11:05 p.m.
Hello all,
During development of applications I'm used to set the schema creation
to 'update' (hbm2ddl.auto = update). This makes life a bit easier.
Issue with the newer version of Hibernate is that the name of the
generated keys changed and so all keys are regenerated. For the large
databases I use this takes hours and has to be done every time a fresh
copy from production is taken to the development environment.
I do use meaningful names for the indexes where possible. But when using
abstract classes used by the entities that is not possible because the
same fields from the abstract are used by many entity classes and so
would end up having the same index names.
I checked the code that decides if the index needs to be created and
found that it only checks the name of the index. Not what the index
actually does. This is why I changed that piece of code to be a bit
smarter. It is desinged for simple constraints from one column to
another column. Not for multi to multi column indexes and constraints.
I created a Jira issue for it but nobody notices it and there are no
comments or anything else. So now I try it here :)
Jira HHH-10934 (https://hibernate.atlassian.net/browse/HHH-10934)
Code fragment I put in SchemaMigratorImpl.java:
private ForeignKeyInformation findMatchingForeignKey(ForeignKey foreignKey,
TableInformation tableInformation) {
if (foreignKey.getName() ==null) {
return null;
}
/*
* Find existing keys based on referencing column and referencedTable
*/
String referencingColumn = foreignKey.getColumn(0).getName();
String referencedTableName = foreignKey.getReferencedTable().getName();
Iterable<ForeignKeyInformation> existingForeignKeys =
tableInformation.getForeignKeys();
for (ForeignKeyInformation existingKey : existingForeignKeys) {
Iterable<ColumnReferenceMapping> columnReferenceMappings =
existingKey.getColumnReferenceMappings();
for (ColumnReferenceMapping mapping : columnReferenceMappings) {
String existingReferencingColumn =
mapping.getReferencingColumnMetadata().getColumnIdentifier().getText();
String existingReferencedTableName =
mapping.getReferencedColumnMetadata().getContainingTableInformation().getName().getTableName().getCanonicalName();
if (referencingColumn.equals(existingReferencingColumn) &&
referencedTableName.equals(existingReferencedTableName)) {
return existingKey;
}
}
}
// If not yet found check based on key name return
tableInformation.getForeignKey(Identifier.toIdentifier(foreignKey.getName()));
}
Or if you prever the Java 8 way:
private ForeignKeyInformation findMatchingForeignKey(ForeignKey foreignKey,
TableInformation tableInformation) {
log.debug("findMatchingForeignKey");
if (foreignKey.getName() ==null)return null;
/*
* Find existing keys based on referencing column and referencedTable
*/
String referencingColumn = foreignKey.getColumn(0).getName();
String referencedTableName = foreignKey.getReferencedTable().getName();
Predicate<ColumnReferenceMapping> mappingPredicate = m ->
referencingColumn.equals(m.getReferencingColumnMetadata().getColumnIdentifier().getText())
&&
referencedTableName.equals(m.getReferencedColumnMetadata().getContainingTableInformation().getName().getTableName().getCanonicalName());
for (ForeignKeyInformation existingKey : tableInformation.getForeignKeys()) {
boolean found =
StreamSupport.stream(existingKey.getColumnReferenceMappings().spliterator(),false).anyMatch(mappingPredicate);
if (found)return existingKey;
}
// If not yet found check based on key name return
tableInformation.getForeignKey(Identifier.toIdentifier(foreignKey.getName()));
}
The calling method does not use the returned value. It only checks if
the returned value is null or not. So this could also be cleaned by
changing the method to return a boolean and then remove the for loop in
java-8 and use flatmap. But first let us agree on the validity of the
idea to change this piece of code.
I hope anybody would like to have a look at it and if there is any
change that the idea (not this actual very quick/dirty implementation)
goes into the system I'll clean it up and do some actual tests for more
complex database structures. I did not even check the junit tests yet.
At the moment it is good enough for me but I think it could be something
more people would benefit from.
Thanks,
Milo van der Zee