Support default as params for function and procedure

src/backend/optimizer/util/clauses.c

@@ -40,6 +40,7 @@
 #include "optimizer/plancat.h"
 #include "optimizer/planmain.h"
 #include "parser/analyze.h"
+#include "parser/parser.h"
 #include "parser/parse_agg.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_func.h"
@@ -92,6 +93,7 @@ typedef struct
 } max_parallel_hazard_context;
 
 insert_pltsql_function_defaults_hook_type insert_pltsql_function_defaults_hook = NULL;
+replace_pltsql_function_defaults_hook_type replace_pltsql_function_defaults_hook = NULL;
 
 static bool contain_agg_clause_walker(Node *node, void *context);
 static bool find_window_functions_walker(Node *node, WindowFuncLists *lists);
@@ -129,6 +131,8 @@ static Expr *simplify_function(Oid funcid,
 							   eval_const_expressions_context *context);
 static List *reorder_function_arguments(List *args, int pronargs,
 										HeapTuple func_tuple);
+static List *replace_function_defaults(List *args, HeapTuple func_tuple, bool *need_replace);
+
 static List *add_function_defaults(List *args, int pronargs,
 								   HeapTuple func_tuple);
 static List *fetch_function_defaults(HeapTuple func_tuple);
@@ -4050,6 +4054,19 @@ expand_function_arguments(List *args, bool include_out_arguments,
 								   func_tuple);
 	}
 
+	/* Not add else here, for the reason to also replace the default keyword after add function defaults */
+	if (list_length(args) == pronargs && sql_dialect == SQL_DIALECT_TSQL)
+	{
+		bool need_replace = false;
+		args = replace_function_defaults(args, func_tuple, &need_replace);
+		if (need_replace)
+		{
+			recheck_cast_function_args(args, result_type,
+									proargtypes, pronargs,
+									func_tuple);
+		}
+	}
+
 	return args;
 }
 
@@ -4129,6 +4146,49 @@ reorder_function_arguments(List *args, int pronargs, HeapTuple func_tuple)
 	return args;
 }
 
+/*
+ * replace_function_defaults: replace default keyword item with default values
+ */
+static List *
+replace_function_defaults(List *args, HeapTuple func_tuple, bool *need_replace)
+{
+	List	   *defaults;
+	ListCell   *lc;
+	List       *ret = NIL;
+	int			nargs = list_length(args);
+
+	*need_replace = false;
+	if (nargs == 0)
+		return args;
+
+	foreach(lc, args)
+	{
+		if (nodeTag((Node*)lfirst(lc)) == T_RelabelType)
+		{
+		 	if( nodeTag(((RelabelType*)lfirst(lc))->arg) == T_SetToDefault)
+				*need_replace = true;
+		}
+		else if (nodeTag((Node*)lfirst(lc)) == T_FuncExpr)
+		{
+		 	if(((FuncExpr*)lfirst(lc))->funcformat == COERCE_IMPLICIT_CAST &&
+				nodeTag(linitial(((FuncExpr*)lfirst(lc))->args)) == T_SetToDefault)
+				*need_replace = true;
+		}
+	}
+
+	if (!(*need_replace))
+		return args;
+
+	/* Get all the default expressions from the pg_proc tuple */
+	defaults = fetch_function_defaults(func_tuple);
+
+	if (replace_pltsql_function_defaults_hook)
+		ret = replace_pltsql_function_defaults_hook(func_tuple, defaults, args);
+	else return args;
+
+	return ret;
+}
+
 /*
  * add_function_defaults: add missing function arguments from its defaults
  *

src/backend/parser/analyze.c

@@ -3119,9 +3119,19 @@ transformCallStmt(ParseState *pstate, CallStmt *stmt)
 	targs = NIL;
 	foreach(lc, stmt->funccall->args)
 	{
-		targs = lappend(targs, transformExpr(pstate,
-											 (Node *) lfirst(lc),
-											 EXPR_KIND_CALL_ARGUMENT));
+		if (sql_dialect == SQL_DIALECT_TSQL && nodeTag((Node*)lfirst(lc)) == T_SetToDefault)
+		{
+			// For Tsql Default in function call, we set it to UNKNOWN in parser stage
+			// In analyzer it'll use other types to detect the right func candidate
+			((SetToDefault *)lfirst(lc))->typeId = UNKNOWNOID;
+			targs = lappend(targs, (Node *) lfirst(lc));
+		}
+		else
+		{
+			targs = lappend(targs, transformExpr(pstate,
+												(Node *) lfirst(lc),
+												EXPR_KIND_CALL_ARGUMENT));
+		}
 	}
 
 	node = ParseFuncOrColumn(pstate,

src/backend/parser/parse_coerce.c

@@ -176,6 +176,10 @@ coerce_type(ParseState *pstate, Node *node,
 		/* no conversion needed */
 		return node;
 	}
+	if (nodeTag((Node*)node) == T_SetToDefault)
+	{
+		return node;
+	}
 	if (targetTypeId == ANYOID ||
 		targetTypeId == ANYELEMENTOID ||
 		targetTypeId == ANYNONARRAYOID ||

src/backend/parser/parse_expr.c

@@ -1489,8 +1489,18 @@ transformFuncCall(ParseState *pstate, FuncCall *fn)
 	targs = NIL;
 	foreach(args, fn->args)
 	{
-		targs = lappend(targs, transformExprRecurse(pstate,
+		if (sql_dialect == SQL_DIALECT_TSQL && nodeTag((Node*)lfirst(args)) == T_SetToDefault)
+		{
+			// For Tsql Default in function call, we set it to UNKNOWN in parser stage
+			// In analyzer it'll use other types to detect the right func candidate
+			((SetToDefault *)lfirst(args))->typeId = UNKNOWNOID;
+			targs = lappend(targs, (Node *) lfirst(args));
+		}
+		else
+		{
+			targs = lappend(targs, transformExprRecurse(pstate,
 													(Node *) lfirst(args)));
+		}
 	}
 
 	/*
@@ -1522,10 +1532,12 @@ transformFuncCall(ParseState *pstate, FuncCall *fn)
        */
 
       if (!schemaname || (strlen(schemaname) == 3 && strncmp(schemaname, "sys", 3) == 0))
-              if (strlen(functionname) == 8 &&
-                          strncmp(functionname, "checksum", 8) == 0 &&
-                          fn->agg_star == true)
-                      targs = ExpandChecksumStar(pstate, fn, fn->location);
+	{
+        if (strlen(functionname) == 8 &&
+            strncmp(functionname, "checksum", 8) == 0 &&
+                fn->agg_star == true)
+            targs = ExpandChecksumStar(pstate, fn, fn->location);
+	}
 
 	/* ... and hand off to ParseFuncOrColumn */
 	return ParseFuncOrColumn(pstate,

src/include/optimizer/clauses.h

@@ -59,4 +59,7 @@ extern Bitmapset *pull_paramids(Expr *expr);
 typedef void (*insert_pltsql_function_defaults_hook_type)(HeapTuple func_tuple, List *defaults, Node **argarray);
 extern PGDLLIMPORT insert_pltsql_function_defaults_hook_type insert_pltsql_function_defaults_hook;
 
+typedef List* (*replace_pltsql_function_defaults_hook_type)(HeapTuple func_tuple, List *defaults, List *fargs);
+extern PGDLLIMPORT replace_pltsql_function_defaults_hook_type replace_pltsql_function_defaults_hook;
+
 #endif							/* CLAUSES_H */