Deyan Tsvetanov wrote:
Here is an example:
On server A ( the one that pushes data ) we insert the following records
with the following sequence and timestamps:
PARTY : party_id: 1000 , created_timestamp_tx : 6-APR -2010
20:00:00.010
PARTY_GROUP : party_group_id : 1000 ( FK to PARTY.party_id ) ,
created_timestamp_tx: 6-APR-2010 20:00:00:013 - three milliseconds
later.
That would the the database contents without issues.
Now imagine we do a NTP time synchronization between the two inserts.
The NTP sync "corrects" the system clock 5 ms back. The database
contents now would be:
PARTY : party_id: 1000 , created_timestamp_tx : 6-APR -2010
20:00:00.010
PARTY_GROUP : party_group_id : 1000 ( FK to PARTY.party_id ) ,
created_timestamp_tx: 6-APR-2010 20:00:00:008 - earlier than the PARTY
record.
When the server queries the records to be sent for synchronization the
result will be:
PARTY_GROUP : party_group_id : 1000 ( FK to PARTY.party_id ) ,
created_timestamp_tx: 6-APR-2010 20:00:00:008
PARTY : party_id: 1000 , created_timestamp_tx : 6-APR -2010
20:00:00.010
The server that accepts the push sync will try to insert first the
PARTY_GROUP record and will get a FK constraint error - the PARTY record
is missing.
Okay, that's a different problem than the one I was imagining.
