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https://issues.apache.org/jira/browse/PHOENIX-1954?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14621522#comment-14621522
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James Taylor commented on PHOENIX-1954:
---------------------------------------
Thanks, [~jfernando_sfdc]. Couple of minor things, then I think we're good to
go:
1) I think there are a couple more calls that use
Sequence.ValueOp.RESERVE_SEQUENCE in PhoenixStatement. I think they all should
be changed to Sequence.ValueOp.VALIDATE_SEQUENCE (given the race condition you
found). Maybe we should just remove the RESERVE_SEQUENCE enum?
2) It looks like you'd always be throwing here and thus always be making an RPC
at validate time. Shouldn't this be calling isSequenceCacheExhausted() instead?
{code}
- public long incrementValue(long timestamp, ValueOp op) throws SQLException
{
+ public long incrementValue(long timestamp, ValueOp op, long numToAllocate)
throws SQLException {
SequenceValue value = findSequenceValue(timestamp);
- if (value == null) {
+ if (value == null || SequenceUtil.isBulkAllocation(numToAllocate)) {
throw EMPTY_SEQUENCE_CACHE_EXCEPTION;
}
+
if (value.currentValue == value.nextValue) {
if (op == ValueOp.VALIDATE_SEQUENCE) {
return value.currentValue;
}
throw EMPTY_SEQUENCE_CACHE_EXCEPTION;
- }
- return increment(value, op);
+ }
+ return increment(value, op, numToAllocate);
}
{code}
> Reserve chunks of numbers for a sequence
> ----------------------------------------
>
> Key: PHOENIX-1954
> URL: https://issues.apache.org/jira/browse/PHOENIX-1954
> Project: Phoenix
> Issue Type: New Feature
> Reporter: Lars Hofhansl
> Assignee: Jan Fernando
> Attachments: PHOENIX-1954-rebased.patch, PHOENIX-1954-wip.patch,
> PHOENIX-1954-wip2.patch.txt, PHOENIX-1954-wip3.patch,
> PHOENIX-1954-wip4.patch, PHOENIX-1954-wip5-rebased.patch,
> PHOENIX-1954-wip6.patch
>
>
> In order to be able to generate many ids in bulk (for example in map reduce
> jobs) we need a way to generate or reserve large sets of ids. We also need to
> mix ids reserved with incrementally generated ids from other clients.
> For this we need to atomically increment the sequence and return the value it
> had when the increment happened.
> If we're OK to throw the current cached set of values away we can do
> {{NEXT VALUE FOR <seq>(,<N>)}}, that needs to increment value and return the
> value it incremented from (i.e. it has to throw the current cache away, and
> return the next value it found at the server).
> Or we can invent a new syntax {{RESERVE VALUES FOR <seq>, <N>}} that does the
> same, but does not invalidate the cache.
> Note that in either case we won't retrieve the reserved set of values via
> {{NEXT VALUE FOR}} because we'd need to be idempotent in our case, all we
> need to guarantee is that after a call to {{RESERVE VALUES FOR <seq>, <N>}},
> which returns a value <M> is that the range [M, M+N) won't be used by any
> other user of the sequence. My might need reserve 1bn ids this way ahead of a
> map reduce run.
> Any better ideas?
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