Fix constraint sync during migration - restore constraints lost during merge in test schema. - use constraint_by_eid in BeforeDeleteCWConstraintHook as done in 3.17.14 for BeforeDeleteConstrainedByHook. Fixes handling of multiple constraints of the same type. - make sync_schema_props_perms() delete the CWConstraint entity instead of the constrained_by relation. In 3.19, the latter doesn't automatically result in the former just because the relation is composite. Simplify the constraint migration to delete all removed constraints and recreate new ones even if they share the same type; that optimization made the code more complicated for (AFAICT) no significant reason.

/* -*- sql -*- 

   mysql specific registered procedures, 

*/

/* XXX limit_size version dealing with format as postgres version does.
   XXX mysql doesn't support overloading, each function should have a different name
       
   NOTE: fulltext renamed since it cause a mysql name conflict
 */

CREATE FUNCTION text_limit_size(vfulltext TEXT, maxsize INT)
RETURNS TEXT
NO SQL
BEGIN
    IF LENGTH(vfulltext) < maxsize THEN
       RETURN vfulltext;
    ELSE
       RETURN SUBSTRING(vfulltext from 1 for maxsize) || '...';
    END IF;
END ;;