[win32] fix deadlock occuring on the sequence tables with SQLServer
actually, this deadlock would occur with any db backend other that PostgreSQL
as the previous code was heavily relying on PG's SEQUENCE facility, not available
elsewhere.
Deadlock description:
Thread1 starts creating entities (and therefore calls create_eid):
-> this creates a DB-level lock on the entities_id_seq table, which
will last until end of transaction
Thread2 calls create_eid, which acquires the Python lock object, but
updating the entities_id_seq is held by the DB lock
Thread1 wants to create a new entity, calls create_eid, and is stuck by
the Python lock object held by Thread2.
Solution:
use a separate connection to read and write the entities_id_seq table.
/* -*- sql -*-
postgres specific registered procedures,
require the plpgsql language installed
*/
DROP FUNCTION IF EXISTS comma_join (anyarray) CASCADE;
CREATE FUNCTION comma_join (anyarray) RETURNS text AS $$
SELECT array_to_string($1, ', ')
$$ LANGUAGE SQL;;
DROP AGGREGATE IF EXISTS group_concat (anyelement) CASCADE;
CREATE AGGREGATE group_concat (
basetype = anyelement,
sfunc = array_append,
stype = anyarray,
finalfunc = comma_join,
initcond = '{}'
);;
DROP FUNCTION IF EXISTS limit_size (fulltext text, format text, maxsize integer);
CREATE FUNCTION limit_size (fulltext text, format text, maxsize integer) RETURNS text AS $$
DECLARE
plaintext text;
BEGIN
IF char_length(fulltext) < maxsize THEN
RETURN fulltext;
END IF;
IF format = 'text/html' OR format = 'text/xhtml' OR format = 'text/xml' THEN
plaintext := regexp_replace(fulltext, '<[\\w/][^>]+>', '', 'g');
ELSE
plaintext := fulltext;
END IF;
IF char_length(plaintext) < maxsize THEN
RETURN plaintext;
ELSE
RETURN substring(plaintext from 1 for maxsize) || '...';
END IF;
END
$$ LANGUAGE plpgsql;;
DROP FUNCTION IF EXISTS text_limit_size (fulltext text, maxsize integer);
CREATE FUNCTION text_limit_size (fulltext text, maxsize integer) RETURNS text AS $$
BEGIN
RETURN limit_size(fulltext, 'text/plain', maxsize);
END
$$ LANGUAGE plpgsql;;