Remove package automatically when it becomes empty

Author: CherkashinSergey

README.md

@@ -38,6 +38,10 @@ SELECT pgv_get('vars', 'trans_int', NULL::int);
      101
 ```
 
+You can aggregate variables into packages. This is done to be able to have
+variables with different names or to quickly remove the whole batch of
+variables. If the package becomes empty, it is automatically deleted.
+
 ## License
 
 This module available under the [license](LICENSE) similar to

expected/pg_variables_trans.out

@@ -1035,7 +1035,7 @@ SELECT pgv_get('vars2', 'any1',NULL::text);
 ROLLBACK TO sp1;
 COMMIT;
 SELECT pgv_get('vars2', 'any1',NULL::text);
-ERROR:  unrecognized variable "any1"
+ERROR:  unrecognized package "vars2"
 SELECT pgv_free();
  pgv_free 
 ----------
@@ -1385,7 +1385,7 @@ SELECT pgv_get('vars2', 'any1',NULL::text);
 
 ROLLBACK;
 SELECT pgv_get('vars2', 'any1',NULL::text);
-ERROR:  unrecognized variable "any1"
+ERROR:  unrecognized package "vars2"
 SELECT pgv_free();
  pgv_free 
 ----------
@@ -1652,7 +1652,7 @@ SELECT pgv_exists('vars', 'any1');
 (1 row)
 
 SELECT pgv_get('vars', 'any1',NULL::text);
-ERROR:  unrecognized variable "any1"
+ERROR:  unrecognized package "vars"
 SELECT * FROM pgv_list() ORDER BY package, name;
  package | name | is_transactional 
 ---------+------+------------------
@@ -1858,7 +1858,7 @@ SELECT pgv_insert('package', 'errs',row(1), true);
 SELECT pgv_insert('vars4', 'r1', row('str1', 'str1'));
 ERROR:  could not identify a hash function for type unknown
 SELECT pgv_select('vars4', 'r1', 0);
-ERROR:  unrecognized variable "r1"
+ERROR:  unrecognized package "vars4"
 -- If variable created and removed in same transaction level,
 -- it should be totally removed and should not be present
 -- in changes list and cache.
@@ -1878,7 +1878,7 @@ SELECT pgv_remove('vars', 'any1');
 
 RELEASE comm;
 SELECT pgv_get('vars', 'any1',NULL::text);
-ERROR:  unrecognized variable "any1"
+ERROR:  unrecognized package "vars"
 COMMIT;
 SELECT pgv_free();
  pgv_free 

pg_variables.c

@@ -955,6 +955,7 @@ removePackageInternal(Package *package)
 	{
 		MemoryContextDelete(package->hctxRegular);
 		package->hctxRegular = NULL;
+		package->varHashRegular = NULL;
 	}
 
 	/* Add to changes list */
@@ -967,6 +968,17 @@ removePackageInternal(Package *package)
 	GetActualState(package)->is_valid = false;
 }
 
+static bool
+isPackageEmpty(Package *package)
+{
+	int var_num = hash_get_num_entries(package->varHashTransact);
+
+	if (package->varHashRegular)
+		var_num += hash_get_num_entries(package->varHashRegular);
+
+	return var_num == 0;
+}
+
 /*
  * Reset cache variables to their default values. It is necessary to do in case
  * of some changes: removing, rollbacking, etc.
@@ -1657,6 +1669,7 @@ removeObject(TransObject *object, TransObjectType type)
 {
 	bool		found;
 	HTAB	   *hash;
+	Package	   *package = NULL;
 
 	/*
 	 * Delete an object from the change history of the overlying
@@ -1666,16 +1679,20 @@ removeObject(TransObject *object, TransObjectType type)
 			removeFromChangesStack(object, type);
 	if (type == TRANS_PACKAGE)
 	{
-		Package    *package = (Package *) object;
+		package = (Package *) object;
 
 		/* Regular variables had already removed */
 		MemoryContextDelete(package->hctxTransact);
 		hash = packagesHash;
 	}
 	else
-		hash = ((Variable *) object)->is_transactional ?
-			   ((Variable *) object)->package->varHashTransact :
-			   ((Variable *) object)->package->varHashRegular;
+	{
+		Variable *var = (Variable *) object;
+		package = var->package;
+		hash = var->is_transactional ?
+			   var->package->varHashTransact :
+			   var->package->varHashRegular;
+	}
 
 	/* Remove all object's states */
 	while (!dlist_is_empty(&object->states))
@@ -1684,6 +1701,12 @@ removeObject(TransObject *object, TransObjectType type)
 	/* Remove object from hash table */
 	hash_search(hash, object->name, HASH_REMOVE, &found);
 
+	/* Remove package if it is became empty */
+	if (type == TRANS_VARIABLE &&
+		isObjectChangedInCurrentTrans(&package->transObject) &&
+		isPackageEmpty(package))
+		GetActualState(&package->transObject)->is_valid = false;
+
 	resetVariablesCache(true);
 }
 
@@ -1725,8 +1748,19 @@ rollbackSavepoint(TransObject *object, TransObjectType type)
 	{
 		if (!state->is_valid)
 		{
-			dlist_pop_head_node(&object->states);
-			pfree(state);
+			if (isPackageEmpty((Package *)object))
+			{
+				removeObject(object, TRANS_PACKAGE);
+				return;
+			}
+
+			if (dlist_has_next(&object->states, &state->node))
+			{
+				dlist_pop_head_node(&object->states);
+				pfree(state);
+			}
+			else
+				state->is_valid = true;
 			/* Restore regular vars HTAB */
 			makePackHTAB((Package *) object, false);
 		}
@@ -1797,6 +1831,13 @@ releaseSavepoint(TransObject *object, TransObjectType type)
 			!dlist_has_next(states, dlist_head_node(states)))
 		{
 			removeObject(object, type);
+			/* Remove package if it becomes empty */
+			if (type == TRANS_VARIABLE)
+			{
+				Package *pack = ((Variable *) object)->package;
+				if (isPackageEmpty(pack))
+					(GetActualState(&pack->transObject))->is_valid = false;
+			}
 			return;
 		}
 	}