在PG数据库中以下哪个语句是 查看表的数据大小？ C A select pg_size_pretty(pg_total_relation_size('.')); B select schemaname ,round(sum(pg_total_relation_size(schemaname||'.'||tablename))/1024/1024) "Size_MB" from pg_tables where schemaname='' group by 1; C select pg_size_pretty(pg_relation_size('.')); D select schemaname,tablename,round(sum(pg_total_relation_size(schemaname || '.' || partitiontablename))/1024/1024) "MB" from pg_partitions where schemaname='' and tablename='' group by 1,2;