1 files changed, 66 insertions, 0 deletions
diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c
index 6d0f3f37673..e27ec78b714 100644
--- a/src/backend/access/common/heaptuple.c
+++ b/src/backend/access/common/heaptuple.c
@@ -847,6 +847,72 @@ heap_modify_tuple(HeapTuple tuple,
 }
 
 /*
+ * heap_modify_tuple_by_cols
+ *		form a new tuple from an old tuple and a set of replacement values.
+ *
+ * This is like heap_modify_tuple, except that instead of specifying which
+ * column(s) to replace by a boolean map, an array of target column numbers
+ * is used.  This is often more convenient when a fixed number of columns
+ * are to be replaced.  The replCols, replValues, and replIsnull arrays must
+ * be of length nCols.  Target column numbers are indexed from 1.
+ *
+ * The result is allocated in the current memory context.
+ */
+HeapTuple
+heap_modify_tuple_by_cols(HeapTuple tuple,
+						  TupleDesc tupleDesc,
+						  int nCols,
+						  int *replCols,
+						  Datum *replValues,
+						  bool *replIsnull)
+{
+	int			numberOfAttributes = tupleDesc->natts;
+	Datum	   *values;
+	bool	   *isnull;
+	HeapTuple	newTuple;
+	int			i;
+
+	/*
+	 * allocate and fill values and isnull arrays from the tuple, then replace
+	 * selected columns from the input arrays.
+	 */
+	values = (Datum *) palloc(numberOfAttributes * sizeof(Datum));
+	isnull = (bool *) palloc(numberOfAttributes * sizeof(bool));
+
+	heap_deform_tuple(tuple, tupleDesc, values, isnull);
+
+	for (i = 0; i < nCols; i++)
+	{
+		int			attnum = replCols[i];
+
+		if (attnum <= 0 || attnum > numberOfAttributes)
+			elog(ERROR, "invalid column number %d", attnum);
+		values[attnum - 1] = replValues[i];
+		isnull[attnum - 1] = replIsnull[i];
+	}
+
+	/*
+	 * create a new tuple from the values and isnull arrays
+	 */
+	newTuple = heap_form_tuple(tupleDesc, values, isnull);
+
+	pfree(values);
+	pfree(isnull);
+
+	/*
+	 * copy the identification info of the old tuple: t_ctid, t_self, and OID
+	 * (if any)
+	 */
+	newTuple->t_data->t_ctid = tuple->t_data->t_ctid;
+	newTuple->t_self = tuple->t_self;
+	newTuple->t_tableOid = tuple->t_tableOid;
+	if (tupleDesc->tdhasoid)
+		HeapTupleSetOid(newTuple, HeapTupleGetOid(tuple));
+
+	return newTuple;
+}
+
+/*
  * heap_deform_tuple
  *		Given a tuple, extract data into values/isnull arrays; this is
  *		the inverse of heap_form_tuple.