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...
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...
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...
EXPLAIN ANALYZESELECT * FROM usersORDER BY email DESC LIMIT 10;-> Index Scan Backward using index_users_on_email on usersExecution 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,如果我们想将它们移...
-> 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 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 Only Scan Backward using idx_num_measurement on test (cost=0.43..15312.45 rows=432001 width=11) (actual tim e=0.019..0.019 rows=1 loops=20) Index Cond: ((num = $0) AND (measurement IS NOT NULL)) Heap Fetches: 0 Planning Time: 0.273 ms ...
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 ...
.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) Index Cond: (tag_id = 41) Buffers: shared ...