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POMySQL Stored Procedure - Can't reopen table (not a temporary table)
 

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  1. POMySQL Stored Procedure - Can't reopen table (not a temporary table)
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    <p>I am converting a stored procedure from MS-SQL to MySQL. It is based around Directed Acyclic Graphs.</p> <p>The original MS-SQL script is in Listing 2 on the following page: <a href="http://www.codeproject.com/Articles/22824/A-Model-to-Represent-Directed-Acyclic-Graphs-DAG-o" rel="nofollow">http://www.codeproject.com/Articles/22824/A-Model-to-Represent-Directed-Acyclic-Graphs-DAG-o</a></p> <p>The stored procedure saves fine but is not removing any rows from the database. I have tried running through Debugger for MySQL and it will pass the first time and seems to update the table I am using for the temporary data, but doesn't update the "edges" table. It also doesn't drop the table at the end.</p> <p>Second run through, if I remove the purgelist table manually, it will run through to the REPEAT statement and then I get Error Code: 1137 SQLState: HY000, Message: Can't reopen table: 'purgelist'. Originally I wanted to use a temporary table but I understand I cannot reference the temporary table multiple times in the way my SELECT does, however, I am surprised this error is occurring on a non-temporary table. Also, I recognise in a multi session environment I will need purgelist to be dynamically named.</p> <p>Here is the MySQL code:</p> <pre><code>DELIMITER // CREATE PROCEDURE RemoveEdge( IN iId int(11) ) MAIN_BLOCK: BEGIN DECLARE counter int default 0; DECLARE rcount int default 0; SET counter = ( SELECT id FROM edges WHERE id = iId AND hops = 0 ); IF counter = 0 THEN BEGIN LEAVE MAIN_BLOCK; END; END IF; CREATE TABLE purgeList (id int); -- step 1: rows that were originally inserted with the first -- AddEdge call for this direct edge INSERT INTO purgeList SELECT id FROM edges WHERE directEdgeId = iId; -- step 2: scan and find all dependent rows that are inserted afterwards REPEAT INSERT INTO purgeList SELECT id FROM edges WHERE hops &gt; 0 AND ( entryEdgeId IN ( SELECT id FROM purgeList ) OR exitEdgeId IN ( SELECT id FROM purgeList ) ) AND id NOT IN (SELECT id FROM purgeList ); SET rcount = ROW_COUNT(); UNTIL rcount = 0 END REPEAT; DELETE FROM edges WHERE id IN ( SELECT id FROM purgeList); DROP TABLE purgeList; END // DELIMITER ; </code></pre> <p>I've double checked my syntax but I assume there is an error in there somewhere. Any help greatly appreciated.</p>
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