c++|训练02｜头文件

#ifndef NDEBUG
  /* Print field value into debug trace, in NULL-aware way. */
  void dbug_print() const {
    if (is_real_null())
      fprintf(DBUG_FILE, "NULL");
    else {
      char buf[256];
      String str(buf, sizeof(buf), &my_charset_bin);
      str.length(0);
      String *pstr;
      pstr = val_str(&str);
      fprintf(DBUG_FILE, "'%s'", pstr->c_ptr_safe());
    }
  }
#endif

#ifndef UNIV_HOTBACKUP
/** Checks if the page in the cursor can be merged with given page.
 If necessary, re-organize the merge_page.
 @return  true if possible to merge. */
static bool btr_can_merge_with_page(
    btr_cur_t *cursor,         /*!< in: cursor on the page to merge */
    page_no_t page_no,         /*!< in: a sibling page */
    buf_block_t **merge_block, /*!< out: the merge block */
    mtr_t *mtr);               /*!< in: mini-transaction */
#endif     

/** Checks if the page in the cursor can be merged with given page.
 If necessary, re-organize the merge_page.
 @return  true if possible to merge. */
static bool btr_can_merge_with_page(
    btr_cur_t *cursor,         /*!< in: cursor on the page to merge */
    page_no_t page_no,         /*!< in: a sibling page */
    buf_block_t **merge_block, /*!< out: the merge block */
    mtr_t *mtr)                /*!< in: mini-transaction */
{
  dict_index_t *index;
  page_t *page;
  ulint n_recs;
  ulint data_size;
  ulint max_ins_size_reorg;
  ulint max_ins_size;
  buf_block_t *mblock;
  page_t *mpage;
  DBUG_TRACE;

  if (page_no == FIL_NULL) {
    *merge_block = nullptr;
    return false;
  }

  index = btr_cur_get_index(cursor);
  page = btr_cur_get_page(cursor);

  const page_id_t page_id(dict_index_get_space(index), page_no);
  const page_size_t page_size(dict_table_page_size(index->table));

  mblock = btr_block_get(page_id, page_size, RW_X_LATCH, index, mtr);
  mpage = buf_block_get_frame(mblock);

  n_recs = page_get_n_recs(page);
  data_size = page_get_data_size(page);

  max_ins_size_reorg = page_get_max_insert_size_after_reorganize(mpage, n_recs);

  if (data_size > max_ins_size_reorg) {
    goto error;
  }

  /* If compression padding tells us that merging will result in
  too packed up page i.e.: which is likely to cause compression
  failure then don't merge the pages. */
  if (page_size.is_compressed() && page_is_leaf(mpage) &&
      (page_get_data_size(mpage) + data_size >=
       dict_index_zip_pad_optimal_page_size(index))) {
    goto error;
  }

  max_ins_size = page_get_max_insert_size(mpage, n_recs);

  if (data_size > max_ins_size) {
    /* We have to reorganize mpage */

    if (!btr_page_reorganize_block(false, page_zip_level, mblock, index, mtr)) {
      goto error;
    }

    max_ins_size = page_get_max_insert_size(mpage, n_recs);

    ut_ad(page_validate(mpage, index));
    ut_ad(max_ins_size == max_ins_size_reorg);

    if (data_size > max_ins_size) {
      /* Add fault tolerance, though this should
      never happen */

      goto error;
    }
  }

  *merge_block = mblock;
  return true;

error:
  *merge_block = nullptr;
  return false;
}