chore: optimize GetPrebuiltWorkspaces query (#18717)

* Adds GetRunningPrebuiltWorkspacesOptimized query
* Runs both original and updated query side-by-side and logs diffs

coderd/database/queries.sql.go

@@ -6843,6 +6843,7 @@ FROM workspace_prebuilds p
 		INNER JOIN workspace_latest_builds b ON b.workspace_id = p.id
 WHERE (b.transition = 'start'::workspace_transition
 	AND b.job_status = 'succeeded'::provisioner_job_status)
+ORDER BY p.id
 `
 
 type GetRunningPrebuiltWorkspacesRow struct {
@@ -6886,6 +6887,106 @@ func (q *sqlQuerier) GetRunningPrebuiltWorkspaces(ctx context.Context) ([]GetRun
 	return items, nil
 }
 
+const getRunningPrebuiltWorkspacesOptimized = `-- name: GetRunningPrebuiltWorkspacesOptimized :many
+WITH latest_prebuilds AS (
+	-- All workspaces that match the following criteria:
+	-- 1. Owned by prebuilds user
+	-- 2. Not deleted
+	-- 3. Latest build is a 'start' transition
+	-- 4. Latest build was successful
+	SELECT
+		workspaces.id,
+		workspaces.name,
+		workspaces.template_id,
+		workspace_latest_builds.template_version_id,
+		workspace_latest_builds.job_id,
+		workspaces.created_at
+	FROM workspace_latest_builds
+	JOIN workspaces ON workspaces.id = workspace_latest_builds.workspace_id
+	WHERE workspace_latest_builds.transition = 'start'::workspace_transition
+	AND workspace_latest_builds.job_status = 'succeeded'::provisioner_job_status
+	AND workspaces.owner_id = 'c42fdf75-3097-471c-8c33-fb52454d81c0'::UUID
+	AND NOT workspaces.deleted
+),
+workspace_latest_presets AS (
+	-- For each of the above workspaces, the preset_id of the most recent
+	-- successful start transition.
+	SELECT DISTINCT ON (latest_prebuilds.id)
+		latest_prebuilds.id AS workspace_id,
+		workspace_builds.template_version_preset_id AS current_preset_id
+	FROM latest_prebuilds
+	JOIN workspace_builds ON workspace_builds.workspace_id = latest_prebuilds.id
+	WHERE workspace_builds.transition = 'start'::workspace_transition
+	AND   workspace_builds.template_version_preset_id IS NOT NULL
+	ORDER BY latest_prebuilds.id, workspace_builds.build_number DESC
+),
+ready_agents AS (
+	-- For each of the above workspaces, check if all agents are ready.
+	SELECT
+		latest_prebuilds.job_id,
+		BOOL_AND(workspace_agents.lifecycle_state = 'ready'::workspace_agent_lifecycle_state)::boolean AS ready
+	FROM latest_prebuilds
+	JOIN workspace_resources ON workspace_resources.job_id = latest_prebuilds.job_id
+	JOIN workspace_agents ON workspace_agents.resource_id = workspace_resources.id
+	WHERE workspace_agents.deleted = false
+	AND workspace_agents.parent_id IS NULL
+	GROUP BY latest_prebuilds.job_id
+)
+SELECT
+	latest_prebuilds.id,
+	latest_prebuilds.name,
+	latest_prebuilds.template_id,
+	latest_prebuilds.template_version_id,
+	workspace_latest_presets.current_preset_id,
+	COALESCE(ready_agents.ready, false)::boolean AS ready,
+	latest_prebuilds.created_at
+FROM latest_prebuilds
+LEFT JOIN ready_agents ON ready_agents.job_id = latest_prebuilds.job_id
+LEFT JOIN workspace_latest_presets ON workspace_latest_presets.workspace_id = latest_prebuilds.id
+ORDER BY latest_prebuilds.id
+`
+
+type GetRunningPrebuiltWorkspacesOptimizedRow struct {
+	ID                uuid.UUID     `db:"id" json:"id"`
+	Name              string        `db:"name" json:"name"`
+	TemplateID        uuid.UUID     `db:"template_id" json:"template_id"`
+	TemplateVersionID uuid.UUID     `db:"template_version_id" json:"template_version_id"`
+	CurrentPresetID   uuid.NullUUID `db:"current_preset_id" json:"current_preset_id"`
+	Ready             bool          `db:"ready" json:"ready"`
+	CreatedAt         time.Time     `db:"created_at" json:"created_at"`
+}
+
+func (q *sqlQuerier) GetRunningPrebuiltWorkspacesOptimized(ctx context.Context) ([]GetRunningPrebuiltWorkspacesOptimizedRow, error) {
+	rows, err := q.db.QueryContext(ctx, getRunningPrebuiltWorkspacesOptimized)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []GetRunningPrebuiltWorkspacesOptimizedRow
+	for rows.Next() {
+		var i GetRunningPrebuiltWorkspacesOptimizedRow
+		if err := rows.Scan(
+			&i.ID,
+			&i.Name,
+			&i.TemplateID,
+			&i.TemplateVersionID,
+			&i.CurrentPresetID,
+			&i.Ready,
+			&i.CreatedAt,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Close(); err != nil {
+		return nil, err
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
 const getTemplatePresetsWithPrebuilds = `-- name: GetTemplatePresetsWithPrebuilds :many
 SELECT
 		t.id                        AS template_id,