PostgreSQL中怎么使用pg_prewarm插件

这篇文章主要介绍"PostgreSQL中怎么使用pg_prewarm插件"，在日常操作中，相信很多人在PostgreSQL中怎么使用pg_prewarm插件问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答"PostgreSQL中怎么使用pg_prewarm插件"的疑惑有所帮助！接下来，请跟着小编一起来学习吧！

使用pg_prewarm插件可"预热"数据.

安装pg_prewarm

[pg12@localhost pg_prewarm]$ makemake -C ../../src/backend generated-headersmake[1]: Entering directory `/home/pg12/source/postgresql-12beta3/src/backend'make -C catalog distprep generated-header-symlinksmake[2]: Entering directory `/home/pg12/source/postgresql-12beta3/src/backend/catalog'make[2]: Nothing to be done for `distprep'.make[2]: Nothing to be done for `generated-header-symlinks'.make[2]: Leaving directory `/home/pg12/source/postgresql-12beta3/src/backend/catalog'make -C utils distprep generated-header-symlinksmake[2]: Entering directory `/home/pg12/source/postgresql-12beta3/src/backend/utils'make[2]: Nothing to be done for `distprep'.make[2]: Nothing to be done for `generated-header-symlinks'.make[2]: Leaving directory `/home/pg12/source/postgresql-12beta3/src/backend/utils'make[1]: Leaving directory `/home/pg12/source/postgresql-12beta3/src/backend'gcc -std=gnu99 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -g -O0 -DOPTIMIZER_DEBUG -g3 -gdwarf-2 -fPIC -I. -I. -I../../src/include  -D_GNU_SOURCE -I/usr/include/libxml2   -c -o pg_prewarm.o pg_prewarm.c -MMD -MP -MF .deps/pg_prewarm.Pogcc -std=gnu99 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -g -O0 -DOPTIMIZER_DEBUG -g3 -gdwarf-2 -fPIC -I. -I. -I../../src/include  -D_GNU_SOURCE -I/usr/include/libxml2   -c -o autoprewarm.o autoprewarm.c -MMD -MP -MF .deps/autoprewarm.Pogcc -std=gnu99 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -g -O0 -DOPTIMIZER_DEBUG -g3 -gdwarf-2 -fPIC -shared -o pg_prewarm.so pg_prewarm.o autoprewarm.o  -L../../src/port -L../../src/common    -Wl,--as-needed -Wl,-rpath,'/appdb/pg12/pg12beta3/lib',--enable-new-dtags  [pg12@localhost pg_prewarm]$ sudo make install[sudo] password for pg12: make -C ../../src/backend generated-headersmake[1]: Entering directory `/home/pg12/source/postgresql-12beta3/src/backend'make -C catalog distprep generated-header-symlinksmake[2]: Entering directory `/home/pg12/source/postgresql-12beta3/src/backend/catalog'make[2]: Nothing to be done for `distprep'.make[2]: Nothing to be done for `generated-header-symlinks'.make[2]: Leaving directory `/home/pg12/source/postgresql-12beta3/src/backend/catalog'make -C utils distprep generated-header-symlinksmake[2]: Entering directory `/home/pg12/source/postgresql-12beta3/src/backend/utils'make[2]: Nothing to be done for `distprep'.make[2]: Nothing to be done for `generated-header-symlinks'.make[2]: Leaving directory `/home/pg12/source/postgresql-12beta3/src/backend/utils'make[1]: Leaving directory `/home/pg12/source/postgresql-12beta3/src/backend'/bin/mkdir -p '/appdb/pg12/pg12beta3/lib/postgresql'/bin/mkdir -p '/appdb/pg12/pg12beta3/share/postgresql/extension'/bin/mkdir -p '/appdb/pg12/pg12beta3/share/postgresql/extension'/bin/install -c -m 755  pg_prewarm.so '/appdb/pg12/pg12beta3/lib/postgresql/pg_prewarm.so'/bin/install -c -m 644 ./pg_prewarm.control '/appdb/pg12/pg12beta3/share/postgresql/extension/'/bin/install -c -m 644 ./pg_prewarm--1.1--1.2.sql ./pg_prewarm--1.1.sql ./pg_prewarm--1.0--1.1.sql  '/appdb/pg12/pg12beta3/share/postgresql/extension/'[pg12@localhost pg_prewarm]$

简单使用

[local]:5432 pg12@testdb=# create extension pg_prewarm;CREATE EXTENSIONTime: 10.460 ms[local]:5432 pg12@testdb=# create table t_prewarm(id int,c1 varchar(20));CREATE TABLETime: 2.796 ms[local]:5432 pg12@testdb=# insert into t_prewarm select x,'c1-'||x from generate_series(1,100000);ERROR:  column "x" does not existLINE 1: insert into t_prewarm select x,'c1-'||x from generate_series...                                     ^Time: 1.565 ms[local]:5432 pg12@testdb=# insert into t_prewarm select x,'c1-'||x from generate_series(1,100000) as x;INSERT 0 100000Time: 242.437 ms[local]:5432 pg12@testdb=# select pg_prewarm('t_prewarm'); pg_prewarm ------------        541(1 row)Time: 2.399 ms

查看buffer cache

[local]:5432 pg12@testdb=# select * from vw_buffercache_hogs;           key            | buffers | dirty_buffers | hog_factor --------------------------+---------+---------------+------------                          |   64640 |             0 |     0.9863 t_prewarm                |     543 |           541 |     0.0083 - system catalogues      |     176 |            26 |     0.0027 - unknown file 32856     |      32 |             1 |     0.0005 - unknown file 32861     |      28 |             2 |     0.0004 - global                 |      19 |             0 |     0.0003 - unknown file 32869     |      15 |             4 |     0.0002 - unknown file 32868     |      13 |             3 |     0.0002 - unknown file 32860     |       8 |             1 |     0.0001 - unknown file 32867     |       8 |             1 |     0.0001 t_copy                   |       8 |             0 |     0.0001 - unknown file 32873     |       7 |             2 |     0.0001 - unknown file 32809     |       7 |             1 |     0.0001 - unknown file 32816     |       6 |             4 |     0.0001 - unknown file 32872     |       5 |             1 |     0.0001 - unknown file 32874     |       4 |             2 |     0.0001 pg_rewrite TOAST         |       4 |             3 |     0.0001 - unknown file 32815     |       4 |             1 |     0.0001 - unknown file 32859     |       3 |             1 |     0.0000 pg_rewrite TOAST index   |       2 |             1 |     0.0000 pg_statistic TOAST index |       2 |             0 |     0.0000 pg_statistic TOAST       |       1 |             0 |     0.0000 t_import                 |       1 |             0 |     0.0000(23 rows)Time: 106.757 ms

使用样例
通过预热,在执行查询前已把数据读取到cache中,可以提升查询性能
测试数据

[local]:5432 pg12@testdb=# drop table if exists t_prewarm;DROP TABLETime: 9.680 ms[local]:5432 pg12@testdb=# create table t_prewarm(id int,c1 varchar(20));CREATE TABLETime: 4.736 ms[local]:5432 pg12@testdb=# [local]:5432 pg12@testdb=# insert into t_prewarm(id,c1) select x,'c1-'||x from generate_series(1,1000000) as x;INSERT 0 1000000Time: 3783.073 ms (00:03.783)

没有预热的情况

[pg12@localhost ~]$ sudo sh -c 'echo 3 >/proc/sys/vm/drop_caches'[sudo] password for pg12: [pg12@localhost ~]$ pg_ctl restartwaiting for server to shut down.... doneserver stoppedwaiting for server to start....2019-08-20 15:26:06.692 CST [2519] LOG:  starting PostgreSQL 12beta3 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16), 64-bit2019-08-20 15:26:06.697 CST [2519] LOG:  listening on IPv6 address "::1", port 54322019-08-20 15:26:06.697 CST [2519] LOG:  listening on IPv4 address "127.0.0.1", port 54322019-08-20 15:26:06.701 CST [2519] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"2019-08-20 15:26:06.739 CST [2519] LOG:  redirecting log output to logging collector process2019-08-20 15:26:06.739 CST [2519] HINT:  Future log output will appear in directory "pg_log". doneserver started[pg12@localhost ~]$ time psql  -d testdb -c "select count(*) from t_prewarm;" -d testdbTiming is on.Expanded display is used automatically.  count  --------- 1000000(1 row)Time: 187.754 msreal  0m0.261suser  0m0.003ssys 0m0.009s

先行预热的情况

[pg12@localhost ~]$ pg_ctl restartwaiting for server to shut down.... doneserver stoppedwaiting for server to start....2019-08-20 15:26:45.444 CST [2537] LOG:  starting PostgreSQL 12beta3 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16), 64-bit2019-08-20 15:26:45.445 CST [2537] LOG:  listening on IPv6 address "::1", port 54322019-08-20 15:26:45.445 CST [2537] LOG:  listening on IPv4 address "127.0.0.1", port 54322019-08-20 15:26:45.448 CST [2537] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"2019-08-20 15:26:45.484 CST [2537] LOG:  redirecting log output to logging collector process2019-08-20 15:26:45.484 CST [2537] HINT:  Future log output will appear in directory "pg_log". doneserver started[pg12@localhost ~]$ sudo sh -c 'echo 3 >/proc/sys/vm/drop_caches'[pg12@localhost ~]$ psql  -d testdb -c "select pg_prewarm('t_prewarm');"Timing is on.Expanded display is used automatically. pg_prewarm ------------       5406(1 row)Time: 109.636 ms[pg12@localhost ~]$ time psql  -d testdb -c "select count(*) from t_prewarm;"Timing is on.Expanded display is used automatically.  count  --------- 1000000(1 row)Time: 88.713 msreal  0m0.103suser  0m0.003ssys 0m0.006s

187.754 ms vs 88.713 ms

下面是使用索引的情况

[pg12@localhost ~]$ sudo sh -c 'echo 3 >/proc/sys/vm/drop_caches'[pg12@localhost ~]$ pg_ctl restartwaiting for server to shut down.... doneserver stoppedwaiting for server to start....2019-08-20 15:30:54.227 CST [2567] LOG:  starting PostgreSQL 12beta3 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16), 64-bit2019-08-20 15:30:54.228 CST [2567] LOG:  listening on IPv6 address "::1", port 54322019-08-20 15:30:54.228 CST [2567] LOG:  listening on IPv4 address "127.0.0.1", port 54322019-08-20 15:30:54.229 CST [2567] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"2019-08-20 15:30:54.249 CST [2567] LOG:  redirecting log output to logging collector process2019-08-20 15:30:54.249 CST [2567] HINT:  Future log output will appear in directory "pg_log". doneserver started[pg12@localhost ~]$ time psql -d testdb -c "select * from t_prewarm where id in (1,500000);"Timing is on.Expanded display is used automatically.   id   |    c1     --------+-----------      1 | c1-1 500000 | c1-500000(2 rows)Time: 8.219 msreal  0m0.041suser  0m0.004ssys 0m0.021s[pg12@localhost ~]$ [pg12@localhost ~]$ sudo sh -c 'echo 3 >/proc/sys/vm/drop_caches'[pg12@localhost ~]$ pg_ctl restartwaiting for server to shut down.... doneserver stoppedwaiting for server to start....2019-08-20 15:31:44.406 CST [2584] LOG:  starting PostgreSQL 12beta3 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-16), 64-bit2019-08-20 15:31:44.409 CST [2584] LOG:  listening on IPv6 address "::1", port 54322019-08-20 15:31:44.409 CST [2584] LOG:  listening on IPv4 address "127.0.0.1", port 54322019-08-20 15:31:44.412 CST [2584] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"2019-08-20 15:31:44.446 CST [2584] LOG:  redirecting log output to logging collector process2019-08-20 15:31:44.446 CST [2584] HINT:  Future log output will appear in directory "pg_log". doneserver started[pg12@localhost ~]$ time psql -d testdb -c "select pg_prewarm('idx_t_prewarm_id');"Timing is on.Expanded display is used automatically. pg_prewarm ------------       2745(1 row)Time: 43.962 msreal  0m0.061suser  0m0.000ssys 0m0.007s[pg12@localhost ~]$ time psql -d testdb -c "select * from t_prewarm where id in (1,500000);"Timing is on.Expanded display is used automatically.   id   |    c1     --------+-----------      1 | c1-1 500000 | c1-500000(2 rows)Time: 5.431 msreal  0m0.010suser  0m0.001ssys 0m0.001s

因为读取索引的block的数不多,因此性能差别不大.

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