add optimized single and batched prefix existence APIs

BUCK

@@ -63,6 +63,7 @@ cpp_library_wrapper(name="rocksdb_lib", srcs=[
         "db/db_impl/db_impl_files.cc",
         "db/db_impl/db_impl_follower.cc",
         "db/db_impl/db_impl_open.cc",
+        "db/db_impl/db_impl_prefix_exists.cc",
         "db/db_impl/db_impl_readonly.cc",
         "db/db_impl/db_impl_secondary.cc",
         "db/db_impl/db_impl_write.cc",
@@ -5410,6 +5411,12 @@ cpp_unittest_wrapper(name="prefetch_test",
             extra_compiler_flags=[])
 
 
+cpp_unittest_wrapper(name="prefix_exists_test",
+            srcs=["db/prefix_exists_test.cc"],
+            deps=[":rocksdb_test_lib"],
+            extra_compiler_flags=[])
+
+
 cpp_unittest_wrapper(name="prefix_test",
             srcs=["db/prefix_test.cc"],
             deps=[":rocksdb_test_lib"],

CMakeLists.txt

@@ -711,6 +711,7 @@ set(SOURCES
         db/db_impl/db_impl_debug.cc
         db/db_impl/db_impl_experimental.cc
         db/db_impl/db_impl_readonly.cc
+        db/db_impl/db_impl_prefix_exists.cc
         db/db_impl/db_impl_secondary.cc
         db/db_info_dumper.cc
         db/db_iter.cc
@@ -1412,6 +1413,7 @@ if(WITH_TESTS)
         db/plain_table_db_test.cc
         db/seqno_time_test.cc
         db/prefix_test.cc
+        db/prefix_exists_test.cc
         db/range_del_aggregator_test.cc
         db/range_tombstone_fragmenter_test.cc
         db/repair_test.cc

Makefile

@@ -1633,6 +1633,9 @@ perf_context_test: $(OBJ_DIR)/db/perf_context_test.o $(TEST_LIBRARY) $(LIBRARY)
 prefix_test: $(OBJ_DIR)/db/prefix_test.o $(TEST_LIBRARY) $(LIBRARY)
 	$(AM_LINK)
 
+prefix_exists_test: $(OBJ_DIR)/db/prefix_exists_test.o $(TEST_LIBRARY) $(LIBRARY)
+	$(AM_LINK)
+
 backup_engine_test: $(OBJ_DIR)/utilities/backup/backup_engine_test.o $(TEST_LIBRARY) $(LIBRARY)
 	$(AM_LINK)
 

db/c.cc

@@ -643,6 +643,108 @@ static inline char* CopyString(const Slice& slice) {
   return result;
 }
 
+unsigned char rocksdb_prefix_exists(rocksdb_t* db,
+                                    const rocksdb_readoptions_t* options,
+                                    const char* prefix, size_t prefix_len,
+                                    char** errptr) {
+  Status s = db->rep->PrefixExists(options->rep, Slice(prefix, prefix_len));
+  if (s.ok()) {
+    return 1;
+  }
+  if (s.IsNotFound()) {
+    return 0;
+  }
+  SaveError(errptr, s);
+  return 0;
+}
+
+unsigned char rocksdb_prefix_exists_cf(
+    rocksdb_t* db, const rocksdb_readoptions_t* options,
+    rocksdb_column_family_handle_t* column_family, const char* prefix,
+    size_t prefix_len, char** errptr) {
+  Status s = db->rep->PrefixExists(options->rep, column_family->rep,
+                                   Slice(prefix, prefix_len));
+  if (s.ok()) {
+    return 1;
+  }
+  if (s.IsNotFound()) {
+    return 0;
+  }
+  SaveError(errptr, s);
+  return 0;
+}
+
+unsigned char rocksdb_prefix_exists_multi(
+    rocksdb_t* db, const rocksdb_readoptions_t* options,
+    unsigned char prefixes_sorted, size_t num_prefixes,
+    const char* const* prefixes, const size_t* prefix_lens,
+    unsigned char* out_exists, char** errptr) {
+  if (num_prefixes == 0) {
+    return 1;
+  }
+  // Build Slice array
+  std::vector<Slice> pfx;
+  pfx.reserve(num_prefixes);
+  for (size_t i = 0; i < num_prefixes; ++i) {
+    pfx.emplace_back(prefixes[i], prefix_lens[i]);
+  }
+  // Output statuses
+  std::vector<Status> statuses(num_prefixes);
+  db->rep->PrefixExistsMulti(options->rep, static_cast<bool>(prefixes_sorted),
+                             num_prefixes, pfx.data(), statuses.data());
+  bool ok = true;
+  for (size_t i = 0; i < num_prefixes; ++i) {
+    if (statuses[i].ok()) {
+      out_exists[i] = 1;
+    } else if (statuses[i].IsNotFound()) {
+      out_exists[i] = 0;
+    } else {
+      ok = false;
+      // capture first error
+      if (errptr && *errptr == nullptr) {
+        SaveError(errptr, statuses[i]);
+      }
+      out_exists[i] = 0;
+    }
+  }
+  return ok ? 1 : 0;
+}
+
+unsigned char rocksdb_prefix_exists_multi_cf(
+    rocksdb_t* db, const rocksdb_readoptions_t* options,
+    rocksdb_column_family_handle_t* column_family,
+    unsigned char prefixes_sorted, size_t num_prefixes,
+    const char* const* prefixes, const size_t* prefix_lens,
+    unsigned char* out_exists, char** errptr) {
+  if (num_prefixes == 0) {
+    return 1;
+  }
+  std::vector<Slice> pfx;
+  pfx.reserve(num_prefixes);
+  for (size_t i = 0; i < num_prefixes; ++i) {
+    pfx.emplace_back(prefixes[i], prefix_lens[i]);
+  }
+  std::vector<Status> statuses(num_prefixes);
+  db->rep->PrefixExistsMulti(options->rep, column_family->rep,
+                             static_cast<bool>(prefixes_sorted), num_prefixes,
+                             pfx.data(), statuses.data());
+  bool ok = true;
+  for (size_t i = 0; i < num_prefixes; ++i) {
+    if (statuses[i].ok()) {
+      out_exists[i] = 1;
+    } else if (statuses[i].IsNotFound()) {
+      out_exists[i] = 0;
+    } else {
+      ok = false;
+      if (errptr && *errptr == nullptr) {
+        SaveError(errptr, statuses[i]);
+      }
+      out_exists[i] = 0;
+    }
+  }
+  return ok ? 1 : 0;
+}
+
 rocksdb_t* rocksdb_open(const rocksdb_options_t* options, const char* name,
                         char** errptr) {
   DB* db;