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MySQL 8.0.40
Source Code Documentation
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MySQL 8.0.40
Source Code Documentation
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Input data that is used to calculate dict_index_t::stat_n_diff_key_vals[] for each n-columns prefix (n from 1 to n_uniq). More...
Public Attributes | |
| ulint | level |
| Index of the level on which the descent through the btree stopped. More... | |
| uint64_t | n_recs_on_level |
| Number of records on the level where the descend through the btree stopped. More... | |
| uint64_t | n_diff_on_level |
| Number of different key values that were found on the mid level. More... | |
| uint64_t | n_leaf_pages_to_analyze |
| Number of leaf pages that are analyzed. More... | |
| uint64_t | n_diff_all_analyzed_pages |
| Cumulative sum of the number of different key values that were found on all analyzed pages. More... | |
| uint64_t | n_external_pages_sum |
| Cumulative sum of the number of external pages (stored outside of the btree but in the same file segment). More... | |
Input data that is used to calculate dict_index_t::stat_n_diff_key_vals[] for each n-columns prefix (n from 1 to n_uniq).
| ulint n_diff_data_t::level |
Index of the level on which the descent through the btree stopped.
level 0 is the leaf level. This is >= 1 because we avoid scanning the leaf level because it may contain too many pages and doing so is useless when combined with the random dives - if we are to scan the leaf level, this means a full scan and we can simply do that instead of fiddling with picking random records higher in the tree and to dive below them. At the start of the analyzing we may decide to do full scan of the leaf level, but then this structure is not used in that code path.
| uint64_t n_diff_data_t::n_diff_all_analyzed_pages |
Cumulative sum of the number of different key values that were found on all analyzed pages.
| uint64_t n_diff_data_t::n_diff_on_level |
Number of different key values that were found on the mid level.
| uint64_t n_diff_data_t::n_external_pages_sum |
Cumulative sum of the number of external pages (stored outside of the btree but in the same file segment).
| uint64_t n_diff_data_t::n_leaf_pages_to_analyze |
Number of leaf pages that are analyzed.
This is also the same as the number of records that we pick from the mid level and dive below them.
| uint64_t n_diff_data_t::n_recs_on_level |
Number of records on the level where the descend through the btree stopped.
When we scan the btree from the root, we stop at some mid level, choose some records from it and dive below them towards a leaf page to analyze.
1.9.2