Drop unnecessary searches in the spill lists

Check with IS_MUTABLE() if an MDB_page is spilled, instead of
searching spill lists.  When unspilling, skip parent spill lists.

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 2076990fa785d8535cf427be01c1087431bd06ec..acab891d3846ebb2782d36923a219211a0205223 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -1037,6 +1037,9 @@ typedef struct MDB_page {
        /** Test if a page is a sub page */
 #define IS_SUBP(p)      F_ISSET((p)->mp_flags, P_SUBP)
 
+       /** Test if this non-sub page belongs to the current snapshot */
+#define IS_MUTABLE(txn, p)     ((p)->mp_txnid == (txn)->mt_txnid)
+
        /** Info about overflow page, stored in an F_BIGDATA node */
 typedef struct MDB_ovpage {
        pgno_t  op_pgno;
@@ -2730,31 +2733,34 @@ mdb_page_copy(MDB_page *dst, MDB_page *src, unsigned int psize)
        }
 }
 
-/** Pull a page off the txn's spill list, if present.
- * If a page being referenced was spilled to disk in this txn, bring
- * it back and make it dirty/writable again.
+/** Bring back a page which this txn spilled to disk; make it writable again.
  * @param[in] txn the transaction handle.
- * @param[in] mp the page being referenced. It must not be dirty.
- * @param[out] ret the writable page, if any. ret is unchanged if
- * mp wasn't spilled.
+ * @param[in] mp the spilled page.
+ * @param[out] ret the writable page.
  */
 static int
 mdb_page_unspill(MDB_txn *txn, MDB_page *mp, MDB_page **ret)
 {
        MDB_env *env = txn->mt_env;
-       const MDB_txn *tx2;
        unsigned x;
        pgno_t pgno = mp->mp_pgno, pn = pgno << 1;
 
-       for (tx2 = txn; tx2; tx2=tx2->mt_parent) {
-               if (!tx2->mt_spill_pgs)
-                       continue;
-               x = mdb_midl_search(tx2->mt_spill_pgs, pn);
-               if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pn) {
+       if (txn->mt_dirty_room == 0)
+               return MDB_TXN_FULL;
+
+       /* x = position in current spill list, or 0 */
+       x = 0;
+       if (txn->mt_spill_pgs) {
+               x = mdb_midl_search(txn->mt_spill_pgs, pn);
+               if (! (x <= txn->mt_spill_pgs[0] && txn->mt_spill_pgs[x] == pn))
+                       x = 0;
+       }
+       if (x == 0 && !txn->mt_parent)
+               return MDB_PROBLEM;             /* should be a spilled page */
+
+       {
                        MDB_page *np;
                        int num;
-                       if (txn->mt_dirty_room == 0)
-                               return MDB_TXN_FULL;
                        if (IS_OVERFLOW(mp))
                                num = mp->mp_pages;
                        else
@@ -2770,7 +2776,7 @@ mdb_page_unspill(MDB_txn *txn, MDB_page *mp, MDB_page **ret)
                                else
                                        mdb_page_copy(np, mp, env->me_psize);
                        }
-                       if (tx2 == txn) {
+                       if (x) {
                                /* If in current txn, this page is no longer spilled.
                                 * If it happens to be the last page, truncate the spill list.
                                 * Otherwise mark it as deleted by setting the LSB.
@@ -2786,10 +2792,8 @@ mdb_page_unspill(MDB_txn *txn, MDB_page *mp, MDB_page **ret)
                        mdb_page_dirty(txn, np);
                        np->mp_flags |= P_DIRTY;
                        *ret = np;
-                       break;
-               }
+                       return MDB_SUCCESS;
        }
-       return MDB_SUCCESS;
 }
 
 /** Touch a page: make it dirty and re-insert into tree with updated pgno.
@@ -2807,13 +2811,11 @@ mdb_page_touch(MDB_cursor *mc)
        int rc;
 
        if (!F_ISSET(mp->mp_flags, P_DIRTY)) {
-               if (txn->mt_flags & MDB_TXN_SPILLS) {
-                       np = NULL;
+               if (IS_MUTABLE(txn, mp)) {
                        rc = mdb_page_unspill(txn, mp, &np);
                        if (rc)
                                goto fail;
-                       if (np)
-                               goto done;
+                       goto done;
                }
                if ((rc = mdb_midl_need(&txn->mt_free_pgs, 1)) ||
                        (rc = mdb_page_alloc(mc, 1, &np)))
@@ -6864,7 +6866,6 @@ mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp)
        pgno_t pg = mp->mp_pgno;
        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;
 
@@ -6877,11 +6878,7 @@ mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp)
         * Unsupported in nested txns: They would need to hide the page
         * range in ancestor txns' dirty and spilled lists.
         */
-       if (env->me_pghead &&
-               !txn->mt_parent &&
-               ((mp->mp_flags & P_DIRTY) ||
-                (sl && (x = mdb_midl_search(sl, pn)) <= sl[0] && sl[x] == pn)))
-       {
+       if (IS_MUTABLE(txn, mp) && env->me_pghead && !txn->mt_parent) {
                unsigned i, j;
                pgno_t *mop;
                MDB_ID2 *dl, ix, iy;
@@ -6889,6 +6886,11 @@ mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp)
                if (rc)
                        return rc;
                if (!(mp->mp_flags & P_DIRTY)) {
+                       MDB_IDL sl = txn->mt_spill_pgs;
+                       if (sl)
+                               x = mdb_midl_search(sl, pn);
+                       if (! (sl && x <= sl[0] && sl[x] == pn))
+                               return MDB_PROBLEM;
                        /* This page is no longer spilled */
                        if (x == sl[0])
                                sl[0]--;
@@ -8073,23 +8075,18 @@ current:
                                return rc2;
                        ovpages = ovp.op_pages;
 
-                       /* Is the ov page large enough? */
-                       if (ovpages >= dpages) {
-                         /* Did we dirty it in this txn? */
-                         if (!(omp->mp_flags & P_DIRTY) &&
-                                 (level || (env->me_flags & MDB_WRITEMAP)))
-                         {
-                               rc = mdb_page_unspill(mc->mc_txn, omp, &omp);
-                               if (rc)
-                                       return rc;
-                               level = 0;              /* dirty in this txn or clean */
-                         }
-                         /* Is it dirty? */
-                         if (omp->mp_flags & P_DIRTY) {
+                       /* Is the ov page big enough and from this txn (or a parent)? */
+                       if (ovpages >= dpages && IS_MUTABLE(mc->mc_txn, omp)) {
                                /* yes, overwrite it. Note in this case we don't
                                 * bother to try shrinking the page if the new data
                                 * is smaller than the overflow threshold.
                                 */
+                               if (!(omp->mp_flags & P_DIRTY)) {
+                                       rc = mdb_page_unspill(mc->mc_txn, omp, &omp);
+                                       if (rc)
+                                               return rc;
+                                       level = 0;              /* dirty in this txn */
+                               }
                                if (level > 1) {
                                        /* It is writable only in a parent txn */
                                        size_t sz = (size_t) env->me_psize * ovpages, off;
@@ -8125,7 +8122,6 @@ current:
                                else
                                        memcpy(METADATA(omp), data->mv_data, data->mv_size);
                                return MDB_SUCCESS;
-                         }
                        }
                        if ((rc2 = mdb_ovpage_free(mc, omp)) != MDB_SUCCESS)
                                return rc2;