Three WHERE slow query down

Question

I have a table adjacency, which stores information about connected lines and their angle to each other is build by

CREATE TABLE public.adjacency
(
    currentedge integer,
    currentgeom geometry(LineString,25832),
    sourcenode integer,
    targetnode integer,
    nextedge integer,
    nextgeom geometry(LineString,25832),
    degrees double precision
)

Now, I want to select only Lines which have angles in specific intervals

DROP TABLE IF EXISTS restriction;
SELECT DISTINCT '100' as to_cost, a.nextedge as target_id, a.currentedge as via_path
INTO restriction
FROM adjacency a ,  adjacency b 
WHERE (a.sourcenode = b.sourcenode AND (a.degrees < 45.0 OR a.degrees > 315.0))  
    OR (a.targetnode = b.targetnode AND (a.degrees < 45.0 OR a.degrees > 315.0))
    OR (a.targetnode = b.sourcenode AND (a.degrees BETWEEN 46.0 AND 224.0))
AND a.nextedge=b.currentedge

The execution of the last command seems endless. Can anyone explain to me what to change here? My execution plan:

Seq Scan on adjacency a  (cost=0.00..2574.30 rows=30630 width=40)

Answer 1

One thing that sometimes works is to rewrite a series of OR conditions into a sequence of UNIONs:

CREATE TABLE restriction
AS
SELECT '100' as to_cost, a.nextedge as target_id, a.currentedge as via_path
FROM adjacency a 
 JOIN adjacency b ON a.nextedge = b.currentedge
WHERE a.sourcenode = b.sourcenode AND (a.degrees < 45.0 OR a.degrees > 315.0)
UNION 
SELECT '100' as to_cost, a.nextedge as target_id, a.currentedge as via_path
FROM adjacency a 
 JOIN adjacency b ON a.nextedge=b.currentedge
WHERE a.targetnode = b.targetnode AND (a.degrees < 45.0 OR a.degrees > 315.0)
UNION 
SELECT '100' as to_cost, a.nextedge as target_id, a.currentedge as via_path
FROM adjacency a 
 JOIN adjacency b ON a.nextedge=b.currentedge
WHERE a.targetnode = b.sourcenode AND (a.degrees BETWEEN 46.0 AND 224.0)
;

You don't need an additional distinct here, as UNION will take care of that. I also replace the ancient, outdated implicit join syntax with an explicit JOIN operator.

You can additionally try indexes on:

• adjacency (nextedge, sourcenode)
• adjacency (currentedge, sourcenode)
• adjacency (nextedge, targetnode)
• adjacency (currentedge, targetnode)