Low performance of listing graph

Hello,
After loaded 100 millions triples into Virtuoso, it’s not able to show graph list by WEB UI(Conductor) because it’s loading all the time, including querying the SPARQL below:

SELECT DISTINCT ?g
WHERE
{GRAPH ?g {?s ?p ?o}}

Thanks!

Graph listing is an expensive operation and as a result the more graph in the Quad Store the longer it will take to list them. How graphs are in the database:

select count(distinct ?g) where {GRAPH ?g{?s a ?t}};

Note also this tip on How to obtain all graphs with provides an alternative query {?s a ?t} which should be more performant and a function for listing graphs.