PSQL 查询耗时问题

[dikT]

下面两个语句

sql> SELECT * FROM ***.trade_record ORDER BY id LIMIT 10 OFFSET 999999
[2017-04-11 11:16:34] 10 rows retrieved starting from 1 in 341ms (execution: 318ms, fetching: 23ms)


sql> SELECT id FROM ***.trade_record ORDER BY id LIMIT 1 OFFSET 999999
[2017-04-11 11:16:56] 1 row retrieved starting from 1 in 7s 691ms (execution: 7s 688ms, fetching: 3ms)

请问为啥查询数量少,字段少的 反而消耗的时间多呢

execution: 执行

fetching: 获取么?..

为啥差距这么大呢

[sagaxu]

EXPLAIN 看一下查询计划

[prasanta]

我也比较关心这个问题