How to set query step of grafana query variable

I am using Thanos as the datasource. In Grafana, the dashboard first loads the query variables at the top and then loads the panels. When I query for a long time range, such as 90 days, the variables take 17 seconds to load. However, if I use Thanos Query Frontend, it only takes 1-2 seconds. After comparing the slow logs, I suspect the reason is that the query step is not set. Does anyone know how to set the query step for the variables or other reasons?

17s grafana: param_match[]="node_uname_info{job=~\"node_exporter\",account=\"xxx\",iid=~\"xxx\"}" param_start=1713839749 param_end=1729650949
1~2s thanos query frontend: param_query="node_uname_info{job=~\"node_exporter\",account=\"xxx\",iid=~\"xxx\"}" param_dedup=false param_tenant= param_engine=prometheus param_analyze=false param_partial_response=true param_start=1698115658.112 param_end=1729651658.112 param_step=126144 param_max_source_resolution=0s