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-- script de calcul des distances sources
set search_path to rht,public;
select cast(ltree2text(subltree(chemin,0,1)) as integer) from rht_topology limit 10
/*
AJOUT D'UN INDEX
ltree supports several types of indexes that can speed up the indicated operators:
    B-tree index over ltree: <, <=, =, >=, >
    GiST index over ltree: <, <=, =, >=, >, @>, <@, @, ~, ? 
*/
CREATE INDEX chemin_btee_index ON rht.rht_topology USING btree(chemin); --27688 ms
VACUUM ANALYSE rht.rht_topology;
CREATE INDEX chemin_gist_index ON rht.rht_topology USING GIST (chemin); -- fait planter mon serveur....
SELECT * from rht.rht_topology where chemin <@ '212340'; -- tronçon source de la Vilaine -- 2360
SELECT chemin from rht.rht_topology where chemin <@ '212340' limit 1
-- La distance source est la distance mer maximale de tous les chemins possibles en ne prenant que le dernier tronçon du chemin.
Select max(dmer) from rht.rht_topology where id_drain in (
Select cast(ltree2text(subpath(chemin, -1, 1))as integer) as chenin_id_drain from rht.rht_topology where chemin ~ '*.212340.*');
--  travail sur les noeuds source et le recalcul des distances mer et source (voir fichier doc joint)
-- en pratique les distances sont calculées a partir du milieu de chaque tronçon, elles prennent par contre toute la distance des tronçons autre que le tronçon considéré.

alter table rht.rht_topology add column noeudsource boolean default FALSE;
-- identification des noeuds source
update rht.rht_topology set noeudsource=TRUE where id_drain in (
select id_drain from rht.rht_topology except (
select rt2.id_drain from rht.rht_topology rt1 join rht.rht_topology rt2 on rt1.nextdownid=rt2.id_drain)
);-- 57533
update rht.rht_topology set dmer=dmer+length/2;-- 114600
alter table rht.rht_topology add column dsource numeric;
update rht.rht_topology set dsource=length/2 where noeudsource;-- 57533
-- voir schéma pour explications


DROP FUNCTION IF EXISTS rht.distance_source();

CREATE OR REPLACE FUNCTION rht.distance_source(min integer, max integer) RETURNS integer AS $$
DECLARE
    ligne integer;
    nbligne integer; 
    id_drains record;
BEGIN
        ligne:=1;
        DROP TABLE IF EXISTS sousselection;
        DROP sequence IF EXISTS  seq;
        CREATE sequence seq;
        EXECUTE 'create temporary table sousselection as SELECT id_drain, nextval(''seq'') as num FROM (SELECT * FROM rht.rht_topology WHERE noeudsource=FALSE ORDER BY id_drain) as sub WHERE id_drain >='|| min || ' AND id_drain<='||max ;
        SELECT COUNT(*) FROM sousselection INTO nbligne;
        WHILE ligne <=nbligne LOOP
                  -- pour vérification décommenter ensuite
                  SELECT * from sousselection where num=ligne INTO id_drains;
                  RAISE NOTICE 'distance_source for %', quote_ident(CAST(id_drains.id_drain as text));
                  EXECUTE 'INSERT INTO rht.distance_source SELECT '||id_drains.id_drain||', MAX(dmer+length/2) as dmer FROM rht.rht_topology WHERE id_drain IN (
                        SELECT CAST(ltree2text(subpath(chemin, -1, 1))as integer) FROM rht.rht_topology where chemin ~  ''*.'||
                        id_drains.id_drain
                        || '.*'' )';  
                ligne=ligne+1;      
        END LOOP;
    RETURN ligne;
END;
$$ LANGUAGE plpgsql;
-- lancement de la requête
DROP TABLE IF EXISTS rht.distance_source;
CREATE TABLE rht.distance_source (id_drain integer,distance  numeric);
select rht.distance_source(1,50000);

-- pour essai pour voir ce qui se passe dans la requête

SELECT 212340,  MAX(dmer+length/2) as dmer FROM rht.rht_topology WHERE id_drain IN (
                        SELECT CAST(ltree2text(subpath(chemin, -1, 1))as integer) FROM rht.rht_topology where chemin ~  '*.212340.*' )
-- il faudra enlever la dmer de 212340

-- POUR LES LANCEMENTS FINAUX IL A FALLU LANCER UN INDEX ET RAJOUTER UNE CLE PRIMAIRE
Alter table rht.rht_topology add constraint c_pk_id_drain primary key (id_drain);
CREATE INDEX id_drain_index  ON rht.rht_topology
  USING btree
  (id_drain);

select rht.distance_source(100000,200000);
select rht.distance_source(200001,300000);
select rht.distance_source(300001,400000);
select rht.distance_source(400001,600000);

-- pour essai pour voir ce qui se passe dans la requête

SELECT 212340,  MAX(dmer+length/2) as dmer FROM rht.rht_topology WHERE id_drain IN (
                        SELECT CAST(ltree2text(subpath(chemin, -1, 1))as integer) FROM rht.rht_topology where chemin ~  '*.212340.*' )


select * from rht.rht_topology t join rht.distance_source s on s.id_drain=t.id_drain where distance is null; --323

-- il faudra enlever la dmer de 212340

-- requête finale pour calculer les distances source (à lancer)
alter table rht.distance_source  add column distance_source numeric;
select count(*) from rht.distance_source; --57067 que les noeuds non source

-- mise à jour des distances source dans la table distance source (il faut encore enlever dmer)
update rht.distance_source d set distance_source = sub.distance_source from (
select t.id_drain, distance-dmer as distance_source from rht.distance_source s join rht.rht_topology t on s.id_drain=t.id_drain) as sub
where sub.id_drain=d.id_drain; --57067

-- copie des valeurs de distance_source dans dsource de la table rht.rht_topology
update rht.rht_topology t set dsource=distance_source
from rht.distance_source d where d.id_drain=t.id_drain; --57067

-- mise à jour des distances_source (pour l'instant valeurs = null) pour les noeuds source (pour les derniers c'est la moitié de la longueur du segment)
update rht.rht_topology t set dsource=length/2 where noeudsource;
-- nombre de 
select count(*)as count, noeudsource from rht.rht_topology where dsource is null group by noeudsource;

utilisation des donnees de parcours

En pratique nous n'aurons probablement besoin que du noeud le plus amont des parcours comme programmé ci dessus. Mais les scripts ci-dessous pourraient s'avérer utiles.
Ci dessous la fonction utilise les expressions régulières ltree => vecteur => table

/*
regexp_split_to_array(string text, pattern text [, flags text ])        regexp_split_to_array('hello world', E'\\s+')   {hello,world}
SELECT regexp_split_to_array('hello world', E'\\s+');
SELECT regexp_split_to_array('hello.world', E'\\.+');
*/
SELECT regexp_split_to_array(ltree2text(chemin),E'\\.+') from rht.rht_topology where chemin <@ '212340';

/*
http://www.pgsql.cz/index.php/PostgreSQL_SQL_Tricks#Array_to_table
SELECT (ARRAY[1,3,4,6,7])[idx.n] FROM generate_series(1,7) idx(n);
CREATE OR REPLACE FUNCTION unpack(anyarray)
RETURNS SETOF anyelement AS $$ 
SELECT $1[i] 
   FROM generate_series(array_lower($1,1), 
                        array_upper($1,1)) g(i);
$$ LANGUAGE sql STRICT IMMUTABLE;
*/
CREATE OR REPLACE FUNCTION unpack(anyarray)
RETURNS SETOF anyelement AS $$ 
SELECT $1[i] 
   FROM generate_series(array_lower($1,1), 
                        array_upper($1,1)) g(i);
$$ LANGUAGE sql STRICT IMMUTABLE;
-- pour convertir un vecteur en table
select unpack(vecteurchemin) from 
        (SELECT regexp_split_to_array(ltree2text(chemin),E'\\.+') as vecteurchemin from rht.rht_topology where chemin <@ '212340' limit 1) as sub
-- j'avais pas vu il y a déjà une fonction magique unest...
select cast(unnest(vecteurchemin) as integer) as chemin_id_drain from
        (SELECT regexp_split_to_array(ltree2text(chemin),E'\\.+') as vecteurchemin from rht.rht_topology where chemin <@ '212340' limit 1) as sub
-- Fonction qui renvoit les identifiants uniques des tronçons en amont d'un ouvrage


CREATE OR REPLACE FUNCTION troncons(integer)
RETURNS SETOF integer AS $$
select cast(unnest(vecteurchemin) as integer) as chemin_id_drain from
        (SELECT regexp_split_to_array(ltree2text(chemin),E'\\.+') as vecteurchemin from rht.rht_topology where chemin <@ text2ltree(cast ($1 as text))  limit 1) as sub;
$$ LANGUAGE sql STRICT IMMUTABLE;       

SELECT troncons_amont(212340); -- OK