SQL/MP Reference Manual

HP NonStop SQL/MP Reference Manual—523352-013
E-19
Considerations—EXPLAIN
Query plan n Specifies the number of the query and whether the plan involves
parallel execution.
Requested Specifies whether the sort or hash operation was requested by the
optimizer or explicitly requested by the user.
SBB for [Insert]
[Update]
Specifies whether virtual sequential block buffering (VSBB) is used
for insert or update operations.
SBB for reads Specifies whether real or virtual sequential block buffering (SBB) is
used for read operations.
Seq Blocksplit Indicates that the user requested blocks to be split as for sequential
inserts by specifying the CONTROL TABLE SEQUENTIAL
BLOCKSPLIT ON option.
Sort cost Indicates the relative cost of the sort operation. Lower numbers
indicate more efficient and less costly execution.
Sort key columns Identifies columns used in the sort by column names qualified by
correlation or table names or (if the sort column is an expression) by
position in the select list. Also lists collations associated with the sort
columns.
Sort rows in the Specifies whether the rows sorted are from the result of a SELECT
statement or a union of SELECT statements, on the current table, or
on a composite table.
Sort technique Describes the sort technique: FastSort or insertion into a
key-sequenced file.
Sort type Describes the type of sort: insertion into an entry-sequenced disk file,
parallel sorting, parallel sort/merge, Sortmerge, or User Process
Sort.
SQL request Specifies the type of statement that is the subject of the plan:
DELETE INSERT-SELECT
UPDATE UNION of SELECT
SELECT UNION of INSERT-SELECTs
INSERT
Table Specifies the fully qualified Guardian name of the table. For scan or
join operations, the name represents the table being accessed; for
an INSERT operation, the name represents the table to receive the
inserted data.
Table selectivity The percentage of the table that is reflected in the result.
Table E-1. EXPLAIN Plan Header Lines (page4of5)
Item Action