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目录

增加guc参数

 initdb参数传递

 pg_ctl参数传递

参数验证

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新增guc参数pg_test_parameter，支持从initdb和pg_ctl命令中传递/覆盖参数，使用场景是TDE透明加密指定算法或者某些定制化需求。

增加guc参数

        pg源码是这样描述guc参数的：它是全局配置管理模式（包括set命令、conf配置文件或其他方式指定参数），我们postgresql.conf文件中所有参数都在这里面，但它是conf文件超集，还有一些配置是不能对用户提供的。

* Support for grand unified configuration scheme, including SET
* command, configuration file, and command line options.
* See src/backend/utils/misc/README for more information.

比如postgresql.conf中定义wal段大小的参数：

		{"max_wal_size", PGC_SIGHUP, WAL_CHECKPOINTS,gettext_noop("Sets the WAL size that triggers a checkpoint."),NULL,GUC_UNIT_MB},

本次我们新增1个guc参数pg_test_parameter，直接仿照src/utils/misc/guc.c文件中的data_directory参数定义，这个参数指定后也是不允许修改的，并且在initdb和pg_ctl都需要指定，跟我们本次想实现的参数类似，但是两者的GucContext和config_group类型有差异；

		{"data_directory", PGC_POSTMASTER, FILE_LOCATIONS,gettext_noop("Sets the server's data directory."),NULL,GUC_SUPERUSER_ONLY | GUC_DISALLOW_IN_AUTO_FILE},&data_directory,NULL,NULL, NULL, NULL},{{"pg_test_parameter", PGC_INTERNAL, PRESET_OPTIONS,gettext_noop("Sets pg test parameter."),NULL,GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE},&pg_test_parameter,NULL,NULL, NULL, NULL},

定义后就会有pg_test_parameter这个全局参数了，但是定义参数要用起来。 

 initdb参数传递

支持initdb方式传递pg_test_parameter，需要接受参数输入，这里增加-p的参数读取与参数解析逻辑，在/src/bin/initdb/initdb.c中：

//增加-p参数printf(_("  -p, --pg-test-parameter                show pg_test_parameter settings\n"));
//在main函数中把它定义为必须传递的参数static struct option long_options[] = {// ...{"pg-test-parameter", required_argument, NULL, 'N'}// ...};
//增加参数解析while ((c = getopt_long(argc, argv, "A:dD:E:gkL:nNsST:U:WX:p:", long_options, &option_index)) != -1){switch (c){// ...case 'p':pg_test_parameter = pg_strdup(optarg);break;// ...}}
// 增加日志if (pg_test_parameter){printf(_("pg_test_parameter ok. \n"));}elseprintf(_("pg_test_parameter not ok..\n"));

这里完成initdb的参数传递，直接通过initdb -p abc方式将pg_test_parameter参数设置成abc。

 pg_ctl参数传递

这里传入后根据需要读取

// 增加参数读入while ((flag = getopt(argc, argv, "B:p:c:d:D:Fkr:x:X:-:")) != -1){switch (flag){// ...case 'p':pg_test_parameter = pstrdup(optarg);break;// ...
}
}

参数验证

initdb指定-p参数：

 ./initdb -D ~/data -p abc
The files belonging to this database system will be owned by user "postgres".
This user must also own the server process.The database cluster will be initialized with locale "en_US.UTF-8".
The default database encoding has accordingly been set to "UTF8".
The default text search configuration will be set to "english".Data page checksums are disabled.creating directory /home/postgres/data ... ok
creating subdirectories ... ok
selecting dynamic shared memory implementation ... posix
selecting default max_connections ... 100
selecting default shared_buffers ... 128MB
selecting default time zone ... Asia/Shanghai
creating configuration files ... ok
running bootstrap script ... ok
performing post-bootstrap initialization ... ok
syncing data to disk ... ok
pg_test_parameter ok.initdb: warning: enabling "trust" authentication for local connections
You can change this by editing pg_hba.conf or using the option -A, or
--auth-local and --auth-host, the next time you run initdb.Success. You can now start the database server using:./pg_ctl -D /home/postgres/data -l logfile start

查看参数（调试中）：

postgres=# show pg_test_parameter;pg_test_parameter
-------------------(1 row)