Re: PostgreSQL array, recursion and more

Hey Ferruccio,

Also consider ltree contrib module as alternative.
http://www.postgresql.org/docs/9.0/static/ltree.html

;-)

2010/11/17 Ferruccio Zamuner <nonsolosoft(at)diff(dot)org>

> MESH Data Tree:
>
> example:
> Hallux;A01.378.610.250.300.792.380
>
> where:
> A01 is Body Regions
> A01.378 is Extremities
> A01.378.610 is Lower Extremity
> A01.378.610.250 is Foot
> A01.378.610.250.300 is Forefoot, Human
> A01.378.610.250.300.792 is Toes
>
> CREATE OR REPLACE FUNCTION mesh_split(text) RETURNS text[]
> AS $$
> return [split('\.',$_[0])];
> $$ LANGUAGE plperlu;
>
> arancia=# select mesh_split('A01.378.610.250.300.792.380');
> mesh_split
> -------------------------------
> {A01,378,610,250,300,792,380}
> (1 row)
>
>
> /*
> Is it a real array?
> If it is, why can I not use index to access its items?
> */
>
> arancia=# select mesh_split('A01.378.610.250.300.792.380')[1];
> ERROR: syntax error at or near "["
> LINE 1: select mesh_split('A01.378.610.250.300.792.380')[1];
> ^
> /*
> but it is an array, it behaves as it is.
> */
> arancia=> select array_length(mesh_split('A01.378.610.250.300.792.380'),1);
> array_length
> --------------
> 7
> (1 row)
>
> /* How to get access to its items then?
> */
>
>
> Another problem related:
>
> arancia=> select * from meshtree where code = ANY
> mesh_split('A01.378.610.250.300.792.380');
> ERROR: syntax error at or near "mesh_split"
> LINE 1: select * from meshtree where code = ANY mesh_split('A01.378....
> ^
>
> select * from meshtree, unnest(mesh_split('A01.378.610.250.300.792.380'))
> as c where c=meshtree.code;
> parent | id | code | description
>
> --------+-------+------+-------------------------------------------------------------------
> 10 | 11 | 300 | Dehydroepiandrosterone Sulfate
> 33 | 34 | 250 | Cymarine
> 48 | 49 | 250 | Cymarine
> 61 | 62 | 250 | Dihydrotachysterol
> 66 | 68 | 300 | Calcitriol
> 65 | 69 | 250 | Calcifediol
> 92 | 93 | 380 | Glycodeoxycholic Acid
> 98 | 99 | 250 | Finasteride
> 111 | 117 | 300 | Chenodeoxycholic Acid
> 145 | 146 | 300 | Dehydroepiandrosterone Sulfate
> 180 | 182 | 250 | Ethinyl Estradiol-Norgestrel Combination
> 190 | 191 | 250 | Desoximetasone
> [..]
> | 18638 | A01 | Body Regions
> [..]
> 190 | 192 | 300 | Dexamethasone Isonicotinate
> 195 | 196 | 250 | Clobetasol
> 199 | 200 | 300 | Fluocinonide
> 206 | 207 | 250 | Diflucortolone
> 266 | 267 | 300 | Dexamethasone Isonicotinate
> 281 | 282 | 250 | Diflucortolone
> 290 | 293 | 250 | Dehydrocholesterols
> 305 | 306 | 250 | Dihydrotachysterol
> 312 | 314 | 300 | Calcitriol
> 311 | 315 | 250 | Calcifediol
> 320 | 321 | 250 | Cholestanol
> 328 | 330 | 300 | Calcitriol
> [..]
> 52135 | 52136 | 250 | Eye Injuries
> 52136 | 52137 | 250 | Eye Burns
> 52149 | 52155 | 300 | Hematoma, Epidural, Cranial
> 52181 | 52196 | 300 | Gallbladder Emptying
> 52269 | 52277 | 300 | Caplan Syndrome
> 52360 | 52368 | 300 | Caplan Syndrome
> 52428 | 52442 | 380 | Hemothorax
> 52476 | 52491 | 610 | Pneumonia
> 52534 | 52535 | 380 | Legionnaires' Disease
> (2204 rows)
>
> I really want to write better similar query:
>
> arancia=> with recursive t(id,parent,codeparts,idx,last,descriptions) as (
> SELECT
> id, parent, mesh_split('A01.378.610.250.300.792.380'), 1,
> array_length(mesh_split('A01.378.610.250.300.792.380'),1),
> ARRAY[description]
> FROM meshtree WHERE code='A01'
> UNION ALL
> SELECT m.id, m.parent, t.codeparts, idx+1, last, descriptions ||
> ARRAY[description]
> FROM meshtree AS m JOIN t ON (t.id=m.parent)
> WHERE idx<=last AND m.code=t.codeparts[idx+1])
> SELECT t.* FROM t;
> id | parent | codeparts | idx | last |
> descriptions
> -------+--------+-------------------------------+-----+------+--------...
> 18638 | | {A01,378,610,250,300,792,380} | 1 | 7 | {"Body
> Regions"}
> 18675 | 18638 | {A01,378,610,250,300,792,380} | 2 | 7 | {"Body
> Regions",Extremities}
> 18676 | 18675 | {A01,378,610,250,300,792,380} | 3 | 7 | {"Body
> Regions",Extremities,"Lower Extremity"}
> 18679 | 18676 | {A01,378,610,250,300,792,380} | 4 | 7 | {"Body
> Regions",Extremities,"Lower Extremity",Foot}
> 18682 | 18679 | {A01,378,610,250,300,792,380} | 5 | 7 | {"Body
> Regions",Extremities,"Lower Extremity",Foot,"Forefoot, Human"}
> 18683 | 18682 | {A01,378,610,250,300,792,380} | 6 | 7 | {"Body
> Regions",Extremities,"Lower Extremity",Foot,"Forefoot, Human",Toes}
> 18684 | 18683 | {A01,378,610,250,300,792,380} | 7 | 7 | {"Body
> Regions",Extremities,"Lower Extremity",Foot,"Forefoot, Human",Toes,Hallux}
> (7 rows)
>
> explain analyze with recursive t(id,parent,codeparts,idx,last,descriptions)
> as (
> select
> id,parent,mesh_split('A01.378.610.250.300.792.380'),1,array_length(mesh_split('A01.378.610.250.300.792.380'),1),ARRAY[description]
> from meshtree where code='A01'
> union all
> select m.id,m.parent,t.codeparts,idx+1,last,descriptions ||
> ARRAY[description] from meshtree as m join t on (t.id=m.parent) where
> idx<=last and m.code=t.codeparts[idx+1]) select t.* from t;
>
> QUERY PLAN
>
> ------------------------------------------------------------------------------------------------------------------------------------------------------
> CTE Scan on t (cost=6336.53..6337.17 rows=32 width=80) (actual
> time=4.850..9.453 rows=7 loops=1)
> CTE t
> -> Recursive Union (cost=0.00..6336.53 rows=32 width=99) (actual
> time=4.839..9.397 rows=7 loops=1)
> -> Index Scan using meshtree_id_code on meshtree
> (cost=0.00..1030.38 rows=22 width=27) (actual time=4.828..8.895 rows=1
> loops=1)
> Index Cond: (code = 'A01'::text)
> -> Nested Loop (cost=0.00..530.55 rows=1 width=99) (actual
> time=0.051..0.061 rows=1 loops=7)
> -> WorkTable Scan on t (cost=0.00..4.95 rows=73 width=76)
> (actual time=0.005..0.008 rows=1 loops=7)
> Filter: (idx <= last)
> -> Index Scan using meshtree_parent_code on meshtree m
> (cost=0.00..7.18 rows=1 width=31) (actual time=0.031..0.034 rows=1 loops=7)
> Index Cond: ((m.parent = t.id) AND (m.code =
> t.codeparts[(t.idx + 1)]))
> Total runtime: 9.758 ms
> (11 rows)
>
>
> PostgreSQL rocks!
>
>
> Thank you in advance, \ferz
>
>
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>

--
// Dmitriy.