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https://issues.apache.org/jira/browse/CAY-2738?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Nikita Timofeev updated CAY-2738:
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Fix Version/s: 5.0.M1
> Mapping Proposal: Directonless DbRelationship
> ---------------------------------------------
>
> Key: CAY-2738
> URL: https://issues.apache.org/jira/browse/CAY-2738
> Project: Cayenne
> Issue Type: Improvement
> Reporter: Andrus Adamchik
> Priority: Major
> Fix For: 5.0.M1
>
>
> _It remains to be seen whether the proposed API gives us more efficient and
> easy-to-use data structure. More experimentation is needed._
> A pair of DbRelationships between two tables is really a single set of joins,
> not two independent relationships. We should represent it in Cayenne as such.
> E.g. [*]:
> {noformat}
> public class DbRelationshipSide {
> DbEntity entity;
> String name;
> // complementary "other" side
> DbRelationshipSide otherSide;
> // list of columns that matches the order on the complementary "other"
> side
> List<String> joinColumns;
> boolean toMany;
> }
> public class DbRelationship {
> Map<String, DbRelationshipSide> sides;
> public DbRelationshipSide getSide(String dbEntityName) {
> DbRelationshipSide side = sides.get(dbEntityName);
> return Objects.requireNonNull(side,
> () -> "Entity " + dbEntityName + " is not a part of the
> relationship");
> }
> }
> {noformat}
> A single DbRelationship will be linked to both DbEntities, and we won't need
> to manage two identical sets of joins. From the perspective of an entity, the
> relationship becomes directed, by accessing its side that matches the entity
> name.
> [*] I am omitting "toDepPk" property in the example. Per CAY-2739 it may be
> renamed to "fk".
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