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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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Andrus Adamchik updated CAY-2738:
---------------------------------
Description:
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.
_It remains to be seen if the new API gives us more efficient and easy-to-use
data structure. More experimentation is needed._
[*] I am omitting "toDepPk" property in the example. Per CAY-2739 it may be
renamed to "fk".
was:
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.
_It remains to be seen if the new API gives us more efficient and easy-to-use
data structure. More experimentation is needed._
[*] I am omitting "toDepPk" property in the example. Will discuss improving
that separately.
> 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
>
> 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.
> _It remains to be seen if the new API gives us more efficient and easy-to-use
> data structure. More experimentation is needed._
> [*] I am omitting "toDepPk" property in the example. Per CAY-2739 it may be
> renamed to "fk".
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