Expert Oracle Exadata - Parent Directory

CHAPTER 2 OFFLOADING / SMART SCANof offload processing. Here’s a quick demonstration to show that projection does affect the amount ofdata returned to the database servers and that selecting fewer columns results in less data transferred:SYS@SANDBOX> select /* single col */ avg(pk_col)2 from kso.skew3;AVG(PK_COL)-----------16093750.31 row selected.Elapsed: 00:00:32.13SYS@SANDBOX> select /* multi col */ avg(pk_col),sum(col1)2 from kso.skew3;AVG(PK_COL) SUM(COL1)----------- ----------16093750.3 1.9003E+141 row selected.Elapsed: 00:00:45.32SYS@SANDBOX> set timing offSYS@SANDBOX> select sql_id,sql_text from v$sql2 where sql_text like '%col */ avg(pk_col)%';SQL_ID SQL_TEXT------------- ----------------------------------------------------------------------bb3z4aaa9du7j select /* single col */ avg(pk_col) from kso.skew3555pskb8aaqct select /* multi col */ avg(pk_col),sum(col1) from kso.skew32 rows selected.SYS@SANDBOX> select sql_id, IO_CELL_OFFLOAD_ELIGIBLE_BYTES eligible,2 IO_INTERCONNECT_BYTES actual,3 100*(IO_CELL_OFFLOAD_ELIGIBLE_BYTES-IO_INTERCONNECT_BYTES)4 /IO_CELL_OFFLOAD_ELIGIBLE_BYTES "IO_SAVED_%", sql_text5 from v$sql where sql_id in ('bb3z4aaa9du7j','555pskb8aaqct');SQL_ID ELIGIBLE ACTUAL IO_SAVED_% SQL_TEXT------------- ---------- ---------- ---------- ------------------------------------bb3z4aaa9du7j 1.6025E+10 4511552296 71.85 select /* single col */ avg(pk_col)555pskb8aaqct 1.6025E+10 6421233960 59.93 select /* multi col */ avg(pk_col),s2 rows selected.SYS@SANDBOX> @fsx4Enter value for sql_text: %col */ avg(pk_col)%Enter value for sql_id:31