postgreSQL pgfincore introduces(二)
--
base/12699/16441 | 4096 | 88496 | 186428
(1 row)
postgres=# select * from pgfincore('t');
relpath | segment | os_page_size | rel_os_pages | pages_mem | group_mem | os_pages_free | databit
------------------+---------+--------------+--------------+-----------+-----------+---------------+---------
base/12699/16441 | 0 | 4096 | 88496 | 88496 | 1 | 186397 |
(1 row)
刷出cache：
postgres=# select * from pgfadvise_dontneed('t');
relpath | os_page_size | rel_os_pages | os_pages_free
------------------+--------------+--------------+---------------
base/12699/16441 | 4096 | 88496 | 275021
(1 row)
postgres=# select * from pgfincore('t');
relpath | segment | os_page_size | rel_os_pages | pages_mem | group_mem | os_pages_free | databit
------------------+---------+--------------+--------------+-----------+-----------+---------------+---------
base/12699/16441 | 0 | 4096 | 88496 | 0 | 0 | 275052 |
(1 row)
pgfadvise_loader:
postgres=# select * from pgfadvise_loader('t', 0, true, true, B'111000');
relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
------------------+--------------+---------------+--------------+----------------
base/12699/16441 | 4096 | 186626 | 3 | 3
(1 row)
loading：
postgres=# select * from pgfadvise_loader('t', 0, true, false, B'111000');
relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
------------------+--------------+---------------+--------------+----------------
base/12699/16441 | 4096 | 186460 | 3 | 0
(1 row)
unloading：
postgres=# select * from pgfadvise_loader('t', 0, false, true, B'111000');
relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
------------------+--------------+---------------+--------------+----------------
base/12699/16441 | 4096 | 186557 | 0 | 3
(1 row)
pgfadvise_NORMAL
pgfadvise_SEQUENTIAL
pgfadvise_RANDOM
这几个可以指定当前内存的属性，正常，顺序，还是随机。
快照与恢复：
做快照：
create table pgfincore_snapshot as
select 't'::text as relname,*,now() as date_snapshot
from pgfincore('t',true);
应用快照：
select * from pgfadvise_loader('t', 0, true, true,
(select databit from pgfincore_snapshot
where relname='t' and segment = 0));
relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
------------------+--------------+---------------+--------------+----------------
base/12699/16441 | 4096 | 186259 | 88490 | 6
(1 row)
postgres=# select * from pgfincore('t');
relpath | segment | os_page_size | rel_os_pages | pages_mem | group_mem | os_pages_free | databit
------------------+---------+--------------+--------------+-----------+-----------+---------------+---------
base/12699/16441 | 0 | 4096 | 88496 | 88490 | 2 | 186097 |
(1 row)
可以看到 88496 和88490，有几个页面是刷出cache，所以不相等
select * from pgfadvise_willneed('t');
postgres=# select * from pgfincore('t');
relpath | segment | os_page_size | rel_os_pages | pages_mem | group_mem | os_pages_free | data