music_library/backlog/archive/tasks/ml-169.5 - Fix-Display-toggle-grid-list-triggers-full-DB-reload.md

id, title, status, assignee, created_date, updated_date, labels, dependencies, references, modified_files, parent_task_id, priority, ordinal

id	title	status	assignee	created_date	updated_date	labels	dependencies	references	modified_files	parent_task_id	priority	ordinal
ML-169.5	Fix: Display toggle (grid/list) triggers full DB reload	Done		2026-05-19 11:45	2026-05-19 15:13	perf fix		backlog/documents/doc-27 - Phase-4-Performance-Audit-Low-Hanging-Fruit-Findings.md	lib/music_library_web/live_helpers/index_actions.ex lib/music_library_web/live/collection_live/index.ex lib/music_library_web/live/wishlist_live/index.ex	ML-169	high	26000

Description

Fix performance issue where toggling between grid and list display views triggers a full FTS database reload.

Problem

handle_set_display in index_actions.ex calls load_and_assign_records/2 which re-executes the full FTS search query (search_records_count + search_records). The toggle only changes a CSS layout class (@display == :grid vs @display == :list) — no data changes.

Impact

Every grid/list toggle wastes 2 FTS queries. This is a common user interaction (clicking the view switcher button).

Files

• lib/music_library_web/live_helpers/index_actions.ex:136-143 — handle_set_display/2 calls load_and_assign_records
• lib/music_library_web/live/collection_live/index.ex:336 — handle_event("set_display")
• lib/music_library_web/live/wishlist_live/index.ex:259 — handle_event("set_display")

Fix

Remove the load_and_assign_records call from handle_set_display. Only assign(:display, mode) is needed. The existing :if={@display == :grid} / :if={@display == :list} conditionals already handle showing/hiding the appropriate view.

Acceptance Criteria

• #1 Grid/list toggle no longer triggers DB queries (verified via QueryReporter)
• #2 Grid view renders correctly after toggle
• #3 List view renders correctly after toggle
• #4 No regression in search/filter functionality after toggle

Archive Reason

Archived after validation showed the proposed optimization is not correct with the current LiveView stream rendering structure.

Collection and wishlist render either <.record_grid> or <.record_list> behind mutually exclusive :if branches, and both components consume the same @streams.records stream. LiveView stream entries are consumed after render and the existing DOM holds the streamed children. When the display mode changes, the previously mounted stream container is removed and a different stream container is mounted. Without re-running stream(:records, records, reset: true), the newly mounted container has no queued stream entries to insert, so only its static empty-state node remains and only:block displays “No records yet”.

The DB reload avoided by this task is therefore also the step that rehydrates the stream for the newly mounted container. A future optimization would need a different rendering shape, such as keeping both containers mounted or avoiding conditional stream container replacement, before removing the reload.

Final Summary

Reverted the proposed handle_set_display/2 change and archived this task as not actionable in the current UI structure. The reload is required because grid/list toggling replaces the mounted stream container.