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Aleksey Yeschenko commented on CASSANDRA-15410:
-----------------------------------------------
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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