SQL/MX 2.x Query Guide (G06.24+, H06.03+)

Operators and Operator Groups
HP NonStop SQL/MX Query Guide—523728-003
7-51
SUBSET_UPDATE Operator
begin_key: (indexcol(\TESTSYS.$BIG18A.WISC32M.BBASE.UNIQUE2) = -
2147483648)
end_key: (indexcol(\TESTSYS.$BIG18A.WISC32M.BBASE.UNIQUE2) =
32000)
SUBSET_UPDATE Operator
DAM Subset Group
The SUBSET_UPDATE operator describes a portion of an execution plan that details
how a certain access path is scanned: it updates more than one row. A subset
operation performs the read and update in a combined operation. This operation differs
from CURSOR_UPDATE, which performs the read and update in separate operations.
The CURSOR_UPDATE operation also involves more messages.
This operator has no child nodes. The description field for this operator contains:
The example of the SUBSET_UPDATE operator is based on:
UPDATE $big18a.wisc32m.abase SET two = two + 1 WHERE unique3 <
320000;
. . 1 subset_update
new_rec_expr: (\TESTSYS.$BIG18A.WISC32M.ABASE.TWO assign
(cast(indexcol(\TESTSYS.$BIG18A.WISC32M.ABASE.TWO)) + cast(1)))
predicate: (indexcol(\TESTSYS.$BIG18A.WISC32M.ABASE.UNIQUE3) <
320000)
begin_key: (indexcol(\TESTSYS.$BIG18A.WISC32M.ABASE.UNIQUE2) = -
2147483648)
end_key: (indexcol(\TESTSYS.$BIG18A.WISC32M.ABASE.UNIQUE2) =
2147483647)
Token Followed by ... Data Type
begin_key Expression of the begin key
predicates
expr(text)
end_key Expression of the end key
predicates
expr(text)
scan_type Information on indexes text
scan_direction Forward or reverse text
lock_mode No lock, share lock, or
exclusive lock
text
access_mode Read committed, read
uncommitted, or serializable
text
new_rec_expr Computation of the row to be
updated
expr(text)
columns_retrieved Estimate of the number of
columns to be returned
integer