Created on 2011-09-06 12:02 by whunger, last changed 2016-07-10 23:43 by rouilj.
|msg4416||Author: [hidden] (whunger)||Date: 2011-09-06 12:02|
We are using Roundup with the MySQL backend for a tracker instance with almost half a million messages and about 32.000 issues. With this amount of data, we saw a degradation of performance over time, mainly because MySQL was unable to answer more complex filter queries without resorting to table scans and on-disk sorting. Wondering, why this should be necessary after all, i found the problem to be the column data types in multilink tables - they are declared as varchar(255) instead of integer. This, for sure, makes many queries quite expensive, as e. g. joins require on-the-fly type conversions and can't make use of the sort order in indexes and the table itself. In our tracker instance, i changed the type to integer for all the existing multilink tables, and the performance improvement really makes a big difference. Now i would like to ask: Is there any good reason for having linkid and nodeid declared as a varchar(255) on MySQL and not going with the default in rdbms_common? def create_multilink_table(self, spec, ml): sql = '''CREATE TABLE `%s_%s` (linkid VARCHAR(255), nodeid VARCHAR(255)) ENGINE=%s'''%(spec.classname, ml, self.mysql_backend) self.sql(sql) self.create_multilink_table_indexes(spec, ml)
|msg4417||Author: [hidden] (schlatterbeck)||Date: 2011-09-07 07:00|
Richard, I guess the varchar in multilink tables is has historical reasons (ID types used to be strings for some time). Do you remember the reason for special-casing this in the mysql backend? Do you see things that would break if we change this? Ralf
|msg4418||Author: [hidden] (richard)||Date: 2011-09-07 07:40|
Yes, ids stored as strings is a historical artefact going all the way back to when Roundup was implemented over Berkley DB style databases. I can think of no reason why the mysql backend should be special-cased like it is. Perhaps the mysql backend changelog might shed some light?
|msg5650||Author: [hidden] (rouilj)||Date: 2016-06-27 02:23|
Open question if we make this change it breaks all mysql installations right? Is there some way we can change this for new installs and keep it varchar for existing installs? (With the option for the existing installs to do the conversion and get the newer schema). Would an update to the migrate code in roundup-admin migrate be able to do the conversion?
|msg5680||Author: [hidden] (whunger)||Date: 2016-06-28 21:50|
> Open question if we make this change it breaks all mysql installations > right? If i remember correctly, the change would not break existing systems, because it's only the multilink association tables that have the VARCHAR type. I would almost go so far to call this a bug that is hidden by automatic type conversion in MySQL. I did not check again by looking at the current code, though.
|msg5825||Author: [hidden] (rouilj)||Date: 2016-07-10 23:43|
Looked at the hg history for changes to lines in that function. Looks like it has always been varchar. To get some stuff working it required the bdb engine at first. Maybe that's why it's a varchar? In any case at this point we should only be using innodb. Werner, was this a "simple": ALTER TABLE tablename_of_mutillink MODIFY linkid INTEGER; ALTER TABLE tablename_of_mutillink MODIFY nodeid INTEGER; followed by a call to self.create_multilink_table_indexes(spec, ml) or maybe just a reindex for the l_idx tables at the mysql level?
|2016-07-10 23:43:06||rouilj||set||messages: + msg5825|
|2016-06-28 21:50:06||whunger||set||messages: + msg5680|
messages: + msg5650
|2011-09-07 07:40:56||richard||set||messages: + msg4418|
+ richard, schlatterbeck|
messages: + msg4417