IndexScan BACKWARD using aircrafts_case_model_idxonaircrafts (1 row) 但是,我们不能使用这个索引来获得按一列降序排序、按另一列升序排序的数据。这将需要分别排序: 1 2 3 4 5 6 7 8 demo=# explain(costsoff) selectclass, modelfromaircrafts_vorderbyclassASC, modelDESC; QUERY PLAN --- Sort Sort...
EXPLAIN ANALYZE SELECT * FROM users ORDER BY email DESC LIMIT 10; -> Index Scan Backward using index_users_on_email on users Execution Time: 0.641 ms 我们可以看到一个Index Scan Backward条目,因此我们的查询正确地使用了索引,并且几乎立即执行。但是,此查询的结果将始终从NULL值开始。因此,如果我们想将...
.1.39 rows=1 width=53) (actual time=0.066..0.067 rows=1 loops=1) Buffers: shared hit=1 read=3 I/O Timings: read=0.051 -> Index Scan Backward using test_table_tag_id_timestamp_idx on test_table (cost=0.42..924.66 rows=953 width=53) (actual time=0.066..0.066 rows=1 loops=1) I...
-> Index Scan Backward using index_tbl_index_table_create_time on tbl_index_table (cost=0.00..66.28 rows=1507 width=8) Index Cond: (create_time >= '2010-10-08 00:00:00'::timestamp without time zone) Filter: (create_time IS NOT NULL) (6 rows) 发现上面的查询走的索引 index_tbl_i...
EXPLAIN ANALYZESELECT * FROM usersORDER BY email DESC LIMIT 10;-> Index Scan Backward using index_users_on_email on users Execution Time: 0.641 ms 我们可以看到一个Index Scan Backward条目,因此我们的查询正确地使用了索引,并且几乎立即执行。但是,此查询的结果将始终从NULL值开始。因此,如果我们想将它们...
-> Index Scan Backward using index_tbl_index_table_create_time on tbl_index_table (cost=0.00..66.28 rows=1507 width=8) Index Cond: (create_time >= '2010-10-08 00:00:00'::timestamp without time zone) Filter: (create_time IS NOT NULL) ...
Index Scan Backward using idx_test_info_1 on public.test (cost=0.29..18253.53 rows=6700 width=41) (actual time=0.013..9.147 rows=8 896 loops=1) Output: id, info, crt_date Buffers: shared hit=8909 Planning time: 0.253 ms Execution time: 9.911 ms ...
Index Scan BACKWARD using aircrafts_case_model_idxonaircrafts (1row) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 然而,如果一列以升序一列以降序的方式获取排序的数据的话,就不能使用索引,只能单独排序: ...
-> Index Only Scan Backward using tab_duplicate_idx on tab_duplicate tab_duplicate_2 (cost=0.15..77.76 rows=1692 width=8) 警告:在这种情况下,如果表tab_duplicate中存在较长时间段的重复项,则可以定期删除TAB_DUPLICATION中的重复记录,比如说在一天结束的时候,它无论如何都会很快,因为TAB_DUPLICATE无论...
.423643.180 rows=10 loops=1) Output: id, order_type...其它字段省略 Buffers: shared hit=778155 read=410205 -> Index Scan Backward using idx_create_date on tops_order.eticket (cost=0.56..9209400.56 rows=6354 width=2628) (actual time=77326.834..423643.149 rows=10 loops=1) Output: id, ...