Neoview Control Query Default (CQD) Reference Guide (R2.5)

Integer
The default value is ‘50000’.
Values
Use this CQD to reduce the number of statistics warnings.Usage
Not applicableProduction usage
Missing statistics warnings are not displayed for smaller tables, which in most cases don't
impact plan quality much. However, there may be some exceptions where missing statistics
on small tables could result in less than optimal plans.
Impact
SystemLevel
Use this CQD with HIST_MISSING_STATS_WARNING_LEVEL. If the warning level CQD
is 0, then this CQD does not have any effect. Also, for tables having fewer rows than set in
this CQD, no warnings are displayed irrespective of the warning level.
Conflicts/Synergies
Not applicableAddressing the real
problem
Neoview Release 2.4Introduced in release
Not applicableDeprecated in release
HIST_USE_SAMPLE_FOR_CARDINALITY_ESTIMATION
HistogramsCategory
Enables the Compile Time Stats feature. Compile Time Stats are produced during query
plan generation by executing a subset of the query on a subset of data to gather more
accurate cardinality estimations.
Description
Compile Time Statistics is enabled.‘ON’
Compile Time Statistics is disabled.‘OFF’
The default value is ‘ON’.
Values
The feature is very helpful for cases when the query contains complex predicates on a table.
These predicates include LIKE, CASE, any other expressions or more than one range
predicates and equality on large character columns.
It can be disabled if most of the queries are single table or at most 2-way joins.
It can also be disabled if the extra collection of statistics seems to be adversely affecting the
total query compile and execution time.
Usage
Not applicableProduction usage
The feature improves cardinality estimates for Scan operators thus improving the plan
quality. However, it can also increase the compile time.
Impact
AnyLevel
In order to use the feature in its default form, sample tables should exist in
public_access_schema.
Conflicts/Synergies
Not applicableAddressing the real
problem
Neoview Release 2.5Introduced in release
Not applicableDeprecated in release
HIST_USE_SAMPLE_FOR_CARDINALITY_ESTIMATION 35