SQL/MX 3.2.1 Reference Manual (H06.26+, J06.15+)

Metadata Tables
HP NonStop SQL/MX Release 3.2.1 Reference Manual—691117-005
10-67
Query Optimization and Performance
CHECK_CONSTRAINT_PRUNING Set to ON, OFF, RESET, or SYSTEM. The default is
ON. If OFF, the constraint based query pruning
optimization will not be tried on the subsequent
queries. The CQD value RESET or SYSTEM sets
the value of CQD back to the default value. The
constraint based pruning uses the Constant Range
Predicate Folding (CRPF) feature. The CRPF uses
EncodedValue objects to store the actual values as
double datatype with up to 15 digit of precision. For
datatypes that have precision more than 15 digits
(such as largeint), this conversion of actual value
from more precision to double, causes
comparisons to go wrong. Hence,constraint pruning
is not applied when the value for comparison
happens to have more than 15 digit of precision.
For information on check constraint pruning feature,
see the SQL/MX Query Guide.
CROSS_PRODUCT_CONTROL Set to ON or OFF. ON reduces compile time by
eliminating query plans that include unnecessary
and expensive cross-products (joins without join
predicates).
For additional information about this setting, see the
SQL/MX Query Guide.
The default is ON.
DATA_FLOW_OPTIMIZATION Set to ON or OFF. Reduces compile time by not
considering some query plans that have relatively
high data flow rates.
The default is ON, resulting in improvement in
compile time without impacting plan quality.
DDL_VIEW_SIMILARITY_CHECK Specifies whether views by default are created with
Similarity Check enabled or disabled. If specified,
the SIMILARITY CHECK clauses in CREATE VIEW
and ALTER VIEW statements take precedence over
this CQD setting. The Similarity Check is not
supported for Nested Views and views with VALUES
clause. The CQD settings determine if an error is
returned for these views. The following are the CQD
settings and behavior:
If set to ENABLE/SYSTEM, Similarity Check is
enabled for supported view definitions, otherwise
Similarity Check is disabled.
If set to ON, Similarity Check is enabled for
supported view definitions, otherwise the view is not
created and an error is returned.
DISABLE/OFF - Similarity Check is disabled.
Attribute Setting