Purge Circulations: Better selection logic

This attempts two things:

1 - Keep the number of circs the library wants based on the most recent
    circulations, regardless of user prefs and such.

    This is accomplished by changing the circ fetching query to use a
    window function in a subquery so we can filter on it easily.

    This also allowed removal of the purge position counter.

2 - Allow removal of circs that are between kept circs if they meet all
    other removal criteria.

    This is accomplished by using CONTINUE instead of EXIT in the loop.

Signed-off-by: Thomas Berezansky <tsbere@mvlc.org>
Signed-off-by: Jason Stephenson <jstephenson@mvlc.org>

diff --git a/Open-ILS/src/sql/Pg/090.schema.action.sql b/Open-ILS/src/sql/Pg/090.schema.action.sql
index 5067242..573b1e7 100644 (file)
--- a/Open-ILS/src/sql/Pg/090.schema.action.sql
+++ b/Open-ILS/src/sql/Pg/090.schema.action.sql
@@ -986,7 +986,6 @@ DECLARE
     circ_chain_head action.circulation%ROWTYPE;
     circ_chain_tail action.circulation%ROWTYPE;
 
-    purge_position  INT;
     count_purged    INT;
     num_incomplete  INT;
 
@@ -1014,22 +1013,23 @@ BEGIN
           GROUP BY target_copy
           HAVING COUNT(*) > org_keep_count
     LOOP
-        purge_position := 0;
         -- And, for those, select circs that are finished and older than keep_age
         FOR circ_chain_head IN
-            SELECT  *
-              FROM  action.circulation
-              WHERE target_copy = target_acp.target_copy
-                    AND parent_circ IS NULL
-              ORDER BY xact_start
+            -- For reference, the subquery uses a window function to order the circs newest to oldest and number them
+            -- The outer query then uses that information to skip the most recent set the library wants to keep
+            -- End result is we don't care what order they come out in, as they are all potentials for deletion.
+            SELECT ac.* FROM action.circulation ac JOIN (
+              SELECT  rank() OVER (ORDER BY xact_start DESC), ac.id
+                FROM  action.circulation ac
+                WHERE ac.target_copy = target_acp.target_copy
+                  AND ac.parent_circ IS NULL
+                ORDER BY ac.xact_start ) ranked USING (id)
+                WHERE ranked.rank > org_keep_count
         LOOP
 
-            -- Stop once we've purged enough circs to hit org_keep_count
-            EXIT WHEN target_acp.total_real_circs - purge_position <= org_keep_count;
-
             SELECT * INTO circ_chain_tail FROM action.circ_chain(circ_chain_head.id) ORDER BY xact_start DESC LIMIT 1;
             SELECT COUNT(CASE WHEN xact_finish IS NULL THEN 1 ELSE NULL END), MAX(xact_finish) INTO num_incomplete, last_finished FROM action.circ_chain(circ_chain_head.id);
-            EXIT WHEN circ_chain_tail.xact_finish IS NULL OR num_incomplete > 0;
+            CONTINUE WHEN circ_chain_tail.xact_finish IS NULL OR num_incomplete > 0;
 
             IF NOT org_use_last THEN
                 last_finished := circ_chain_tail.xact_finish;
@@ -1054,7 +1054,7 @@ BEGIN
                 keep_age := COALESCE( org_keep_age::INTERVAL, '2000 years'::INTERVAL );
             END IF;
 
-            EXIT WHEN AGE(NOW(), last_finished) < keep_age;
+            CONTINUE WHEN AGE(NOW(), last_finished) < keep_age;
 
             -- We've passed the purging tests, purge the circ chain starting at the end
             DELETE FROM action.circulation WHERE id = circ_chain_tail.id;
@@ -1064,7 +1064,6 @@ BEGIN
             END LOOP;
 
             count_purged := count_purged + 1;
-            purge_position := purge_position + 1;
 
         END LOOP;
     END LOOP;