how to aggregate data by month overlapping postgresql

Question

I have SCD table type 2 that I join with various other tables and I am looking to aggregate sum total from any entity that was active (by active I mean the ones that don't yet have an end_date) during an individual month.

currently, I have a query similar to this (let's say aggregating data for the month of May 2022 and April 2022):

select
        count(1) as enitities_agg,
        DATE_TRUNC('Month', h.start) as date,
        sum(h.price) filter (where c.name='HIGH') as sum_total,
        ----....----

    from 
        project as p
        join class as c on p.class_id = c.id
        join stage as s on s.project_id = p.id
        join stage_info as si on si.stage_id = s.id 
        join history as h on h.stage_info_id = si.id 
        
    where 
        h.start <= '2022-06-01' and
        h.end_date >= '2022-04-01' and
        COALESCE(p.end_date, '2099-01-01') >= '2022-04-01' and
        COALESCE(p.start_date, '2099-01-01') <= '2022-06-01' and
        COALESCE(stage.end, '2099-01-01') >= '2022-04-01' and
        h.price is not null and
        h.price != 0 
            
    group by DATE_TRUNC('Month', h.start)

It aggregates fine only those whose history starts in May or April, not the ones that overlap those months and are still active.

The problem I have is that some history entities start in April, March, etc., and still haven't ended by May. Because I group with group by DATE_TRUNC('Month', h.start) ie by history start date, I don't get the entities that start earlier than April or May and continue to be active after May, I get aggregates only in those months that they have started in.

I was trying to do it by generating series and group by the generated month, however, I didn't find a way that would group them correctly. Example, of one experimentation that I tried.

 from 
        generate_series('2022-03-01', '2022-07-01', INTERVAL '1 month') as mt
        join project as p on    COALESCE(p.end_date, '2099-01-01') >= mt and
                                COALESCE(p.start_date, '2099-01-01') <= mt + INTERVAL '1 month'
    
        join class as c on p.class_id = c.id
        join stage as stage on  stage.project_id = p.id and 
                                        COALESCE(stage.end, '2099-01-01') >= mt
        join stage_info as si on si.stage_id = stage.id 
        join history as h on h.stage_info_id = si.id 
        
    where 
        h.start <= mt and
        h.end_date >= mt + INTERVAL '1 month' and
        h.price is not null and
        h.price != 0 
            
    group by mt

How would it be possible to iterate through the history table aggregating any active entities in a month and group them by the same month and get something like this?

"enitities_agg" |  "date"                 |   "sum_total"
832             |  "2022-04-01 00:00:00"  |   15432234
1020            |  "2022-05-01 00:00:00"  |   19979458

Answer 1

You want all history entities was happened during 2022-May? If so, the following maybe help.

daterange(h.start,
    h.end_date,
    '[]') && daterange('2022-05-01', '2022-06-01', '[]');

---

demo:

CREATE temp TABLE test (
    begin_ date,
    _end date
);

INSERT INTO test
    VALUES ('2022-01-01', '2022-05-01');

INSERT INTO test
    VALUES ('2022-01-01', '2022-05-11');

INSERT INTO test
    VALUES ('2022-05-01', '2022-07-11');

INSERT INTO test
    VALUES ('2022-06-11', '2022-07-11');

SELECT
    *,
    daterange(begin_, _end, '[]')
FROM
    test t
WHERE
    daterange(t.begin_, t._end, '[]') && daterange('2022-05-01', '2022-05-31', '[]');

---

&& range operator reference: https://www.postgresql.org/docs/current/functions-range.html#RANGE-OPERATORS-TABLE

Answer 2

Seems your logic is: if any day of begin_ - _end interval falls into month, count it in. This was the hardest part to guess from the desired results.

So I guess you need this:

with dim as (
  select
  m::date as month_start
  ,(date_trunc('month', m) + interval '1 month - 1 day')::date as month_end
  ,to_char(date_trunc('month', m), 'Mon') as month
  from generate_series('2022-01-01', '2022-08-01', INTERVAL '1 month') as m
)
SELECT
dim.month
, sum(coalesce(t.price, 0)) as sum_price
FROM dim
left join test as t
on t.begin_ <= dim.month_end
and t._end >= dim.month_start
group by dim.month_start, dim.month
order by dim.month_start, dim.month
;

https://dbfiddle.uk/?rdbms=postgres_14&fiddle=614030d4db5e03876f693a9a8a5ff122