Add database logic to clear out requests that have 0 votes

Also, clean up some db constraints.

Fixes #29

db/20-requests.sql

@@ -1,5 +1,5 @@
 CREATE TABLE requests (
-	url varchar NOT NULL UNIQUE,
+	url varchar NOT NULL,
 	requester int NOT NULL,
 	state varchar NOT NULL DEFAULT 'Requested',
 	reqTimestamp timestamptz NOT NULL DEFAULT NOW(),

db/30-votes.sql

@@ -1,6 +1,6 @@
 CREATE TABLE votes (
-	requestUrl varchar,
-	userId int,
+	requestUrl varchar NOT NULL,
+	userId int NOT NULL,
 	PRIMARY KEY (requestUrl,userId),
 	FOREIGN KEY (requestUrl) REFERENCES requests(url) ON DELETE CASCADE,
 	FOREIGN KEY (userId) REFERENCES users(userId) ON DELETE CASCADE

db/95-procedures.sql

@@ -16,6 +16,13 @@ CREATE OR REPLACE PROCEDURE add_request(url varchar,requester int)
 		CALL update_scores();
 	$$;
 
+CREATE OR REPLACE PROCEDURE clear_zero_votes()
+	LANGUAGE SQL
+	AS $$
+		DELETE FROM requests WHERE NOT EXISTS
+			(SELECT FROM votes WHERE requests.url = votes.requesturl);
+	$$;
+
 CREATE OR REPLACE PROCEDURE add_vote(url varchar,voteuser int)
 	LANGUAGE SQL
 	AS $$
@@ -28,6 +35,7 @@ CREATE OR REPLACE PROCEDURE delete_vote(url varchar,voteuser int)
 	AS $$
 		DELETE FROM votes WHERE requesturl = url AND userid = voteuser;
 		CALL update_scores();
+		CALL clear_zero_votes();
 	$$;
 
 CREATE OR REPLACE PROCEDURE update_request_score_modifier(updateurl varchar, scoreDiff int)

db/upgrade/v0.6-v0.7.sql

@@ -0,0 +1,24 @@
+BEGIN;
+
+UPDATE version SET minor = 7;
+
+ALTER TABLE votes
+	ALTER COLUMN requestUrl SET NOT NULL
+	ALTER COLUMN userId SET NOT NULL;
+
+CREATE OR REPLACE PROCEDURE clear_zero_votes()
+	LANGUAGE SQL
+	AS $$
+		DELETE FROM requests WHERE NOT EXISTS
+			(SELECT FROM votes WHERE requests.url = votes.requesturl);
+	$$;
+
+CREATE OR REPLACE PROCEDURE delete_vote(url varchar,voteuser int)
+	LANGUAGE SQL
+	AS $$
+		DELETE FROM votes WHERE requesturl = url AND userid = voteuser;
+		CALL update_scores();
+		CALL clear_zero_votes();
+	$$;
+
+COMMIT;