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mdbx: backport - clean up and comment C_UNTRACK.

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Don't use it as a "cursor is tracked" hint in mdb_pages_xkeep().
It's been harmless so far, but would break after mdb_cursor_copy().
Checking m0 directly short-circuits better anyway.

Change-Id: Ibf180214db603e08ed11e298cff85866eb79f4bb
This commit is contained in:
Hallvard Furuseth 2016-12-10 21:42:39 +01:00 committed by Leo Yuriev
parent fe4e9993d6
commit fca2f4d929
1 changed files with 12 additions and 11 deletions
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23
mdb.c
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@ -1723,13 +1723,9 @@ mdb_pages_xkeep(MDB_cursor *mc, unsigned pflags, int all)
unsigned i, j; unsigned i, j;
int rc = MDB_SUCCESS, level; int rc = MDB_SUCCESS, level;
/* Mark pages seen by cursors */ /* Mark pages seen by cursors: First m0, then tracked cursors */
if (mc->mc_flags & C_UNTRACK) for (i = txn->mt_numdbs;; ) {
mc = NULL; /* will find mc in mt_cursors */ if (mc->mc_flags & C_INITIALIZED) {
for (i = txn->mt_numdbs;; mc = txn->mt_cursors[--i]) {
for (; mc; mc=mc->mc_next) {
if (!(mc->mc_flags & C_INITIALIZED))
continue;
for (m3 = mc;; m3 = &mx->mx_cursor) { for (m3 = mc;; m3 = &mx->mx_cursor) {
mp = NULL; mp = NULL;
for (j=0; j<m3->mc_snum; j++) { for (j=0; j<m3->mc_snum; j++) {
@ -1748,10 +1744,13 @@ mdb_pages_xkeep(MDB_cursor *mc, unsigned pflags, int all)
break; break;
} }
} }
if (i == 0) mc = mc->mc_next;
break; for (; !mc || mc == m0; mc = txn->mt_cursors[--i])
if (i == 0)
goto mark_done;
} }
mark_done:
if (all) { if (all) {
/* Mark dirty root pages */ /* Mark dirty root pages */
for (i=0; i<txn->mt_numdbs; i++) { for (i=0; i<txn->mt_numdbs; i++) {
@ -7727,7 +7726,10 @@ mdb_cursor_close(MDB_cursor *mc)
if (mc) { if (mc) {
mdb_ensure(NULL, mc->mc_signature == MDBX_MC_SIGNATURE); mdb_ensure(NULL, mc->mc_signature == MDBX_MC_SIGNATURE);
if (!mc->mc_backup) { if (!mc->mc_backup) {
/* remove from txn, if tracked */ /* Remove from txn, if tracked.
* A read-only txn (!C_UNTRACK) may have been freed already,
* so do not peek inside it. Only write txns track cursors.
*/
if ((mc->mc_flags & C_UNTRACK) && mc->mc_txn->mt_cursors) { if ((mc->mc_flags & C_UNTRACK) && mc->mc_txn->mt_cursors) {
MDB_cursor **prev = &mc->mc_txn->mt_cursors[mc->mc_dbi]; MDB_cursor **prev = &mc->mc_txn->mt_cursors[mc->mc_dbi];
while (*prev && *prev != mc) prev = &(*prev)->mc_next; while (*prev && *prev != mc) prev = &(*prev)->mc_next;
@ -8578,7 +8580,6 @@ mdb_del0(MDB_txn *txn, MDB_dbi dbi,
* run out of space, triggering a split. We need this * run out of space, triggering a split. We need this
* cursor to be consistent until the end of the rebalance. * cursor to be consistent until the end of the rebalance.
*/ */
mc.mc_flags |= C_UNTRACK;
mc.mc_next = txn->mt_cursors[dbi]; mc.mc_next = txn->mt_cursors[dbi];
txn->mt_cursors[dbi] = &mc; txn->mt_cursors[dbi] = &mc;
rc = mdb_cursor_del(&mc, flags); rc = mdb_cursor_del(&mc, flags);