add c-api to get default cf handle (#12514)

Summary:
rocksdb_batched_multi_get_cf has performance improvement than normal multi_get, however it needs a cf_handle arg, so add a C-API to get and destroy the default cf_handle, as many user only use the default cf.

Fixes #12316

Pull Request resolved: #12514

Reviewed By: hx235

Differential Revision: D55922517

Pulled By: ajkr

fbshipit-source-id: c4cc4289f2cfd9efbb8f390a44a9d8d1ed08d9f0

db/c.cc

@@ -231,6 +231,7 @@ struct rocksdb_livefiles_t {
 };
 struct rocksdb_column_family_handle_t {
   ColumnFamilyHandle* rep;
+  bool immortal;  /* only true for default cf */
 };
 struct rocksdb_column_family_metadata_t {
   ColumnFamilyMetaData rep;
@@ -906,6 +907,7 @@ rocksdb_t* rocksdb_open_and_trim_history(
     rocksdb_column_family_handle_t* c_handle =
         new rocksdb_column_family_handle_t;
     c_handle->rep = handles[i];
+    c_handle->immortal = false;
     column_family_handles[i] = c_handle;
   }
   rocksdb_t* result = new rocksdb_t;
@@ -936,6 +938,7 @@ rocksdb_t* rocksdb_open_column_families(
     rocksdb_column_family_handle_t* c_handle =
         new rocksdb_column_family_handle_t;
     c_handle->rep = handles[i];
+    c_handle->immortal = false;
     column_family_handles[i] = c_handle;
   }
   rocksdb_t* result = new rocksdb_t;
@@ -971,6 +974,7 @@ rocksdb_t* rocksdb_open_column_families_with_ttl(
     rocksdb_column_family_handle_t* c_handle =
         new rocksdb_column_family_handle_t;
     c_handle->rep = handles[i];
+    c_handle->immortal = false;
     column_family_handles[i] = c_handle;
   }
   rocksdb_t* result = new rocksdb_t;
@@ -1004,6 +1008,7 @@ rocksdb_t* rocksdb_open_for_read_only_column_families(
     rocksdb_column_family_handle_t* c_handle =
         new rocksdb_column_family_handle_t;
     c_handle->rep = handles[i];
+    c_handle->immortal = false;
     column_family_handles[i] = c_handle;
   }
   rocksdb_t* result = new rocksdb_t;
@@ -1035,6 +1040,7 @@ rocksdb_t* rocksdb_open_as_secondary_column_families(
     rocksdb_column_family_handle_t* c_handle =
         new rocksdb_column_family_handle_t;
     c_handle->rep = handles[i];
+    c_handle->immortal = false;
     column_family_handles[i] = c_handle;
   }
   rocksdb_t* result = new rocksdb_t;
@@ -1072,6 +1078,7 @@ rocksdb_column_family_handle_t* rocksdb_create_column_family(
   SaveError(errptr, db->rep->CreateColumnFamily(
                         ColumnFamilyOptions(column_family_options->rep),
                         std::string(column_family_name), &(handle->rep)));
+  handle->immortal = false;
   return handle;
 }
 
@@ -1095,6 +1102,7 @@ rocksdb_column_family_handle_t** rocksdb_create_column_families(
   for (size_t i = 0; i != handles.size(); ++i) {
     c_handles[i] = new rocksdb_column_family_handle_t;
     c_handles[i]->rep = handles[i];
+    c_handles[i]->immortal = false;
   }
 
   return c_handles;
@@ -1114,6 +1122,7 @@ rocksdb_column_family_handle_t* rocksdb_create_column_family_with_ttl(
   SaveError(errptr, db_with_ttl->CreateColumnFamilyWithTtl(
                         ColumnFamilyOptions(column_family_options->rep),
                         std::string(column_family_name), &(handle->rep), ttl));
+  handle->immortal = false;
   return handle;
 }
 
@@ -1135,9 +1144,19 @@ char* rocksdb_column_family_handle_get_name(
   return CopyString(name);
 }
 
+rocksdb_column_family_handle_t* rocksdb_get_default_column_family_handle(
+    rocksdb_t* db) {
+  rocksdb_column_family_handle_t* handle = new rocksdb_column_family_handle_t;
+  handle->rep = db->rep->DefaultColumnFamily();
+  handle->immortal = true;
+  return handle;
+}
+
 void rocksdb_column_family_handle_destroy(
     rocksdb_column_family_handle_t* handle) {
-  delete handle->rep;
+  if (!handle->immortal) {
+    delete handle->rep;
+  }
   delete handle;
 }
 
@@ -5789,6 +5808,7 @@ rocksdb_column_family_handle_t* rocksdb_transactiondb_create_column_family(
   SaveError(errptr, txn_db->rep->CreateColumnFamily(
                         ColumnFamilyOptions(column_family_options->rep),
                         std::string(column_family_name), &(handle->rep)));
+  handle->immortal = false;
   return handle;
 }
 
@@ -5831,6 +5851,7 @@ rocksdb_transactiondb_t* rocksdb_transactiondb_open_column_families(
     rocksdb_column_family_handle_t* c_handle =
         new rocksdb_column_family_handle_t;
     c_handle->rep = handles[i];
+    c_handle->immortal = false;
     column_family_handles[i] = c_handle;
   }
   rocksdb_transactiondb_t* result = new rocksdb_transactiondb_t;
@@ -6625,6 +6646,7 @@ rocksdb_optimistictransactiondb_open_column_families(
     rocksdb_column_family_handle_t* c_handle =
         new rocksdb_column_family_handle_t;
     c_handle->rep = handles[i];
+    c_handle->immortal = false;
     column_family_handles[i] = c_handle;
   }
   rocksdb_optimistictransactiondb_t* result =

include/rocksdb/c.h

@@ -434,6 +434,9 @@ rocksdb_create_column_family_with_ttl(
 extern ROCKSDB_LIBRARY_API void rocksdb_drop_column_family(
     rocksdb_t* db, rocksdb_column_family_handle_t* handle, char** errptr);
 
+extern ROCKSDB_LIBRARY_API rocksdb_column_family_handle_t*
+    rocksdb_get_default_column_family_handle(rocksdb_t* db);
+
 extern ROCKSDB_LIBRARY_API void rocksdb_column_family_handle_destroy(
     rocksdb_column_family_handle_t*);