See for details about how to use this
clause.
The following example shows a SELECT statement in which the optimizer was
forced to use a particular index:
SELECT * FROM t1 -- DERBY-PROPERTIES index = t1_c1
FOR UPDATE OF c2, c1
RUNTIMESTATISTICS returns the following information about this statement:
Statement Name:
null
Statement Text: select * from t1 --DERBY-PROPERTIES index = t1_c1
for update of c2, c1
Parse Time: 0
Bind Time: 0
Optimize Time: 0
Generate Time: 0
Compile Time: 0
Execute Time: 0
Begin Compilation Timestamp : null
End Compilation Timestamp : null
Begin Execution Timestamp : null
End Execution Timestamp : null
Statement Execution Plan Text:
Index Row to Base Row ResultSet for T1:
Number of opens = 1
Rows seen = 4
Columns accessed from heap = {0, 1, 2}
constructor time (milliseconds) = 0
open time (milliseconds) = 0
next time (milliseconds) = 0
close time (milliseconds) = 0
User supplied optimizer overrides on T1 are { index=T1_C1 }
Index Scan ResultSet for T1 using index T1_C1 at read committed isolation level
using exclusive row locking chosen by the optimizer
Number of opens = 1
Rows seen = 4
Rows filtered = 0
Fetch Size = 1
constructor time (milliseconds) = 0
open time (milliseconds) = 0
next time (milliseconds) = 0
close time (milliseconds) = 0
next time in milliseconds/row = 0
scan information:
Bit set of columns fetched=All
Number of columns fetched=2
Number of deleted rows visited=0
Number of pages visited=1
Number of rows qualified=4
Number of rows visited=4
Scan type=btree
Tree height=1
start position:
None
stop position:
None
qualifiers:
None