[C-API] added the possiblity to create a HashSkipList or HashLinkedList to support prefix seeks

Author: Thomas Adam

db/c.cc

@@ -983,6 +983,26 @@ void rocksdb_options_set_memtable_prefix_bloom_probes(
   opt->rep.memtable_prefix_bloom_probes = v;
 }
 
+void rocksdb_options_set_hash_skip_list_rep(
+    rocksdb_options_t *opt, size_t bucket_count,
+    int32_t skiplist_height, int32_t skiplist_branching_factor) {
+  static rocksdb::MemTableRepFactory* factory = 0;
+  if (!factory) {
+    factory = rocksdb::NewHashSkipListRepFactory(
+        bucket_count, skiplist_height, skiplist_branching_factor);
+  }
+  opt->rep.memtable_factory.reset(factory);
+}
+
+void rocksdb_options_set_hash_link_list_rep(
+    rocksdb_options_t *opt, size_t bucket_count) {
+  static rocksdb::MemTableRepFactory* factory = 0;
+  if (!factory) {
+    factory = rocksdb::NewHashLinkListRepFactory(bucket_count);
+  }
+  opt->rep.memtable_factory.reset(factory);
+}
+
 void rocksdb_options_set_max_successive_merges(
     rocksdb_options_t* opt, size_t v) {
   opt->rep.max_successive_merges = v;

db/c_test.c

@@ -433,6 +433,52 @@ int main(int argc, char** argv) {
 
   }
 
+  StartPhase("prefix");
+  {
+    // Create new database
+    rocksdb_close(db);
+    rocksdb_destroy_db(options, dbname, &err);
+
+    rocksdb_options_set_filter_policy(options, rocksdb_filterpolicy_create_bloom(10));
+    rocksdb_options_set_prefix_extractor(options, rocksdb_slicetransform_create_fixed_prefix(3));
+    rocksdb_options_set_hash_skip_list_rep(options, 50000, 4, 4);
+
+    db = rocksdb_open(options, dbname, &err);
+    CheckNoError(err);
+
+    rocksdb_put(db, woptions, "foo1", 4, "foo", 3, &err);
+    CheckNoError(err);
+    rocksdb_put(db, woptions, "foo2", 4, "foo", 3, &err);
+    CheckNoError(err);
+    rocksdb_put(db, woptions, "foo3", 4, "foo", 3, &err);
+    CheckNoError(err);
+    rocksdb_put(db, woptions, "bar1", 4, "bar", 3, &err);
+    CheckNoError(err);
+    rocksdb_put(db, woptions, "bar2", 4, "bar", 3, &err);
+    CheckNoError(err);
+    rocksdb_put(db, woptions, "bar3", 4, "bar", 3, &err);
+    CheckNoError(err);
+
+    rocksdb_readoptions_set_prefix_seek(roptions, 1);
+
+    rocksdb_iterator_t* iter = rocksdb_create_iterator(db, roptions);
+    CheckCondition(!rocksdb_iter_valid(iter));
+
+    rocksdb_iter_seek(iter, "bar", 3);
+    rocksdb_iter_get_error(iter, &err);
+    CheckNoError(err);
+    CheckCondition(rocksdb_iter_valid(iter));
+
+    CheckIter(iter, "bar1", "bar");
+    rocksdb_iter_next(iter);
+    CheckIter(iter, "bar2", "bar");
+    rocksdb_iter_next(iter);
+    CheckIter(iter, "bar3", "bar");
+    rocksdb_iter_get_error(iter, &err);
+    CheckNoError(err);
+    rocksdb_iter_destroy(iter);
+  }
+
   StartPhase("cleanup");
   rocksdb_close(db);
   rocksdb_options_destroy(options);

include/rocksdb/c.h

@@ -346,6 +346,8 @@ extern void rocksdb_options_set_delete_obsolete_files_period_micros(
 extern void rocksdb_options_set_source_compaction_factor(rocksdb_options_t*, int);
 extern void rocksdb_options_prepare_for_bulk_load(rocksdb_options_t*);
 extern void rocksdb_options_set_memtable_vector_rep(rocksdb_options_t*);
+extern void rocksdb_options_set_hash_skip_list_rep(rocksdb_options_t*, size_t, int32_t, int32_t);
+extern void rocksdb_options_set_hash_link_list_rep(rocksdb_options_t*, size_t);
 
 extern void rocksdb_options_set_max_bytes_for_level_base(rocksdb_options_t* opt, uint64_t n);
 extern void rocksdb_options_set_stats_dump_period_sec(rocksdb_options_t* opt, unsigned int sec);