-===========
- PgFincore
-===========
+# PgFincore
--------------------------------------------------------------
A set of functions to manage pages in memory from PostgreSQL
A set of functions to handle low-level management of relations using mincore to
explore cache memory.
-DESCRIPTION
-===========
+## DESCRIPTION
With PostgreSQL, each Table or Index is splitted in segments of (usually) 1GB,
and each segment is splitted in pages in memory then in blocks for the
Each functions are call with at least a table name or an index name (or oid)
as a parameter and walk each segment of the relation.
-DOWNLOAD
-========
+## DOWNLOAD
-You can grab the latest code with git::
+You can grab the latest code with git:
- git clone git://git.postgresql.org/git/pgfincore.git
- or
- git://github.com/klando/pgfincore.git
+ git clone git://git.postgresql.org/git/pgfincore.git
+ or
+ git://github.com/klando/pgfincore.git
And the project is on pgfoundry : http://pgfoundry.org/projects/pgfincore
-INSTALL
-=======
+## INSTALL
-From source code::
+From source code:
- make clean
- make
- su
- make install
+ make clean
+ make
+ su
+ make install
-For PostgreSQL >= 9.1, log in your database and::
+For PostgreSQL >= 9.1, log in your database and:
- mydb=# CREATE EXTENSION pgfincore;
+ mydb=# CREATE EXTENSION pgfincore;
For other release, create the functions from the sql script (it should be in
-your contrib directory)::
+your contrib directory):
- psql mydb -f pgfincore.sql
+ psql mydb -f pgfincore.sql
-PgFincore is also shipped with Debian scripts to build your own package::
+PgFincore is also shipped with Debian scripts to build your own package:
- aptitude install debhelper postgresql-server-dev-all postgresql-server-dev-9.1
- # or postgresql-server-dev-8.4|postgresql-server-dev-9.0
- make deb
- dpkg -i ../postgresql-9.1-pgfincore_1.1.1-1_amd64.deb
+ aptitude install debhelper postgresql-server-dev-all postgresql-server-dev-9.1
+ # or postgresql-server-dev-8.4|postgresql-server-dev-9.0
+ make deb
+ dpkg -i ../postgresql-9.1-pgfincore_1.1.1-1_amd64.deb
PgFincore is packaged for *RPM* at http://yum.postgresql.org/
PgFincore is packaged for *debian* at http://pgapt.debian.net/
-EXAMPLES
-========
+## EXAMPLES
Here are some examples of usage. If you want more details go to Documentation_
-Get current state of a relation
--------------------------------
+### Get current state of a relation
-May be useful::
+May be useful:
- cedric=# select * from pgfincore('pgbench_accounts');
- relpath | segment | os_page_size | rel_os_pages | pages_mem | group_mem | os_pages_free | databit | pages_dirty | group_dirty
- --------------------+---------+--------------+--------------+-----------+-----------+---------------+---------+-------------+-------------
- base/11874/16447 | 0 | 4096 | 262144 | 262144 | 1 | 81016 | | 0 | 0
- base/11874/16447.1 | 1 | 4096 | 65726 | 65726 | 1 | 81016 | | 0 | 0
- (2 rows)
-
- Time: 31.563 ms
+ cedric=# select * from pgfincore('pgbench_accounts');
+ relpath | segment | os_page_size | rel_os_pages | pages_mem | group_mem | os_pages_free | databit | pages_dirty | group_dirty
+ --------------------+---------+--------------+--------------+-----------+-----------+---------------+---------+-------------+-------------
+ base/11874/16447 | 0 | 4096 | 262144 | 262144 | 1 | 81016 | | 0 | 0
+ base/11874/16447.1 | 1 | 4096 | 65726 | 65726 | 1 | 81016 | | 0 | 0
+ (2 rows)
+
+ Time: 31.563 ms
-Load a table or an index in OS Page Buffer
-------------------------------------------
+### Load a table or an index in OS Page Buffer
You may want to try to keep a table or an index into the OS Page Cache, or
preload a table before your well know big query is executed (reducing the query
time).
-To do so, just execute the following query::
+To do so, just execute the following query:
- cedric=# select * from pgfadvise_willneed('pgbench_accounts');
- relpath | os_page_size | rel_os_pages | os_pages_free
- --------------------+--------------+--------------+---------------
- base/11874/16447 | 4096 | 262144 | 169138
- base/11874/16447.1 | 4096 | 65726 | 103352
- (2 rows)
-
- Time: 4462,936 ms
+ cedric=# select * from pgfadvise_willneed('pgbench_accounts');
+ relpath | os_page_size | rel_os_pages | os_pages_free
+ --------------------+--------------+--------------+---------------
+ base/11874/16447 | 4096 | 262144 | 169138
+ base/11874/16447.1 | 4096 | 65726 | 103352
+ (2 rows)
+
+ Time: 4462,936 ms
* The column *os_page_size* report that page size is 4KB.
* The column *rel_os_pages* is the number of pages of the specified file.
* The column *os_pages_free* is the number of free pages in memory (for caching).
-Snapshot and Restore the OS Page Buffer state of a table or an index (or more)
-------------------------------------------------------------------------------
+### Snapshot and Restore the OS Page Buffer state of a table or an index (or more)
You may want to restore a table or an index into the OS Page Cache as it was
while you did the snapshot. For example if you have to reboot your server, then
PostgreSQL or the OS have pages in their respective cache about the relations
involved in those first queries.
-Executing a snapshot and a restore is very simple::
-
- -- Snapshot
- cedric=# create table pgfincore_snapshot as
- cedric-# select 'pgbench_accounts'::text as relname,*,now() as date_snapshot
- cedric-# from pgfincore('pgbench_accounts',true);
-
- -- Restore
- cedric=# select * from pgfadvise_loader('pgbench_accounts', 0, true, true,
- (select databit from pgfincore_snapshot
- where relname='pgbench_accounts' and segment = 0));
- relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
- ------------------+--------------+---------------+--------------+----------------
- base/11874/16447 | 4096 | 80867 | 262144 | 0
- (1 row)
-
- Time: 35.349 ms
+Executing a snapshot and a restore is very simple:
+
+ -- Snapshot
+ cedric=# create table pgfincore_snapshot as
+ cedric-# select 'pgbench_accounts'::text as relname,*,now() as date_snapshot
+ cedric-# from pgfincore('pgbench_accounts',true);
+
+ -- Restore
+ cedric=# select * from pgfadvise_loader('pgbench_accounts', 0, true, true,
+ (select databit from pgfincore_snapshot
+ where relname='pgbench_accounts' and segment = 0));
+ relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
+ ------------------+--------------+---------------+--------------+----------------
+ base/11874/16447 | 4096 | 80867 | 262144 | 0
+ (1 row)
+
+ Time: 35.349 ms
* The column *pages_loaded* report how many pages have been read to memory
(they may have already been in memoy)
* The column *pages_unloaded* report how many pages have been removed from
memory (they may not have already been in memoy);
-SYNOPSIS
-========
-
-::
+## SYNOPSIS
pgsysconf(OUT os_page_size bigint, OUT os_pages_free bigint,
OUT os_total_pages bigint)
OUT group_dirty bigint)
RETURNS setof record
-DOCUMENTATION
-=============
+## DOCUMENTATION
-pgsysconf
----------
+### pgsysconf
This function output size of OS blocks, number of free page in the OS Page Buffer.
-::
+ cedric=# select * from pgsysconf();
+ os_page_size | os_pages_free | os_total_pages
+ --------------+---------------+----------------
+ 4096 | 80431 | 4094174
- cedric=# select * from pgsysconf();
- os_page_size | os_pages_free | os_total_pages
- --------------+---------------+----------------
- 4096 | 80431 | 4094174
-
-pgsysconf_pretty
-----------------
+### pgsysconf_pretty
The same as above, but with pretty output.
-::
-
- cedric=# select * from pgsysconf_pretty();
- os_page_size | os_pages_free | os_total_pages
- --------------+---------------+----------------
+ cedric=# select * from pgsysconf_pretty();
+ os_page_size | os_pages_free | os_total_pages
+ --------------+---------------+----------------
4096 bytes | 314 MB | 16 GB
-pgfadvise_WILLNEED
-------------------
+### pgfadvise_WILLNEED
This function set *WILLNEED* flag on the current relation. It means that the
Operating Sytem will try to load as much pages as possible of the relation.
Main idea is to preload files on server startup, perhaps using cache hit/miss
ratio or most required relations/indexes.
-::
+ cedric=# select * from pgfadvise_willneed('pgbench_accounts');
+ relpath | os_page_size | rel_os_pages | os_pages_free
+ --------------------+--------------+--------------+---------------
+ base/11874/16447 | 4096 | 262144 | 80650
+ base/11874/16447.1 | 4096 | 65726 | 80650
- cedric=# select * from pgfadvise_willneed('pgbench_accounts');
- relpath | os_page_size | rel_os_pages | os_pages_free
- --------------------+--------------+--------------+---------------
- base/11874/16447 | 4096 | 262144 | 80650
- base/11874/16447.1 | 4096 | 65726 | 80650
-
-pgfadvise_DONTNEED
-------------------
+### pgfadvise_DONTNEED
This function set *DONTNEED* flag on the current relation. It means that the
Operating System will first unload pages of the file if it need to free some
memory. Main idea is to unload files when they are not usefull anymore (instead
of perhaps more interesting pages)
-::
-
- cedric=# select * from pgfadvise_dontneed('pgbench_accounts');
- relpath | os_page_size | rel_os_pages | os_pages_free
- --------------------+--------------+--------------+---------------
- base/11874/16447 | 4096 | 262144 | 342071
- base/11874/16447.1 | 4096 | 65726 | 408103
+ cedric=# select * from pgfadvise_dontneed('pgbench_accounts');
+ relpath | os_page_size | rel_os_pages | os_pages_free
+ --------------------+--------------+--------------+---------------
+ base/11874/16447 | 4096 | 262144 | 342071
+ base/11874/16447.1 | 4096 | 65726 | 408103
-pgfadvise_NORMAL
-----------------
+### pgfadvise_NORMAL
This function set *NORMAL* flag on the current relation.
-pgfadvise_SEQUENTIAL
---------------------
+### pgfadvise_SEQUENTIAL
This function set *SEQUENTIAL* flag on the current relation.
-pgfadvise_RANDOM
-----------------
+### pgfadvise_RANDOM
This function set *RANDOM* flag on the current relation.
-pgfadvise_loader
-----------------
+### pgfadvise_loader
This function allow to interact directly with the Page Cache.
It can be used to load and/or unload page from memory based on a varbit
representing the map of the pages to load/unload accordingly.
-Work with relation pgbench_accounts, segment 0, arbitrary varbit map::
-
- -- Loading and Unloading
- cedric=# select * from pgfadvise_loader('pgbench_accounts', 0, true, true, B'111000');
- relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
- ------------------+--------------+---------------+--------------+----------------
- base/11874/16447 | 4096 | 408376 | 3 | 3
-
- -- Loading
- cedric=# select * from pgfadvise_loader('pgbench_accounts', 0, true, false, B'111000');
- relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
- ------------------+--------------+---------------+--------------+----------------
- base/11874/16447 | 4096 | 408370 | 3 | 0
-
- -- Unloading
- cedric=# select * from pgfadvise_loader('pgbench_accounts', 0, false, true, B'111000');
+Work with relation pgbench_accounts, segment 0, arbitrary varbit map:
+
+ -- Loading and Unloading
+ cedric=# select * from pgfadvise_loader('pgbench_accounts', 0, true, true, B'111000');
+ relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
+ ------------------+--------------+---------------+--------------+----------------
+ base/11874/16447 | 4096 | 408376 | 3 | 3
+
+ -- Loading
+ cedric=# select * from pgfadvise_loader('pgbench_accounts', 0, true, false, B'111000');
+ relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
+ ------------------+--------------+---------------+--------------+----------------
+ base/11874/16447 | 4096 | 408370 | 3 | 0
+
+ -- Unloading
+ cedric=# select * from pgfadvise_loader('pgbench_accounts', 0, false, true, B'111000');
relpath | os_page_size | os_pages_free | pages_loaded | pages_unloaded
- ------------------+--------------+---------------+--------------+----------------
- base/11874/16447 | 4096 | 408370 | 0 | 3
+ ------------------+--------------+---------------+--------------+----------------
+ base/11874/16447 | 4096 | 408370 | 0 | 3
-pgfincore
----------
+### pgfincore
This function provide information about the file system cache (page cache).
-::
-
- cedric=# select * from pgfincore('pgbench_accounts');
- relpath | segment | os_page_size | rel_os_pages | pages_mem | group_mem | os_pages_free | databit | pages_dirty | group_dirty
- --------------------+---------+--------------+--------------+-----------+-----------+---------------+---------+-------------+-------------
- base/11874/16447 | 0 | 4096 | 262144 | 3 | 1 | 408444 | | 0 | 0
- base/11874/16447.1 | 1 | 4096 | 65726 | 0 | 0 | 408444 | | 0 | 0
+ cedric=# select * from pgfincore('pgbench_accounts');
+ relpath | segment | os_page_size | rel_os_pages | pages_mem | group_mem | os_pages_free | databit | pages_dirty | group_dirty
+ --------------------+---------+--------------+--------------+-----------+-----------+---------------+---------+-------------+-------------
+ base/11874/16447 | 0 | 4096 | 262144 | 3 | 1 | 408444 | | 0 | 0
+ base/11874/16447.1 | 1 | 4096 | 65726 | 0 | 0 | 408444 | | 0 | 0
For the specified relation it returns:
* pages_dirty : if HAVE_FINCORE constant is define and the platorm provides the relevant information, like pages_mem but for dirtied pages
* group_dirty : if HAVE_FINCORE constant is define and the platorm provides the relevant information, like group_mem but for dirtied pages
-DEBUG
-=====
+## DEBUG
You can debug the PgFincore with the following error level: *DEBUG1* and
*DEBUG5*.
-For example::
+For example:
- set client_min_messages TO debug1; -- debug5 is only usefull to trace each block
+ set client_min_messages TO debug1; -- debug5 is only usefull to trace each block
-REQUIREMENTS
-============
+## REQUIREMENTS
* PgFincore needs mincore() or fincore() and POSIX_FADVISE
-LIMITATIONS
-===========
+## LIMITATIONS
* PgFincore has a limited mode when POSIX_FADVISE is not provided by the platform.
* PgFincore does not work on windows.
-SEE ALSO
-========
+## SEE ALSO
2ndQuadrant, PostgreSQL Expertise, developement, training and 24x7 support:
projects / pgfincore.git / commitdiff