commit cannot be resolved #24384 42 – Fix a GC issue of statistics that might cause duplicated fm-sketch records #24357 – Avoid unnecessary pessimistic rollback when the pessimistic locking receives the restored: • Tables related to statistics: “stats_buckets”, “stats_extended”, “stats_feedback”, “stats_fm_sketch”, “stats_histograms”, “stats_meta”, “stats_top_n” • Tables related to privileges or the system: to- tal num- ber of rows in the ta- ble √ √ Column Count- Min Sketch √ × 598 Information Version 1 Version 2 Index Count- Min Sketch √ × Column Top- N √ √ (Main- te- nance meth- ods and pre- ci-

the feature, TiDB can synchronously load large-sized statistics (such as histograms, TopN, and Count-Min Sketch statistics) into memory when you execute SQL statements, which improves the completeness of restored: • Tables related to statistics: “stats_buckets”, “stats_extended”, “stats_feedback”, “stats_fm_sketch”, “stats_histograms”, “stats_meta”, “stats_top_n” • Tables related to privileges or the system: Version 1 Version 2 The to- tal num- ber of rows in the ta- ble √ √ Column Count- Min Sketch √ × Index Count- Min Sketch √ × Column Top- N √ √ (Main- te- nance meth- ods and pre- ci- sion are im- proved)

gc_delete_range_done | | global_variables | | stats_buckets | | stats_extended | | stats_feedback | | stats_fm_sketch | | stats_histograms | | stats_history | | stats_meta | | stats_meta_history | | stats_table_locked TOPNs. • WITH NUM CMSKETCH DEPTH specifies the depth of the CM Sketch. • WITH NUM CMSKETCH WIDTH specifies the width of the CM Sketch. • WITH NUM SAMPLES specifies the number of samples. 2097 • WITH correspond to two different algo- rithms of collecting samples. See Histograms, Top-N and CMSketch (Count-Min Sketch) for detailed explanations. For SAMPLES/SAMPLERATE, see Improve collection performance. For

gc_delete_range_done | | global_variables | | stats_buckets | | stats_extended | | stats_feedback | | stats_fm_sketch | | stats_histograms | | stats_history | | stats_meta | | stats_meta_history | | stats_table_locked TOPNs. • WITH NUM CMSKETCH DEPTH specifies the depth of the CM Sketch. • WITH NUM CMSKETCH WIDTH specifies the width of the CM Sketch. • WITH NUM SAMPLES specifies the number of samples. 1673 • WITH correspond to two different algo- rithms of collecting samples. See Histograms, Top-N and CMSketch (Count-Min Sketch) for detailed explanations. For SAMPLES/SAMPLERATE, see Improve collection performance. For

gc_delete_range_done | | global_variables | | stats_buckets | | stats_extended | | stats_feedback | | stats_fm_sketch | | stats_histograms | | stats_history | | stats_meta | | stats_meta_history | | stats_table_locked TOPNs. • WITH NUM CMSKETCH DEPTH specifies the depth of the CM Sketch. • WITH NUM CMSKETCH WIDTH specifies the width of the CM Sketch. • WITH NUM SAMPLES specifies the number of samples. 1681 • WITH correspond to two different algo- rithms of collecting samples. See Histograms, Top-N and CMSketch (Count-Min Sketch) for detailed explanations. For SAMPLES/SAMPLERATE, see Improve collection performance. For

gc_delete_range_done | | global_variables | | stats_buckets | | stats_extended | | stats_feedback | | stats_fm_sketch | | stats_histograms | | stats_history | | stats_meta | | stats_meta_history | | stats_table_locked TOPNs. • WITH NUM CMSKETCH DEPTH specifies the depth of the CM Sketch. • WITH NUM CMSKETCH WIDTH specifies the width of the CM Sketch. • WITH NUM SAMPLES specifies the number of samples. 1794 • WITH correspond to two different algo- rithms of collecting samples. See Histograms, Top-N and CMSketch (Count-Min Sketch) for detailed explanations. For SAMPLES/SAMPLERATE, see Improve collection performance. For

gc_delete_range_done | | global_variables | | stats_buckets | | stats_extended | | stats_feedback | | stats_fm_sketch | | stats_histograms | | stats_history | | stats_meta | | stats_meta_history | | stats_table_locked TOPNs. • WITH NUM CMSKETCH DEPTH specifies the depth of the CM Sketch. • WITH NUM CMSKETCH WIDTH specifies the width of the CM Sketch. • WITH NUM SAMPLES specifies the number of samples. 1669 • WITH correspond to two different algo- rithms of collecting samples. See Histograms, Top-N and CMSketch (Count-Min Sketch) for detailed explanations. For SAMPLES/SAMPLERATE, see Improve collection performance. For

| | schema_index_usage | | stats_buckets | | stats_extended | | stats_feedback | | stats_fm_sketch | | stats_histograms | | stats_history | | stats_meta | | stats_meta_history | | stats_table_locked TOPNs. • WITH NUM CMSKETCH DEPTH specifies the depth of the CM Sketch. • WITH NUM CMSKETCH WIDTH specifies the width of the CM Sketch. • WITH NUM SAMPLES specifies the number of samples. 1624 • WITH correspond to two different algo- rithms of collecting samples. See Histograms, Top-N and CMSketch (Count-Min Sketch) for detailed explanations. For SAMPLES/SAMPLERATE, see Improve collection performance. For

restored: • Tables related to statistics: “stats_buckets”, “stats_extended”, “stats_feedback”, “stats_fm_sketch”, “stats_histograms”, “stats_meta”, “stats_top_n” • Tables related to privileges or the system: Version 1 Version 2 The to- tal num- ber of rows in the ta- ble √ √ Column Count- Min Sketch √ × Index Count- Min Sketch √ × Column Top- N √ √ (Main- te- nance meth- ods and pre- ci- sion are im- proved) maintains the estimate precision in most scenarios. This document briefly introduces the histogram, Count-Min Sketch, and Top-N, and details the collection and maintenance of statistics. Histogram A histogram

restored: • Tables related to statistics: “stats_buckets”, “stats_extended”, “stats_feedback”, “stats_fm_sketch”, “stats_histograms”, “stats_meta”, “stats_top_n” • Tables related to privileges or the system: Version 1 Version 2 The to- tal num- ber of rows in the ta- ble √ √ Column Count- Min Sketch √ × Index Count- Min Sketch √ × 620 Information Version 1 Version 2 Column Top- N √ √ (Main- te- nance meth- maintains the estimate precision in most scenarios. This document briefly introduces the histogram, Count-Min Sketch, and Top-N, and details the collection and maintenance of statistics. Histogram A histogram