Reuse relationship selection
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Key: OPENJPA-2099
URL: https://issues.apache.org/jira/browse/OPENJPA-2099
Project: OpenJPA
Issue Type: Improvement
Reporter: Pinaki Poddar
Assignee: Pinaki Poddar
Related entities are often loaded via a separate select operation when an
unloaded field is accessed. The select operation for a relationship field
structurally (i.e. which tables it joins to or what columns it selects) is
invariant at instance level. Only thing that changes across entity instances is
the foreign/primary key identifier values used in joining. The major
computation cost is paid to analyze to build the select structure by analyzing
the mapping metadata of class/field involved. As noted, this computation is
invariant for each instance access except the primary/foreign key values
involved.
However, the core infrastructure for this frequent operation (because it is
carried out whenever a relationship field is loaded for every instance) is not
designed for reuse. The select gets constructed every time, the class/field
mapping metadata gets analyzed every time, before the select is executed on the
database.
What is required to avoid this repeated and unnecessary cost is to reuse a
select instance computed for every relationship field only once but binding
different parameters on every execution.
The task is non-trivial because of the select abstraction (a highly complex and
critical data structure) is not designed with such parameter rebinding in mind.
This issue attempts to remedy that limitation.
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