1. infomask
/* 元组包含NULL值字段 */
#define HEAP_HASNULL 0x0001 /* has null attribute(s) */
/* 元组包含可变长度的字段 */
#define HEAP_HASVARWIDTH 0x0002 /* has variable-width attribute(s) */
/* 元组包含外部存储的字段 */
#define HEAP_HASEXTERNAL 0x0004 /* has external stored attribute(s) */
/* 由函数 heap_fill_tuple 赋值 */
/* 元组包含OID系统字段 */
#define HEAP_HASOID 0x0008 /* has an object-id field */
/* 由函数 heap_form_tuple, heap_form_minimal_tuple 赋值 */
/*
* 元组的t_cid是组合command id
* 这个标记，常用来标记本事务内的老记录。具体可参看函数：heap_delete, heap_update
*/
#define HEAP_COMBOCID 0x0020 /* t_cid is a combo cid */
/* 元组的xmax用来标志key-shared锁拥有者 */
#define HEAP_XMAX_KEYSHR_LOCK 0x0010 /* xmax is a key-shared locker */
/* 元组的xmax用来标志独占锁拥有者 */
#define HEAP_XMAX_EXCL_LOCK 0x0040 /* xmax is exclusive locker */
/* 元组的xmax如果有效，仅仅是个锁拥有者 */
#define HEAP_XMAX_LOCK_ONLY 0x0080 /* xmax, if valid, is only a locker */
/* 元组的xmax用来标记共享锁拥有者，xmax is a shared locker */
#define HEAP_XMAX_SHR_LOCK (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)
#define HEAP_LOCK_MASK (HEAP_XMAX_SHR_LOCK | HEAP_XMAX_EXCL_LOCK | \
HEAP_XMAX_KEYSHR_LOCK)
/* ------------------------------------------------------------------
* 通过以下代码，可以看出以上关于锁的infomask，是在哪种情况下需要赋值的
* ------------------------------------------------------------------ */
/*
* Possible lock modes for a tuple.
*/
typedef enum LockTupleMode
{
/* SELECT FOR KEY SHARE */
LockTupleKeyShare,
/* SELECT FOR SHARE */
LockTupleShare,
/* SELECT FOR NO KEY UPDATE, and UPDATEs that don't modify key columns */
LockTupleNoKeyExclusive,
/* SELECT FOR UPDATE, UPDATEs that modify key columns, and DELETE */
LockTupleExclusive
} LockTupleMode;
new_infomask |= HEAP_XMAX_LOCK_ONLY;
switch (mode)
{
case LockTupleKeyShare:
new_xmax = add_to_xmax;
new_infomask |= HEAP_XMAX_KEYSHR_LOCK;
break;
case LockTupleShare:
new_xmax = add_to_xmax;
new_infomask |= HEAP_XMAX_SHR_LOCK;
break;
case LockTupleNoKeyExclusive:
new_xmax = add_to_xmax;
new_infomask |= HEAP_XMAX_EXCL_LOCK;
break;
case LockTupleExclusive:
new_xmax = add_to_xmax;
new_infomask |= HEAP_XMAX_EXCL_LOCK;
new_infomask2 |= HEAP_KEYS_UPDATED;
break;
default:
new_xmax = InvalidTransactionId; /* silence compiler */
elog(ERROR, "invalid lock mode");
}
/* 元组的xmin是提交的 */
#define HEAP_XMIN_COMMITTED 0x0100 /* t_xmin committed */
/* 元组的xmin是无效的或回滚的 */
#define HEAP_XMIN_INVALID 0x0200 /* t_xmin invalid/aborted */
#define HEAP_XMIN_FROZEN (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)
/* 元组的xmax是提交的 */
#define HEAP_XMAX_COMMITTED 0x0400 /* t_xmax committed */
/* 元组的xmax是无效的或回滚的 */
#define HEAP_XMAX_INVALID 0x0800 /* t_xmax invalid/aborted */
/*
* 以上infomask，通常通过clog判定。
*/
/* 没找到是怎么赋值的 */
#define HEAP_XMAX_IS_MULTI 0x1000 /* t_xmax is a MultiXactId */
/* 元组是更新版本 */
#define HEAP_UPDATED 0x2000 /* this is UPDATEd version of row */
/* 该infomask的赋值，发生在函数：heap_update */
#define HEAP_MOVED_OFF 0x4000 /* moved to another place by pre-9.0
* VACUUM FULL; kept for binary
* upgrade support */
#define HEAP_MOVED_IN 0x8000 /* moved from another place by pre-9.0
* VACUUM FULL; kept for binary
* upgrade support */
#define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN)
/* 以上infomask，用于9.0以前的vacuum full操作 */
#define HEAP_XACT_MASK 0xFFF0 /* visibility-related bits */
2. infomask2
/* 用11个bits表示表的字段个数 */
#define HEAP_NATTS_MASK 0x07FF /* 11 bits for number of attributes */
/* 赋值操作见函数 HeapTupleHeaderSetNatts */
#define MaxTupleAttributeNumber 1664 /* 8 * 208 */
#define MaxHeapAttributeNumber 1600 /* 8 * 200 */
/* bits 0x1800 are available */
#define HEAP_KEYS_UPDATED 0x2000 /* tuple was updated and key cols
* modified, or tuple deleted */
/* 赋值操作见函数 compute_new_xmax_infomask */
#define HEAP_HOT_UPDATED 0x4000 /* tuple was HOT-updated */
/* 赋值操作减函数：heap_update => HeapTupleSetHotUpdated => HeapTupleHeaderSetHotUpdated */
#define HEAP_ONLY_TUPLE 0x8000 /* this is heap-only tuple */
/* 赋值操作减函数：heap_update => HeapTupleSetHeapOnly => HeapTupleHeaderSetHeapOnly */
#define HEAP2_XACT_MASK 0xE000 /* visibility-related bits */
