Is a link traced direct or reversed by a path (path$, plink$)

Question

Hello
After analyzing an "undirected" network via the java api, we stored the results in the path$ table and also filled the plink$ table, containing the sequence and the link_id's that made up the paths.
Is there an easy way, or does anybody already created a way, to check or list in which "direction" (direct or reversed) the path traced the links? Is a link traced direct or reversed by a path?
tx
Luc

Answer 1

Ok
This is what I came up with, without guarantee that this is the best/fastest code/approach.
The concept comes from the SDO_UTIL.GETVERTICES function (see spatial users guide).
1. create type LINK_DIR_TYPE where direct holds a bit 0 = reversed, 1 direct)
========================================================
Create type LINK_DIR_TYPE AS OBJECT
PATH_ID NUMBER,
LINK_ID NUMBER,
SEQ_NO NUMBER,
DIRECT NUMBER
2. create type PLINK_DIR_TYPE
=================================================
CREATE TYPE PLINK_DIR_TYPE AS TABLE OF LINK_DIR_TYPE;
3. A function returning the type PLINK_DIR_TYPE
=====================================
CREATE OR REPLACE FUNCTION GET_PLINK_DIRECTION (myNETWORK IN
VARCHAR2, PATH_ID IN NUMBER) RETURN PLINK_DIR_TYPE
AS
PLTN VARCHAR2(50);
LTN VARCHAR2(50);
PTN VARCHAR2(50);
PATH_START_NODE_ID NUMBER;
Prev_stN NUMBER;
Prev_dir NUMBER;
v_sql VARCHAR2(500);
TYPE cur_type IS REF CURSOR;
c_cursor cur_type;
c_cursor2 cur_type;
TYPE NUMTAB IS TABLE OF NUMBER;
LinkIDS NUMTAB;
L_startids NUMTAB;
L_endids NUMTAB;
Directs NUMTAB;
pl_DIR_TAB PLINK_DIR_TYPE := PLINK_DIR_TYPE(NULL) ;
BEGIN
SELECT PATH_TABLE_NAME, PATH_LINK_TABLE_NAME, LINK_TABLE_NAME INTO PTN, PLTN, LTN
FROM USER_SDO_NETWORK_METADATA
WHERE NETWORK = myNETWORK;
v_sql := 'SELECT START_NODE_ID FROM ' || PTN || ' WHERE PATH_ID = ' || path_id;
EXECUTE IMMEDIATE v_sql into PATH_START_NODE_ID;
v_sql := 'select pl.link_id, l.start_node_id, l.end_node_id, 1 as DIRECT ' ||
'from ' || pltn || ' pl, ' || ltn || ' l ' ||
'where pl.path_id = :1 AND pl.link_id = l.link_id ' ||
'ORDER BY pl.path_id, pl.seq_no ';
OPEN c_cursor2 FOR v_sql using path_id;
FETCH c_CURSOR2 BULK COLLECT INTO linkids, l_startids, l_endids, directs;
CLOSE c_CURSOR2;
pl_DIR_TAB.EXTEND(Linkids.last -1);
Prev_stN := PATH_START_NODE_ID;
Prev_dir := 0;
IF (L_startIDs(1) = Prev_stN) THEN
DIRECTS(1) := 1;
ELSE
DIRECTS(1) := 0;
END IF;
Prev_dir := DIRECTS(1);
pl_DIR_TAB(1) := LINK_DIR_TYPE (PATH_ID, LINKIDS(1), 1, DIRECTS(1));
FOR i IN 1..Linkids.last loop
IF (L_startIDs(i) = Prev_STN) THEN
DIRECTS(i) := 1;
ELSE
IF (Prev_dir = 0) THEN
DIRECTS(i) := 0;
ELSE
IF (L_STARTIDS(i) = L_ENDIDs(i-1)) THEN
DIRECTS(i) := 1;
ELSE
DIRECTS(i) := 0;
END IF;
END IF;
END IF;
Prev_stN := L_STARTIDS(i);
Prev_dir := DIRECTS(i);
pl_DIR_TAB(i) := LINK_DIR_TYPE (PATH_ID, LINKIDS(i), i, DIRECTS(i));
END LOOP;
RETURN pl_DIR_TAB;
END;
4.USE IN SQL:
============================================
select t.path_id, t.link_id, t.seq_no, t.direct
from
table(GET_PLINK_DIRECTION(network_name, path_id)) t
Maybe this can be of use
Luc