Hi, hackers
I don't quite understand FullTransactionIdAdvance(), correct me if I’m wrong.
/*
* Advance a FullTransactionId variable, stepping over xids that would appear
* to be special only when viewed as 32bit XIDs.
*/
static inline void
FullTransactionIdAdvance(FullTransactionId *dest)
{
dest->value++;
/* see FullTransactionIdAdvance() */
if (FullTransactionIdPrecedes(*dest, FirstNormalFullTransactionId))
return;
while (XidFromFullTransactionId(*dest) < FirstNormalTransactionId)
dest->value++;
}
#define XidFromFullTransactionId(x) ((x).value)
#define FullTransactionIdPrecedes(a, b) ((a).value < (b).value)
Can the codes reach line: while (XidFromFullTransactionId(*dest) < FirstNormalTransactionId)?
As we will return if (FullTransactionIdPrecedes(*dest, FirstNormalFullTransactionId)), and the two judgements seem equal.
Another confusion is the comments: /* see FullTransactionIdAdvance() */, is its own itself.
Could anyone explain this? Thanks in advance.