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https://issues.apache.org/jira/browse/CASSANDRA-15410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16974246#comment-16974246
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Aleksey Yeschenko commented on CASSANDRA-15410:
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I welcome this change in principle, but it makes me feel a little uneasy.
Specifically, it relies implicitly on how the method is used two levels of
abstraction up, and feels slightly brittle to me.
I wonder if you'd be open instead to a slightly less efficient but,
importantly, still resize-avoiding alternative: modify {{CBUtil#writeString()}}
(and {{CBUtil#writeLongString()}} while at it, just for consistency sake) to
explicitly calculate the precise size of encoded string using
{{TypeSizes#encodedUTF8Length()}} method, and then pass that value to
{{ByteBufUtil#reserveAndWriteUtf8()}}. This way, yes, you would effectively
calculate the size of the string twice, but the abstraction won't leak
assumptions, and will still avoid unnecessary resizing.
> Avoid over-allocation of bytes for UTF8 string serialization
> -------------------------------------------------------------
>
> Key: CASSANDRA-15410
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15410
> Project: Cassandra
> Issue Type: Improvement
> Components: Messaging/Client
> Reporter: Yifan Cai
> Assignee: Yifan Cai
> Priority: Normal
> Fix For: 4.0
>
>
> In the current message encoding implementation, it first calculates the
> `encodeSize` and allocates the bytebuffer with that size.
> However, during encoding, it assumes the worst case of writing UTF8 string to
> allocate bytes, i.e. assuming each letter takes 3 bytes.
> The over-estimation further leads to resizing the underlying array and data
> copy.
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