2022-11-21 mysql列存储引擎-架构实现缺陷梳理-P2

摘要:

收集现有代码的糟糕实现，前事不忘后事之师，把这些烂东西定死在耻辱柱上以免再次发生

糟糕的设计:

一. DGMaterializedIterator::GetNextPackrow

函数实现:

int DimensionGroupMaterialized::DGMaterializedIterator::GetNextPackrow(int dim, int ahead) {
  MEASURE_FET("DGMaterializedIterator::GetNextPackrow(int dim, int ahead)");
  if (ahead == 0) return GetCurPackrow(dim);
  IndexTable *cur_t = t[dim];
  if (cur_t == NULL) return -1;
  uint64_t end_block = cur_t->EndOfCurrentBlock(cur_pos);
  if (next_pack[dim] >= no_obj || uint64_t(next_pack[dim]) >= end_block) return -1;
  uint64_t ahead_pos = 0;
  //	cout << "dim " << dim << ",  " << next_pack[dim] << " -> " <<
  // ahead1[dim