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[t:3063] #3063 Add comments.

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git-svn-id: file:///svn/toku/tokudb@29786 c7de825b-a66e-492c-adef-691d508d4ae1
This commit is contained in:
Barry Perlman 2013-04-16 23:59:38 -04:00 • committed by Yoni Fogel
parent 3ab1a51c77
commit 6ec3ddee0b
1 changed files with 19 additions and 3 deletions
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20
newbrt/txn.c
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@ -64,6 +64,8 @@ fill_xids (OMTVALUE xev, u_int32_t idx, void *varray) {
return 0;
}
// Create list of root transactions that were live when this txn began.
static int
setup_live_root_txn_list(TOKUTXN txn) {
int r;
@ -84,6 +86,9 @@ setup_live_root_txn_list(TOKUTXN txn) {
return r;
}
// Add this txn to the global list of txns that have their own snapshots.
// (Note, if a txn is a child that creates its own snapshot, then that child xid
// is the xid stored in the global list.)
static int
snapshot_txnids_note_txn(TOKUTXN txn) {
int r;
@ -95,11 +100,14 @@ snapshot_txnids_note_txn(TOKUTXN txn) {
return r;
}
// If live txn is not in reverse live list, then add it.
// If live txn is in reverse live list, update it by setting second xid in pair to new txn that is being started.
static int
live_list_reverse_note_txn_start_iter(OMTVALUE live_xidv, u_int32_t UU(index), void*txnv) {
TOKUTXN txn = txnv;
TXNID xid = txn->txnid64;
TXNID *live_xid = live_xidv;
TXNID xid = txn->txnid64; // xid of new txn that is being started
TXNID *live_xid = live_xidv; // xid on the new txn's live list
OMTVALUE pairv;
XID_PAIR pair;
uint32_t idx;
@ -125,6 +133,14 @@ live_list_reverse_note_txn_start_iter(OMTVALUE live_xidv, u_int32_t UU(index), v
return r;
}
// Maintain the reverse live list. The reverse live list is a list of xid pairs. The first xid in the pair
// is a txn that was live when some txn began, and the second xid in the pair is the newest still-live xid to
// have that first xid in its live list. (The first xid may be closed, it only needed to be live when the
// second txn began.)
// When a new txn begins, we need to scan the live list of this new txn. For each live txn, we either
// add it to the reverse live list (if it is not already there), or update to the reverse live list so
// that this new txn is the second xid in the pair associated with the txn in the live list.
static int
live_list_reverse_note_txn_start(TOKUTXN txn) {
int r;