右查询以获取PostgreSQL数据库中的当前连接数 [英] Right query to get the current number of connections in a PostgreSQL DB

问题描述

以下哪两个更好？

select numbackends from pg_stat_database;

select count(*) from pg_stat_activity;

推荐答案

第一个的等效版本是：

SELECT sum(numbackends) FROM pg_stat_database;

在这种情况下，我期望版本比第二个略快，具有较少的行数。

In that case, I would expect that version to be slightly faster than the second one, simply because it has fewer rows to count. But you are not likely going to be able to measure a difference.

这两个查询都是基于完全相同的数据，因此它们同样准确。

Both queries are based on exactly the same data, so they will be equally accurate.

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