Fixes to parametrized generalization expressions after review

Author: pdobacz

pg_diffix/node_funcs.h

@@ -7,8 +7,12 @@
 /*
  * Returns `true` if the node represents a constant from pg_diffix perspective, i.e. `1` or `$1`.
  */
-extern bool is_simple_constant(Node *node);
+extern bool is_stable_expression(Node *node);
 
-extern void get_simple_constant_typed_value(Node *node, ParamListInfo bound_params, Oid *type, Datum *value, bool *isnull);
+/*
+ * Fills `type`, `value` and `isnull` with what the stable expression `node` holds.
+ * `bound_params` must be provided, since `node` might be a `Param` node.
+ */
+extern void get_stable_expression_value(Node *node, ParamListInfo bound_params, Oid *type, Datum *value, bool *isnull);
 
 #endif /* PG_DIFFIX_NODE_FUNCS_H */

src/node_funcs.c

@@ -11,12 +11,12 @@ static ParamExternData *get_param_data(ParamListInfo bound_params, int one_based
     return &bound_params->params[one_based_paramid - 1];
 }
 
-bool is_simple_constant(Node *node)
+bool is_stable_expression(Node *node)
 {
   return IsA(node, Const) || (IsA(node, Param) && ((Param *)node)->paramkind == PARAM_EXTERN);
 }
 
-void get_simple_constant_typed_value(Node *node, ParamListInfo bound_params, Oid *type, Datum *value, bool *isnull)
+void get_stable_expression_value(Node *node, ParamListInfo bound_params, Oid *type, Datum *value, bool *isnull)
 {
   if (IsA(node, Const))
   {

src/query/anonymization.c

@@ -378,12 +378,12 @@ static bool collect_seed_material(Node *node, CollectMaterialContext *context)
     append_seed_material(context->material, attribute_name, '.');
   }
 
-  if (is_simple_constant(node))
+  if (is_stable_expression(node))
   {
     Oid type;
     Datum value;
     bool isnull;
-    get_simple_constant_typed_value(node, context->bound_params, &type, &value, &isnull);
+    get_stable_expression_value(node, context->bound_params, &type, &value, &isnull);
 
     if (!is_supported_numeric_type(type))
       FAILWITH_LOCATION(exprLocation(node), "Unsupported constant type used in bucket definition!");

src/query/validation.c

@@ -228,7 +228,7 @@ static void verify_bucket_expression(Node *node)
 
     for (int i = 1; i < list_length(func_expr->args); i++)
     {
-      if (!is_simple_constant(unwrap_cast((Node *)list_nth(func_expr->args, i))))
+      if (!is_stable_expression(unwrap_cast((Node *)list_nth(func_expr->args, i))))
         FAILWITH_LOCATION(func_expr->location, "Non-primary arguments for a bucket function have to be simple constants.");
     }
   }
@@ -237,7 +237,7 @@ static void verify_bucket_expression(Node *node)
     OpExpr *op_expr = (OpExpr *)node;
     FAILWITH_LOCATION(op_expr->location, "Use of operators to define buckets is not supported.");
   }
-  else if (is_simple_constant(node))
+  else if (is_stable_expression(node))
   {
     FAILWITH_LOCATION(exprLocation(node), "Simple constants are not allowed as bucket expressions.");
   }
@@ -267,11 +267,11 @@ static void verify_bucket_expression(Node *node)
 static void verify_substring(FuncExpr *func_expr, ParamListInfo bound_params)
 {
   Node *node = unwrap_cast(list_nth(func_expr->args, 1));
-  Assert(is_simple_constant(node)); /* Checked by prior validations */
+  Assert(is_stable_expression(node)); /* Checked by prior validations */
   Oid type;
   Datum value;
   bool isnull;
-  get_simple_constant_typed_value(node, bound_params, &type, &value, &isnull);
+  get_stable_expression_value(node, bound_params, &type, &value, &isnull);
 
   if (DatumGetUInt32(value) != 1)
     FAILWITH_LOCATION(exprLocation(node), "Generalization used in the query is not allowed in untrusted access level.");
@@ -294,11 +294,11 @@ static bool is_money_style(double number)
 static void verify_bin_size(Node *range_expr, ParamListInfo bound_params)
 {
   Node *range_node = unwrap_cast(range_expr);
-  Assert(is_simple_constant(range_node)); /* Checked by prior validations */
+  Assert(is_stable_expression(range_node)); /* Checked by prior validations */
   Oid type;
   Datum value;
   bool isnull;
-  get_simple_constant_typed_value(range_node, bound_params, &type, &value, &isnull);
+  get_stable_expression_value(range_node, bound_params, &type, &value, &isnull);
 
   if (!is_supported_numeric_type(type))
     FAILWITH_LOCATION(exprLocation(range_node), "Unsupported constant type used in generalization.");

test/expected/noiseless.out

@@ -231,3 +231,14 @@ SELECT discount, COUNT(DISTINCT id) FROM test_customers GROUP BY 1;
         2 |     4
 (4 rows)
 
+----------------------------------------------------------------
+-- Prepared statements
+----------------------------------------------------------------
+PREPARE prepared_floor_by(numeric) AS SELECT diffix.floor_by(discount, $1), count(*) FROM test_customers GROUP BY 1;
+EXECUTE prepared_floor_by(2.0);
+ floor_by | count 
+----------+-------
+        0 |    13
+        2 |     4
+(2 rows)
+

test/sql/noiseless.sql

@@ -74,3 +74,10 @@ SELECT COUNT(DISTINCT planet) FROM test_customers;
 -- `low_count_min_threshold` for queries with GROUP BY
 SELECT city, COUNT(DISTINCT city) FROM test_customers GROUP BY 1;
 SELECT discount, COUNT(DISTINCT id) FROM test_customers GROUP BY 1;
+
+----------------------------------------------------------------
+-- Prepared statements
+----------------------------------------------------------------
+
+PREPARE prepared_floor_by(numeric) AS SELECT diffix.floor_by(discount, $1), count(*) FROM test_customers GROUP BY 1;
+EXECUTE prepared_floor_by(2.0);