PostgreSQL数据库WAL——BootStrapXLOG

我会带着你远行 2022-09-01 13:53 142阅读 0赞

void BootStrapXLOG(void) { 
    	CheckPoint	checkPoint;
    	XLogLongPageHeader longpage;
    	XLogRecord *record;
    	char	   *recptr;
    	bool		use_existent;	
    	pg_crc32c	crc;

为安装选择唯一的系统标识符。

struct timeval tv;
    	uint64		sysidentifier;
    	gettimeofday(&tv, NULL);
    	sysidentifier = ((uint64) tv.tv_sec) << 32;
    	sysidentifier |= ((uint64) tv.tv_usec) << 12;
    	sysidentifier |= getpid() & 0xFFF;

产生随机的nonce，主要用于用户不存在时认证失败时的认证请求。nonce用于为不存在的用户创建genuine-looking密码challenge，用于代替真实存储的密码。

char		mock_auth_nonce[MOCK_AUTH_NONCE_LEN];
    	if (!pg_strong_random(mock_auth_nonce, MOCK_AUTH_NONCE_LEN))
    		ereport(PANIC,(errcode(ERRCODE_INTERNAL_ERROR),errmsg("could not generate secret authorization token")));

申请两个XLOG\_BLCKSZ的内存，并将其强制为XLogPageHeader的指针。

char	   *buffer;
        XLogPageHeader page;
    	/* page buffer must be aligned suitably for O_DIRECT */
    	buffer = (char *) palloc(XLOG_BLCKSZ + XLOG_BLCKSZ);
    	page = (XLogPageHeader) TYPEALIGN(XLOG_BLCKSZ, buffer);
    	memset(page, 0, XLOG_BLCKSZ);

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为初始的checkpoint record建立信息

/* First timeline ID is always 1 */
    	ThisTimeLineID = 1;
    	checkPoint.redo = wal_segment_size + SizeOfXLogLongPHD;
    	checkPoint.ThisTimeLineID = ThisTimeLineID;
    	checkPoint.PrevTimeLineID = ThisTimeLineID;
    	checkPoint.fullPageWrites = fullPageWrites;
    	checkPoint.nextFullXid = FullTransactionIdFromEpochAndXid(0, FirstNormalTransactionId);
    	checkPoint.nextOid = FirstBootstrapObjectId;
    	checkPoint.nextMulti = FirstMultiXactId;
    	checkPoint.nextMultiOffset = 0;
    	checkPoint.oldestXid = FirstNormalTransactionId;
    	checkPoint.oldestXidDB = TemplateDbOid;
    	checkPoint.oldestMulti = FirstMultiXactId;
    	checkPoint.oldestMultiDB = TemplateDbOid;
    	checkPoint.oldestCommitTsXid = InvalidTransactionId;
    	checkPoint.newestCommitTsXid = InvalidTransactionId;
    	checkPoint.time = (pg_time_t) time(NULL);
    	checkPoint.oldestActiveXid = InvalidTransactionId;

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