Another take on spill_pgs and deletes

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 59a0d51f168ca8c1b08094c72777ebad9d7c37aa..c56d09266ca62bf32e10ada682cd058fa41d3dfb 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -847,7 +847,8 @@ struct MDB_txn {
         */
        MDB_IDL         mt_free_pgs;
        /** The sorted list of dirty pages we temporarily wrote to disk
-        *      because the dirty list was full.
+        *      because the dirty list was full. page numbers in here are
+        *      shifted left by 1, deleted slots have the LSB set.
         */
        MDB_IDL         mt_spill_pgs;
        union {
@@ -1476,12 +1477,12 @@ mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
                if (!txn->mt_spill_pgs)
                        return ENOMEM;
        } else {
-               /* strip any dups */
+               /* purge deleted slots */
                MDB_IDL sl = txn->mt_spill_pgs;
                unsigned int num = sl[0];
-               j=1;
+               j=0;
                for (i=1; i<=num; i++) {
-                       if (sl[j] != sl[i])
+                       if (!(sl[i] & 1))
                                sl[++j] = sl[i];
                }
                sl[0] = j;
@@ -1504,6 +1505,7 @@ mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
        /* Save the page IDs of all the pages we're flushing */
        /* flush from the tail forward, this saves a lot of shifting later on. */
        for (i=dl[0].mid; i && need; i--) {
+               MDB_ID pn = dl[i].mid << 1;
                dp = dl[i].mptr;
                if (dp->mp_flags & P_KEEP)
                        continue;
@@ -1514,8 +1516,8 @@ mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
                        MDB_txn *tx2;
                        for (tx2 = txn->mt_parent; tx2; tx2 = tx2->mt_parent) {
                                if (tx2->mt_spill_pgs) {
-                                       j = mdb_midl_search(tx2->mt_spill_pgs, dl[i].mid);
-                                       if (j <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[j] == dl[i].mid) {
+                                       j = mdb_midl_search(tx2->mt_spill_pgs, pn);
+                                       if (j <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[j] == pn) {
                                                dp->mp_flags |= P_KEEP;
                                                break;
                                        }
@@ -1524,7 +1526,7 @@ mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
                        if (tx2)
                                continue;
                }
-               if ((rc = mdb_midl_append(&txn->mt_spill_pgs, dl[i].mid)))
+               if ((rc = mdb_midl_append(&txn->mt_spill_pgs, pn)))
                        goto done;
                need--;
        }
@@ -1798,13 +1800,13 @@ mdb_page_unspill(MDB_txn *tx0, MDB_page *mp, MDB_page **ret)
        MDB_env *env = tx0->mt_env;
        MDB_txn *txn;
        unsigned x;
-       pgno_t pgno = mp->mp_pgno;
+       pgno_t pgno = mp->mp_pgno, pn = pgno << 1;
 
        for (txn = tx0; txn; txn=txn->mt_parent) {
                if (!txn->mt_spill_pgs)
                        continue;
-               x = mdb_midl_search(txn->mt_spill_pgs, pgno);
-               if (x <= txn->mt_spill_pgs[0] && txn->mt_spill_pgs[x] == pgno) {
+               x = mdb_midl_search(txn->mt_spill_pgs, pn);
+               if (x <= txn->mt_spill_pgs[0] && txn->mt_spill_pgs[x] == pn) {
                        MDB_page *np;
                        int num;
                        if (IS_OVERFLOW(mp))
@@ -1825,13 +1827,12 @@ mdb_page_unspill(MDB_txn *tx0, MDB_page *mp, MDB_page **ret)
                        if (txn == tx0) {
                                /* If in current txn, this page is no longer spilled.
                                 * If it happens to be the last page, truncate the spill list.
-                                * Otherwise temporarily dup its neighbor over it. Dups will
-                                * be stripped out later by the next mdb_page_spill run.
+                                * Otherwise mark it as deleted by setting the LSB.
                                 */
                                if (x == txn->mt_spill_pgs[0])
                                        txn->mt_spill_pgs[0]--;
                                else
-                                       txn->mt_spill_pgs[x] = txn->mt_spill_pgs[x+1];
+                                       txn->mt_spill_pgs[x] |= 1;
                        }       /* otherwise, if belonging to a parent txn, the
                                 * page remains spilled until child commits
                                 */
@@ -2823,9 +2824,10 @@ mdb_txn_commit(MDB_txn *txn)
                        len = x;
                        /* zero out our dirty pages in parent spill list */
                        for (i=1; i<=src[0].mid; i++) {
-                               if (src[i].mid < parent->mt_spill_pgs[x])
+                               MDB_ID pn = src[i].mid << 1;
+                               if (pn < parent->mt_spill_pgs[x])
                                        continue;
-                               if (src[i].mid > parent->mt_spill_pgs[x]) {
+                               if (pn > parent->mt_spill_pgs[x]) {
                                        if (x <= 1)
                                                break;
                                        x--;
@@ -4533,8 +4535,9 @@ mdb_page_get(MDB_txn *txn, pgno_t pgno, MDB_page **ret, int *lvl)
                         * leave that unless page_touch happens again).
                         */
                        if (tx2->mt_spill_pgs) {
-                               x = mdb_midl_search(tx2->mt_spill_pgs, pgno);
-                               if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pgno) {
+                               MDB_ID pn = pgno << 1;
+                               x = mdb_midl_search(tx2->mt_spill_pgs, pn);
+                               if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pn) {
                                        p = (MDB_page *)(env->me_map + env->me_psize * pgno);
                                        goto done;
                                }
@@ -4764,6 +4767,7 @@ mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp)
        unsigned x = 0, ovpages = mp->mp_pages;
        MDB_env *env = txn->mt_env;
        MDB_IDL sl = txn->mt_spill_pgs;
+       MDB_ID pn = pg << 1;
        int rc;
 
        DPRINTF(("free ov page %"Z"u (%d)", pg, ovpages));
@@ -4778,7 +4782,7 @@ mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp)
        if (env->me_pghead &&
                !txn->mt_parent &&
                ((mp->mp_flags & P_DIRTY) ||
-                (sl && (x = mdb_midl_search(sl, pg)) <= sl[0] && sl[x] == pg)))
+                (sl && (x = mdb_midl_search(sl, pn)) <= sl[0] && sl[x] == pn)))
        {
                unsigned i, j;
                pgno_t *mop;
@@ -4788,9 +4792,10 @@ mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp)
                        return rc;
                if (!(mp->mp_flags & P_DIRTY)) {
                        /* This page is no longer spilled */
-                       for (; x < sl[0]; x++)
-                               sl[x] = sl[x+1];
-                       sl[0]--;
+                       if (x == sl[0])
+                               sl[0]--;
+                       else
+                               sl[x] |= 1;
                        goto release;
                }
                /* Remove from dirty list */