postgresql xlog初始化分析

• 初始化步骤

在initdb的initialize_data_directory

create_xlog_or_symlink()  创建wal日志目录

PG_CMD_OPEN通过 popen打开主程序postgres 

    snprintf(cmd, sizeof(cmd),

             ""%s" --boot -x1 -X %u %s %s %s",

             backend_exec,

             wal_segment_size_mb * (1024 * 1024),

             data_checksums ? "-k" : "",

             boot_options,

             debug ? "-d 5" : "");

 

 

    PG_CMD_OPEN;

    此时，是--boot模式启动，进入到 AuxiliaryProcessMain 

    根据MyAuxProcType 取值为 BootstrapProcess 

BootStrapXLOG();  此处开始初始化

        case 'x':

                MyAuxProcType = atoi(optarg);

                break;

 

    ......

 

        case BootstrapProcess:

 

            /*

             * There was a brief instant during which mode was Normal; this is

             * okay.  We need to be in bootstrap mode during BootStrapXLOG for

             * the sake of multixact initialization.

             */

            SetProcessingMode(BootstrapProcessing);

            bootstrap_signals();

            BootStrapXLOG();

            BootstrapModeMain();

            proc_exit(1);        /* should never return */

• 详细过程

BootStrapXLOG() 只在initdb时执行一次，会创建pg_control文件和wal segment

本文转载自博主原创文章，原文链接：https://blog.csdn.net/senllang/article/details/108433909