Query to find all lines connected to other

Question

I have problem with one spatial (Oracle) query. Simplified overview of the problem is:

I have two tables:

CREATE TABLE thin_lines (
  id NUMBER PRIMARY KEY,
  geom SDO_GEOMETRY),
  color VARCHAR2(32);

CREATE TABLE thick_lines (
  id NUMBER PRIMARY KEY,
  geom SDO_GEOMETRY),
  color VARCHAR2(32);

Both tables contain 2D lines. The example picture:

The problem:

I want to create SQL query or PL/SQL procedure to find ids of all blue thin lines (whole blue branch comprising of blue lines) connected to the thick green lines.

Thank you for your assistance.

Answer 1

You should look into the Oracle Spatial Data Type and SDO_INTERSECTION .

I have not tested this and it likely does not work; but it should be a helpful starting point:

DECLARE
    type intersecting_blue_line is table of NUMBER;
    RT_GL thick_lines%ROWTYPE;
    CURSOR get_GreenLines IS
        SELECT *
        FROM thick_lines TKL
        WHERE TKL.color = 'Green';

BEGIN
    OPEN get_GreenLines;
    LOOP
        FETCH get_GreenLines INTO RT_GL;

        for x in (SELECT TNL.id, 
                  FROM thin_lines TNL
                  WHERE TNL.color = 'Blue'
                  AND SDO_GEOM.SDO_INTERSECTION(RT_GL.geom, TNL.geom, 0.005) IS NOT NULL;)
        LOOP
            intersecting_blue_line := x.id;
        END LOOP;

    END LOOP;
    CLOSE get_tables;
END;

SELECT * FROM intersecting_blue_line;

Answer 2

I have found some solution to do this with one query (Oracle 11.2):

WITH recursive (p1, p2) AS (
  SELECT thin.connection_id, thin.geom FROM thin_lines thin, thick_lines thick
    WHERE sdo_touch(thin.geom, thick.geom) = 'TRUE' AND thick.color = 'green' AND thin.color = 'blue'
  UNION ALL
  SELECT thin.connection_id, thin.geom FROM thin_lines thin, recursive r
    WHERE sdo_touch(thin.geom, r.p2) = 'TRUE' and thin.color='blue'
)
CYCLE p1 SET is_cycle TO 1 DEFAULT 0
SELECT distinct p1 FROM recursive order by p1;

It works, but for small set of thin and thick lines. For huge set it is unusable for me.