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Question

我有一个带有abc列的表，其中包含unix时间戳（例如13898161481435），我想在日期之间运行select。

执行

效率不高

where TO_CHAR(TO_TIMESTAMP(abc / 1000), 'DD/MM/YYYY') > '14/01/2014 00:00:00' and ..;

会转换每条记录。

而是做类似的事情 其中abc> （'14 / 01/2014 00:00:00'tobigint（））和abc＆lt; ......

但我找不到任何参考，但反过来说。

Answer 1

试试这个

WHERE abc > extract(epoch from timestamp '2014-01-28 00:00:00')

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Answer 2

您无需将其转换为char即可进行比较。

WHERE to_timestamp(abc/1000) > timestamp '2014-01-28 00:00:00'

我不认为转换效率会非常低，因为时间戳内部存储的格式与epoch secs类似（不可否认具有不同的来源和分辨率）。

如果你真的想走另一条路：

WHERE abc > extract(epoch from timestamp '2014-01-28 00:00:00')

Answer 3

虽然有趣的观察，但是

select count(*) from cb.logs where to_timestamp(timestmp/1000) > timestamp '2014-01-15 00:00:00' and to_timestamp(timestmp/1000) < timestamp '2014-01-15 23:59:59';

需要将近10秒钟（我的数据库有1.5个记录），下面只有1.5秒

select count(*) from cb.logs where (timestmp > (select extract(epoch from timestamp '2014-01-15 00:00:00') * 1000) and timestmp < (select extract(epoch from timestamp '2014-01-15 23:59:59') * 1000));

及以下约1秒

select count(*) from cb.logs where (timestmp > extract(epoch from timestamp '2014-01-15 00:00:00') * 1000) and (timestmp < extract(epoch from timestamp '2014-01-15 23:59:59') * 1000);

计算~40,000条记录

最有可能的原因是我会说这个部门。

Answer 4

1

select count(*) from cb.logs where to_timestamp(timestmp/1000) > timestamp '2014-01-15 00:00:00' and to_timestamp(timestmp/1000) < timestamp '2014-01-15 23:59:59';  
8600ms

"Aggregate  (cost=225390.52..225390.53 rows=1 width=0)"
"  ->  Seq Scan on logs  (cost=0.00..225370.34 rows=8073 width=0)"
"        Filter: ((to_timestamp(((timestmp / 1000))::double precision) > '2014-01-15 00:00:00'::timestamp without time zone) AND (to_timestamp(((timestmp / 1000))::double precision) < '2014-01-15 23:59:59'::timestamp without time zone))"

2

select count(*) from cb.logs where (timestmp > (select extract(epoch from timestamp '2014-01-15 00:00:00') * 1000) and timestmp < (select extract(epoch from timestamp '2014-01-15 23:59:59') * 1000));
1199ms
"Aggregate  (cost=209245.94..209245.95 rows=1 width=0)"
"  InitPlan 1 (returns $0)"
"    ->  Result  (cost=0.00..0.01 rows=1 width=0)"
"  InitPlan 2 (returns $1)"
"    ->  Result  (cost=0.00..0.01 rows=1 width=0)"
"  ->  Seq Scan on logs  (cost=0.00..209225.74 rows=8073 width=0)"
"        Filter: (((timestmp)::double precision > $0) AND ((timestmp)::double precision < $1))"

在postgresql中将日期转换为unix时间戳

4 个答案:

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