cf_merge_strategy.cpp

static int8_t TryAppend(const ColumnFamily *__restrict const self, const ColumnFamily *__restrict const cf, colNameCmpProc_t cmpProc)
{
        const uint32_t cfColumnsCnt = cf->columns.Size();

        if (unlikely(cfColumnsCnt == 0))
                return 0;

        const uint32_t selfColumnsCnt = self->columns.Size();

        if (unlikely(selfColumnsCnt == 0))
                return 1;       // Should append cf->columns to self->columns


        const column_name *const sn = &self->columns.LastValueUnsafe()->name, *const cn = &cf->columns[0]->name;
        const auto r = cmpProc(cn->Name(), cn->Length(), sn->Name(), sn->Length());

        if (r > 0)
        {
                // Yes, we can just append all cf->columns[] to self->columns#endif
                return 1;
        }
        else
        {

                const column_name *const snFirst = &self->columns[0]->name, *const cnLast = &cf->columns.LastValueUnsafe()->name;
                const auto r = cmpProc(cnLast->Name(), cnLast->Length(), snFirst->Name(), snFirst->Length());

                if (r < 0)
                {
                        // Yes, we can just insert all cf->columns[] at self->columns[0]
                        return -1;
                }
                else if (cfColumnsCnt < 32)
                {
#pragma mark arbitrary
                        if (cfColumnsCnt < 8)
                        {
                                // We almost always end up updating/setting the same columns anyway
                                return 2;
                        }



#pragma mark arbitrary
                        const int32_t index = Max<int32_t>(0, ((int32_t)selfColumnsCnt) - 8);
                        const column_name *const boundaryName = &self->columns.Values()[index]->name;

                        if (cmpProc(cnLast->Name(), cnLast->Length(), boundaryName->Name(), boundaryName->Length()) >= 0)
                        {
                                // Yes, we should perform in-place updates
                                return 2;
                        }
                }
        }

        // Overlapping names, cannot append or insert, cannot advice in-place updates        

        return 0;
}