std::shared_ptr<inserter> m_ins;

size_t m_flush_size, m_unflushed;

bool m_ok;

explicit insert_iterator(std::shared_ptr<inserter> ins, size_t flush_size = 0)

: m_ins(ins), m_flush_size(flush_size), m_unflushed(0), m_ok(true)

{}

~insert_iterator()

{ if (m_ok) m_ins->flush(); }

insert_iterator& operator *()

{ return *this; }

insert_iterator& operator ++()

{ return *this; }

insert_iterator operator ++(int)

{ return *this; }

insert_iterator& operator =(std::vector<variant>& row)

{

m_ok = false;

m_ins->insert(row);

++m_unflushed;

if (m_unflushed == m_flush_size)

{

m_ins->flush();

m_unflushed = 0;

}

m_ok = true;

return *this;

}