multimap-memcachedb.patch

Index: memcachedb.c
===================================================================
--- memcachedb.c	(revision 98)
+++ memcachedb.c	(working copy)
@@ -910,6 +910,69 @@
     out_string(c, "ERROR");
 }
 
+static int txn_begin_and_cursor(DB_TXN **txn, DBC **cursorp, u_int32_t flags)
+{
+    int ret;
+
+    /* transcation and cursor */
+    ret = env->txn_begin(env, NULL, txn, 0);
+    if (ret != 0)
+        return ret;
+
+    /* Get a cursor, we use 2 degree isolation */
+    ret = dbp->cursor(dbp, *txn, cursorp, flags); 
+    if (ret != 0)
+        return ret;
+
+    return 0;
+}
+
+static int conn_grow(conn *c, int i)
+{
+    if (i < c->isize)
+        return 0;
+
+    item **new_list = realloc(c->ilist, sizeof(item *) * c->isize * 2);
+
+    if (!new_list)
+        return -1;
+
+    c->isize *= 2;
+    c->ilist = new_list;
+
+    return 0;
+}
+
+static int conn_push_value(conn *c, item *it, int i)
+{
+    int ret;
+
+    ret = conn_grow(c, i);
+    if (ret)
+        return ret;
+
+    /*
+     * Construct the response. Each hit adds three elements to the
+     * outgoing data list:
+     *   "VALUE "
+     *   key
+     *   " " + flags + " " + data length + "\r\n" + data (with \r\n)
+     */
+
+    if (add_iov(c, "VALUE ", 6) != 0 ||
+       add_iov(c, ITEM_key(it), it->nkey) != 0 ||
+       add_iov(c, ITEM_suffix(it), it->nsuffix + it->nbytes) != 0) {
+        return -1;
+    }
+
+    if (settings.verbose > 1)
+        fprintf(stderr, ">%d sending key %s\n", c->sfd, ITEM_key(it));
+
+    *(c->ilist + i) = it;
+
+    return 0;
+}
+
 /* ntokens is overwritten here... shrug.. */
 static inline void process_get_command(conn *c, token_t *tokens, size_t ntokens) {
     char *key;
@@ -924,6 +987,9 @@
 
     do {
         while(key_token->length != 0) {
+            int ret;
+            DB_TXN *txn;
+            DBC *cursorp;
 
             key = key_token->value;
             nkey = key_token->length;
@@ -939,48 +1005,38 @@
             }
 
             stats_get_cmds++;
-            
-            it = item_get(key, nkey);
 
-            if (it) {
-                if (i >= c->isize) {
-                    item **new_list = realloc(c->ilist, sizeof(item *) * c->isize * 2);
-                    if (new_list) {
-                        c->isize *= 2;
-                        c->ilist = new_list;
-                    } else { 
-                        item_free(it);
-                        it = NULL;
-                        break;
-                    }
-                }
+            ret = txn_begin_and_cursor(&txn, &cursorp, DB_READ_COMMITTED);
+            if (ret != 0) {
+                fprintf(stderr, "envp->txn_begin or dbp->cursor: %s\n",
+                        db_strerror(ret));
+                out_string(c, "SERVER_ERROR envp->txn_begin or dbp->cursor");
+                return;
+            }
 
-                /*
-                 * Construct the response. Each hit adds three elements to the
-                 * outgoing data list:
-                 *   "VALUE "
-                 *   key
-                 *   " " + flags + " " + data length + "\r\n" + data (with \r\n)
-                 */
+            it = item_cget(cursorp, key, nkey, DB_SET);
+            if (it)
+                stats_get_hits++;
+            else
+                stats_get_misses++;
 
-                if (add_iov(c, "VALUE ", 6) != 0 ||
-                   add_iov(c, ITEM_key(it), it->nkey) != 0 ||
-                   add_iov(c, ITEM_suffix(it), it->nsuffix + it->nbytes) != 0)
-                   {
-                       item_free(it);
-                       it = NULL;
-                       break;
-                   }
-
-                if (settings.verbose > 1)
-                    fprintf(stderr, ">%d sending key %s\n", c->sfd, ITEM_key(it));
-
-                stats_get_hits++;
-                *(c->ilist + i) = it;
+            while (it) {
+                ret = conn_push_value(c, it, i);
+                if (ret) {
+                    item_free(it);
+                    it = NULL;
+                    break;
+                }
                 i++;
+                it = item_cget(cursorp, NULL, 0, DB_NEXT_DUP);
+            }
+            cursorp->close(cursorp);
 
-            } else {
-                stats_get_misses++;
+            /* txn commit */
+            ret = txn->commit(txn, 0);
+            if (ret != 0) {
+                fprintf(stderr, "txn->commit: %s\n", db_strerror(ret));
+                txn->abort(txn);
             }
 
             key_token++;
Index: doc/multimap.txt
===================================================================
--- doc/multimap.txt	(revision 0)
+++ doc/multimap.txt	(revision 0)
@@ -0,0 +1,39 @@
+Multimap MemcacheDB
+===================
+
+Multimap MemcacheDB permits storing duplicate data items for the same key.
+Retrieval request may response multiple items for just one key.
+
+All commands supported by MemcacheDB are also supported by Multimap MemcacheDB.
+But some commands ("append", "prepend", "replace", "incr", "decr") do not
+behave as expected and undefined.
+
+Examples
+========
+
+libmemcached client example
+
+  // store duplicate data items for the same key
+  memcached_set(&memc, "key", 3, "value1", 7, 0, 0);
+  memcached_set(&memc, "key", 3, "value2", 7, 0, 0);
+  memcached_set(&memc, "key", 3, "value3", 7, 0, 0);
+
+  // retrieve multiple items for a key
+  const char *keys[] = { "key", };
+  const size_t key_lens[] = { 3, };
+  memcached_mget(&memc, keys, key_lens, 1);
+
+  value1 = memcached_fetch(&memc, NULL, NULL, &value1_length, &flags, &ret);
+  value2 = memcached_fetch(&memc, NULL, NULL, &value2_length, &flags, &ret);
+  value3 = memcached_fetch(&memc, NULL, NULL, &value3_length, &flags, &ret);
+
+  // MEMCACHED_END is returned when all object that have been found are
+  // returned
+  value4 = memcached_fetch(&memc, NULL, NULL, &value4_length, &flags, &ret);
+  assert(value4 == NULL && ret == MEMCACHED_END);
+
+  // values returned by memcached_fetch() must be freed
+  free(value1);
+  free(value2);
+  free(value3);
+
Index: bdb.c
===================================================================
--- bdb.c	(revision 98)
+++ bdb.c	(working copy)
@@ -306,6 +306,11 @@
             exit(EXIT_FAILURE);
         }
 
+        if ((ret = dbp->set_flags(dbp, DB_DUP)) != 0) {
+            fprintf(stderr, "dbp->set_flags: %s\n", db_strerror(ret));
+            exit(EXIT_FAILURE);
+        }
+
         /* try to open db*/
         ret = dbp->open(dbp, NULL, bdb_settings.db_file, NULL, bdb_settings.db_type, bdb_settings.db_flags, 0664);         
         switch (ret){