Re: Given a set of daterange, finding the continuous range thatincludes a particular date

On 02/22/2018 04:44 PM, Ken Tanzer wrote:

Hi, hoping to get some help with this.  I'm needing to take a specific date, a series of dateranges  and, given a specific date, return a single conitinuous daterange that includes that date.

To elaborate a bit, I've got lots of tables that include start and end dates.  For example:

CREATE TABLE tbl_staff_assign (
     staff_assign_id         SERIAL PRIMARY KEY,
     client_id               INTEGER NOT NULL REFERENCES tbl_client (client_id),
     staff_id                INTEGER REFERENCES tbl_staff(staff_id),
     staff_assign_type_code      VARCHAR(10) NOT NULL REFERENCES tbl_l_staff_assign_type (staff_assign_type_code),
     staff_assign_date           DATE NOT NULL,
     staff_assign_date_end       DATE,
...

So a client might leave a progrma and then return later, or they might simply switch to another staff_id.  (In which case one record will have and end date, and the next record will start on the next day.)  In this case I need to know "what period were they continuously in the program that includes X date?"  So I'd like to be able to do something like:

"SELECT staff_assign_date,continuous_daterange( staff_assign_date, (SELECT array_agg(daterange(staff_assign_date,staff_assign_date_end,'[]')
) FROM staff_assign sa2 WHERE sa2.client_id=sa.client_id) FROM staff_assign sa

I've done this before with procedures specific to a particular table, and working with the start and end dates.  I'm now wanting to try to do this once generically that will work for all my cases.  So I'm hoping to do this in a way that performance isn't horrible.  And it's a little unclear to me how much and how I might be able to use the daterange operators to accomplish this efficiently.

The operator I use to solve similar problems:

https://www.postgresql.org/docs/10/static/functions-range.html

@>      contains element        '[2011-01-01,2011-03-01)'::tsrange @> '2011-01-10'::timestamp   t