????????卸??????写???TokuDB???????????????????(heurstic)??seqinsert_score????????????
????1) ???写????????????seqinsert_score?????(???)
????2) ???写?????????????seqinsert_score????(???)
??????seqinsert_score????100?????????????????写?????鈥�?写??????????????????????pivot???卸???卸???????????写?????写???y????????compare????????????????效??
????MariaDB·?????????·filesort with small LIMIT optimization
??????MySQL 5.6.2/MariaDB 10.0.0?姹�?????MySQL/MariaDB???”ORDER BY …LIMIT n”????????????渭???????????n??小??????????????????????n????????????????????????????????????????????n???? ????????????????????????????ASC????
??????????????n????????????校???????????????写????
?????????????????????未??????????????
???????????械?????????小???????????????婊�?????????Shift??????????
?????????????????2???瑁�????????????????????5
??????????????械????????小?????????????????小???????????????ASC????????
????????????????鑷�????m*log(n)??m?????????????????n?LIMIT?????????????????????????鑷�????m*log(m)????n?小??m????????????效??
??????????MySQL 5.6?校?????optimizer_trace????泻???????????????渭???屑????????????????谩?MariaDB 10.013?????????????????????????屑????????????
????Sort_priority_queue_sorts
????????: ???????????????????????(?????????=Sort_range+Sort_scan)
??????围: Global?? Session
????????????: numeric
????????姹�: MariaDB 10.0.13
????????MariaDB???????????????Slow Log?小?????? log_slow_verbosity=query_plan????????Slow Log?锌?????????????
????# Time: 140714 18:30:39
????# User@Host: root[root] @ localhost []
????# Thread_id: 3  Schema: test  QC_hit: No
????# Query_time: 0.053857  Lock_time: 0.000188  Rows_sent: 11  Rows_examined: 100011
????# Full_scan: Yes  Full_join: No  Tmp_table: No  Tmp_table_on_disk: No
????# Filesort: Yes  Filesort_on_disk: No  Merge_passes: 0  Priority_queue: Yes
????SET timestamp=1405348239;SET timestamp=1405348239;
????select * from t1 where col1 between 10 and 20 order by col2 limit 100;
????“Priority_queue: Yes” ??????Query????????????械???屑??(pt-query-digest ???????????? Priority_queue ?????)??????????????????????