IMO, a generic sync process would should be:
* First stage : * upload *
1. # client fetch local changes occured since last sync
2. # client send the changes to server
3. # server apply the changes and generate conflict report
4. # client mark the upload success or process the conflict report
5. # if no conflict, goto second stage
* Second stage : * download *
1. # client fetch remote changes occured since last sync
2. # server send the changes to client
3. # client apply the changes and generate conflict report
4. # client mark the download success or process the conflict report
For each committed transaction, if any changes occured, Envers
will generate a revision record in database.
When upload, if no conflicts or errors, a client id should be
persisted on server with a new server revision number. So the
persisted revision info should including:
{code}
revisionNumber
clientId
{code}
When download, if no conflicts or errors, the server revision
number should be persisted on client with a new client revision
number. So the persisted revision info should including:
{code}
revisionNumber
serverRevisionNumber
{code}
To select the changes from client :
{code:title=Select last sync rev}
SELECT MAX(ri.revisionNumber) FROM revinfo ri
WHERE ri.serverRevisionNumber IS NOT NULL
{code}
{code:title=Select incremental Inserts}
SELECT e FROM Entity e
WHERE e.id IN (
SELECT er.originalId.id FROM AuditEntity er
WHERE er.REVTYPE = ADD
AND er.originalId.REV.id > :lastSyncRev
)
{code}
{code:title=Select incremental Updates}
SELECT e FROM Entity e
WHERE e.id IN (
SELECT er.originalId.id FROM AuditEntity er
WHERE er.REVTYPE = MOD
AND er.originalId.REV.id > :lastSyncRev
) AND e.id NOT IN(
SELECT er.originalId.id FROM AuditEntity er
WHERE er.REVTYPE = ADD
AND er.originalId.REV.id > :lastSyncRev
)
{code}
{code:title=Select incremental Deletes}
SELECT er FROM AuditEntity er
WHERE er.REVEND = (
SELECT ier.originalId.REV.id FROM AuditEntity ier
WHERE ier.REVTYPE = DEL
AND ier.originalId.REV.id > :lastSyncRev
)
{code}
To select the changes from server :
{code:title=Select last sync rev}
SELECT MAX(ri.revisionNumber) FROM revinfo ri
WHERE ri.clientId = :clientId
{code}
{code:title=Select max sync rev}
SELECT MAX(ri.revisionNumber) FROM revinfo ri
WHERE ri.clientId != :clientId OR
ri.clientId IS NULL
{code}
{code:title=Select incremental Inserts}
SELECT e FROM Entity e
WHERE e.id IN (
SELECT er.originalId.id FROM AuditEntity er
WHERE er.REVTYPE = ADD
AND er.originalId.REV.id > :lastSyncRev
AND er.originalId.REV.id <= maxSyncRev
AND (
er.originalId.REV.clientId != :clientId
OR er.originalId.REV.clientId IS NULL
)
)
{code}
{code:title=Select incremental Updates}
SELECT e FROM Entity e
WHERE e.id IN (
SELECT er.originalId.id FROM AuditEntity er
WHERE er.REVTYPE = MOD
AND er.originalId.REV.id > :lastSyncRev
AND er.originalId.REV.id <= : maxSyncRev
AND (
er.originalId.REV.clientId != :clientId
OR er.originalId.REV.clientId IS NULL
)
) AND e.id NOT IN(
SELECT er.originalId.id FROM AuditEntity er
WHERE er.REVTYPE = ADD
AND er.originalId.REV.id > :lastSyncRev
AND er.originalId.REV.id <= : maxSyncRev
AND (
er.originalId.REV.clientId != :clientId
OR er.originalId.REV.clientId IS NULL
)
)
{code}
{code:title=Select incremental Deletes}
SELECT er FROM AuditEntity er
WHERE er.REVEND = (
SELECT ier.originalId.REV.id FROM AuditEntity ier
WHERE ier.REVTYPE = DEL
AND ier.originalId.REV.id > :lastSyncRev
AND ier.originalId.REV.id <= : maxSyncRev
AND (
ier.originalId.REV.clientId != :clientId
OR ier.originalId.REV.clientId IS NULL
)
)
{code}
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