fix RPS service: Provide closure for view insertion
[oweals/gnunet.git] / src / datacache / plugin_datacache_sqlite.c
index 1901bdedd596cfb1bbcba6b9500fe6bf89ea2100..dc4236a8b8fd4ba2254a81f716410b32fb4e3f6e 100644 (file)
@@ -1,21 +1,19 @@
 /*
      This file is part of GNUnet
-     (C) 2006, 2009 Christian Grothoff (and other contributing authors)
+     Copyright (C) 2006, 2009, 2015 GNUnet e.V.
 
-     GNUnet is free software; you can redistribute it and/or modify
-     it under the terms of the GNU General Public License as published
-     by the Free Software Foundation; either version 3, or (at your
-     option) any later version.
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     or (at your option) any later version.
 
      GNUnet is distributed in the hope that it will be useful, but
      WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-     General Public License for more details.
+     Affero General Public License for more details.
 
-     You should have received a copy of the GNU General Public License
-     along with GNUnet; see the file COPYING.  If not, write to the
-     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-     Boston, MA 02111-1307, USA.
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 /**
@@ -26,6 +24,7 @@
 #include "platform.h"
 #include "gnunet_util_lib.h"
 #include "gnunet_datacache_plugin.h"
+#include "gnunet_sq_lib.h"
 #include <sqlite3.h>
 
 #define LOG(kind,...) GNUNET_log_from (kind, "datacache-sqlite", __VA_ARGS__)
@@ -37,7 +36,7 @@
  * How much overhead do we assume per entry in the
  * datacache?
  */
-#define OVERHEAD (sizeof(struct GNUNET_HashCode) + 32)
+#define OVERHEAD (sizeof(struct GNUNET_HashCode) + 36)
 
 /**
  * Context for all functions in this plugin.
@@ -58,30 +57,93 @@ struct Plugin
    * Filename used for the DB.
    */
   char *fn;
+
+  /**
+   * Prepared statement for #sqlite_plugin_put.
+   */
+  sqlite3_stmt *insert_stmt;
+
+  /**
+   * Prepared statement for #sqlite_plugin_get.
+   */
+  sqlite3_stmt *get_count_stmt;
+
+  /**
+   * Prepared statement for #sqlite_plugin_get.
+   */
+  sqlite3_stmt *get_stmt;
+
+  /**
+   * Prepared statement for #sqlite_plugin_del.
+   */
+  sqlite3_stmt *del_select_stmt;
+
+  /**
+   * Prepared statement for #sqlite_plugin_del.
+   */
+  sqlite3_stmt *del_expired_stmt;
+
+  /**
+   * Prepared statement for #sqlite_plugin_del.
+   */
+  sqlite3_stmt *del_stmt;
+
+  /**
+   * Prepared statement for #sqlite_plugin_get_random.
+   */
+  sqlite3_stmt *get_random_stmt;
+
+  /**
+   * Prepared statement for #sqlite_plugin_get_closest.
+   */
+  sqlite3_stmt *get_closest_stmt;
+
+  /**
+   * Number of key-value pairs in the database.
+   */
+  unsigned int num_items;
 };
 
 
 /**
- * Log an error message at log-level 'level' that indicates
- * a failure of the command 'cmd' on file 'filename'
- * with the message given by strerror(errno).
+ * Log an error message at log-level @a level that indicates
+ * a failure of the command @a cmd with the error from the database @a db
+ *
+ * @param db database handle
+ * @param level log level
+ * @param cmd failed command
  */
 #define LOG_SQLITE(db, level, cmd) do { LOG (level, _("`%s' failed at %s:%d with error: %s\n"), cmd, __FILE__, __LINE__, sqlite3_errmsg(db)); } while(0)
 
 
+/**
+ * Execute SQL statement.
+ *
+ * @param db database handle
+ * @param cmd SQL command to execute
+ */
 #define SQLITE3_EXEC(db, cmd) do { emsg = NULL; if (SQLITE_OK != sqlite3_exec(db, cmd, NULL, NULL, &emsg)) { LOG (GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK, _("`%s' failed at %s:%d with error: %s\n"), "sqlite3_exec", __FILE__, __LINE__, emsg); sqlite3_free(emsg); } } while(0)
 
 
 /**
  * @brief Prepare a SQL statement
+ *
+ * @param dbh database handle
+ * @param zsql SQL statement text
+ * @param[out] ppStmt set to the prepared statement
+ * @return 0 on success
  */
 static int
-sq_prepare (sqlite3 * dbh, const char *zSql,    /* SQL statement, UTF-8 encoded */
-            sqlite3_stmt ** ppStmt)
+sq_prepare (sqlite3 *dbh,
+            const char *zSql,    /* SQL statement, UTF-8 encoded */
+            sqlite3_stmt **ppStmt)
 {                               /* OUT: Statement handle */
   char *dummy;
 
-  return sqlite3_prepare (dbh, zSql, strlen (zSql), ppStmt,
+  return sqlite3_prepare (dbh,
+                          zSql,
+                          strlen (zSql),
+                          ppStmt,
                           (const char **) &dummy);
 }
 
@@ -89,74 +151,71 @@ sq_prepare (sqlite3 * dbh, const char *zSql,    /* SQL statement, UTF-8 encoded
 /**
  * Store an item in the datastore.
  *
- * @param cls closure (our "struct Plugin")
- * @param key key to store data under
- * @param size number of bytes in data
+ * @param cls closure (our `struct Plugin`)
+ * @param key key to store @a data under
+ * @param xor_distance how close is @a key to our PID?
+ * @param size number of bytes in @a data
  * @param data data to store
  * @param type type of the value
  * @param discard_time when to discard the value in any case
- * @param path_info_len number of entries in 'path_info'
+ * @param path_info_len number of entries in @a path_info
  * @param path_info array of peers that have processed the request
  * @return 0 if duplicate, -1 on error, number of bytes used otherwise
  */
 static ssize_t
 sqlite_plugin_put (void *cls,
                   const struct GNUNET_HashCode *key,
-                  size_t size, const char *data,
+                   uint32_t xor_distance,
+                  size_t size,
+                   const char *data,
                   enum GNUNET_BLOCK_Type type,
                    struct GNUNET_TIME_Absolute discard_time,
                   unsigned int path_info_len,
                   const struct GNUNET_PeerIdentity *path_info)
 {
   struct Plugin *plugin = cls;
-  sqlite3_stmt *stmt;
-  int64_t dval;
+  uint32_t type32 = type;
+  struct GNUNET_SQ_QueryParam params[] = {
+    GNUNET_SQ_query_param_uint32 (&type32),
+    GNUNET_SQ_query_param_absolute_time (&discard_time),
+    GNUNET_SQ_query_param_auto_from_type (key),
+    GNUNET_SQ_query_param_uint32 (&xor_distance),
+    GNUNET_SQ_query_param_fixed_size (data, size),
+    GNUNET_SQ_query_param_fixed_size (path_info,
+                                      path_info_len * sizeof (struct GNUNET_PeerIdentity)),
+    GNUNET_SQ_query_param_end
+  };
 
   LOG (GNUNET_ERROR_TYPE_DEBUG,
-       "Processing `%s' of %u bytes with key `%4s' and expiration %s\n",
-       "PUT", (unsigned int) size, GNUNET_h2s (key),
-       GNUNET_STRINGS_relative_time_to_string (GNUNET_TIME_absolute_get_remaining (discard_time), GNUNET_YES));
-  dval = (int64_t) discard_time.abs_value_us;
-  if (dval < 0)
-    dval = INT64_MAX;
-  if (sq_prepare
-      (plugin->dbh,
-       "INSERT INTO ds090 (type, expire, key, value, path) VALUES (?, ?, ?, ?, ?)",
-       &stmt) != SQLITE_OK)
-  {
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
-                "sq_prepare");
-    return -1;
-  }
-  if ((SQLITE_OK != sqlite3_bind_int (stmt, 1, type)) ||
-      (SQLITE_OK != sqlite3_bind_int64 (stmt, 2, dval)) ||
-      (SQLITE_OK !=
-       sqlite3_bind_blob (stmt, 3,
-                         key, sizeof (struct GNUNET_HashCode),
-                          SQLITE_TRANSIENT)) ||
-      (SQLITE_OK != sqlite3_bind_blob (stmt, 4,
-                                      data, size,
-                                      SQLITE_TRANSIENT)) ||
-      (SQLITE_OK != sqlite3_bind_blob (stmt, 5,
-                                      path_info,
-                                      path_info_len * sizeof (struct GNUNET_PeerIdentity),
-                                      SQLITE_TRANSIENT)))
+       "Processing PUT of %u bytes with key `%s' and expiration %s\n",
+       (unsigned int) size,
+       GNUNET_h2s (key),
+       GNUNET_STRINGS_relative_time_to_string (GNUNET_TIME_absolute_get_remaining (discard_time),
+                                               GNUNET_YES));
+  if (GNUNET_OK !=
+      GNUNET_SQ_bind (plugin->insert_stmt,
+                      params))
   {
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
+    LOG_SQLITE (plugin->dbh,
+                GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
                 "sqlite3_bind_xxx");
-    sqlite3_finalize (stmt);
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->insert_stmt);
     return -1;
   }
-  if (SQLITE_DONE != sqlite3_step (stmt))
+  if (SQLITE_DONE !=
+      sqlite3_step (plugin->insert_stmt))
   {
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
+    LOG_SQLITE (plugin->dbh,
+                GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
                 "sqlite3_step");
-    sqlite3_finalize (stmt);
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->insert_stmt);
     return -1;
   }
-  if (SQLITE_OK != sqlite3_finalize (stmt))
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
-                "sqlite3_finalize");
+  plugin->num_items++;
+  GNUNET_SQ_reset (plugin->dbh,
+                   plugin->insert_stmt);
   return size + OVERHEAD;
 }
 
@@ -165,134 +224,156 @@ sqlite_plugin_put (void *cls,
  * Iterate over the results for a particular key
  * in the datastore.
  *
- * @param cls closure (our "struct Plugin")
+ * @param cls closure (our `struct Plugin`)
  * @param key
  * @param type entries of which type are relevant?
  * @param iter maybe NULL (to just count)
- * @param iter_cls closure for iter
+ * @param iter_cls closure for @a iter
  * @return the number of results found
  */
 static unsigned int
-sqlite_plugin_get (void *cls, const struct GNUNET_HashCode * key,
-                   enum GNUNET_BLOCK_Type type, GNUNET_DATACACHE_Iterator iter,
+sqlite_plugin_get (void *cls,
+                   const struct GNUNET_HashCode *key,
+                   enum GNUNET_BLOCK_Type type,
+                   GNUNET_DATACACHE_Iterator iter,
                    void *iter_cls)
 {
   struct Plugin *plugin = cls;
-  sqlite3_stmt *stmt;
+  uint32_t type32 = type;
   struct GNUNET_TIME_Absolute now;
   struct GNUNET_TIME_Absolute exp;
-  unsigned int size;
-  const char *dat;
+  size_t size;
+  void *dat;
   unsigned int cnt;
-  unsigned int off;
+  uint32_t off;
   unsigned int total;
-  unsigned int psize;
-  char scratch[256];
-  int64_t ntime;
-  const struct GNUNET_PeerIdentity *path;
+  size_t psize;
+  struct GNUNET_PeerIdentity *path;
+  struct GNUNET_SQ_QueryParam params_count[] = {
+    GNUNET_SQ_query_param_auto_from_type (key),
+    GNUNET_SQ_query_param_uint32 (&type32),
+    GNUNET_SQ_query_param_absolute_time (&now),
+    GNUNET_SQ_query_param_end
+  };
+  struct GNUNET_SQ_QueryParam params_select[] = {
+    GNUNET_SQ_query_param_auto_from_type (key),
+    GNUNET_SQ_query_param_uint32 (&type32),
+    GNUNET_SQ_query_param_absolute_time (&now),
+    GNUNET_SQ_query_param_uint32 (&off),
+    GNUNET_SQ_query_param_end
+  };
+  struct GNUNET_SQ_ResultSpec rs[] = {
+    GNUNET_SQ_result_spec_variable_size (&dat,
+                                         &size),
+    GNUNET_SQ_result_spec_absolute_time (&exp),
+    GNUNET_SQ_result_spec_variable_size ((void **) &path,
+                                         &psize),
+    GNUNET_SQ_result_spec_end
+  };
 
   now = GNUNET_TIME_absolute_get ();
-  LOG (GNUNET_ERROR_TYPE_DEBUG, "Processing `%s' for key `%4s'\n", "GET",
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Processing GET for key `%s'\n",
        GNUNET_h2s (key));
-  if (sq_prepare
-      (plugin->dbh,
-       "SELECT count(*) FROM ds090 WHERE key=? AND type=? AND expire >= ?",
-       &stmt) != SQLITE_OK)
-  {
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
-                "sq_prepare");
-    return 0;
-  }
-  ntime = (int64_t) now.abs_value_us;
-  GNUNET_assert (ntime >= 0);
-  if ((SQLITE_OK !=
-       sqlite3_bind_blob (stmt, 1, key, sizeof (struct GNUNET_HashCode),
-                          SQLITE_TRANSIENT)) ||
-      (SQLITE_OK != sqlite3_bind_int (stmt, 2, type)) ||
-      (SQLITE_OK != sqlite3_bind_int64 (stmt, 3, now.abs_value_us)))
+
+  if (GNUNET_OK !=
+      GNUNET_SQ_bind (plugin->get_count_stmt,
+                      params_count))
   {
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
+    LOG_SQLITE (plugin->dbh,
+                GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
                 "sqlite3_bind_xxx");
-    sqlite3_finalize (stmt);
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->get_count_stmt);
     return 0;
   }
-
-  if (SQLITE_ROW != sqlite3_step (stmt))
+  if (SQLITE_ROW !=
+      sqlite3_step (plugin->get_count_stmt))
   {
     LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
                 "sqlite_step");
-    sqlite3_finalize (stmt);
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->get_count_stmt);
     LOG (GNUNET_ERROR_TYPE_DEBUG,
-         "No content found when processing `%s' for key `%4s'\n", "GET",
+         "No content found when processing GET for key `%s'\n",
          GNUNET_h2s (key));
     return 0;
   }
-  total = sqlite3_column_int (stmt, 0);
-  sqlite3_finalize (stmt);
-  if ((total == 0) || (iter == NULL))
+  total = sqlite3_column_int (plugin->get_count_stmt,
+                              0);
+  GNUNET_SQ_reset (plugin->dbh,
+                   plugin->get_count_stmt);
+  if ( (0 == total) ||
+       (NULL == iter) )
   {
     if (0 == total)
       LOG (GNUNET_ERROR_TYPE_DEBUG,
-           "No content found when processing `%s' for key `%4s'\n", "GET",
+           "No content found when processing GET for key `%s'\n",
            GNUNET_h2s (key));
     return total;
   }
 
   cnt = 0;
-  off = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, total);
+  off = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
+                                  total);
   while (cnt < total)
   {
     off = (off + 1) % total;
-    GNUNET_snprintf (scratch, sizeof (scratch),
-                     "SELECT value,expire,path FROM ds090 WHERE key=? AND type=? AND expire >= ? LIMIT 1 OFFSET %u",
-                     off);
-    if (sq_prepare (plugin->dbh, scratch, &stmt) != SQLITE_OK)
+    if (GNUNET_OK !=
+        GNUNET_SQ_bind (plugin->get_stmt,
+                        params_select))
     {
-      LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
-                  "sq_prepare");
-      return cnt;
-    }
-    if ((SQLITE_OK !=
-         sqlite3_bind_blob (stmt, 1, key, sizeof (struct GNUNET_HashCode),
-                            SQLITE_TRANSIENT)) ||
-        (SQLITE_OK != sqlite3_bind_int (stmt, 2, type)) ||
-        (SQLITE_OK != sqlite3_bind_int64 (stmt, 3, now.abs_value_us)))
-    {
-      LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
+      LOG_SQLITE (plugin->dbh,
+                  GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
                   "sqlite3_bind_xxx");
-      sqlite3_finalize (stmt);
+      GNUNET_SQ_reset (plugin->dbh,
+                       plugin->get_stmt);
       return cnt;
     }
-    if (sqlite3_step (stmt) != SQLITE_ROW)
+    if (SQLITE_ROW !=
+        sqlite3_step (plugin->get_stmt))
+      break;
+    if (GNUNET_OK !=
+        GNUNET_SQ_extract_result (plugin->get_stmt,
+                                  rs))
+    {
+      GNUNET_break (0);
+      GNUNET_SQ_reset (plugin->dbh,
+                       plugin->get_stmt);
       break;
-    size = sqlite3_column_bytes (stmt, 0);
-    dat = sqlite3_column_blob (stmt, 0);
-    exp.abs_value_us = sqlite3_column_int64 (stmt, 1);
-    psize = sqlite3_column_bytes (stmt, 2);
+    }
     if (0 != psize % sizeof (struct GNUNET_PeerIdentity))
     {
       GNUNET_break (0);
       psize = 0;
+      path = NULL;
     }
     psize /= sizeof (struct GNUNET_PeerIdentity);
-    if (0 != psize)
-      path = sqlite3_column_blob (stmt, 2);
-    else
-      path = NULL;
-    ntime = (int64_t) exp.abs_value_us;
-    if (ntime == INT64_MAX)
-      exp = GNUNET_TIME_UNIT_FOREVER_ABS;
     cnt++;
     LOG (GNUNET_ERROR_TYPE_DEBUG,
-         "Found %u-byte result when processing `%s' for key `%4s'\n",
-         (unsigned int) size, "GET", GNUNET_h2s (key));
-    if (GNUNET_OK != iter (iter_cls, key, size, dat, type, exp, psize, path))
+         "Found %u-byte result when processing GET for key `%s'\n",
+         (unsigned int) size,
+         GNUNET_h2s (key));
+    if (GNUNET_OK != iter (iter_cls,
+                           key,
+                           size,
+                           dat,
+                           type,
+                           exp,
+                           psize,
+                           path))
     {
-      sqlite3_finalize (stmt);
+      GNUNET_SQ_cleanup_result (rs);
+      GNUNET_SQ_reset (plugin->dbh,
+                       plugin->get_stmt);
       break;
     }
-    sqlite3_finalize (stmt);
+    GNUNET_SQ_cleanup_result (rs);
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->get_stmt);
   }
+  GNUNET_SQ_reset (plugin->dbh,
+                   plugin->get_stmt);
   return cnt;
 }
 
@@ -301,83 +382,313 @@ sqlite_plugin_get (void *cls, const struct GNUNET_HashCode * key,
  * Delete the entry with the lowest expiration value
  * from the datacache right now.
  *
- * @param cls closure (our "struct Plugin")
- * @return GNUNET_OK on success, GNUNET_SYSERR on error
+ * @param cls closure (our `struct Plugin`)
+ * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
  */
 static int
 sqlite_plugin_del (void *cls)
 {
   struct Plugin *plugin = cls;
-  unsigned long long rowid;
-  unsigned int dsize;
-  sqlite3_stmt *stmt;
-  sqlite3_stmt *dstmt;
+  uint64_t rowid;
+  void *data;
+  size_t dsize;
   struct GNUNET_HashCode hc;
+  struct GNUNET_TIME_Absolute now;
+  struct GNUNET_SQ_ResultSpec rs[] = {
+    GNUNET_SQ_result_spec_uint64 (&rowid),
+    GNUNET_SQ_result_spec_auto_from_type (&hc),
+    GNUNET_SQ_result_spec_variable_size ((void **) &data,
+                                         &dsize),
+    GNUNET_SQ_result_spec_end
+  };
+  struct GNUNET_SQ_QueryParam params[] = {
+    GNUNET_SQ_query_param_uint64 (&rowid),
+    GNUNET_SQ_query_param_end
+  };
+  struct GNUNET_SQ_QueryParam time_params[] = {
+    GNUNET_SQ_query_param_absolute_time (&now),
+    GNUNET_SQ_query_param_end
+  };
 
-  LOG (GNUNET_ERROR_TYPE_DEBUG, "Processing `%s'\n", "DEL");
-  stmt = NULL;
-  dstmt = NULL;
-  if (sq_prepare
-      (plugin->dbh,
-       "SELECT _ROWID_,key,value FROM ds090 ORDER BY expire ASC LIMIT 1",
-       &stmt) != SQLITE_OK)
-  {
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
-                "sq_prepare");
-    if (stmt != NULL)
-      (void) sqlite3_finalize (stmt);
-    return GNUNET_SYSERR;
-  }
-  if (SQLITE_ROW != sqlite3_step (stmt))
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Processing DEL\n");
+  now = GNUNET_TIME_absolute_get ();
+  if (GNUNET_OK !=
+      GNUNET_SQ_bind (plugin->del_expired_stmt,
+                      time_params))
   {
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
-                "sqlite3_step");
-    (void) sqlite3_finalize (stmt);
+    LOG_SQLITE (plugin->dbh,
+                GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
+                "sqlite3_bind");
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->del_expired_stmt);
     return GNUNET_SYSERR;
   }
-  rowid = sqlite3_column_int64 (stmt, 0);
-  GNUNET_assert (sqlite3_column_bytes (stmt, 1) == sizeof (struct GNUNET_HashCode));
-  memcpy (&hc, sqlite3_column_blob (stmt, 1), sizeof (struct GNUNET_HashCode));
-  dsize = sqlite3_column_bytes (stmt, 2);
-  if (SQLITE_OK != sqlite3_finalize (stmt))
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
-                "sqlite3_step");
-  if (sq_prepare (plugin->dbh, "DELETE FROM ds090 WHERE _ROWID_=?", &dstmt) !=
-      SQLITE_OK)
+  if ( (SQLITE_ROW !=
+        sqlite3_step (plugin->del_expired_stmt)) ||
+       (GNUNET_OK !=
+        GNUNET_SQ_extract_result (plugin->del_expired_stmt,
+                                  rs)) )
   {
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
-                "sq_prepare");
-    if (stmt != NULL)
-      (void) sqlite3_finalize (stmt);
-    return GNUNET_SYSERR;
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->del_expired_stmt);
+    if (SQLITE_ROW !=
+        sqlite3_step (plugin->del_select_stmt))
+    {
+      LOG_SQLITE (plugin->dbh,
+                  GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
+                  "sqlite3_step");
+      GNUNET_SQ_reset (plugin->dbh,
+                       plugin->del_select_stmt);
+      return GNUNET_SYSERR;
+    }
+    if (GNUNET_OK !=
+        GNUNET_SQ_extract_result (plugin->del_select_stmt,
+                                  rs))
+    {
+      GNUNET_SQ_reset (plugin->dbh,
+                       plugin->del_select_stmt);
+      GNUNET_break (0);
+      return GNUNET_SYSERR;
+    }
   }
-  if (SQLITE_OK != sqlite3_bind_int64 (dstmt, 1, rowid))
+  GNUNET_SQ_cleanup_result (rs);
+  GNUNET_SQ_reset (plugin->dbh,
+                   plugin->del_select_stmt);
+  if (GNUNET_OK !=
+      GNUNET_SQ_bind (plugin->del_stmt,
+                      params))
   {
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
+    LOG_SQLITE (plugin->dbh,
+                GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
                 "sqlite3_bind");
-    (void) sqlite3_finalize (dstmt);
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->del_stmt);
     return GNUNET_SYSERR;
   }
-  if (sqlite3_step (dstmt) != SQLITE_DONE)
+  if (SQLITE_DONE !=
+      sqlite3_step (plugin->del_stmt))
   {
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
+    LOG_SQLITE (plugin->dbh,
+                GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
                 "sqlite3_step");
-    (void) sqlite3_finalize (dstmt);
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->del_stmt);
     return GNUNET_SYSERR;
   }
-  plugin->env->delete_notify (plugin->env->cls, &hc, dsize + OVERHEAD);
-  if (SQLITE_OK != sqlite3_finalize (dstmt))
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
-                "sqlite3_finalize");
+  plugin->num_items--;
+  plugin->env->delete_notify (plugin->env->cls,
+                              &hc,
+                              dsize + OVERHEAD);
+  GNUNET_SQ_reset (plugin->dbh,
+                   plugin->del_stmt);
   return GNUNET_OK;
 }
 
 
+/**
+ * Obtain a random key-value pair from the datacache.
+ *
+ * @param cls closure (our `struct Plugin`)
+ * @param iter maybe NULL (to just count)
+ * @param iter_cls closure for @a iter
+ * @return the number of results found, zero (datacache empty) or one
+ */
+static unsigned int
+sqlite_plugin_get_random (void *cls,
+                          GNUNET_DATACACHE_Iterator iter,
+                          void *iter_cls)
+{
+  struct Plugin *plugin = cls;
+  struct GNUNET_TIME_Absolute exp;
+  size_t size;
+  void *dat;
+  uint32_t off;
+  size_t psize;
+  uint32_t type;
+  struct GNUNET_PeerIdentity *path;
+  struct GNUNET_HashCode key;
+  struct GNUNET_SQ_QueryParam params[] = {
+    GNUNET_SQ_query_param_uint32 (&off),
+    GNUNET_SQ_query_param_end
+  };
+  struct GNUNET_SQ_ResultSpec rs[] = {
+    GNUNET_SQ_result_spec_variable_size (&dat,
+                                         &size),
+    GNUNET_SQ_result_spec_absolute_time (&exp),
+    GNUNET_SQ_result_spec_variable_size ((void **) &path,
+                                         &psize),
+    GNUNET_SQ_result_spec_auto_from_type (&key),
+    GNUNET_SQ_result_spec_uint32 (&type),
+    GNUNET_SQ_result_spec_end
+  };
+
+  if (0 == plugin->num_items)
+    return 0;
+  if (NULL == iter)
+    return 1;
+  off = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE,
+                                  plugin->num_items);
+  if (GNUNET_OK !=
+      GNUNET_SQ_bind (plugin->get_random_stmt,
+                      params))
+  {
+    return 0;
+  }
+  if (SQLITE_ROW !=
+      sqlite3_step (plugin->get_random_stmt))
+  {
+    GNUNET_break (0);
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->get_random_stmt);
+    return 0;
+  }
+  if (GNUNET_OK !=
+      GNUNET_SQ_extract_result (plugin->get_random_stmt,
+                                rs))
+  {
+    GNUNET_break (0);
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->get_random_stmt);
+    return 0;
+  }
+  if (0 != psize % sizeof (struct GNUNET_PeerIdentity))
+  {
+    GNUNET_break (0);
+    psize = 0;
+    path = NULL;
+  }
+  psize /= sizeof (struct GNUNET_PeerIdentity);
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Found %u-byte result with key %s when processing GET-RANDOM\n",
+       (unsigned int) size,
+       GNUNET_h2s (&key));
+  (void) iter (iter_cls,
+               &key,
+               size,
+               dat,
+               (enum GNUNET_BLOCK_Type) type,
+               exp,
+               psize,
+               path);
+  GNUNET_SQ_cleanup_result (rs);
+  GNUNET_SQ_reset (plugin->dbh,
+                   plugin->get_random_stmt);
+  return 1;
+}
+
+
+/**
+ * Iterate over the results that are "close" to a particular key in
+ * the datacache.  "close" is defined as numerically larger than @a
+ * key (when interpreted as a circular address space), with small
+ * distance.
+ *
+ * @param cls closure (internal context for the plugin)
+ * @param key area of the keyspace to look into
+ * @param num_results number of results that should be returned to @a iter
+ * @param iter maybe NULL (to just count)
+ * @param iter_cls closure for @a iter
+ * @return the number of results found
+ */
+static unsigned int
+sqlite_plugin_get_closest (void *cls,
+                           const struct GNUNET_HashCode *key,
+                           unsigned int num_results,
+                           GNUNET_DATACACHE_Iterator iter,
+                           void *iter_cls)
+{
+  struct Plugin *plugin = cls;
+  uint32_t num_results32 = num_results;
+  struct GNUNET_TIME_Absolute now;
+  struct GNUNET_TIME_Absolute exp;
+  size_t size;
+  void *dat;
+  unsigned int cnt;
+  size_t psize;
+  uint32_t type;
+  struct GNUNET_HashCode hc;
+  struct GNUNET_PeerIdentity *path;
+  struct GNUNET_SQ_QueryParam params[] = {
+    GNUNET_SQ_query_param_auto_from_type (key),
+    GNUNET_SQ_query_param_absolute_time (&now),
+    GNUNET_SQ_query_param_uint32 (&num_results32),
+    GNUNET_SQ_query_param_end
+  };
+  struct GNUNET_SQ_ResultSpec rs[] = {
+    GNUNET_SQ_result_spec_variable_size (&dat,
+                                         &size),
+    GNUNET_SQ_result_spec_absolute_time (&exp),
+    GNUNET_SQ_result_spec_variable_size ((void **) &path,
+                                         &psize),
+    GNUNET_SQ_result_spec_uint32 (&type),
+    GNUNET_SQ_result_spec_auto_from_type (&hc),
+    GNUNET_SQ_result_spec_end
+  };
+
+  now = GNUNET_TIME_absolute_get ();
+  LOG (GNUNET_ERROR_TYPE_DEBUG,
+       "Processing GET_CLOSEST for key `%s'\n",
+       GNUNET_h2s (key));
+  if (GNUNET_OK !=
+      GNUNET_SQ_bind (plugin->get_closest_stmt,
+                      params))
+  {
+    LOG_SQLITE (plugin->dbh,
+                GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
+                "sqlite3_bind_xxx");
+    GNUNET_SQ_reset (plugin->dbh,
+                     plugin->get_closest_stmt);
+    return 0;
+  }
+  cnt = 0;
+  while (SQLITE_ROW ==
+         sqlite3_step (plugin->get_closest_stmt))
+  {
+    if (GNUNET_OK !=
+        GNUNET_SQ_extract_result (plugin->get_closest_stmt,
+                                  rs))
+    {
+      GNUNET_break (0);
+      break;
+    }
+    if (0 != psize % sizeof (struct GNUNET_PeerIdentity))
+    {
+      GNUNET_break (0);
+      psize = 0;
+      path = NULL;
+    }
+    psize /= sizeof (struct GNUNET_PeerIdentity);
+    cnt++;
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Found %u-byte result at %s when processing GET_CLOSE\n",
+         (unsigned int) size,
+         GNUNET_h2s (&hc));
+    if (GNUNET_OK != iter (iter_cls,
+                           &hc,
+                           size,
+                           dat,
+                           type,
+                           exp,
+                           psize,
+                           path))
+    {
+      GNUNET_SQ_cleanup_result (rs);
+      break;
+    }
+    GNUNET_SQ_cleanup_result (rs);
+  }
+  GNUNET_SQ_reset (plugin->dbh,
+                   plugin->get_closest_stmt);
+  return cnt;
+}
+
+
 /**
  * Entry point for the plugin.
  *
- * @param cls closure (the "struct GNUNET_DATACACHE_PluginEnvironmnet")
- * @return the plugin's closure (our "struct Plugin")
+ * @param cls closure (the `struct GNUNET_DATACACHE_PluginEnvironment`)
+ * @return the plugin's closure (our `struct Plugin`)
  */
 void *
 libgnunet_plugin_datacache_sqlite_init (void *cls)
@@ -422,7 +733,6 @@ libgnunet_plugin_datacache_sqlite_init (void *cls)
   SQLITE3_EXEC (dbh, "PRAGMA locking_mode=EXCLUSIVE");
   SQLITE3_EXEC (dbh, "PRAGMA journal_mode=OFF");
   SQLITE3_EXEC (dbh, "PRAGMA synchronous=OFF");
-  SQLITE3_EXEC (dbh, "PRAGMA count_changes=OFF");
   SQLITE3_EXEC (dbh, "PRAGMA page_size=4092");
   if (GNUNET_YES ==
       GNUNET_CONFIGURATION_get_value_yesno (env->cfg,
@@ -431,23 +741,81 @@ libgnunet_plugin_datacache_sqlite_init (void *cls)
     SQLITE3_EXEC (dbh, "PRAGMA sqlite_temp_store=3");
 
   SQLITE3_EXEC (dbh,
-                "CREATE TABLE ds090 (" "  type INTEGER NOT NULL DEFAULT 0,"
-                "  expire INTEGER NOT NULL DEFAULT 0,"
+                "CREATE TABLE ds091 ("
+                "  type INTEGER NOT NULL DEFAULT 0,"
+                "  expire INTEGER NOT NULL,"
                 "  key BLOB NOT NULL DEFAULT '',"
-                "  value BLOB NOT NULL DEFAULT '',"
+                "  prox INTEGER NOT NULL,"
+                "  value BLOB NOT NULL,"
                "  path BLOB DEFAULT '')");
-  SQLITE3_EXEC (dbh, "CREATE INDEX idx_hashidx ON ds090 (key,type,expire)");
-  SQLITE3_EXEC (dbh, "CREATE INDEX idx_expire ON ds090 (expire)");
-  plugin = GNUNET_malloc (sizeof (struct Plugin));
+  SQLITE3_EXEC (dbh, "CREATE INDEX idx_hashidx ON ds091 (key,type,expire)");
+  SQLITE3_EXEC (dbh, "CREATE INDEX idx_prox_expire ON ds091 (prox,expire)");
+  SQLITE3_EXEC (dbh, "CREATE INDEX idx_expire_only ON ds091 (expire)");
+  plugin = GNUNET_new (struct Plugin);
   plugin->env = env;
   plugin->dbh = dbh;
   plugin->fn = fn_utf8;
-  api = GNUNET_malloc (sizeof (struct GNUNET_DATACACHE_PluginFunctions));
+
+  if ( (SQLITE_OK !=
+        sq_prepare (plugin->dbh,
+                    "INSERT INTO ds091 (type, expire, key, prox, value, path) "
+                    "VALUES (?, ?, ?, ?, ?, ?)",
+                    &plugin->insert_stmt)) ||
+       (SQLITE_OK !=
+        sq_prepare (plugin->dbh,
+                    "SELECT count(*) FROM ds091 "
+                    "WHERE key=? AND type=? AND expire >= ?",
+                    &plugin->get_count_stmt)) ||
+       (SQLITE_OK !=
+        sq_prepare (plugin->dbh,
+                    "SELECT value,expire,path FROM ds091"
+                    " WHERE key=? AND type=? AND expire >= ? LIMIT 1 OFFSET ?",
+                    &plugin->get_stmt)) ||
+       (SQLITE_OK !=
+        sq_prepare (plugin->dbh,
+                    "SELECT _ROWID_,key,value FROM ds091"
+                    " WHERE expire < ?"
+                    " ORDER BY expire ASC LIMIT 1",
+                    &plugin->del_expired_stmt)) ||
+       (SQLITE_OK !=
+        sq_prepare (plugin->dbh,
+                    "SELECT _ROWID_,key,value FROM ds091"
+                    " ORDER BY prox ASC, expire ASC LIMIT 1",
+                    &plugin->del_select_stmt)) ||
+       (SQLITE_OK !=
+        sq_prepare (plugin->dbh,
+                    "DELETE FROM ds091 WHERE _ROWID_=?",
+                    &plugin->del_stmt)) ||
+       (SQLITE_OK !=
+        sq_prepare (plugin->dbh,
+                    "SELECT value,expire,path,key,type FROM ds091 "
+                    "ORDER BY key LIMIT 1 OFFSET ?",
+                    &plugin->get_random_stmt)) ||
+       (SQLITE_OK !=
+        sq_prepare (plugin->dbh,
+                    "SELECT value,expire,path,type,key FROM ds091 "
+                    "WHERE key>=? AND expire >= ? ORDER BY KEY ASC LIMIT ?",
+                    &plugin->get_closest_stmt))
+       )
+  {
+    LOG_SQLITE (plugin->dbh,
+                GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
+                "sq_prepare");
+    GNUNET_break (SQLITE_OK ==
+                  sqlite3_close (plugin->dbh));
+    GNUNET_free (plugin);
+    return NULL;
+  }
+
+  api = GNUNET_new (struct GNUNET_DATACACHE_PluginFunctions);
   api->cls = plugin;
   api->get = &sqlite_plugin_get;
   api->put = &sqlite_plugin_put;
   api->del = &sqlite_plugin_del;
-  LOG (GNUNET_ERROR_TYPE_INFO, _("Sqlite datacache running\n"));
+  api->get_random = &sqlite_plugin_get_random;
+  api->get_closest = &sqlite_plugin_get_closest;
+  LOG (GNUNET_ERROR_TYPE_INFO,
+       "Sqlite datacache running\n");
   return api;
 }
 
@@ -455,7 +823,7 @@ libgnunet_plugin_datacache_sqlite_init (void *cls)
 /**
  * Exit point from the plugin.
  *
- * @param cls closure (our "struct Plugin")
+ * @param cls closure (our `struct Plugin`)
  * @return NULL
  */
 void *
@@ -472,36 +840,50 @@ libgnunet_plugin_datacache_sqlite_done (void *cls)
 #if !WINDOWS || defined(__CYGWIN__)
   if ( (NULL != plugin->fn) &&
        (0 != UNLINK (plugin->fn)) )
-    LOG_STRERROR_FILE (GNUNET_ERROR_TYPE_WARNING, "unlink", plugin->fn);
+    LOG_STRERROR_FILE (GNUNET_ERROR_TYPE_WARNING,
+                       "unlink",
+                       plugin->fn);
   GNUNET_free_non_null (plugin->fn);
 #endif
+  sqlite3_finalize (plugin->insert_stmt);
+  sqlite3_finalize (plugin->get_count_stmt);
+  sqlite3_finalize (plugin->get_stmt);
+  sqlite3_finalize (plugin->del_select_stmt);
+  sqlite3_finalize (plugin->del_expired_stmt);
+  sqlite3_finalize (plugin->del_stmt);
+  sqlite3_finalize (plugin->get_random_stmt);
+  sqlite3_finalize (plugin->get_closest_stmt);
   result = sqlite3_close (plugin->dbh);
 #if SQLITE_VERSION_NUMBER >= 3007000
-  if (result == SQLITE_BUSY)
+  if (SQLITE_BUSY == result)
   {
     LOG (GNUNET_ERROR_TYPE_WARNING,
-         _
-         ("Tried to close sqlite without finalizing all prepared statements.\n"));
+         _("Tried to close sqlite without finalizing all prepared statements.\n"));
     stmt = sqlite3_next_stmt (plugin->dbh, NULL);
-    while (stmt != NULL)
+    while (NULL != stmt)
     {
-      LOG (GNUNET_ERROR_TYPE_DEBUG, "Closing statement %p\n", stmt);
       result = sqlite3_finalize (stmt);
       if (result != SQLITE_OK)
-        LOG (GNUNET_ERROR_TYPE_WARNING, _("Failed to close statement %p: %d\n"),
-             stmt, result);
+        LOG (GNUNET_ERROR_TYPE_WARNING,
+             "Failed to close statement %p: %d\n",
+             stmt,
+             result);
       stmt = sqlite3_next_stmt (plugin->dbh, NULL);
     }
     result = sqlite3_close (plugin->dbh);
   }
 #endif
   if (SQLITE_OK != result)
-    LOG_SQLITE (plugin->dbh, GNUNET_ERROR_TYPE_ERROR, "sqlite3_close");
+    LOG_SQLITE (plugin->dbh,
+                GNUNET_ERROR_TYPE_ERROR,
+                "sqlite3_close");
 
 #if WINDOWS && !defined(__CYGWIN__)
   if ( (NULL != plugin->fn) &&
        (0 != UNLINK (plugin->fn)) )
-    LOG_STRERROR_FILE (GNUNET_ERROR_TYPE_WARNING, "unlink", plugin->fn);
+    LOG_STRERROR_FILE (GNUNET_ERROR_TYPE_WARNING,
+                       "unlink",
+                       plugin->fn);
   GNUNET_free_non_null (plugin->fn);
 #endif
   GNUNET_free (plugin);