Merge remote-tracking branch 'origin/main'

# Conflicts:
#	demo/main.cpp

src/sql/backend_provider.cpp

@@ -2,6 +2,7 @@
 #include "matador/sql/noop_connection.hpp"
 #include "matador/sql/dialect_builder.hpp"
 
+#include <algorithm>
 #include <stdexcept>
 
 namespace matador::sql {

src/sql/record.cpp

@@ -7,23 +7,27 @@
 namespace matador::sql {
 
 record::record(std::initializer_list<field> columns)
-: fields_(columns)
 {
-  init();
+  for (auto &&col :columns) {
+    const auto it = fields_by_name_.emplace(col.name(), field_index_pair {col, fields_.size()});
+    fields_.push_back(std::ref(it.first->second.first));
+  }
 }
 
 record::record(const std::vector<field> &columns)
-: fields_(columns)
 {
-  init();
+  for (auto &&col :columns) {
+    const auto it = fields_by_name_.emplace(col.name(), field_index_pair {col, fields_.size()});
+    fields_.push_back(std::ref(it.first->second.first));
+  }
 }
 
 record::record(const record &x)
-: fields_(x.fields_)
+: fields_by_name_(x.fields_by_name_)
 //, pk_index_(x.pk_index_)
 {
-  for (auto& col : fields_) {
-    add_to_map(col, col.index());
+  for (auto& col : fields_by_name_) {
+    fields_.push_back(std::ref(col.second.first));
   }
 }
 
@@ -33,16 +37,16 @@ record &record::operator=(const record &x)
     return *this;
   }
 
-  fields_ = x.fields_;
-  fields_by_name_.clear();
+  fields_by_name_ = x.fields_by_name_;
+  fields_.clear();
 //  pk_index_ = x.pk_index_;
-  for (auto& col : fields_) {
-    add_to_map(col, col.index());
+  for (auto& col : fields_by_name_) {
+    fields_.push_back(std::ref(col.second.first));
   }
   return *this;
 }
 
-const std::vector<field> &record::columns() const
+const std::vector<record::field_ref> &record::columns() const
 {
   return fields_;
 }
@@ -63,7 +67,9 @@ const std::vector<field> &record::columns() const
 
 const field &record::at(const column &col) const
 {
-  return fields_by_name_.at(col.name).first;
+  const auto &res = fields_by_name_.at(col.name);
+  const auto &f = res.first;
+  return f;
 }
 
 const field &record::at(size_t index) const
@@ -82,10 +88,10 @@ record::const_iterator record::find(const std::string &column_name) const {
   return it != fields_by_name_.end() ? fields_.begin() + it->second.second : fields_.end();
 }
 
-void record::append(field col)
+void record::append(const field &col)
 {
-  auto &ref = fields_.emplace_back(std::move(col));
-  add_to_map(ref, fields_.size() - 1);
+  const auto it = fields_by_name_.emplace(col.name(), field_index_pair {col, fields_.size()});
+  fields_.push_back(std::ref(it.first->second.first));
 }
 
 record::iterator record::begin()