如何使用PostgreSQL查询获取机器的内存详细信息？

SELECT
    pg_size_pretty(pg_stat_bgwriter.shared_buffers * current_setting('block_size')::int8) AS shared_buffers,
    pg_size_pretty(pg_stat_bgwriter.temp_buffers * current_setting('block_size')::int8) AS temp_buffers,
    pg_size_pretty(pg_stat_bgwriter.maxwritten_clean * current_setting('block_size')::int8) AS maxwritten_clean,
    pg_size_pretty(pg_stat_bgwriter.buf_written * current_setting('block_size')::int8) AS buf_written,
    pg_size_pretty(pg_stat_bgwriter.buf_fsync * current_setting('block_size')::int8) AS buf_fsync,
    pg_size_pretty(pg_stat_bgwriter.buf_alloc * current_setting('block_size')::int8) AS buf_alloc,
    pg_size_pretty(pg_stat_bgwriter.checkpoint_write_time) AS checkpoint_write_time,
    pg_size_pretty(pg_stat_bgwriter.checkpoint_sync_time) AS checkpoint_sync_time,
    pg_size_pretty(pg_stat_bgwriter.buf_checkpoint) AS buf_checkpoint,
    pg_size_pretty(pg_stat_bgwriter.buf_clean) AS buf_clean,
    pg_size_pretty(pg_stat_bgwriter.backend_flush_requested * current_setting('block_size')::int8) AS backend_flush_requested,
    pg_size_pretty(pg_stat_bgwriter.backend_flush_avg_duration) AS backend_flush_avg_duration,
    pg_size_pretty(pg_stat_bgwriter.backend_flush_max_duration) AS backend_flush_max_duration,
    pg_size_pretty(pg_stat_bgwriter.backend_flush_samples) AS backend_flush_samples,
    pg_size_pretty(pg_stat_bgwriter.bgwriter_delay) AS bgwriter_delay,
    pg_size_pretty(pg_stat_bgwriter.bgwriter_lru_multiplier) AS bgwriter_lru_multiplier,
    pg_stat_bgwriter.stats_reset AS stats_reset
FROM
    pg_stat_bgwriter;

SELECT
    pid,
    datname,
    phase,
    heap_blks_total,
    heap_blks_scanned,
    heap_blks_vacuumed,
    index_vacuum_count,
    max_dead_tuples,
    num_dead_tuples,
    tup_del_count,
    tup_upd_count,
    tup_hot_upd_count,
    tup_ins_count,
    vacuum_time
FROM
    pg_stat_progress_vacuum;