Ok, the whole thing is done and dusted - Thank you everybody for your
input. Apologies if I sometimes missed the obvious. For the sake of
anyone having the same problems and happens across this post, I learned
that:
- The result of a cursor assignment cannot be row counted, unless you
iterate through it
- Fetching a row at the end of a cursor returns an empty set
- Fancy IDEs can be deceiving, especially when trying to debug a
function.
Included below is the finished procedure.
Thanks again,
Neil.
-----Original Message-----
DECLARE
cur_overlap refcursor;
new_id INTEGER;
row_one record;
row_two record;
clashes record;
BEGIN
LOCK TABLE calendar_entries IN EXCLUSIVE MODE;
SELECT INTO clashes * FROM bookings WHERE (start_date, end_date)
OVERLAPS (new_start_date - interval '1 day',new_end_date + interval '1
day') AND property_id = prop_id LIMIT 1;
IF NOT FOUND THEN
DELETE FROM calendar_entries WHERE property_id = prop_id
AND (start_date >= new_start_date) AND (end_date <= new_end_date);
OPEN cur_overlap FOR EXECUTE 'SELECT *, pg_class.relname
AS table FROM calendar_entries, pg_class WHERE (start_date, end_date)
OVERLAPS (DATE ''' || new_start_date || ''' - interval ''2 days'', DATE
''' || new_end_date || ''' + interval ''2 days'') AND property_id = ' ||
prop_id || ' AND pg_class.oid = calendar_entries.tableoid ORDER BY
start_date';
FETCH cur_overlap INTO row_one;
FETCH cur_overlap INTO row_two;
IF (row_two.id IS NULL) THEN
/* We're overlapping one row. Either we're enveloped by a
single row,
or we have one row overlapping either the start date or
the end
date.
*/
IF (row_one.start_date <= new_start_date) AND
(row_one.end_date >= new_end_date) THEN
/* We're enveloped. The enveloping row needs to be split
in to
two so that we can insert ourselves. */
IF row_one.table = into_table THEN
/* This period is already marked appropriately. Do
nothing. */
RETURN row_one.id;
ELSE
/* We need to perform a split/insert.
1. Adjust the end date of the enveloping row to
the new
start - 1 day.
2. Insert a new row as the same type as the
enveloping row
from new_end_date + 1 to the existing end date.
3. Insert the new row in to the required table */
EXECUTE 'UPDATE ' || row_one.table || ' SET end_date
= DATE ''' || new_start_date || ''' - interval ''1 day'' WHERE id = ' ||
row_one.id;
EXECUTE 'INSERT INTO ' || row_one.table || '
(property_id, start_date, end_date) VALUES (' || prop_id || ', DATE '''
|| new_end_date || ''' + interval ''1 day'', DATE ''' ||
row_one.end_date || ''')';
EXECUTE 'INSERT INTO ' || into_table || '
(property_id, start_date, end_date) VALUES (' || prop_id || ', DATE '''
|| new_start_date || ''', DATE ''' || new_end_date || ''')';
SELECT currval('calendar_id_seq') INTO new_id;
RETURN new_id;
END IF;
ELSIF row_one.start_date <= new_start_date THEN
/* This row is earlier than the proposed
period - It's overlapping
our start date - But is it of the same type? */
IF row_one.table = into_table THEN
/* A single row overlapping the start only and of
the same
type - Update the end date and return the
existing row ID */
EXECUTE 'UPDATE ' || into_table
|| ' SET end_date = DATE ''' || new_end_date || ''' WHERE id = ' ||
row_one.id;
RETURN row_one.id;
ELSE
/* Single row, overlapping the start, and of a
different type.
Trim back the existing row and Insert and return
newly generated ID. */
EXECUTE 'INSERT INTO ' || into_table ||
'(property_id, start_date, end_date) VALUES (' || prop_id || ', DATE '''
|| new_start_date || ''', DATE ''' || new_end_date || ''')';
SELECT
currval('calendar_id_seq') INTO new_id;
RETURN new_id;
END IF;
ELSIF row_one.start_date > new_end_date THEN
/* This period is after the proposed
period */
IF row_one.table = into_table THEN
/* Single row, overlapping the end, and of the same
type.
Update the start_date of the existing row, and
return it's
id. */
EXECUTE 'UPDATE ' || into_table
|| ' SET start_date = DATE ''' || new_start_date || ''' WHERE id = ' ||
row_one.id;
RETURN row_one.id;
ELSE
/* Single row, overlapping the end, and of a
different type.
Update the existing rows start_date, insert a new
row,
and return the new ID. */
EXECUTE 'UPDATE ' || into_table || ' SET start_date
= DATE ''' || new_end_date || ''' + interval ''1 day''';
EXECUTE 'INSERT INTO ' ||
into_table || ' (property_id, start_date, end_date) VALUES (' || prop_id
|| ', DATE ''' || new_start || ''',DATE ''' || new_end || ''')';
SELECT
currval('calendar_id_seq') INTO new_id;
RETURN new_id;
END IF;
END IF;
ELSIF (row_one.id IS NOT NULL AND row_two.id IS NOT
NULL) THEN
/* Two rows */
IF (row_one.table = into_table) AND
(row_two.table = into_table) THEN
/* Two overlapping/adjactent rows, both of the same type
as the
new entry. Delete the second row, and adjust the
end_date of
the first to stretch across until the end o the old
second
row.
*/
EXECUTE 'DELETE FROM ' || into_table ||
' WHERE id = ' || row_two.id;
EXECUTE 'UPDATE ' || into_table || ' SET end_date = DATE
''' || row_two.end_date || ''' WHERE id = ' || row_one.id;
RETURN row_one.id;
ELSIF row_one.table = into_table THEN
/* Two overlapping/adjacent rows, only the row
overlapping the
start is of the same type. Adjust the end date of
this row to
be the end date of the new row.*/
EXECUTE 'UPDATE ' || into_table || ' SET
end_date = DATE''' || new_end_date || ''' WHERE id = ' || row_one.id;
RETURN row_one.id;
ELSIF row_two.table = into_table THEN
/* Two overlapping/adjacent rows, only the row
overlapping the
end is of the same type. Adjust the start date of
this row
to be the start date of the new row.*/
EXECUTE 'UPDATE ' || into_table || ' SET
start_date = DATE ''' || new_start_date || ''' WHERE id = ' ||
row_two.id;
RETURN row_two.id;
ELSE
/* Two overlapping/adjacent rows, neither of which are
of the
same type as the new row */
EXECUTE 'INSERT INTO ' || into_table ||
' (property_id, start_date, end_date) VALUES (' || prop_id || ', DATE
''' || new_start_date || ''', DATE ''' || new_end_date || ''')';
SELECT currval('calendar_id_seq') INTO
new_id;
RETURN new_id;
END IF;
ELSE
/* Row one is null too! We have nothing to fear. Go ahead
and
insert it */
EXECUTE 'INSERT INTO ' || into_table ||
' (property_id, start_date, end_date) VALUES (' || prop_id || ', DATE
''' || new_start_date || ''', DATE ''' || new_end_date || ''')';
SELECT currval('calendar_id_seq') INTO
new_id;
RETURN new_id;
END IF;
ELSE
RAISE EXCEPTION 'Operation aborted: Clashing booking detected';
END IF;
END;
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