Add defaultFetchSize property to JDBC driver to make it easier to handle very
large result sets in the controller
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Key: SEQUOIA-1002
URL: https://forge.continuent.org/jira/browse/SEQUOIA-1002
Project: Sequoia
Type: New Feature
Versions: Sequoia 2.9
Environment: All
Reporter: Robert Hodges
Assigned to: Robert Hodges
Priority: Critical
Fix For: sequoia 2.10.10
Controllers run out of heap space for very large requests that are typical of
reporting or large batch operations. It is possible to alleviate this by
using set fetch size hints (Statement.setFetchSize() or
ResultSet.setFetchSize()). However, these hints may be impractical to put in
many applications after the fact or the application itself may be non-Java and
connecting through Myosotis.
To help manage fetch size hints more easily the Sequoia JDBC driver will be
extended to add a defaultFetchSize property. This property value replaces the
default 0 fetch size hint and allows users to specify connections that use
result set fetching without having to change application code. The property
behavior is as follows:
1.) If the defaultFetchSize property is 0, it is ignored. This is the default
behavior.
2.) If the client request has a fetch size other than 0, the request value
takes precendence and the defaultFetchSize property is ignored.
3.) If the client request has a 0 fetch size *and* the defaultFetchSize is
non-zero, the request will be assigned the defaultFetchSize property value.
Users whose applications generate very large result sets or who have
encountered Java heap out of memory errors should define the defaultFetchSize
property. For reporting or other applications it is best to define a separate
connection, as using fetch size slows down result set processing and generates
load on databases for longer.
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