Neoview Query Guide (R2.3, R2.4, R2.5)

ManualsBrandsHP ManualsSoftwareHP Neoview Release 2.3 Software

cardinalities are often shown as “1” on the SPLIT_TOP and PARTITION_ACCESS operators.

For these operators, the PROBES field in the COST_DETAILS panel of NPA show the expected

rows accessed, and the cardinality value for the plan step shows the expected number of rows

accessed per probe.

NESTED_JOIN Operator

The NESTED_JOIN operator describes a portion of an execution plan that involves a nested join.

This operator sends each outer row to the inner table, where it eventually goes to a scan operation.

Normally, the inner scan access is keyed, and the number of outer probes is small, resulting in

an efficient join. The actual join is done in the inner scan instead of the NESTED_JOIN operator.

Nested joins support range operations (>=, >, <, <=) in addition to equijoins.

The NESTED_JOIN has two child operators. The description field for this operator contains:

Data TypeToken DescriptionToken

integerA sequential number assigned to the fragment. 0 is always master

executor and 1 is reserved for the Explain plan. Numbers 2 to n will be

ESP or DAM fragments.

fragment_id

integerThe fragment_id for the parent fragment of the current fragment. Value

is (none) for master executor.

parent_frag

textmaster, ESP, or DAMfragment_type

textInner or natural joinjoin_type

textName of join method: nested or in-order nestedjoin_method

text1 for Type1 or 2 for Type2, depending on parallel join algorithmparallel_join_type

expr(text)Expression of the ON clause that has not been pushed down to the inner

scan, typically empty

join_predicate

expr(text)Expression of the WHERE clause that has not been pushed down to the

inner scan, typically empty

selection_predicates

NESTED_SEMI_JOIN Operator

The NESTED_SEMI_JOIN operator returns only one matched row from the inner table and

ignores duplicate matches. See “NESTED_JOIN Operator” (page 25).

The NESTED_SEMI_JOIN operator has two child operators. The description field for this operator

contains:

Data TypeToken DescriptionToken

integerA sequential number assigned to the fragment. 0 is always master executor

and 1 is reserved for the Explain plan. Numbers 2 to n will be ESP or DAM

fragments.