Question

我理解为什么范围的差值运算符如果结果是两个不相交的范围则会失败。但我不确定解决方法是什么。

一个简单的概念示例是，如果我保留日历并为每个会议记录一个记录，时间戳范围字段存储会议时间;什么是一种简单的方法来生成一个人在某一天免费的时间列表？

对于范围来说，这似乎是一个简单，基本的事情，但我无法想出一种方法，这看起来并不复杂。

Answer 1

create or replace function range_exclude(anyelement, anyelement) returns anyarray as $$
declare
  r1 text;
  r2 text;
begin
  -- Check input parameters
  if not pg_typeof($1) in ('numrange'::regtype, 'int8range'::regtype, 'daterange'::regtype, 'tstzrange'::regtype) then
    raise exception 'Function accepts only range types but got % type.', pg_typeof($1);
  end if;

  -- If result is single element
  if ($1 &< $2 or $1 &> $2) then
    return array[$1 - $2];
  end if;

  -- Else build array of two intervals
  if lower_inc($1) then r1 := '['; else r1 := '('; end if;
  r1 := r1 || lower($1) || ',' || lower($2);
  if lower_inc($2) then r1 := r1 || ')'; else r1 := r1 || ']'; end if;

  if upper_inc($2) then r2 := '('; else r2 := '['; end if;
  r2 := r2 || upper($2) || ',' || upper($1);
  if upper_inc($1) then r2 := r2 || ']'; else r2 := r2 || ')'; end if;
  return array[r1, r2];
end $$ immutable language plpgsql;

create or replace function range_exclude(anyelement, anyarray) returns anyarray as $$
declare
  i int;
  j int;
begin
  -- Check input parameters
  if not pg_typeof($1) in ('numrange'::regtype, 'int8range'::regtype, 'daterange'::regtype, 'tstzrange'::regtype) then
    raise exception 'Function accepts only range types but got % type.', pg_typeof($1);
  end if;

  if array_length($2,1) is null then
    return array[$1];
  end if;

  $0 := range_exclude($1,$2[array_lower($2,1)]);
  for i in array_lower($2,1) + 1 .. array_upper($2,1) loop
    select array(select x from (select unnest(range_exclude(x,$2[i])) from unnest($0) as t(x)) as t(x) where not isempty(x)) into $0;
  end loop;
  return $0;
end $$ immutable language plpgsql;

select range_exclude(numrange(8,17), array[numrange(10,11), numrange(13,20)]);

试验：

select range_exclude(numrange(1,10), numrange(5,6));
select range_exclude(numrange(8,17), array[numrange(10,11), numrange(13,15)]);

结果：

{"[1,5)","[6,10)"}
{"[8,10)","[11,13)","[15,17)"}

时间戳也一样：

select range_exclude(
  tstzrange('2016-07-28 8:00','2016-07-28 17:00'), 
  array[
    tstzrange('2016-07-28 10:00','2016-07-28 11:00'),
    tstzrange('2016-07-28 13:00','2016-07-28 15:00')]);

结果：

{"[\"2016-07-28 08:00:00+03\",\"2016-07-28 10:00:00+03\")","[\"2016-07-28 11:00:00+03\",\"2016-07-28 13:00:00+03\")","[\"2016-07-28 15:00:00+03\",\"2016-07-28 17:00:00+03\")"}

Answer 2

如果范围不相交，请使用窗口函数lead()或lag()：

create table plan (duration tsrange);
insert into plan values
('[2015-01-01 10:00:00, 2015-01-01 12:00:00)'),
('[2015-01-01 14:00:00, 2015-01-01 16:00:00)'),
('[2015-01-01 18:00:00, 2015-01-01 20:00:00)');

select tsrange(upper(duration), lower(lead(duration) over (order by duration))) free_time
from plan;

                   free_time                   
-----------------------------------------------
 ["2015-01-01 12:00:00","2015-01-01 14:00:00")
 ["2015-01-01 16:00:00","2015-01-01 18:00:00")
 ["2015-01-01 20:00:00",)
(3 rows)

查找未包含在任何范围内的数字

2 个答案: