From: Shaun McDonald <shaun@shaunmcdonald.me.uk>
Date: Thu, 6 Nov 2008 17:15:22 +0000 (+0000)
Subject: Doing the update version part of the migration in chunks of 10000 instead of all... 
X-Git-Tag: live~7625^2~221
X-Git-Url: https://git.openstreetmap.org/rails.git/commitdiff_plain/6855b2604cb356b814d7853fb56988924af24eb3

Doing the update version part of the migration in chunks of 10000 instead of all at once so that MySQL doesn't choke with running out of table locks.
---

diff --git a/db/migrate/018_move_to_innodb.rb b/db/migrate/018_move_to_innodb.rb
index c551b0ef8..d17da8fd5 100644
--- a/db/migrate/018_move_to_innodb.rb
+++ b/db/migrate/018_move_to_innodb.rb
@@ -19,8 +19,23 @@ class MoveToInnodb < ActiveRecord::Migration
 
     @@ver_tbl.each { |tbl|
       add_column "current_#{tbl}", "version", :bigint, :limit => 20, :null => false
-      execute "UPDATE current_#{tbl} SET version = " +
-	"(SELECT max(version) FROM #{tbl} WHERE #{tbl}.id = current_#{tbl}.id)"
+      # As the initial version of all nodes, ways and relations is 0, we set the 
+      # current version to something less so that we can update the version in 
+      # batches of 10000
+      tbl.classify.constantize.update_all("version=-1")
+      while tbl.classify.constantize.count(:conditions => {:version => -1}) > 0
+        tbl.classify.constantize.update_all("version=(SELECT max(version) FROM #{tbl} WHERE #{tbl}.id = current_#{tbl}.id)", {:version => -1}, :limit => 10000)
+      end
+     # execute "UPDATE current_#{tbl} SET version = " +
+      #  "(SELECT max(version) FROM #{tbl} WHERE #{tbl}.id = current_#{tbl}.id)"
+        # The above update causes a MySQL error:
+        # -- add_column("current_nodes", "version", :bigint, {:null=>false, :limit=>20})
+        # -> 1410.9152s
+        # -- execute("UPDATE current_nodes SET version = (SELECT max(version) FROM nodes WHERE nodes.id = current_nodes.id)")
+        # rake aborted!
+        # Mysql::Error: The total number of locks exceeds the lock table size: UPDATE current_nodes SET version = (SELECT max(version) FROM nodes WHERE nodes.id = current_nodes.id)
+
+        # The above rails version will take longer, however will no run out of locks
     }
   end