還是之前的項目的數據庫優化過程，這次換成了分析AWR報告中的TOP SQL
項目中有一個很長的SQL，篇幅原因就不給大家寫出來了，一共4個UNION組合。。。很長。
一共這個sql查出來了20多條數據，但是用了2.1秒左右，考慮到該sql在業務中的實際應用情況，每2分鐘都要刷新一次，這樣的話對DB性能消耗也是個影響，于是決定優化這個SQL一下。
獲取該sql的執行計劃
Plan Hash Value : 1613327291
---------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost | Time |
---------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 40 | 45240 | 66239 | 00:13:15 |
| * 1 | VIEW | | 40 | 45240 | 66239 | 00:13:15 |
| * 2 | COUNT STOPKEY | | | | | |
| 3 | VIEW | | 5586 | 6245148 | 66239 | 00:13:15 |
| * 4 | SORT UNIQUE STOPKEY | | 5586 | 3376642 | 65901 | 00:13:11 |
| 5 | UNION-ALL | | | | | |
| 6 | NESTED LOOPS OUTER | | 4919 | 1485538 | 43893 | 00:08:47 |
| * 7 | HASH JOIN | | 4919 | 1323211 | 29271 | 00:05:52 |
| * 8 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARM_DEAL | 23800 | 2332400 | 8512 | 00:01:43 |
| 9 | BITMAP CONVERSION TO ROWIDS | | | | | |
| 10 | BITMAP AND | | | | | |
| 11 | BITMAP OR | | | | | |
| 12 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 13 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALSTATE | | | 551 | 00:00:07 |
| 14 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 15 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALSTATE | | | 122 | 00:00:02 |
| 16 | BITMAP OR | | | | | |
| 17 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 18 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 19 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 20 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 21 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 22 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 23 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 24 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 25 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 26 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 969 | 00:00:12 |
| 27 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 28 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 29 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 30 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 31 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 32 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 33 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 34 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 35 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 36 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 37 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 38 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 39 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 40 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 41 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 42 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 43 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 44 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 163 | 00:00:02 |
| 45 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 46 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 47 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 48 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 49 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 50 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 51 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 52 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 53 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 54 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 55 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 56 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 57 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 58 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 59 | TABLE ACCESS FULL | RAMS_ALARM_WORKSHEET | 681549 | 116544879 | 14736 | 00:02:57 |
| 60 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARMMAIN | 1 | 33 | 3 | 00:00:01 |
| * 61 | INDEX RANGE SCAN | RAMS_ALARMMAIN_SHEETNO | 1 | | 2 | 00:00:01 |
| 62 | NESTED LOOPS OUTER | | 1 | 344 | 15062 | 00:03:01 |
| 63 | NESTED LOOPS | | 1 | 311 | 15059 | 00:03:01 |
| * 64 | HASH JOIN | | 273 | 38220 | 14240 | 00:02:51 |
| * 65 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARM_DEAL | 6819 | 722814 | 4937 | 00:01:00 |
| 66 | BITMAP CONVERSION TO ROWIDS | | | | | |
| 67 | BITMAP AND | | | | | |
| 68 | BITMAP OR | | | | | |
| 69 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 70 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALSTATE | | | 551 | 00:00:07 |
| 71 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 72 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALSTATE | | | 122 | 00:00:02 |
| 73 | BITMAP OR | | | | | |
| 74 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 75 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 76 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 77 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 78 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 79 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 80 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 81 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 969 | 00:00:12 |
| 82 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 83 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 84 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 85 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 86 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 87 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 88 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 89 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 90 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 91 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 92 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 93 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 94 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 95 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 96 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 97 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 98 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 99 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 100 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 101 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 163 | 00:00:02 |
| 102 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 103 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 104 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 105 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 106 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 107 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 108 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 109 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 110 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 111 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 112 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 113 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 114 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 115 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_B | | | 7 | 00:00:01 |
| 116 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 117 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALTYPE | | | 1389 | 00:00:17 |
| 118 | VIEW | VW_SQ_1 | 73352 | 2493968 | 9302 | 00:01:52 |
| 119 | HASH GROUP BY | | 73352 | 3227488 | 9302 | 00:01:52 |
| * 120 | INDEX FAST FULL SCAN | RAMS_ALARM_DEAL_SHEETNO | 76580 | 3369520 | 8468 | 00:01:42 |
| 121 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARM_WORKSHEET | 1 | 171 | 3 | 00:00:01 |
| * 122 | INDEX RANGE SCAN | RAMS_WORKSHEET_WS_NUM | 1 | | 2 | 00:00:01 |
| 123 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARMMAIN | 1 | 33 | 3 | 00:00:01 |
| * 124 | INDEX RANGE SCAN | RAMS_ALARMMAIN_SHEETNO | 1 | | 2 | 00:00:01 |
| 125 | NESTED LOOPS OUTER | | 665 | 202160 | 6620 | 00:01:20 |
| 126 | NESTED LOOPS | | 661 | 179131 | 4656 | 00:00:56 |
| * 127 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARM_DEAL | 661 | 66100 | 2672 | 00:00:33 |
| 128 | BITMAP CONVERSION TO ROWIDS | | | | | |
| 129 | BITMAP AND | | | | | |
| 130 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 131 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALTYPE | 61440 | | 145 | 00:00:02 |
| 132 | BITMAP OR | | | | | |
| 133 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 134 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALSTATE | 61440 | | 551 | 00:00:07 |
| 135 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 136 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALSTATE | 61440 | | 122 | 00:00:02 |
| 137 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARM_WORKSHEET | 1 | 171 | 3 | 00:00:01 |
| * 138 | INDEX RANGE SCAN | RAMS_WORKSHEET_WS_NUM | 1 | | 2 | 00:00:01 |
| 139 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARMMAIN | 1 | 33 | 3 | 00:00:01 |
| * 140 | INDEX RANGE SCAN | RAMS_ALARMMAIN_SHEETNO | 1 | | 2 | 00:00:01 |
| * 141 | FILTER | | | | | |
| 142 | NESTED LOOPS OUTER | | 1 | 279 | 35 | 00:00:01 |
| 143 | NESTED LOOPS | | 1 | 246 | 32 | 00:00:01 |
| * 144 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARM_DEAL | 1 | 75 | 29 | 00:00:01 |
| 145 | BITMAP CONVERSION TO ROWIDS | | | | | |
| 146 | BITMAP AND | | | | | |
| 147 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 148 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALROLE | 449 | | 4 | 00:00:01 |
| 149 | BITMAP OR | | | | | |
| 150 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 151 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALTYPE | 449 | | 10 | 00:00:01 |
| 152 | BITMAP CONVERSION FROM ROWIDS | | | | | |
| * 153 | INDEX RANGE SCAN | RAMS_ALARM_DEAL_DEALTYPE | 449 | | 15 | 00:00:01 |
| * 154 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARM_WORKSHEET | 1 | 171 | 3 | 00:00:01 |
| * 155 | INDEX RANGE SCAN | RAMS_WORKSHEET_WS_NUM | 1 | | 2 | 00:00:01 |
| 156 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARMMAIN | 1 | 33 | 3 | 00:00:01 |
| * 157 | INDEX RANGE SCAN | RAMS_ALARMMAIN_SHEETNO | 1 | | 2 | 00:00:01 |
---------------------------------------------------------------------------------------------------------------------------
看這個執行計劃，發現計劃中有很多BITMAP CONVERSION TO ROWIDS 字樣，看起來貌似用了位圖索引。
位圖索引說明：
從這篇資料中可以分析出來，位圖索引使用的場景為:
位圖索引適合靜態數據，而不適合索引頻繁更新的列
但是我們的表沒有建立bitmap類型的索引，詢問過開發，都是建立的Normal索引，這是為什么呢？
通過詢問公司DBA同事，推薦了一篇文檔給我：
看到這里：
出現這樣的情況，是因為表中存在不適當的索引，這些索引列的唯一度不高，oracle就有可能選擇兩個這樣的索引轉為bitmap來執行
之后詢問開發，發現有一張表中建立了很多不能通過該字段判斷唯一性的索引列，這樣導致oracle自行判斷，就在執行計劃中觸發了bitmap。
知道原因后，將表中不能判斷唯一性的字段索引去掉，重新執行SQL，觀察執行計劃：
Plan Hash Value : 1709251740
----------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost | Time |
----------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 40 | 45240 | 71112 | 00:14:14 |
| * 1 | VIEW | | 40 | 45240 | 71112 | 00:14:14 |
| * 2 | COUNT STOPKEY | | | | | |
| 3 | VIEW | | 39042 | 43648956 | 71112 | 00:14:14 |
| * 4 | SORT UNIQUE STOPKEY | | 39042 | 22727766 | 68852 | 00:13:47 |
| 5 | UNION-ALL | | | | | |
| * 6 | HASH JOIN OUTER | | 37719 | 10976229 | 37682 | 00:07:33 |
| * 7 | HASH JOIN | | 35734 | 9219372 | 17105 | 00:03:26 |
| * 8 | TABLE ACCESS FULL | RAMS_ALARM_DEAL | 15417 | 1464615 | 7353 | 00:01:29 |
| 9 | TABLE ACCESS FULL | RAMS_ALARM_WORKSHEET | 457958 | 74647154 | 9751 | 00:01:58 |
| 10 | TABLE ACCESS FULL | RAMS_ALARMMAIN | 458155 | 15119115 | 19143 | 00:03:50 |
| 11 | NESTED LOOPS OUTER | | 1 | 332 | 15431 | 00:03:06 |
| 12 | NESTED LOOPS | | 1 | 299 | 15427 | 00:03:06 |
| * 13 | HASH JOIN | | 175 | 23800 | 15248 | 00:03:03 |
| * 14 | TABLE ACCESS FULL | RAMS_ALARM_DEAL | 4396 | 452788 | 7347 | 00:01:29 |
| 15 | VIEW | VW_SQ_1 | 49438 | 1631454 | 7900 | 00:01:35 |
| 16 | HASH GROUP BY | | 49438 | 2125834 | 7900 | 00:01:35 |
| * 17 | TABLE ACCESS FULL | RAMS_ALARM_DEAL | 51696 | 2222928 | 7346 | 00:01:29 |
| * 18 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARM_WORKSHEET | 1 | 163 | 2 | 00:00:01 |
| * 19 | INDEX RANGE SCAN | RAMS_WORKSHEET_WS_NUM | 1 | | 1 | 00:00:01 |
| 20 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARMMAIN | 1 | 33 | 4 | 00:00:01 |
| * 21 | INDEX RANGE SCAN | RAMS_ALARMMAIN_SHEETNO | 1 | | 2 | 00:00:01 |
| 22 | NESTED LOOPS OUTER | | 1321 | 387053 | 13375 | 00:02:41 |
| 23 | NESTED LOOPS | | 1251 | 325260 | 8370 | 00:01:41 |
| * 24 | TABLE ACCESS FULL | RAMS_ALARM_DEAL | 507 | 49179 | 7347 | 00:01:29 |
| * 25 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARM_WORKSHEET | 2 | 326 | 8 | 00:00:01 |
| * 26 | INDEX RANGE SCAN | RAMS_WORKSHEET_WS_NUM | 7 | | 1 | 00:00:01 |
| 27 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARMMAIN | 1 | 33 | 4 | 00:00:01 |
| * 28 | INDEX RANGE SCAN | RAMS_ALARMMAIN_SHEETNO | 1 | | 2 | 00:00:01 |
| * 29 | FILTER | | | | | |
| 30 | NESTED LOOPS OUTER | | 1 | 269 | 7357 | 00:01:29 |
| 31 | NESTED LOOPS | | 1 | 236 | 7353 | 00:01:29 |
| * 32 | TABLE ACCESS FULL | RAMS_ALARM_DEAL | 1 | 73 | 7345 | 00:01:29 |
| * 33 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARM_WORKSHEET | 1 | 163 | 8 | 00:00:01 |
| * 34 | INDEX RANGE SCAN | RAMS_WORKSHEET_WS_NUM | 7 | | 1 | 00:00:01 |
| 35 | TABLE ACCESS BY INDEX ROWID | RAMS_ALARMMAIN | 1 | 33 | 4 | 00:00:01 |
| * 36 | INDEX RANGE SCAN | RAMS_ALARMMAIN_SHEETNO | 1 | | 2 | 00:00:01 |
----------------------------------------------------------------------------------------------------------------
可以看到，這次的執行計劃中就沒有BITMAP CONVERSION TO ROWIDS了，在測試系統上進行測試，sql的執行時間為1.2秒，比之前快了不少。
但是將這個改動搬移到正式庫上的時候，一會兒就有用戶反映項目卡的不能用。。。
之后對比了下正式和測試庫的數據量，發現正式庫比測試庫這幾張表的數量級大了一倍多，并且都已經到了百萬級以上。
觀察大表是否有分區情況，答案是沒有。。。。。so sad
看來SQL慢的原因不只是因為索引建立不當，跟庫表設計還有關系。
這樣的話后續優化方向基本明確了，交給開發部門吧。后續有進展的話繼續更新此文。
