Fix adding defaults for concurrent column renamesrename-column-concurrently-defaults

By adding the default value _after_ adding the column we avoid updating
all rows in a table, saving a lot of time and unnecessary work in the
process.

1 files changed, 5 insertions, 1 deletions

diff --git a/lib/gitlab/database/migration_helpers.rb b/lib/gitlab/database/migration_helpers.rb
index f04a907004c..f3476dadec8 100644
--- a/lib/gitlab/database/migration_helpers.rb
+++ b/lib/gitlab/database/migration_helpers.rb
@@ -283,11 +283,15 @@ module Gitlab
 
         add_column(table, new, new_type,
                    limit: old_col.limit,
-                   default: old_col.default,
                    null: old_col.null,
                    precision: old_col.precision,
                    scale: old_col.scale)
 
+        # We set the default value _after_ adding the column so we don't end up
+        # updating any existing data with the default value. This isn't
+        # necessary since we copy over old values further down.
+        change_column_default(table, new, old_col.default) if old_col.default
+
         trigger_name = rename_trigger_name(table, old, new)
         quoted_table = quote_table_name(table)
         quoted_old = quote_column_name(old)