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Table Of Contents
DescriptionTypeProperty Name
on base tables; it cannot be specied on views
or derived tables.
The index property is similar to the constraint
property. To force use of a particular index,
Table propertyindex
specify the unqualied index name. To force a
table scan, specify null for the index name. The
index property can be used only within a
TableExpression, and it can be specied only
on base tables; it cannot be specied on views
or derived tables.
Use the joinOrder property to override the
optimizer's choice of join order for two tables.
FROM clause propertyjoinOrder
When the value FIXED is specied, the
optimizer will choose the order of tables as they
appear in the FROM clause as the join order.
Valid values for the joinOrder property include
FIXED and UNFIXED. The joinOrder property
can be used with a FROM clause.
Use the joinStrategy property to override the
optimizer's choice of join strategy. The two
Table propertyjoinStrategy
types of join strategy are called nested loop and
hash. In a nested loop join strategy, for each
qualifying row in the outer table, SQLFire uses
the appropriate access path (index or table scan)
to nd the matching rows in the inner table. In
a hash join strategy, SQLFire constructs a hash
table that represents the inner table. For each
qualifying row in the outer table, SQLFire does
a quick lookup on the hash table to nd the
matching rows in the inner table. SQLFire needs
to scan the inner table or index only once to
create the hash table. The --
SQLFIRE-PROPERTIES parameter must
immediately follow the inner table.
Typically, you will use the joinStrategy property
only in conjunction with the joinOrder property.
Specifying a join strategy without knowing the
join order can result in less-than-optimal
performance.
Valid values include HASH and
NESTEDLOOP. The joinStrategy property can
be used only within a TableExpression.
Use this property to create an alias for a user
query. When using the Visual Statistics Display
FROM clause propertystatementAlias
(VSD), SQLFire displays the alias name instead
of the original, system-generated statement alias.
vFabric SQLFire User's Guide266
Managing and Monitoring vFabric SQLFire