Provides a more efficient implementation for statements which select a single-row result from DUAL such as SYSDATE, USER or arithmetic calculations
This operation is implemented in the following versions
|
This example was developed using Oracle 10.2.0.1 on Linux
This example does not require any table definitions
The statement
SELECT SYSDATE FROM dual;
generates the following execution plan
0 SELECT STATEMENT Optimizer=CHOOSE 1 0 FAST DUAL
If the "_fast_dual_enabled" parameter is set to FALSE (default TRUE) then the FAST DUAL operation is disabled. For example
ALTER SESSION SET "_fast_dual_enabled" = FALSE;
Now the statement
SELECT SYSDATE FROM dual;
generates the following execution plan
0 SELECT STATEMENT Optimizer=CHOOSE 1 0 TABLE ACCESS (FULL) OF 'DUAL'