Fix N+1 queries in dashboard widget loading

[jrafanie]

Eliminates N+1 queries by eager loading widget contents and passing
widgets to view via instance variable hash instead of using find_by_id.

The view was calling MiqWidget.find_by_id for each widget, bypassing
any eager loading done in the controller. This caused individual queries
for each widget plus their contents.

1. Eager load widget contents with .includes(:miq_widget_contents)
2. Create widgets_by_id hash for fast lookup in view
3. Update view to use hash instead of find_by_id

• Before: 49 queries (9 cached)
• After: 39 queries (8 cached)
• Eliminated: 8 individual MiqWidget queries + improved content loading

View makes individual widget queries:

  MiqWidget Load (0.8ms) WHERE "miq_widgets"."id" = $1 (widget 4)
  MiqWidget Load (0.5ms) WHERE "miq_widgets"."id" = $1 (widget 3)
  MiqWidget Load (0.4ms) WHERE "miq_widgets"."id" = $1 (widget 9)
  MiqWidget Load (0.3ms) WHERE "miq_widgets"."id" = $1 (widget 24)
  MiqWidget Load (0.4ms) WHERE "miq_widgets"."id" = $1 (widget 22)
  MiqWidget Load (0.4ms) WHERE "miq_widgets"."id" = $1 (widget 1)
  MiqWidget Load (4.5ms) WHERE "miq_widgets"."id" = $1 (widget 6)
  MiqWidget Load (2.4ms) WHERE "miq_widgets"."id" = $1 (widget 21)
  MiqWidget Load (0.1ms) WHERE "miq_widgets"."id" = $1 (widget 10)

Plus individual MiqWidgetContent queries for each widget.

Result: Completed 200 OK in 299ms (49 queries, 9 cached)

Single bulk load with eager loading:

  MiqWidget Load (3.5ms) WHERE "miq_widgets"."id" IN ($1, $2, ..., $27)
  MiqWidgetContent Load (4.1ms) WHERE "miq_widget_contents"."miq_widget_id" IN ($1, $2, ..., $27)

View uses preloaded data - all subsequent queries are CACHE hits (0.0-0.8ms).

Result: Completed 200 OK in 311ms (39 queries, 8 cached)

[jrafanie]

WIP: investigating cypress failures locally and seeing it it happens in CI.

[miq-bot]

Checked commit jrafanie@d5d8091 with ruby 3.3.10, rubocop 1.86.0, haml-lint 0.72.0, and yamllint 1.37.1
2 files checked, 0 offenses detected
Everything looks fine. ⭐

[jrafanie]

WIP: investigating cypress failures locally and seeing it it happens in CI.

ok, all green!

[Fryguy]

Is MiqWidget.available_for_user a scope? If not, can it be? Asking because it looks like we pull back the widgets, and then we pull them back again. If available_for_user cannot be turned into a scope, then instead of pull back the records a second time, may we can use MiqPreloader here instead.

Suggested change

	widgets = MiqWidget.available_for_user(current_user)
	eager_loaded_widgets = MiqWidget.where(:id => widgets.map(&:id)).includes(:miq_widget_contents).sort_by { |a| a.content_type + a.title.downcase }
	widgets = MiqWidget.available_for_user(current_user)
	eager_loaded_widgets = MiqPreloader.preload(widgets, :miq_widget_contents).sort_by { |a| a.content_type + a.title.downcase }