ----- Original Message ----- > > > From: "Eli Mesika" <emesika(a)redhat.com&gt; > > > To: "Laszlo Hornyak" <lhornyak(a)redhat.com&gt; > > > Cc: "engine-devel" <engine-devel(a)ovirt.org&gt; > > > Sent: Wednesday, August 28, 2013 11:45:14 AM > > > Subject: Re: [Engine-devel] Opimizing Postgres Stored Procedures > > > > > > > > > > > > ----- Original Message ----- > > > > From: "Laszlo Hornyak" <lhornyak(a)redhat.com&gt; > > > > To: "Eli Mesika" <emesika(a)redhat.com&gt; > > > > Cc: "engine-devel" <engine-devel(a)ovirt.org&gt; > > > > Sent: Tuesday, August 27, 2013 11:40:27 AM > > > > Subject: Re: [Engine-devel] Opimizing Postgres Stored Procedures > > > > > > > > Hi Eli, > > > > > > > > Most of the functions that we have in the DB are doing very simple > > > > jobs > > > > like > > > > run a query, insert/update and I see that now you have all QUERY > > > > functions > > > > as STABLE. > > > > My questions: > > > > Is this required for new functions from now on? > > > Yes and a email asking that was posted to engine_devel > > > > > > > Is this done in order to improve performance? > > > Yes > > > > Do you have any documents/benchmarks on how and why does this improve > > performance? > > STABLE functions should improve performance if they return the same > > result > > for the same parameters in the same statement. > > E.g. if you have a stable function like "select foo(x) from y" then the > > function can be invoked only once to evaluate each distinct value of y.x > > - > > this is kind of useful > > Functions running queries for the ovirt engine are typically invoked from > > client side, therefore they are only ivoked once from the parameters list > > and therefore will be only executed once for that single statement. > > > > > > > > > > > > > Thank you, > > > > Laszlo > > > > > > > > ----- Original Message ----- > > > > > From: "Eli Mesika" <emesika(a)redhat.com&gt; > > > > > To: "engine-devel" <engine-devel(a)ovirt.org&gt; > > > > > Sent: Monday, August 26, 2013 11:22:20 AM > > > > > Subject: [Engine-devel] Opimizing Postgres Stored Procedures > > > > > > > > > > Hi > > > > > > > > > > I had merged the following patch > > > > > http://gerrit.ovirt.org/#/c/17962/ > > > > > > > > > > This patch introduce usage of the IMMUTABLE, STABLE and STRICT > > > > > keywords > > > > > in > > > > > order to boost performance of the Postgres SPs. > > > > > > > > > > Please make sure that your current/and future DB scripts applied > > > > > that. > > > > > > > > > > > > > > > Volatility > > > > > ---------- > > > > > * A function should be marked as IMMUTABLE if it doesn't change the > > > > > database, > > > > > and if it doesn't perform any lookups (even for database > > > > > configuration > > > > > values) during its operation. > > > > > * A function should be marked STABLE if it doesn't change the > > > > > database, > > > > > but > > > > > might perform lookups (IMMUTABLE is preferable if function meets > > > > > the > > > > > requirements). > > > > > * A function doesn't need to be marked VOLATILE, because that's the > > > > > default. > > > > > > > > > > STRICTNESS > > > > > ---------- > > > > > A function should be marked STRICT if it should return NULL when it > > > > > is > > > > > passed > > > > > a NULL argument, and then the function won't even be called if it > > > > > is > > > > > indeed > > > > > passed a NULL argument. > > > > > > > > > > > > > > > I am available for any questions. > > > > > > > > > > Thanks > > > > > > > > > > Eli > > > > > _______________________________________________ > > > > > Engine-devel mailing list > > > > > Engine-devel(a)ovirt.org > > > > > http://lists.ovirt.org/mailman/listinfo/engine-devel > > > > > > > > > > > > > > _______________________________________________ > > Engine-devel mailing list > > Engine-devel(a)ovirt.org > > http://lists.ovirt.org/mailman/listinfo/engine-devel > > >