# 使用 EXPLAIN 查看执行计划 + `EXPLAIN SELECT count(*) FROM trips WHERE start_date BETWEEN '2017-07-01 00:00:00' AND '2017-07-01 23:59:59';` ```7 +------------------------------+----------+-----------+---------------+------------------------------------------------------------------------------------------------------------------------+ | id | estRows | task | access object | operator info | +------------------------------+----------+-----------+---------------+------------------------------------------------------------------------------------------------------------------------+ | StreamAgg_20 | 1.00 | root | | funcs:count(Column#13)->Column#11 | | └─TableReader_21 | 1.00 | root | | data:StreamAgg_9 | | └─StreamAgg_9 | 1.00 | cop[tikv] | | funcs:count(1)->Column#13 | | └─Selection_19 | 250.00 | cop[tikv] | | ge(bikeshare.trips.start_date, 2017-07-01 00:00:00.000000), le(bikeshare.trips.start_date, 2017-07-01 23:59:59.000000) | | └─TableFullScan_18 | 10000.00 | cop[tikv] | table:trips | keep order:false, stats:pseudo | +------------------------------+----------+-----------+---------------+------------------------------------------------------------------------------------------------------------------------+ 5 rows in set (0.00 sec) ``` ------------------------------------------------------------- 使用 EXPLAIN 查看执行计划 我们使用标准的数据库 bikeshare 来举例，统计 2017 年 7 月 1 日的行程次数。通过 ANALYZE 语句，我们可以清晰的看到语句的执行计划使用的算子，算子的下推情况，预估访问的行数等信息。 ``` EXPLAIN SELECT count(*) FROM trips WHERE start_date BETWEEN '2017-07-01 00:00:00' AND '2017-07-01 23:59:59'; +------------------------------+----------+-----------+---------------+------------------------------------------------------------------------------------------------------------------------+ | id | estRows | task | access object | operator info | +------------------------------+----------+-----------+---------------+------------------------------------------------------------------------------------------------------------------------+ | StreamAgg_20 | 1.00 | root | | funcs:count(Column#13)->Column#11 | | └─TableReader_21 | 1.00 | root | | data:StreamAgg_9 | | └─StreamAgg_9 | 1.00 | cop[tikv] | | funcs:count(1)->Column#13 | | └─Selection_19 | 250.00 | cop[tikv] | | ge(bikeshare.trips.start_date, 2017-07-01 00:00:00.000000), le(bikeshare.trips.start_date, 2017-07-01 23:59:59.000000) | | └─TableFullScan_18 | 10000.00 | cop[tikv] | table:trips | keep order:false, stats:pseudo | +------------------------------+----------+-----------+---------------+------------------------------------------------------------------------------------------------------------------------+ 5 rows in set (0.00 sec) ```