接前文,初步学习pg_control文件之三  继续分析 何时出现 DB_SHUTDOWNING状态: 在正常的shutdown的时候,需要进行checkpoint,所以就在此处,设置pg_control文件的state状态为DB_SHUTDOWNING. /* * Perform a checkpoint --- either during shutdown, or on-the-fly * * flags is a bitwise OR of the following: * CHECKPO…

接前文 初步学习pg_control文件之四,继续看何时出现  DB_IN_CRASH_RECOVERY: 看下面代码就比较清楚了:如果对 InArchiveRecovery 判断值为假,而且 读取出来pg_control文件的 state不是 SHUTDOWNED状态,表明当初没有来得及把SHUTDOWNED状态写入到pg_control文件,那么就是说系统已经崩溃了. /* * This must be called ONCE during postmaster or standalone-…

接前文  初步学习pg_control文件之十四 再看如下这个: int MaxConnections; 应该说,它是一个参考值,在global.c中有如下定义 /* * Primary determinants of sizes of shared-memory structures. MaxBackends is * MaxConnections + autovacuum_max_workers + 1 (it is computed by the GUC * assign hooks fo…

接前文 初步学习pg_control文件之十三 看如下几个: /* * Parameter settings that determine if the WAL can be used for archival * or hot standby. */ int wal_level; int MaxConnections; int max_prepared_xacts; int max_locks_per_xact; PostgreSQL中多次用到了函数数组: /* * Method table…

接前文,初步学习pg_control文件之十二 看这个: * backupStartPoint is the redo pointer of the backup start checkpoint, if * we are recovering from an online backup and haven't reached the end of * backup yet. It is reset to zero when the end of backup is reached, and *…

接前问,初步学习pg_control文件之十一,再来看下面这个 XLogRecPtr minRecoveryPoint; 看其注释: * minRecoveryPoint is updated to the latest replayed LSN whenever we * flush a data change during archive recovery. That guards against * starting archive recovery, aborting it, and r…

接前文  初步学习pg_control文件之十,再看这个 XLogRecPtr prevCheckPoint; /* previous check point record ptr */ 发生了checkpoint的时候,肯定要处理的: /* * Perform a checkpoint --- either during shutdown, or on-the-fly * * flags is a bitwise OR of the following: * CHECKPOINT_IS_SHU…

接前文 初步学习pg_control文件之九 看下面这个 XLogRecPtr checkPoint; /* last check point record ptr */ 看看这个pointer究竟保留了什么 初始化的时候: /* * This func must be called ONCE on system install. It creates pg_control * and the initial XLOG segment. */ void BootStrapXLOG(void) {…

接前文,初步学习pg_control文件之八 来看这个: pg_time_t time; /* time stamp of last pg_control update */ 当初初始化的时候,是这样的: /* * This func must be called ONCE on system install. It creates pg_control * and the initial XLOG segment. */ void BootStrapXLOG(void) { ... Check…

接前文  初步学习pg_control文件之七  继续 看:catalog_version_no 代码如下: static void WriteControlFile(void) { ... /* * Initialize version and compatibility-check fields */ ControlFile->pg_control_version = PG_CONTROL_VERSION; ControlFile->catalog_version_no = CATALOG…