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https://issues.apache.org/jira/browse/THRIFT-2062?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14142707#comment-14142707
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Konrad Grochowski commented on THRIFT-2062:
-------------------------------------------
linked "implementation issue"
> cpp flag for using unordered_set instead of set
> -----------------------------------------------
>
> Key: THRIFT-2062
> URL: https://issues.apache.org/jira/browse/THRIFT-2062
> Project: Thrift
> Issue Type: Improvement
> Components: C++ - Compiler
> Reporter: Vitali Lovich
>
> It would be nice if the cpp compiler could generate code to use unordered_set
> instead of set. unordered_set is faster & usually an unordered_set is wanted
> rather than an ordered one. Furthermore, since unordered_set only needs a
> hash function, we could generate one for every type.
> The hash code generated can be along the lines of what Eclipse does for
> auto-generated hash codes:
> struct ThriftObj {
> 1: string f1;
> 2: i32 f2;
> 3: SomeOtherThriftObj f3;
> }
> // header file:
> namespace std {
> template <> struct hash<ThriftObj> {
> size_t operator()(const ThriftObj& o);
> }
> }
> // cpp file:
> namespace std {
> template <> struct hash<ThriftObj> {
> size_t operator()(const ThriftObj& o)
> constexpr size_t prime = 31;
> size_t hashcode = 1;
> hashcode += o.__isset.f1 ? prime *
> std::hash<decltype(o.f1)>()(o.f1) : 0;
> hashcode += o.__isset.f2 ? prime *
> std::hash<decltype(o.f1)>()(o.f2) : 0;
> hashcode += o.__isset.f3 ? prime *
> std::hash<decltype(o.f1)>()(o.f3) : 0;
> }
> }
> }
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