Client side result set cache

Question

Hello,
I try to get the client side result set cache working, but i have no luck :-(
I'm using Oracle Enterprise Edition 11.2.0.1.0 and as client diver 11.2.0.2.0.
Executing the query select /*+ result_cache*/ * from p_item via sql plus or toad will generate an nice execution plan with an RESULT CACHE node and the v$result_cache_objects contains some rows.
After I've check the server side cache works. I want to cache the client side
My simple Java Application looks like
private static final String ID = UUID.randomUUID().toString();
private static final String JDBC_URL = "jdbc:oracle:oci:@server:1521:ORCL";
private static final String USER = "user";
private static final String PASSWORD = "password";
public static void main(String[] args) throws SQLException {
OracleDataSource ds = new OracleDataSource();
ds.setImplicitCachingEnabled(true);
ds.setURL( JDBC_URL );
ds.setUser( USER );
ds.setPassword( PASSWORD );
String sql = "select /*+ result_cache */ /* " + ID + " */ * from p_item d " +
"where d.i_size = :1";
for( int i=0; i<100; i++ ) {
OracleConnection connection = (OracleConnection) ds.getConnection();
connection.setImplicitCachingEnabled(true);
connection.setStatementCacheSize(10);
OraclePreparedStatement stmt = (OraclePreparedStatement) connection.prepareStatement( sql );
stmt.setLong( 1, 176 );
ResultSet rs = stmt.executeQuery();
int count = 0;
for(; rs.next(); count++ );
rs.close();
stmt.close();
System.out.println( "Execution: " + getExecutions(connection) + " Fetched: " + count );
connection.close();
private static int getExecutions( Connection connection ) throws SQLException {
String sql = "select executions from v$sqlarea where sql_text like ?";
PreparedStatement stmt = connection.prepareStatement(sql);
stmt.setString(1, "%" + ID + "%" );
ResultSet rs = stmt.executeQuery();
if( rs.next() == false )
return 0;
int result = rs.getInt(1);
if( rs.next() )
throw new IllegalArgumentException("not unique");
rs.close();
stmt.close();
return result;
100 times the same query is executed and the statement exection count is incemented every time. I expect just 1 statement execution ( client database roundtrip ) and 99 hits in client result set cache. The view CLIENT_RESULT_CACHE_STATS$ is empty :-(
I'm using the oracle documentation at http://download.oracle.com/docs/cd/E14072_01/java.112/e10589/instclnt.htm#BABEDHFF and I don't kown why it does't work :-(
I'm thankful for every tip,
André Kullmann

Answer 1

I wanted to post a follow-up to (hopefully) clear up a point of potential confusion. That is, with the OCI Client Result Cache, the results are indeed cached on the client in memory managed by OCI.
As I mentioned in my previous reply, I am not a JDBC (or Java) expert so there is likely a great deal of improvement that can be made to my little test program. However, it is not intended to be exemplary, didactic code - rather, it's hopefully just enough to illustrate that the caching happens on the client (when things are configured correctly, etc).
My environment for this exercise is Windows 7 64-bit, Java SE 1.6.0_27 32-bit, Oracle Instant Client 11.2.0.2 32-bit, and Oracle Database 11.2.0.2 64-bit.
Apologies if this is a messy post, but I wanted to make it as close to copy/paste/verify as possible.
Here's the test code I used:
import java.sql.ResultSet;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import oracle.jdbc.pool.OracleDataSource;
import oracle.jdbc.OracleConnection;
class OCIResultCache
  public static void main(String args []) throws SQLException
    OracleDataSource ods = null;
    OracleConnection conn = null;
    PreparedStatement stmt = null;
    ResultSet rset = null;
    String sql1 = "select /*+ no_result_cache */ first_name, last_name " +
                  "from hr.employees";
    String sql2 = "select /*+ result_cache */ first_name, last_name " +
                  "from hr.employees";
    int fetchSize = 128;
    long start, end;
    try
      ods = new OracleDataSource();
      ods.setURL("jdbc:oracle:oci:@liverpool:1521:V112");
      ods.setUser("orademo");
      ods.setPassword("orademo");
      conn = (OracleConnection) ods.getConnection();
      conn.setImplicitCachingEnabled(true);
      conn.setStatementCacheSize(20);
      stmt = conn.prepareStatement(sql1);
      stmt.setFetchSize(fetchSize);
      start = System.currentTimeMillis();
      for (int i=0; i < 10000; i++)
        rset = stmt.executeQuery();
        while (rset.next())
        if (rset != null) rset.close();
      end = System.currentTimeMillis();
      if (stmt != null) stmt.close();
      System.out.println();
      System.out.println("Execution time [sql1] = " + (end-start) + " ms.");
      stmt = conn.prepareStatement(sql2);
      stmt.setFetchSize(fetchSize);
      start = System.currentTimeMillis();
      for (int i=0; i < 10000; i++)
        rset = stmt.executeQuery();
        while (rset.next())
        if (rset != null) rset.close();
      end = System.currentTimeMillis();
      if (stmt != null) stmt.close();
      System.out.println();
      System.out.println("Execution time [sql2] = " + (end-start) + " ms.");
      System.out.println();
      System.out.print("Enter to continue...");
      System.console().readLine();
    finally
      if (rset != null) rset.close();
      if (stmt != null) stmt.close();
      if (conn != null) conn.close();
}In order to show that the results are cached on the client and thus server round-trips are avoided, I generated a 10046 level 12 trace from the database for this session. This was done using the following database logon trigger:
create or replace trigger logon_trigger
after logon on database
begin
  if (user = 'ORADEMO') then
    execute immediate
    'alter session set events ''10046 trace name context forever, level 12''';
  end if;
end;
/With that in place I then did some environmental setup and executed the test:
C:\Projects\Test\Java\OCIResultCache>set ORACLE_HOME=C:\Oracle\instantclient_11_2
C:\Projects\Test\Java\OCIResultCache>set CLASSPATH=.;%ORACLE_HOME%\ojdbc6.jar
C:\Projects\Test\Java\OCIResultCache>set PATH=%ORACLE_HOME%\;%PATH%
C:\Projects\Test\Java\OCIResultCache>java OCIResultCache
Execution time [sql1] = 1654 ms.
Execution time [sql2] = 686 ms.
Enter to continue...This is all on my laptop, so results are not stellar in terms of performance; however, you can see that the portion of the test that uses the OCI client result cache did execute in approximately half of the time as the non-cached portion.
But, the more compelling data is in the resulting trace file which I ran through the tkprof utility to make it nicely formatted and summarized:
SQL ID: cqx6mdvs7mqud Plan Hash: 2228653197
select /*+ no_result_cache */ first_name, last_name
from
hr.employees
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute  10000      0.10       0.10          0          0          0           0
Fetch    10001      0.49       0.54          0      10001          0     1070000
total    20002      0.60       0.65          0      10001          0     1070000
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 94 
Number of plan statistics captured: 1
Rows (1st) Rows (avg) Rows (max)  Row Source Operation
       107        107        107  INDEX FULL SCAN EMP_NAME_IX (cr=2 pr=0 pw=0 time=21 us cost=1 size=1605 card=107)(object id 75241)
Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  SQL*Net message to client                   10001        0.00          0.00
  SQL*Net message from client                 10001        0.00          1.10
SQL ID: frzmxy93n71ss Plan Hash: 2228653197
select /*+ result_cache */ first_name, last_name
from
hr.employees
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.01          0         11         22           0
Fetch        2      0.00       0.00          0          0          0         107
total        4      0.00       0.01          0         11         22         107
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 94 
Number of plan statistics captured: 1
Rows (1st) Rows (avg) Rows (max)  Row Source Operation
       107        107        107  RESULT CACHE  0rdkpjr5p74cf0n0cs95ntguh7 (cr=0 pr=0 pw=0 time=12 us)
         0          0          0   INDEX FULL SCAN EMP_NAME_IX (cr=0 pr=0 pw=0 time=0 us cost=1 size=1605 card=107)(object id 75241)
Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  SQL*Net message to client                       2        0.00          0.00
  log file sync                                   1        0.00          0.00
  SQL*Net message from client                     2        1.13          1.13The key differences here are the execute, fetch, and SQL*Net message values. Using the client-side cache, the values drop dramatically due to getting the results from client memory rather than round-trips to the server.
Of course, corrections, clarifications, etc. welcome and so on...
Regards,
Mark