perf(v2only): use constraint workload in rolling transfer

Author: invis-bitfly

backend/pkg/commons/db/clickhouse.go

@@ -67,6 +67,7 @@ func MustInitClickhouseNative(writer *types.DatabaseConfig) ch.Conn {
 			// trade of higher background overhead for lower query specific memory pressure
 			// reduces memory usage by 20-30% in our prod insert queries
 			"optimize_on_insert": "0",
+			"compatibility":      "25.6", // enables spill to disk when memory usage is too high, among other things
 		},
 		ClientInfo: ch.ClientInfo{
 			Products: []struct {

backend/pkg/commons/db/migrations/clickhouse/20250915131938_workload_scheduling.sql

@@ -0,0 +1,15 @@
+-- +goose Up
+-- +goose StatementBegin
+CREATE RESOURCE IF NOT EXISTS query (query);
+-- +goose StatementEnd
+-- +goose StatementBegin
+CREATE WORKLOAD IF NOT EXISTS exporter_rollings SETTINGS max_concurrent_queries = 1;
+-- +goose StatementEnd
+
+-- +goose Down
+-- +goose StatementBegin
+DROP WORKLOAD IF EXISTS exporter_rollings;
+-- +goose StatementEnd
+-- +goose StatementBegin
+DROP RESOURCE IF EXISTS query;
+-- +goose StatementEnd

backend/pkg/exporter/db/db.go

@@ -1664,6 +1664,7 @@ func TransferRollingSourceToRolling(rolling Rollings, source RollingSourcesSuffi
 		"select_sequential_consistency": 1,
 		"use_skip_indexes_if_final":     1, // this is only safe because our index is over a column from the primary key
 		"max_threads":                   2,
+		"workload":                      "exporter_rollings", // configured to 2 concurrent queries per node at the time of writing
 	}))
 	column := "t"
 	selector := `

backend/pkg/exporter/modules/dashboard_data_rollings.go

@@ -36,9 +36,8 @@ func (d *dashboardData) handleRollings() error {
 		edb.Rolling90d,
 		edb.RollingTotal,
 	}
-	// but lets limit to x rollings
 	eg := errgroup.Group{}
-	eg.SetLimit(int(utils.Config.DashboardExporter.RollingsInParallel))
+	//eg.SetLimit(int(utils.Config.DashboardExporter.RollingsInParallel))
 	for _, rolling := range rollings {
 		rolling := rolling
 		eg.Go(func() error {