Log Scan.
When an insert, update, or delete statement causes a trigger to fire, and the trigger includes access to the inserted or deleted tables, these tables are built by scanning the transaction log.
This example shows the output for the update to the titles table when this insert fires the totalsales_trig trigger on the salesdetail table:
insert salesdetail values (’7896’, ’234518’, ’TC3218’, 75, 40)
QUERY PLAN FOR STATEMENT 1 (at line 1).
STEP 1
The type of query is UPDATE.
The update mode is direct.
FROM TABLE
titles
Nested iteration.
Table Scan.
Forward scan.
Positioning at start of table.
Using I/O Size 2 Kbytes for data pages.
With LRU Buffer Replacement Strategy for data pages.
FROM TABLE
salesdetail
EXISTS TABLE : nested iteration.
Log Scan.
Forward scan.
Positioning at start of table.
Run subquery 1 (at nesting level 1).
Using I/O Size 2 Kbytes for data pages.
With LRU Buffer Replacement Strategy for data pages.
TO TABLE
titles
NESTING LEVEL 1 SUBQUERIES FOR STATEMENT 4.
QUERY PLAN FOR SUBQUERY 1 (at nesting level 1 and at line 23).
Correlated Subquery.
Subquery under an EXPRESSION predicate.
STEP 1
The type of query is SELECT.
Evaluate Ungrouped SUM OR AVERAGE AGGREGATE.
FROM TABLE
salesdetail
Nested iteration.
Log Scan.
Forward scan.
Positioning at start of table.
Using I/O Size 2 Kbytes for data pages.
With MRU Buffer Replacement Strategy for data pages.
