Converting a script from MSSQL to PL/pgSQL - sql

Question

I just started working with the EVE static dump, which is just a lot of tables with data about the game, such as a list of what solar systems connect, which is what I'm dealing with.
I want to make a webpage that lets you filter out systems, and the first step is getting a list of systems nearby, with the distance to them.
I found a script that does it for MSSQL
--By Joanna Davaham http://forum.eveuniversity.org/viewtopic.php?t=44601&p=396107#p424943
--set values
DECLARE #jumpsAway INT =10
DECLARE #MiddleSystemName VARCHAR(50) = 'Aldrat'
DECLARE #Level INT =1
IF OBJECT_ID('tempdb..#map') IS NOT NULL
DROP TABLE #map
CREATE TABLE #map
(fromSolarSystemID INT, toSolarSystemID INT, Level INT)
INSERT INTO #map
SELECT -1, mSS.solarSystemID, 0 FROM mapSolarSystems mSS
WHERE mSS.solarSystemName= #MiddleSystemName
WHILE #Level <= #jumpsAway
BEGIN
INSERT INTO #map
SELECT mSSJ.fromSolarSystemID, mSSJ.toSolarSystemID, #Level FROM mapSolarSystemJumps mSSJ
WHERE mSSJ.fromSolarSystemID IN (SELECT toSolarSystemID FROM #map WHERE Level = #Level-1)
AND mSSJ.fromSolarSystemID NOT IN (SELECT fromSolarSystemID FROM #map)
SET #Level=#Level+1
END
SELECT m.*, mSS.solarSystemName, mSS.security FROM #map m
JOIN mapSolarSystems mSS ON m.toSolarSystemID=mSS.solarSystemID
--WHERE mSS.security<0.45 --uncomment to check all nearby lowsec system
I know that I could probably just use the MSSQL version of the dump, but I also want to be learning more about how to use PostgreSQL better.
I understand what it's doing and everything, but I just don't understand PL/pgSQL well enough to make it work.
My attempt is
CREATE FUNCTION near(VARCHAR, INTEGER) RETURNS TABLE(fromID INT,toID INT,jumps INT,name VARCHAR,security VARCHAR) AS $$
DECLARE --Declaration from here http://www.postgresql.org/docs/9.1/static/plpgsql-declarations.html
MiddleSystemName ALIAS FOR $1;
jumpsAway ALIAS FOR $2;
jumps INTEGER :=1;
BEGIN
--http://stackoverflow.com/questions/11979154/select-into-to-create-a-table-in-pl-pgsql
CREATE TEMP TABLE map AS
SELECT -1, mSS.solarSystemID, 0
FROM mapSolarSystems mSS
WHERE mSS.solarSystemName= MiddleSystemName;
LOOP
--http://www.postgresql.org/docs/9.1/static/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN
--If you don't do it with execute, you can only do one row, I guess?
EXECUTE 'SELECT
|| mSSJ.fromSolarSystemID,
|| mSSJ.toSolarSystemID,
|| $1
|| FROM
|| mapSolarSystemJumps mSSJ
|| WHERE
|| mSSJ.fromSolarSystemID EXISTS (SELECT toSolarSystemID FROM map WHERE jumps = $1 - 1)
|| AND mSSJ.fromSolarSystemID NOT EXISTS (SELECT fromSolarSystemID FROM map)'
INTO map
USING jumps;
jumps := jumps + 1
EXIT WHEN jumps > jumpsAway;
END LOOP;
RETURN QUERY SELECT m.*,mSS.solarSystemName, mSS.security FROM JOIN mapSolarSystems mSS ON m.toSolarSystemID = mSS.solarSystemID;
END;
$$ LANGUAGE plpgsql;
And the error that produces is
Error is
ERROR: "map" is not a known variable
LINE 27: INTO map
^
Thanks for all the help.

Answer 1

PL/pgSQL
This should be a valid translation to plpgsql:
CREATE OR REPLACE FUNCTION f_near(_middlesystemname text, _jumpsaway int)
RETURNS TABLE(fromid int, toid int, jumps int, name text, security text) AS
$func$
DECLARE
_jumps integer;
BEGIN
CREATE TEMP TABLE map AS
SELECT -1 AS "fromSolarSystemID"
,m."solarSystemID" AS "toSolarSystemID"
,0 AS level
FROM "mapSolarSystems" m
WHERE "solarSystemName" = _middlesystemname;
-- potentially add indexes on the temp table and ANALYZE if it gets big
FOR _jumps IN 1 .. _jumpsaway LOOP
INSERT INTO map ("fromSolarSystemID", "toSolarSystemID", level)
SELECT sj."fromSolarSystemID", sj."toSolarSystemID", _jumps AS level
FROM "mapSolarSystemJumps" sj
JOIN map m ON m."toSolarSystemID" = sj."fromSolarSystemID"
AND m."level" = _jumps - 1
LEFT JOIN map mx ON mx."fromSolarSystemID" = sj."fromSolarSystemID"
WHERE mx."fromSolarSystemID" IS NULL;
END LOOP;
RETURN QUERY
SELECT m.*, s."solarSystemName", s."security"
FROM map m
JOIN "mapSolarSystems" s ON m."toSolarSystemID" = s."solarSystemID";
END
$func$ LANGUAGE plpgsql;
RECURSIVE CTE - doesn't seem to work
This short SQL query with a recursive CTE should have done it:
WITH RECURSIVE map AS (
SELECT -1 AS fromsolarsystemid, m.solarsystemid, 0 AS level
FROM mapsolarsystems m
WHERE m.solarsystemname = from_id
UNION ALL
SELECT sj.fromsolarsystemid, sj.tosolarsystemid, level + 1
FROM mapsolarsystemjumps sj
JOIN map m USING (level)
LEFT JOIN map mx USING (fromsolarsystemid)
WHERE sj.fromsolarsystemid = m.tosolarsystemid
AND mx.fromsolarsystemid IS NULL
AND m.level < 10 -- jumpsAway
)
SELECT m.*, s.solarsystemname, s.security
FROM map m
JOIN mapsolarsystems s ON m.tosolarsystemid = s.solarsystemid
-- WHERE s.security < 0.45 -- uncomment to check all nearby lowsec system
However:
ERROR: recursive reference to query "map" must not appear within an outer join
LINE 9: LEFT JOIN map mx USING (fromsolarsystemid)