Hi,
as I need this functionality really bad (production code in three
weeks), I came up with this class. It is in a state we love to call: "It
compiles.". Can you please review it? How do I use this class, once we
agree on the correct behaviour?
public class MyJdbcPkGenerator extends JdbcPkGenerator {
/* (non-Javadoc)
* @see
org.objectstyle.cayenne.dba.JdbcPkGenerator#createAutoPk(org.objectstyle.cayenne.access.DataNode,
java.util.List)
*/
@Override
public void createAutoPk(DataNode node, List dbEntities) throws
Exception {
// check if a table exists
// create AUTO_PK_SUPPORT table
if (!autoPkTableExists(node)) {
runUpdate(node, pkTableCreateString());
}
// will hold only entities to be added to AUTO_PK_SUPPORT table
List<DbEntity> targetDbEntities = new ArrayList<DbEntity>();
// create a set of model entity names
Set<String> modelDbEntities = new HashSet<String>();
for (Iterator iter = dbEntities.iterator(); iter.hasNext();) {
DbEntity dbEntity = (DbEntity) iter.next();
modelDbEntities.add(dbEntity.getName());
}
// create a set of existing entity names (already in db)
Set<String> existingDbEntities = getExistingTables(node);
if (modelDbEntities.size() >= existingDbEntities.size()) {
// new tables added in modeler after database creation
modelDbEntities.removeAll(existingDbEntities);
// modelDbEntities now contains only entity names to be added
to AUTO_PK_SUPPORT table
for (String dbEntityName : modelDbEntities) {
targetDbEntities.add(new DbEntity(dbEntityName));
}
dbEntities = targetDbEntities;
}
// TODO if (model < existing) then existing.removeAll(model) then
delete
// TODO if (model={T1, T2} and existing={T3, T4}) then insert
T1,T2 and delete T3,T4
// delete any existing pk entries
// runUpdate(node, pkDeleteString(dbEntities));
// insert all needed entries
Iterator it = dbEntities.iterator();
while (it.hasNext()) {
DbEntity ent = (DbEntity) it.next();
runUpdate(node, pkCreateString(ent.getName()));
}
super.createAutoPk(node, dbEntities);
}
protected Set<String> getExistingTables(DataNode node) throws
SQLException {
Set<String> existingTables = new HashSet<String>();
Connection con = node.getDataSource().getConnection();
Statement stmt = con.createStatement();
String query = "SELECT 'TABLE_NAME' FROM AUTO_PK_SUPPORT";
try {
ResultSet rs = stmt.executeQuery(query);
try {
while (rs.next()) {
String s = rs.getString("TABLE_NAME");
existingTables.add(s);
}
} finally {
rs.close();
}
} finally {
con.close();
}
return existingTables;
}
}
Regards,
Borut
On 23.4.2006 11:34, Andrus Adamchik wrote:
On Apr 23, 2006, at 1:21 PM, Borut Bolčina wrote:
If I understand you correctly, the above algorithm would create a
statement
DELETE FROM AUTO_PK_SUPPORT WHERE TABLE_NAME IN ('tableA', 'tableB',
'tableC')
but not, say, tableD, as it is already present (created before).
In my case this pkDeleteString would look like (empty table names)
DELETE FROM AUTO_PK_SUPPORT WHERE TABLE_NAME IN ('')
INSERT INTO AUTO_PK_SUPPORT (TABLE_NAME, NEXT_ID) VALUES ('', 200)
Sorry, my first message and the correction that followed was a bit
confusing. "DELETE FROM .." is not needed at all. You need to do a
SELECT to see what's there, compare with the full entity list, and
only insert the missing records.
Also see Mike's suggestion on how to figure out the right starting
value. It may work as an alternative or an addition to the algorithm
above.
One "workaround" I can think of is to do a SELECT on AUTO_PK_SUPPORT
and if no error is thrown I must assume the table exists, so I skip
generator.runGenerator(dataSource); altogether.
This is not generic enough as you may end up with missing records if
you added a few new tables since the last run (so AUTO_PK_SUPPORT is
there, but its contents are incomplete).
Andrus
