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https://issues.apache.org/jira/browse/KAFKA-5285?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16367553#comment-16367553
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Xavier Léauté edited comment on KAFKA-5285 at 2/16/18 4:37 PM:
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{quote}# For lower range, we just use the {{keyFrom bytes}}, instead of
{{keyFrom + minSuffix (0000s)}}. Since we know there would be no data in
between these two keys at all, we can save some overhead of bytes alloc and
puts.{quote}
This assumption only holds if {{minSuffix}} only consists of zeros. If that is
not the case, then there exists a suffix {{S}} that is smaller in order than
{{minSuffix}} and is not a prefix of {{minSuffix}}. In that case I can
construct a new key by appending this suffix to {{keyFrom}}, i.e. my new key is
{{keyFrom + S}}. The smallest byte sequence for that key will be {{keyFrom + S
+ minSuffix}} which is greater than {{keyFrom}}, but still smaller than
{{keyFrom + minSuffix}}
was (Author: xvrl):
{quote}# For lower range, we just use the {{keyFrom bytes}}, instead of
{{keyFrom + minSuffix (0000s)}}. Since we know there would be no data in
between these two keys at all, we can save some overhead of bytes alloc and
puts.{quote}
This assumption only holds if {{minSuffix}} only consists of zeros. If that is
not the case, then there exists a suffix S that is smaller in order than
minSuffix and is not a prefix of minSuffix. In that case I can construct a new
key by appending this suffix to {{keyFrom}}, i.e. my new key is {{keyFrom +
S}}. The smallest byte sequence for that key will be {{keyFrom + S +
minSuffix}} which is greater than {{keyFrom}}, but still smaller than {{keyFrom
+ minSuffix}}
> Optimize upper / lower byte range for key range scan on windowed stores
> -----------------------------------------------------------------------
>
> Key: KAFKA-5285
> URL: https://issues.apache.org/jira/browse/KAFKA-5285
> Project: Kafka
> Issue Type: Improvement
> Components: streams
> Reporter: Xavier Léauté
> Assignee: Guozhang Wang
> Priority: Major
> Labels: performance
>
> The current implementation of {{WindowKeySchema}} / {{SessionKeySchema}}
> {{upperRange}} and {{lowerRange}} does not make any assumptions with respect
> to the other key bound (e.g. the upper byte bound does not depends on lower
> key bound).
> It should be possible to optimize the byte range somewhat further using the
> information provided by the lower bound.
> More specifically, by incorporating that information, we should be able to
> eliminate the corresponding {{upperRangeFixedSize}} and
> {{lowerRangeFixedSize}}, since the result should be the same if we implement
> that optimization.
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