[eclipselink-dev] Question about performance issue with SeqencingManager

[Mitesh Meswani <Mitesh.Meswani@xxxxxxx>]

Hi,

We seem to have a performance issue with Table Sequences while running 
inside container ( => external transaction controller). If multiple 
threads try to do getNextValue() on a table sequence and our 
preallocation bucket is empty and external transaction controller is 
used, all of them can reach the code at line 468 of 
SequencingManager.Preallocation_Transaction_NoAccessor_State.getNextValue() 
which calls sequence.getGeneratedVector(...) . This would result in all 
of them issuing an update statement to the sequence table and being 
blocked out by database till preceding threads' transaction commits. The 
code of Preallocation_Transaction_NoAccessor_State.getNextValue() is 
explicitly written to not obtain locks around 
sequence.getGeneratedVector(...) if running with external transaction 
controller. There is fair amount of comment written but some how I am 
still not able to figure out why we are not obtaining locks for this 
case. Can some one familiar with history of the code comment on this.

Thanks,
Mitesh