· 第二层(Buffer Descriptor) 描述层包含了很多重要的信息,包括buffer_tag与缓冲池插槽id的映射关系,访问次数统计,锁等信息。 · Tag · buffer_id · refcount (被进程访问过一次加一,被时钟扫描过后减一,为零时可用) · usage_count · context_lock and io_in_progress_lock · Flags dirty bit valid bi...
The default value is set by server variable vacuum_buffer_usage_limit, which also controls autovacuum. PG16 autovacuum 运行中影响性能后,调节延迟参数生效性的改变 Allow autovacuum to more frequently honor changes to delay settings Rather than honor changes only at the start of each relation, honor ...
tuples: 31 removed, 1000 remain, 0 are dead butnotyet removable, oldest xmin: 4040 buffer usage: 78 hits, 0 misses, 0 dirtied avgreadrate: 0.000 MB/s,avgwrite rate: 0.000 MB/s system usage: CPU:user: 0.00 s, system: 0.00 s, elapsed: 0.00 s 2019-05-21 11:59:55.676 MSK [973...
· 第二层(Buffer Descriptor) 描述层包含了很多重要的信息,包括buffer_tag与缓冲池插槽id的映射关系,访问次数统计,锁等信息。 · Tag · buffer_id · refcount (被进程访问过一次加一,被时钟扫描过后减一,为零时可用) · usage_count · context_lock and io_in_progress_lock · Flags dirty bit valid bi...
一、pg_buffercache 主要作用是查看pg的共享池中缓存的对象信息 1.1 创建扩展postgres=# create extension pg_buffercache;CREATE EXTENSION 1.2 查看视图pg_buffercache postgres=# \d pg_buffercache View "public.pg_buffercache" Column | Type | Collation | Nullable | Default ---+---+...
· usage_count · context_lock and io_in_progress_lock · Flags dirty bit valid bit io_in_progress bit · freeNext · Buffer Descriptors Layer (Loading the first page) 先请求一个缓冲区空间,buffer table层把描述层的buffer_id与buffer_tag进行映射;然后在描述层把buffer_tag与缓冲区id进行映射;最...
tag保存了相应缓冲池槽中存储页的buffer_tag。 ·buf_id 标识描述符。 ·content_lock 是一个轻量级锁,用于控制对关联存储页面的访问。 ·freeNext 是指向下一个描述符的指针,用于生成空闲列表。 ·states可以保存关联存储页面的多个状态和变量,例如refcount和usage_count。
CREATE OR REPLACE VIEW pg_buffercache AS SELECT P.* FROM pg_buffercache_pages() AS P ( bufferid integer, relfilenode oid, reltablespace oid, reldatabase oid, relforknumber int2, relblocknumber int8, isdirty bool, usagecount int2, ...
General \copyright show PostgreSQL usage and distribution terms \crosstabview [COLUMNS] execute query and display result in crosstab \errverbose show most recent error message at maximum verbosity \g [(OPTIONS)] [FILE] execute query (and send result to file or |pipe); \g with...
[LINE]] edit view definition with external editor\p show the contents of the query buffer\r reset (clear) the query buffer\s [FILE] display history or save it to file\w FILE write query buffer to fileInput/Output\copy ... perform SQL COPY with data stream to the client host\echo [...