C: add MultiGet support

db/c.cc

@@ -836,6 +836,69 @@ char* rocksdb_get_cf(
   return result;
 }
 
+void rocksdb_multi_get(
+    rocksdb_t* db,
+    const rocksdb_readoptions_t* options,
+    size_t num_keys, const char* const* keys_list,
+    const size_t* keys_list_sizes,
+    char** values_list, size_t* values_list_sizes,
+    char** errs) {
+  std::vector<Slice> keys(num_keys);
+  for (size_t i = 0; i < num_keys; i++) {
+    keys[i] = Slice(keys_list[i], keys_list_sizes[i]);
+  }
+  std::vector<std::string> values(num_keys);
+  std::vector<Status> statuses = db->rep->MultiGet(options->rep, keys, &values);
+  for (size_t i = 0; i < num_keys; i++) {
+    if (statuses[i].ok()) {
+      values_list[i] = CopyString(values[i]);
+      values_list_sizes[i] = values[i].size();
+      errs[i] = nullptr;
+    } else {
+      values_list[i] = nullptr;
+      values_list_sizes[i] = 0;
+      if (!statuses[i].IsNotFound()) {
+        errs[i] = strdup(statuses[i].ToString().c_str());
+      } else {
+        errs[i] = nullptr;
+      }
+    }
+  }
+}
+
+void rocksdb_multi_get_cf(
+    rocksdb_t* db,
+    const rocksdb_readoptions_t* options,
+    const rocksdb_column_family_handle_t* const* column_families,
+    size_t num_keys, const char* const* keys_list,
+    const size_t* keys_list_sizes,
+    char** values_list, size_t* values_list_sizes,
+    char** errs) {
+  std::vector<Slice> keys(num_keys);
+  std::vector<ColumnFamilyHandle*> cfs(num_keys);
+  for (size_t i = 0; i < num_keys; i++) {
+    keys[i] = Slice(keys_list[i], keys_list_sizes[i]);
+    cfs[i] = column_families[i]->rep;
+  }
+  std::vector<std::string> values(num_keys);
+  std::vector<Status> statuses = db->rep->MultiGet(options->rep, cfs, keys, &values);
+  for (size_t i = 0; i < num_keys; i++) {
+    if (statuses[i].ok()) {
+      values_list[i] = CopyString(values[i]);
+      values_list_sizes[i] = values[i].size();
+      errs[i] = nullptr;
+    } else {
+      values_list[i] = nullptr;
+      values_list_sizes[i] = 0;
+      if (!statuses[i].IsNotFound()) {
+        errs[i] = strdup(statuses[i].ToString().c_str());
+      } else {
+        errs[i] = nullptr;
+      }
+    }
+  }
+}
+
 rocksdb_iterator_t* rocksdb_create_iterator(
     rocksdb_t* db,
     const rocksdb_readoptions_t* options) {
@@ -1766,7 +1829,6 @@ void rocksdb_options_set_fifo_compaction_options(
 /*
 TODO:
 DB::OpenForReadOnly
-DB::MultiGet
 DB::KeyMayExist
 DB::GetOptions
 DB::GetSortedWalFiles

db/c_test.c

@@ -505,6 +505,33 @@ int main(int argc, char** argv) {
     rocksdb_iter_destroy(iter);
   }
 
+  StartPhase("multiget");
+  {
+    const char* keys[3] = { "box", "foo", "notfound" };
+    const size_t keys_sizes[3] = { 3, 3, 8 };
+    char* vals[3];
+    size_t vals_sizes[3];
+    char* errs[3];
+    rocksdb_multi_get(db, roptions, 3, keys, keys_sizes, vals, vals_sizes, errs);
+
+    int i;
+    for (i = 0; i < 3; i++) {
+      CheckEqual(NULL, errs[i], 0);
+      switch (i) {
+      case 0:
+        CheckEqual("c", vals[i], vals_sizes[i]);
+        break;
+      case 1:
+        CheckEqual("hello", vals[i], vals_sizes[i]);
+        break;
+      case 2:
+        CheckEqual(NULL, vals[i], vals_sizes[i]);
+        break;
+      }
+      Free(&vals[i]);
+    }
+  }
+
   StartPhase("approximate_sizes");
   {
     int i;
@@ -778,12 +805,36 @@ int main(int argc, char** argv) {
     CheckGetCF(db, roptions, handles[1], "box", "c");
     rocksdb_writebatch_destroy(wb);
 
+    const char* keys[3] = { "box", "box", "bar" };
+    const rocksdb_column_family_handle_t* get_handles[3] = { handles[0], handles[1], handles[1] };
+    const size_t keys_sizes[3] = { 3, 3, 8 };
+    char* vals[3];
+    size_t vals_sizes[3];
+    char* errs[3];
+    rocksdb_multi_get_cf(db, roptions, get_handles, 3, keys, keys_sizes, vals, vals_sizes, errs);
+
+    int i;
+    for (i = 0; i < 3; i++) {
+      CheckEqual(NULL, errs[i], 0);
+      switch (i) {
+      case 0:
+        CheckEqual(NULL, vals[i], vals_sizes[i]); // wrong cf
+        break;
+      case 1:
+        CheckEqual("c", vals[i], vals_sizes[i]); // bingo
+        break;
+      case 2:
+        CheckEqual(NULL, vals[i], vals_sizes[i]); // normal not found
+        break;
+      }
+      Free(&vals[i]);
+    }
+
     rocksdb_iterator_t* iter = rocksdb_create_iterator_cf(db, roptions, handles[1]);
     CheckCondition(!rocksdb_iter_valid(iter));
     rocksdb_iter_seek_to_first(iter);
     CheckCondition(rocksdb_iter_valid(iter));
 
-    int i;
     for (i = 0; rocksdb_iter_valid(iter) != 0; rocksdb_iter_next(iter)) {
       i++;
     }

include/rocksdb/c.h

@@ -264,6 +264,34 @@ extern char* rocksdb_get_cf(
     size_t* vallen,
     char** errptr);
 
+// if values_list[i] == NULL and errs[i] == NULL,
+// then we got status.IsNotFound(), which we will not return.
+// all errors except status status.ok() and status.IsNotFound() are returned.
+//
+// errs, values_list and values_list_sizes must be num_keys in length,
+// allocated by the caller.
+// errs is a list of strings as opposed to the conventional one error,
+// where errs[i] is the status for retrieval of keys_list[i].
+// each non-NULL errs entry is a malloc()ed, null terminated string.
+// each non-NULL values_list entry is a malloc()ed array, with
+// the length for each stored in values_list_sizes[i].
+extern void rocksdb_multi_get(
+    rocksdb_t* db,
+    const rocksdb_readoptions_t* options,
+    size_t num_keys, const char* const* keys_list,
+    const size_t* keys_list_sizes,
+    char** values_list, size_t* values_list_sizes,
+    char** errs);
+
+extern void rocksdb_multi_get_cf(
+    rocksdb_t* db,
+    const rocksdb_readoptions_t* options,
+    const rocksdb_column_family_handle_t* const* column_families,
+    size_t num_keys, const char* const* keys_list,
+    const size_t* keys_list_sizes,
+    char** values_list, size_t* values_list_sizes,
+    char** errs);
+
 extern rocksdb_iterator_t* rocksdb_create_iterator(
     rocksdb_t* db,
     const rocksdb_readoptions_t* options);