PostgreSQL中ReadBuffer_common函數

數據結構

BufferDesc
共享緩沖區的共享描述符(狀態)數據

typedef struct BufferDesc
{//buffer tagBufferTag   tag;            /* ID of page contained in buffer *///buffer索引編號(0開始)int         buf_id;         /* buffer's index number (from 0) *//* state of the tag, containing flags, refcount and usagecount *///tag狀態,包括flags/refcount和usagecountpg_atomic_uint32 state;//pin-count等待進程IDint         wait_backend_pid;   /* backend PID of pin-count waiter *///空閑鏈表鏈中下一個空閑的bufferint         freeNext;       /* link in freelist chain *///緩沖區內容鎖LWLock      content_lock;   /* to lock access to buffer contents */
} BufferDesc;

BufferTag
Buffer tag標記了buffer存儲的是磁盤中哪個block

typedef struct buftag
{//物理relation標識符RelFileNode rnode;          /* physical relation identifier */ForkNu