Merge pull request '表达式计算函数注释' (#14) from Rorre/openGauss-server:master into master

src/gausskernel/runtime/executor/execQual.cpp

@@ -1901,6 +1901,13 @@ static void set_result_for_plpgsql_language_function_with_outparam(FuncExprState
  * @bool has_cursor_return - need store out-args cursor info.
  * @bool has_refcursor - need store in-args cursor info.
  * @bool isSetReturnFunc - indicate function returns a set.
+ *The execution process of the ExecMakeFunctionResult function is as follows.
+ * (1) Check whether funcResultStore exists, if so, get the result and return it
+(2) The calculated parameter values are stored in fcinfo.
+(3) Pass the parameter into the expression function to calculate the expression, 
+first determine whether the parameter args exists null, and then determine the return mode of the function that returns the set, 
+SFRM_ValuePerCall mode is to return a value each time the call, The SFRM_Materialize schema is the result set instantiated in Tuplestore.
+(4) Calculate and return results according to different modes.
  */
 template <bool has_refcursor, bool has_cursor_return, bool isSetReturnFunc>
 static Datum ExecMakeFunctionResult(FuncExprState* fcache, ExprContext* econtext, bool* isNull, ExprDoneCond* isDone)
@@ -3082,6 +3089,10 @@ no_function_result:
 /* ----------------------------------------------------------------
  *		ExecEvalFunc
  * ----------------------------------------------------------------
+ *The execution process of the ExecEvalFunc function is as follows.
+(1) Initialize the FuncExprState node by init_fcache function, including initialization parameters, memory management, etc.
+(2) Judge whether the returned result is of set type according to the data in the FuncExprState function, 
+and call the corresponding function to calculate the result.
  */
 static Datum ExecEvalFunc(FuncExprState* fcache, ExprContext* econtext, bool* isNull, ExprDoneCond* isDone)
 {
@@ -3526,6 +3537,10 @@ static Datum ExecEvalNot(BoolExprState* notclause, ExprContext* econtext, bool*
 /* ----------------------------------------------------------------
  *		ExecEvalOr
  * ----------------------------------------------------------------
+ *The main execution process of ExecEvalOr function is as follows.
+(1) Traverse child expression clauses.
+(2) Use the function ExecEvalExpr to call the expression calculation function in clause and calculate the result.
+(3) To judge the results, if there is a result in the or expression that meets the conditions, it will jump out of the loop and return directly.
  */
 static Datum ExecEvalOr(BoolExprState* orExpr, ExprContext* econtext, bool* isNull, ExprDoneCond* isDone)
 {
@@ -5164,6 +5179,11 @@ Datum ExecEvalExprSwitchContext(ExprState* expression, ExprContext* econtext, bo
  * 'parent' may be NULL if we are preparing an expression that is not
  * associated with a plan tree.  (If so, it can't have aggs or subplans.)
  * This case should usually come through ExecPrepareExpr, not directly here.
+ *The execution process of the ExecInitExpr function is as follows.
+(1) Determine whether the input node is empty. If it is empty,return NULL directly, indicating that there is no restriction for expression.
+(2) According to the type of node input,Initialize variable evalfunc which is the execution function corresponding to node,
+If the node has parameters or expressions, the function ExecInitExpr will be recursively called and ExprState tree will be generated.
+(3) Return ExprState tree, and execute the expression recursively according to ExprState tree.
  */
 ExprState* ExecInitExpr(Expr* node, PlanState* parent)
 {
@@ -6123,6 +6143,10 @@ Datum fetch_lob_value_from_tuple(varatt_lob_pointer* lob_pointer, Oid update_oid
  * of *isDone = ExprMultipleResult signifies a set element, and a return
  * of *isDone = ExprEndResult signifies end of the set of tuple.
  * We assume that *isDone has been initialized to ExprSingleResult by caller.
+  * The execution process of the ExecTargetList function is as follows.
+(1) Iterate over the expressions in targetlist.
+(2) Calculation of expression results.
+(3) Judge the itemIsDone[resind] parameter in the results and generate the final tuple.
  */
 static bool ExecTargetList(List* targetlist, ExprContext* econtext, Datum* values, bool* isnull,
     ExprDoneCond* itemIsDone, ExprDoneCond* isDone)