利用系统缓存提高PostgreSQL操作效率
环境介绍：
OS：Centos 6.4 64bit
Database：PostgreSQL9.4
Memory：2G
CPU：1核
下载安装：
在pgfoundry下载pgfincore-v1.1.1.tar.gz，，将源码解压到数据库源码下的contrib下。不要在其github上下载，目前应该有一些bug，最新版本为1.1.1，1.1.2在我试用的时候发现大部分函数无法使用。
其次在我编译时一直出现如下错误：
[postgres@localhost pgfincore-1.1.1]$ make /bin/sh: pg_config: command not found make: pg_config: Command not found cp pgfincore.sql pgfincore--1.1.1.sql cp: cannot create regular file `pgfincore--1.1.1.sql': Permission denied make: *** [pgfincore--1.1.1.sql] Error 1所以在此我修改了一下Makefile文件，内容如下：
# contrib/pgfincore/Makefile MODULE_big = pgfincore OBJS = pgfincore.o EXTENSION = pgfincore DATA = pgfincore--1.1.1.sql pgfincore--unpackaged--1.1.1.sql ifdef USE_PGXS PG_CONFIG = pg_config PGXS := $(shell $(PG_CONFIG) --pgxs) include $(PGXS) else subdir = contrib/pgfincore top_builddir = ../.. include $(top_builddir)/src/Makefile.global include $(top_srcdir)/contrib/contrib-global.mk现在进行make，即可：
[postgres@localhost pgfincore-1.1.1]$ make gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -g -O2 -fpic -I. -I. -I../../src/include -D_GNU_SOURCE -c -o pgfincore.o pgfincore.c pgfincore.c: In function ‘pgsysconf’: pgfincore.c:227: warning: implicit declaration of function ‘heap_form_tuple’ pgfincore.c:227: warning: assignment makes pointer from integer without a cast pgfincore.c: In function ‘pgfadvise’: pgfincore.c:477: warning: assignment makes pointer from integer without a cast pgfincore.c: In function ‘pgfadvise_loader’: pgfincore.c:710: warning: assignment makes pointer from integer without a cast pgfincore.c: In function ‘pgfincore’: pgfincore.c:1016: warning: assignment makes pointer from integer without a cast gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -g -O2 -fpic -shared -o pgfincore.so pgfincore.o -L../../src/port -L../../src/common -Wl,--as-needed -Wl,-rpath,'/opt/hg3.0/lib',--enable-new-dtags [postgres@localhost pgfincore-1.1.1]$ make install /bin/mkdir -p '/opt/hg3.0/lib/postgresql' /bin/mkdir -p '/opt/hg3.0/share/postgresql/extension' /bin/mkdir -p '/opt/hg3.0/share/postgresql/extension' /usr/bin/install -c -m 755 pgfincore.so '/opt/hg3.0/lib/postgresql/pgfincore.so' /usr/bin/install -c -m 644 pgfincore.control '/opt/hg3.0/share/postgresql/extension/' /usr/bin/install -c -m 644 pgfincore--1.1.1.sql pgfincore--unpackaged--1.1.1.sql '/opt/hg3.0/share/postgresql/extension/' [postgres@localhost pgfincore-1.1.1]$实验记录：
1、安装：
[postgres@localhost bin]$ ./psql psql (9.4.5) Type "help" for help. postgres=# create extension pgfincore ; CREATE EXTENSION postgres=# select * from pg_extension ; extname | extowner | extnamespace | extrelocatable | extversion | extconfig | extcondition -----------+----------+--------------+----------------+------------+-----------+ -------------- plpgsql | 10 | 11 | f | 1.0 | | pgfincore | 10 | 2200 | t | 1.1.1 | | (2 rows) postgres=#
2、准备工作：记录比较使用pgfincore前后的性能差，使用插件pg_stat_statments记录每条sql的使用时间。
其次将shared_buffer改为16mb，减少其对pgfincore的影响。
postgres=# create extension pg_stat_statements ; CREATE EXTENSION postgres=# select * from pg_extension ; extname | extowner | extnamespace | extrelocatable | extversion | ex tconfig | extcondition --------------------+----------+--------------+----------------+------------+--- --------+-------------- plpgsql | 10 | 11 | f | 1.0 | | pgfincore | 10 | 2200 | t | 1.1.1 | | pg_stat_statements | 10 | 2200 | t | 1.2 | | (3 rows)
3、建立表testmem，分别在使用和不适用pgfincore情况下进行select, update, delete的操作，并对比执行时间，在这里为了更好的去作比较，建立三张表testmem1，testmem2，testmem3，分别进行三种操作进行对比。并插入相同的数据。
[postgres@localhost bin]$ ./psql psql (9.4.5) Type "help" for help. postgres=# \d No relations found. postgres=# create table testmem1(t1 int, t2 text, t3 text, t4 bigint, t5 text, t6 text, t7 varchar, t8 char(22), t9 numeric);CREATE TABLE postgres=# create table testmem2(t1 int, t2 text, t3 text, t4 bigint, t5 text, t6 text, t7 varchar, t8 char(22), t9 numeric); CREATE TABLE postgres=# create table testmem3(t1 int, t2 text, t3 text, t4 bigint, t5 text, t6 text, t7 varchar, t8 char(22), t9 numeric); CREATE TABLE postgres=# insert into testmem1 select generate_series(1,999999), 'wangshuo'||generate_series(1,999999)::text||random()::text, generate_series(1,999999)::text||'sure',generate_series(1,999999), random()::text,random()::text,random()::text,'liuyuanyuan', generate_series(1,999999); INSERT 0 999999 postgres=# select pg_relation_size('testmem1')/1024/1024||'MB'; ?column? ---------- 166MB (1 row) postgres=# insert into testmem2 select generate_series(1,999999), 'wangshuo'||generate_series(1,999999)::text||random()::text, generate_series(1,999999)::text||'sure',generate_series(1,999999), random()::text,random()::text,random()::text,'liuyuanyuan', generate_series(1,999999); INSERT 0 999999 postgres=# insert into testmem3 select generate_series(1,999999), 'wangshuo'||generate_series(1,999999)::text||random()::text, generate_series(1,999999)::text||'sure',generate_series(1,999999), random()::text,random()::text,random()::text,'liuyuanyuan', generate_series(1,999999); INSERT 0 999999 postgres=# select pg_relation_size('testmem2')/1024/1024||'MB'; ?column? ---------- 166MB (1 row) postgres=# select pg_relation_size('testmem3')/1024/1024||'MB'; ?column? ---------- 166MB (1 row) postgres=# 三种操作性能对比：
postgres=# select * from testmem1 where t1 < 789432 and t1 > 1208; t1 | t2 | t3 | t4 | t5 | t6 | t7 | t8 | t9 --------+------------------------------------+------------+--------+------------ ----------+----------------------+----------------------+----------------------- -+-------- 1209 | wangshuo12090.964191045146435 | 1209sure | 1209 | 0.075409890 152514 | 0.468206159770489 | 0.692714618053287 | liuyuanyuan | 1209 1210 | wangshuo12100.652063825167716 | 1210sure | 1210 | 0.026932121 720165 | 0.802233531605452 | 0.706556385848671 | liuyuanyuan | 1210 1211 | wangshuo12110.724962076637894 | 1211sure | 1211 | 0.732285636 477172 | 0.816857317462564 | 0.868489125277847 | liuyuanyuan | 1211 1212 | wangshuo12120.0478062951005995 | 1212sure | 1212 | 0.190716865 006834 | 0.898683389648795 | 0.537546805106103 | liuyuanyuan | 1212 1213 | wangshuo12130.582098880317062 | 1213sure | 1213 | 0.161297460 086644 | 0.395338968373835 | 0.684920639265329 | liuyuanyuan | 1213 1214 | wangshuo12140.53120110463351 | 1214sure | 1214 | 0.253457680 810243 | 0.428548218682408 | 0.671272001229227 | liuyuanyuan postgres=# update testmem2 set t7 = random()::text where t1 < 789432 and t1 > 1208; UPDATE 788223 postgres=# delete from testmem3 where t1 < 789432 and t1 > 1208; DELETE 788223
使用pgfincore前：通过查询表pg_stat_statments查看三种操作时间：
postgres=# SELECT query, calls, total_time, rows, 100.0 * shared_blks_hit / nullif(shared_blks_hit + shared_blks_read, 0) AS hit_percent FROM pg_stat_statements ORDER BY total_time DESC; -[ RECORD 1 ]------------------------------------------------------ query | update testmem2 set t7 = random()::text where t1 < ? and t1 > ?; calls | 1 total_time | 14303.53 rows | 788223 hit_percent | 97.7162513440240383 -[ RECORD 2 ]------------------------------------------------------ query | delete from testmem3 where t1 < ? and t1 > ?; calls | 1 total_time | 5256.305 rows | 788223 hit_percent | 97.4004941321803582 -[ RECORD 6 ]------------------------------------------------------ query | select * from testmem1 where t1 < ? and t1 > ?; calls | 1 total_time | 2397.866 rows | 788223 hit_percent | 0.15039714245429336843
使用pgfincore后：通过查询表pg_stat_statments查看三种操作时间（重启机器后，重新建库，重新建表、插数据）：
SELECT query, calls, total_time, rows, 100.0 * shared_blks_hit / nullif(shared_blks_hit + shared_blks_read, 0) AS hit_percent FROM pg_stat_statements ORDER BY total_time DESC; -[ RECORD 1 ]------------------------------------------------------ query | update testmem2 set t7 = random()::text where t1 < ? and t1 > ?; calls | 1 total_time | 6800.237 rows | 788223 hit_percent | 97.6908892215405358 -[ RECORD 2 ]------------------------------------------------------ query | delete from testmem3 where t1 < ? and t1 > ?; calls | 1 total_time | 3295.312 rows | 788223 hit_percent | 97.3715873996294009 -[ RECORD 3 ]------------------------------------------------------ query | select * from testmem1 where t1 < ? and t1 > ?; calls | 1 total_time | 891.002 rows | 788223 hit_percent | 0.000000000000000000000000
明显看出当执行select时速度提升明显，其他的时间提升并不明显，这是因为数据还需要进行IO操作，所以在这里速度提升应该仅仅是读入的时间节省掉了。
postgres=# select pgfadvise_willneed('testmem1'); -[ RECORD 1 ]------+------------------------------------- pgfadvise_willneed | (base/13003/16384,4096,42554,279311) postgres=# select * from pgfincore('testmem1'); -[ RECORD 1 ]-+----------------- relpath | base/13003/16384 segment | 0 os_page_size | 4096 rel_os_pages | 42554 pages_mem | 42554 group_mem | 1 os_pages_free | 279317 databit | postgres=# select count(*) from testmem1 where t1 < 99999 and t1 > 12; -[ RECORD 1 ] count | 99986 postgres=# insert into testmem1 select generate_series(1,9999), 'wangshuo'||generate_series(1,9999)::text||random()::text, generate_series(1,9999)::text||'sure',generate_series(1,9999), random()::text,random()::text,random()::text,'liuyuanyuan', generate_series(1,9999); INSERT 0 9999 postgres=# select * from pgfincore('testmem1');-[ RECORD 1 ]-+----------------- relpath | base/13003/16384 segment | 0 os_page_size | 4096 rel_os_pages | 42980 pages_mem | 42980 group_mem | 1 os_pages_free | 277433 databit | postgres=# select pg_relation_size('testmem1'); -[ RECORD 1 ]----+---------- pg_relation_size | 176046080 postgres=# select 42980*4096; -[ RECORD 1 ]------- ?column? | 176046080 postgres=# insert into testmem1 select generate_series(1,999999), 'wangshuo'||generate_series(1,999999)::text||random()::text, generate_series(1,999999)::text||'sure',generate_series(1,999999), random()::text,random()::text,random()::text,'liuyuanyuan', generate_series(1,999999); INSERT 0 999999 postgres=# select * from pgfincore('testmem1'); -[ RECORD 1 ]-+----------------- relpath | base/13003/16384 segment | 0 os_page_size | 4096 rel_os_pages | 85532 pages_mem | 6188 group_mem | 22 os_pages_free | 403050 databit | postgres=# 上面这个实验验证了willneed会将小部分新加入的数据加载到cache中，能够快速的定位查找，但是当插入数据量较大时，就不会及时的写入到cache中了。 总结：pgfincore目前适用于数据量非常大、更新不频繁、更新量较小的表去加载到缓存中，有助于提高应用效率。
插件函数介绍：
这里会对函数进行介绍，并对所有函数进行操作实验。
1、pgsysconf：
这个函数输出OS block的大小（os_page_size），OS中剩余的page数(os_pages_free)和OS拥有的page总数(os_total_pages)。
postgres=# select * from pgsysconf()； os_page_size | os_pages_free | os_total_pages --------------+---------------+---------------- 4096 | 167445 | 476688 (1 row)2、pgsysconf_pretty：
这个函数和上面的一样，仅仅是输出更易懂些。
postgres=# select * from pgsysconf_pretty(); os_page_size | os_pages_free | os_total_pages --------------+---------------+---------------- 4096 bytes | 654 MB | 1862 MB (1 row)
3、pgfadvise_willneed：
这个函数是
输出文件名（relpath），OS block大小（os_page_size），对象占用系统page数（rel_os_pages）,OS剩余的page数（os_pages_free）。
postgres=# select * from pgfadvise_willneed('testmem1'); relpath | os_page_size | rel_os_pages | os_pages_free ------------------+--------------+--------------+--------------- base/13003/16384 | 4096 | 42554 | 167294 (1 row) 4、pgfadvise_dontneed： 这个函数对当前对象设置dontneed标记。dontneed标记的意思就是当操作系统需要释放内存时优先释放标记为dontneed的pages。输出的意义和上面一致，就不多做介绍了。
postgres=# select * from pgfadvise_dontneed('testmem1'); relpath | os_page_size | rel_os_pages | os_pages_free ------------------+--------------+--------------+--------------- base/13003/16384 | 4096 | 42554 | 332798 (1 row) 5、pgfadvise_NORMAL、pgfadvise_SEQUENTIAL、pgfadvise_RANDOM： 和pgfadvise_dontneed大同小异，分别将对象标记为normal、sequential、random，意思按照字面意思理解就可以了。
其实pgfadvise是一个单独的函数，参数是relname,fork,action,含义分别为对象名、文件分支名以及行为id，上面的3、4、5函数都是输入不同参数而设置的函数，其中willneed、dontneed、normal、sequential、random的值分别是10、20、30、40、50，且默认fork为main，即表文件。
这里的pgfadvise主要调用了Linux下的函数posix_fadvise，标记值也是posix_fadvise所需要的。
6、pgfincore：
这个函数是是提供对象在操作系统缓存中的信息的。
它分为三个函数，参数分别为（relname, fork, getdatabit），（relname, getdatabit），（relname），三个参数意思为对象名，进程名（这个地方默认是main），是否要显示databit（很长，注意显示），第一个函数需要全部输入，第二个函数默认fork为main，第三个函数默认fork为main，getdatabit为false。
它输出的是文件位置及名称（relpath），文件顺序（segment），OS page或block大小（os_page_size），对象占用系统缓存需要的页面个数（rel_os_pages），对象已经占用缓存页面个数（pages_mem），在缓存中连续的页面组的个数（group_mem），OS剩余的page数（os_pages_free），加载信息的位图（databit）。
postgres=# select * from pgfincore('testmem1', 'main', false); -[ RECORD 1 ]-+----------------- relpath | base/13003/16384 segment | 0 os_page_size | 4096 rel_os_pages | 42554 pages_mem | 2 group_mem | 1 os_pages_free | 325475 databit | postgres=# select * from pgfincore('testmem1', false); -[ RECORD 1 ]-+----------------- relpath | base/13003/16384 segment | 0 os_page_size | 4096 rel_os_pages | 42554 pages_mem | 2 group_mem | 1 os_pages_free | 325475 databit | postgres=# select * from pgfincore('testmem1'); -[ RECORD 1 ]-+----------------- relpath | base/13003/16384 segment | 0 os_page_size | 4096 rel_os_pages | 42554 pages_mem | 2 group_mem | 1 os_pages_free | 325475 databit | 7、pgfadvise_loader：
这个函数可以对页面缓存直接进行两方面的作用。因此，它能通过页面的位图在缓存中来对页面进行加载或卸载。
它分为两个函数和上边的类似，就是设置缺省值，的输入参数是（relname, fork, segment, load, unload, databit）和（relname, segment, load, unload, databit），分别是对象名，文件分支名，文件序号，是否加载，是否卸载，位图信息。第二个函数默认fork为main。
它输出的是物理文件名及path（relpath），OS page或block大小（os_page_size）, OS中剩余的page数(os_pages_free)，加载的page数（pages_load），卸载的page数（pages_unload）。
postgres=# select * from pgfincore('testmem1'); -[ RECORD 1 ]-+----------------- relpath | base/13003/16384 segment | 0 os_page_size | 4096 rel_os_pages | 42554 pages_mem | 0 group_mem | 0 os_pages_free | 331290 databit | postgres=# select * from pgfadvise_loader('testmem1', 0, true, true, B'1100'); -[ RECORD 1 ]--+----------------- relpath | base/13003/16384 os_page_size | 4096 os_pages_free | 331294 pages_loaded | 2 pages_unloaded | 2 postgres=# select * from pgfincore('testmem1'); -[ RECORD 1 ]-+----------------- relpath | base/13003/16384 segment | 0 os_page_size | 4096 rel_os_pages | 42554 pages_mem | 2 group_mem | 1 os_pages_free | 331290 databit | 本文由用户 jopen 自行上传分享，仅供网友学习交流。所有权归原作者，若您的权利被侵害，请联系管理员。
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