查看表膨胀（对所有表产进行膨胀率排序）
SQL文如下：
SELECT
schemaname||'.'||relname as table_name,
pg_size_pretty(pg_relation_size(schemaname||'.'||relname)) as table_size,
n_dead_tup,
n_live_tup,
round(n_dead_tup * 100 / (n_live_tup + n_dead_tup),2) AS dead_tup_ratio
FROM
pg_stat_all_tables
WHERE
n_dead_tup >= 1000
ORDER BY dead_tup_ratio DESC
LIMIT 10;
