SQL/MX 3.1 Query Guide (H06.23+, J06.12+)

SQL/MX Operators
HP NonStop SQL/MX Release 3.1 Query Guide—663851-001
7-76
SUBSET_UPDATE Operator
The following is an example of the SUBSET_DELETE operator:
PREPARE TestQuery1 FROM
DELETE FROM customer
WHERE c_nationkey<300;
DESCRIPTION
fragment_id ............ 2
parent_frag ............ 0
fragment_type .......... dp2
Scan_Direction ......... forward
olt_optimization ....... not used
olt_opt_lean ........... not used
iud_type ............... subset_delete DETCAT.DETSCH.CUSTOMER
lock_mode .............. not specified, defaulted to lock
cursor
access_mode ............ not specified, defaulted to read
committed
columns_retrieved ...... 8
predicate .............. (C_NATIONKEY < 300)
begin_key .............. (C_CUSTKEY = <min>)
end_key .................. (C_CUSTKEY = <max>)
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.
lock_mode The lock mode specified: shared, exclusive, not
specified (defaulted to lock cursor), or unknown.
text
access_mode The access specified: read uncommitted, skip
conflict, read committed, stable, serializable,
mx serializable, not specified (defaulted to read
committed), or unknown.
text
columns_retrieved Estimate of the number of columns to be
returned.
integer
TP663851.fm Page 76 Monday, October 17, 2011 11:48 AM