Expose KeyMayExist in the C API (#7021)

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/7021

Reviewed By: ajkr

Differential Revision: D22246297

Pulled By: pdillinger

fbshipit-source-id: 81dfd0a49e4d5ce0c9f00772c17cca425757ea24

db/c.cc

@@ -996,6 +996,55 @@ void rocksdb_multi_get_cf(
   }
 }
 
+unsigned char rocksdb_key_may_exist(rocksdb_t* db,
+                                    const rocksdb_readoptions_t* options,
+                                    const char* key, size_t key_len,
+                                    char** value, size_t* val_len,
+                                    const char* timestamp, size_t timestamp_len,
+                                    unsigned char* value_found) {
+  std::string tmp;
+  std::string time;
+  if (timestamp) {
+    time.assign(timestamp, timestamp_len);
+  }
+  bool found = false;
+  const bool result = db->rep->KeyMayExist(options->rep, Slice(key, key_len),
+                                           &tmp, timestamp ? &time : nullptr,
+                                           value_found ? &found : nullptr);
+  if (value_found) {
+    *value_found = found;
+    if (found) {
+      *val_len = tmp.size();
+      *value = CopyString(tmp);
+    }
+  }
+  return result;
+}
+
+unsigned char rocksdb_key_may_exist_cf(
+    rocksdb_t* db, const rocksdb_readoptions_t* options,
+    rocksdb_column_family_handle_t* column_family, const char* key,
+    size_t key_len, char** value, size_t* val_len, const char* timestamp,
+    size_t timestamp_len, unsigned char* value_found) {
+  std::string tmp;
+  std::string time;
+  if (timestamp) {
+    time.assign(timestamp, timestamp_len);
+  }
+  bool found = false;
+  const bool result = db->rep->KeyMayExist(
+      options->rep, column_family->rep, Slice(key, key_len), &tmp,
+      timestamp ? &time : nullptr, value_found ? &found : nullptr);
+  if (value_found) {
+    *value_found = found;
+    if (found) {
+      *val_len = tmp.size();
+      *value = CopyString(tmp);
+    }
+  }
+  return result;
+}
+
 rocksdb_iterator_t* rocksdb_create_iterator(
     rocksdb_t* db,
     const rocksdb_readoptions_t* options) {

db/c_test.c

@@ -1296,6 +1296,29 @@ int main(int argc, char** argv) {
       Free(&vals[i]);
     }
 
+    {
+      unsigned char value_found = 0;
+
+      CheckCondition(!rocksdb_key_may_exist(db, roptions, "invalid_key", 11,
+                                            NULL, NULL, NULL, 0, NULL));
+      CheckCondition(!rocksdb_key_may_exist(db, roptions, "invalid_key", 11,
+                                            &vals[0], &vals_sizes[0], NULL, 0,
+                                            &value_found));
+      if (value_found) {
+        Free(&vals[0]);
+      }
+
+      CheckCondition(!rocksdb_key_may_exist_cf(db, roptions, handles[1],
+                                               "invalid_key", 11, NULL, NULL,
+                                               NULL, 0, NULL));
+      CheckCondition(!rocksdb_key_may_exist_cf(db, roptions, handles[1],
+                                               "invalid_key", 11, &vals[0],
+                                               &vals_sizes[0], NULL, 0, NULL));
+      if (value_found) {
+        Free(&vals[0]);
+      }
+    }
+
     rocksdb_iterator_t* iter = rocksdb_create_iterator_cf(db, roptions, handles[1]);
     CheckCondition(!rocksdb_iter_valid(iter));
     rocksdb_iter_seek_to_first(iter);

include/rocksdb/c.h

@@ -320,6 +320,21 @@ extern ROCKSDB_LIBRARY_API void rocksdb_multi_get_cf(
     const size_t* keys_list_sizes, char** values_list,
     size_t* values_list_sizes, char** errs);
 
+// The value is only allocated (using malloc) and returned if it is found and
+// value_found isn't NULL. In that case the user is responsible for freeing it.
+extern ROCKSDB_LIBRARY_API unsigned char rocksdb_key_may_exist(
+    rocksdb_t* db, const rocksdb_readoptions_t* options, const char* key,
+    size_t key_len, char** value, size_t* val_len, const char* timestamp,
+    size_t timestamp_len, unsigned char* value_found);
+
+// The value is only allocated (using malloc) and returned if it is found and
+// value_found isn't NULL. In that case the user is responsible for freeing it.
+extern ROCKSDB_LIBRARY_API unsigned char rocksdb_key_may_exist_cf(
+    rocksdb_t* db, const rocksdb_readoptions_t* options,
+    rocksdb_column_family_handle_t* column_family, const char* key,
+    size_t key_len, char** value, size_t* val_len, const char* timestamp,
+    size_t timestamp_len, unsigned char* value_found);
+
 extern ROCKSDB_LIBRARY_API rocksdb_iterator_t* rocksdb_create_iterator(
     rocksdb_t* db, const rocksdb_readoptions_t* options);