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boost::unrodered_flat_map for join #3824

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boost::unrodered_flat_map for join
mariadb-LeonidFedorov Oct 23, 2025
da1212e
Merge branch 'stable-23.10' into boost_flat
mariadb-LeonidFedorov Oct 23, 2025
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29 changes: 19 additions & 10 deletions dbcon/joblist/largehashjoin.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@
#include <vector>
#include <list>
#include <unordered.h>
#include <boost/unordered/unordered_flat_map.hpp>

#include <boost/thread.hpp>
#include <boost/scoped_array.hpp>
Expand Down Expand Up @@ -107,13 +108,12 @@ class HashJoin
// than a list of ElementType to reduce memory utilization and to increase the performance of loading the
// map. typedef std::tr1::unordered_map<typename element_t::second_type, std::list<element_t>,
// HjHasher<element_t> > hash_t;
typedef
typename std::tr1::unordered_multimap<typename element_t::second_type, typename element_t::first_type>
hash_t;
typedef typename std::tr1::unordered_multimap<typename element_t::second_type,
typename element_t::first_type>::iterator hashIter_t;
typedef typename std::tr1::unordered_multimap<typename element_t::second_type,
typename element_t::first_type>::value_type hashPair_t;
// Now using boost::unordered_flat_map with vector for better cache locality
typedef typename boost::unordered_flat_map<typename element_t::second_type,
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@mariadb-AlexeyAntipovsky mariadb-AlexeyAntipovsky Oct 27, 2025

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using instead of typedef?

std::vector<typename element_t::first_type>>
hash_t;
typedef typename hash_t::iterator hashIter_t;
typedef typename hash_t::value_type hashPair_t;

// allow each thread to have its own pointers
struct control_struct
Expand Down Expand Up @@ -503,9 +503,18 @@ void HashJoin<element_t>::createHash(BucketDL<element_t>* srcBucketDL, hash_t* d

try
{
// std::list<element_t> tmp(1,e);
destHashTbl->insert(
std::pair<typename element_t::second_type, typename element_t::first_type>(e.second, e.first));
// For boost::unordered_flat_map, we store vectors of values
auto it = destHashTbl->find(e.second);
if (it != destHashTbl->end())
{
it->second.push_back(e.first);
}
else
{
std::vector<typename element_t::first_type> vec;
vec.push_back(e.first);
destHashTbl->emplace(e.second, std::move(vec));
}
}
catch (exception& exc)
{
Expand Down
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