fetchSIze 对性能的影响
class DemoPrefetch
{
public static void main(String[] args)
{
int connLevelDefaultPrefetch = 5;
int stmtLevelFetchSize = 20;
int rsetLevelFetchSize = 50;
Connection conn = null;
try
{
conn = JDBCUtil.getConnection("fuyou", "fuyou", "orcl");
System.out.println( "\nDefault connection fetch size: " + ((OracleConnection) conn).getDefaultRowPrefetch() );
System.out.println( "setting the default fetch size at connection level to " + connLevelDefaultPrefetch );
((OracleConnection) conn).setDefaultRowPrefetch( connLevelDefaultPrefetch );
System.out.println( "Now the connection fetch size: " + ((OracleConnection) conn).getDefaultRowPrefetch() );
JDBCUtil.getTraceName(conn);//取得跟踪文件
JDBCUtil.startTrace( conn );//设置跟踪
_demoPstmtFetchSize( conn, connLevelDefaultPrefetch, stmtLevelFetchSize);
_demoPstmtFetchSizeWithRsetOverride( conn, connLevelDefaultPrefetch, stmtLevelFetchSize, rsetLevelFetchSize );
_demoCstmtFetchSize( conn, connLevelDefaultPrefetch, stmtLevelFetchSize );
_demoCstmtFetchSizeWithRsetOverride( conn, connLevelDefaultPrefetch, stmtLevelFetchSize, rsetLevelFetchSize );
JDBCUtil.cancleTrace(conn);
}
catch (SQLException e)
{
// handle the exception properly - in this case, we just
// print the stack trace.
JDBCUtil.printException ( e );
}
finally
{
// release the JDBC resources in the finally clause.
JDBCUtil.close( conn );
}
} // end of main()
private static void _demoPstmtFetchSize( Connection conn,
int connLevelDefaultPrefetch, int stmtLevelFetchSize ) throws SQLException
{
System.out.println( "Inside _demoPstmtFetchSize" );
String sqlTag = "/*+" +
"(CONN=" + connLevelDefaultPrefetch + ")" +
"(PSTMT=" + stmtLevelFetchSize + ")" +
"*/";
String stmtString = "select x "+ sqlTag + " from t1 where rownum <= ?";
PreparedStatement pstmt = null;
ResultSet rset = null;
try
{
pstmt = conn.prepareStatement( stmtString );
System.out.println( "\tDefault statement fetch size: " + pstmt.getFetchSize());
pstmt.setFetchSize( stmtLevelFetchSize );
System.out.println( "\tnew statement fetch size: " + pstmt.getFetchSize());
pstmt.setInt( 1, 100 );
rset = pstmt.executeQuery();
System.out.println( "\tResult set fetch size: " + rset.getFetchSize());
int i=0;
while (rset.next())
{
i++;
}
System.out.println( "\tnumber of times in the loop: " + i );
}
finally
{
// release JDBC related resources in the finally clause.
JDBCUtil.close( rset );
JDBCUtil.close( pstmt );
}
}
private static void _demoPstmtFetchSizeWithRsetOverride( Connection conn,
int connLevelDefaultPrefetch, int stmtLevelFetchSize,
int rsetLevelFetchSize ) throws SQLException
{
System.out.println( "Inside _demoPstmtFetchSizeWithRsetOverride" );
String sqlTag = "/*+" +
"(CONN=" + connLevelDefaultPrefetch + ")" +
"(PSTMT=" + stmtLevelFetchSize + ")" +
"(RSET=" + rsetLevelFetchSize + ")" +
"*/";
String stmtString = "select x "+ sqlTag + " from t1 where rownum <= ?";
PreparedStatement pstmt = null;
ResultSet rset = null;
try
{
pstmt = conn.prepareStatement( stmtString );
System.out.println( "\tDefault statement fetch size: " + pstmt.getFetchSize());
pstmt.setFetchSize( stmtLevelFetchSize );
System.out.println( "\tnew statement fetch size: " + pstmt.getFetchSize());
pstmt.setInt( 1, 100 );
rset = pstmt.executeQuery();
rset.setFetchSize( rsetLevelFetchSize );
System.out.println( "\tnew result set fetch size: " + rset.getFetchSize());
int i=0;
while (rset.next())
{
i++;
}
System.out.println( "\tnumber of times in the loop: " + i );
}
finally
{
// release JDBC related resources in the finally clause.
JDBCUtil.close( rset );
JDBCUtil.close( pstmt );
}
}
// demo fetch size using callable statement
private static void _demoCstmtFetchSize( Connection conn, int connLevelDefaultPrefetch, int stmtLevelFetchSize ) throws SQLException
{
System.out.println( "Inside _demoCstmtFetchSize" );
String sqlTag = "/*+" +
"(CONN=" + connLevelDefaultPrefetch + ")" +
"(CSTMT=" + stmtLevelFetchSize + ")" +
"*/";
String stmtString = "{ call prefetch_pkg.get_details ( ?, ?, ? ) }";
CallableStatement cstmt = null;
ResultSet rset = null;
try
{
cstmt = conn.prepareCall( stmtString );
System.out.println( "\tDefault statement fetch size: " + cstmt.getFetchSize());
cstmt.setFetchSize( stmtLevelFetchSize );
System.out.println( "\tnew statement fetch size: " + cstmt.getFetchSize());
cstmt.setInt( 1, 100); // number of rows to be fetched
cstmt.setString( 2, sqlTag );
cstmt.registerOutParameter( 3, OracleTypes.CURSOR );
// execute the query
cstmt.execute();
rset = (ResultSet) cstmt.getObject( 3 );
System.out.println( "\tresult set fetch size: " + rset.getFetchSize());
System.out.println( "\tHowever, in case of callable statement, the real fetch size for all result sets obtained from the statement is the same as the one set at the connection level." );
int i=0;
while (rset.next())
{
i++;
}
System.out.println( "\tnumber of times in the loop: " + i );
}
finally
{
// release JDBC related resources in the finally clause.
JDBCUtil.close( rset );
JDBCUtil.close( cstmt );
}
}
// demo fetch size using callable statement
private static void _demoCstmtFetchSizeWithRsetOverride( Connection conn, int connLevelDefaultPrefetch, int stmtLevelFetchSize, int rsetLevelFetchSize ) throws SQLException
{
System.out.println( "Inside _demoCstmtFetchSizeWithRsetOverride" );
String sqlTag = "/*+" +
"(CONN=" + connLevelDefaultPrefetch + ")" +
"(CSTMT=" + stmtLevelFetchSize + ")" +
"(RSET=" + rsetLevelFetchSize + ")" +
"*/";
String stmtString = "{ call prefetch_pkg.get_details ( ?, ?, ? ) }";
CallableStatement cstmt = null;
ResultSet rset = null;
try
{
cstmt = conn.prepareCall( stmtString );
System.out.println( "\tDefault statement fetch size: " + cstmt.getFetchSize());
cstmt.setFetchSize( stmtLevelFetchSize );
System.out.println( "\tnew statement fetch size: " + cstmt.getFetchSize());
cstmt.setInt( 1, 100); // number of rows to be fetched
cstmt.setString( 2, sqlTag );
cstmt.registerOutParameter( 3, OracleTypes.CURSOR );
// execute the query
cstmt.execute();
rset = (ResultSet) cstmt.getObject( 3 );
rset.setFetchSize( rsetLevelFetchSize );
System.out.println( "\tnew result set fetch size: " + rset.getFetchSize());
System.out.println( "\tHowever, in case of callable statement, the real fetch size for all result sets obtained from the statement is the same as the one set at the connection level." );
int i=0;
while (rset.next())
{
i++;
}
System.out.println( "\tnumber of times in the loop: " + i );
}
finally
{
// release JDBC related resources in the finally clause.
JDBCUtil.close( rset );
JDBCUtil.close( cstmt );
}
}
} // end of program
上面是测试类
下面是tkporf 出来的文件，只摘取了相关数据
select x /*+(CONN=5)(PSTMT=20)(RSET=50)*/
from
t1 where rownum <= :1
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.01 0.00 0 2 0 0
Fetch 3 0.00 0.00 0 6 0 100
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 5 0.01 0.00 0 8 0 100
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 62
Rows Row Source Operation
------- ---------------------------------------------------
100 COUNT STOPKEY (cr=6 pr=0 pw=0 time=1055 us)
100 TABLE ACCESS FULL T1 (cr=6 pr=0 pw=0 time=449 us)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 4 0.00 0.00
SQL*Net message from client 4 0.01 0.01
********************************************************************************
BEGIN prefetch_pkg.get_details ( :1, :2, :3 ) ; END;
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 2 0.00 0.00 0 0 0 0
Execute 2 0.04 0.05 0 276 0 2
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 4 0.04 0.05 0 276 0 2
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 62
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
SQL*Net message from client 2 0.00 0.00
********************************************************************************
select /*+(CONN=5)(CSTMT=20)*/x
from
t1 where rownum <= :p_fetch_size
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 2 0 0
Fetch 21 0.00 0.00 0 23 0 100
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 23 0.00 0.00 0 25 0 100
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 62
Rows Row Source Operation
------- ---------------------------------------------------
100 COUNT STOPKEY (cr=23 pr=0 pw=0 time=1063 us)
100 TABLE ACCESS FULL T1 (cr=23 pr=0 pw=0 time=454 us)
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
SQL*Net message to client 21 0.00 0.00
SQL*Net message from client 21 0.00 0.00
********************************************************************************
select /*+(CONN=5)(CSTMT=20)(RSET=50)*/x
from
t1 where rownum <= :p_fetch_size
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 1 0.00 0.00 0 2 0 0
Fetch 3 0.00 0.00 0 5 0 100
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 5 0.00 0.00 0 7 0 100
Misses in library cache during parse: 1
Misses in library cache during execute: 1
Optimizer mode: ALL_ROWS
Parsing user id: 62
Rows Row Source Operation
------- ---------------------------------------------------
100 COUNT STOPKEY (cr=5 pr=0 pw=0 time=949 us)
100 TABLE ACCESS FULL T1 (cr=5 pr=0 pw=0 time=342 us)
代码已经很明显了，我就不多说了