OpenEdge Data Management: DataServer for Microsoft SQL Server

Chapter 4: Additional Features to Enhance DataServer Performance
Table 24: Query-tuning options (3 of 4)
Option Description
NO-QUERY-UNIQUE-ADDED Specifies that OpenEdge should omit the record
identifier from the end of the query’s generated
ORDER BY clause when trying to obtain record
uniqueness from a selected non-unique index. A
sort order that is modified to derive uniqueness
may produce a query that can’t find a useful index
to perform sorting thus impacting query
performance.
Note: If you elect to use this option, the query
may find an index match to provide better
performance. However, turning off uniqueness in
a query where scrolling is required may result in
behavior that is incompatible with the OpenEdge
ABL. Only use this option when compatibility is
not required and can be overlooked for the sake
of better performance.
FIREHOSE-CURSOR Specifies at the query level that the firehose
cursor type should be considered to satisfy the
query when the NO-LOCK phrase is used.
Note: This query-level option overrides the
connection-level -Dsrv options, QT_FIREHOSE
and QT_NO_FIREHOSE that determine if firehose
cursors should be considered for the DataServer
connection.
NO-FIREHOSE-CURSOR Specifies at the query level that the firehose
cursor type should not be considered to satisfy
the query when the NO-LOCK phrase is used.
Notes:This query-level option overrides the
connection-level -Dsrv options, QT_FIREHOSE
and QT-NO-FIREHOSE that determine if firehose
cursors should be considered for the DataServer
connection.
By default, firehose cursors are available to
satisfy NO-LOCK queries during a DataServer
session. It is generally recommended this default
use be retained and overridden by
QT-NO-FIREHOSE on an individual query basis in
the event that slow query performance is
observed on a very large result set.
172 OpenEdge Data Management: DataServer for Microsoft SQL Server