Remove Value node struct

The Value node struct is a weird construct.  It is its own node type,
but most of the time, it actually has a node type of Integer, Float,
String, or BitString.  As a consequence, the struct name and the node
type don't match most of the time, and so it has to be treated
specially a lot.  There doesn't seem to be any value in the special
construct.  There is very little code that wants to accept all Value
variants but nothing else (and even if it did, this doesn't provide
any convenient way to check it), and most code wants either just one
particular node type (usually String), or it accepts a broader set of
node types besides just Value.

This change removes the Value struct and node type and replaces them
by separate Integer, Float, String, and BitString node types that are
proper node types and structs of their own and behave mostly like
normal node types.

Also, this removes the T_Null node tag, which was previously also a
possible variant of Value but wasn't actually used outside of the
Value contained in A_Const.  Replace that by an isnull field in
A_Const.

Reviewed-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/5ba6bc5b-3f95-04f2-2419-f8ddb4c046fb@enterprisedb.com

1 files changed, 26 insertions, 24 deletions

diff --git a/src/backend/parser/parse_node.c b/src/backend/parser/parse_node.c
index 17c900da31b..8cfe6f67c04 100644
--- a/src/backend/parser/parse_node.c
+++ b/src/backend/parser/parse_node.c
@@ -333,7 +333,7 @@ transformContainerSubscripts(ParseState *pstate,
 /*
  * make_const
  *
- *	Convert a Value node (as returned by the grammar) to a Const node
+ *	Convert an A_Const node (as returned by the grammar) to a Const node
  *	of the "natural" type for the constant.  Note that this routine is
  *	only used when there is no explicit cast for the constant, so we
  *	have to guess what type is wanted.
@@ -349,7 +349,7 @@ transformContainerSubscripts(ParseState *pstate,
  *	too many examples that fail if we try.
  */
 Const *
-make_const(ParseState *pstate, Value *value, int location)
+make_const(ParseState *pstate, A_Const *aconst)
 {
 	Const	   *con;
 	Datum		val;
@@ -359,10 +359,24 @@ make_const(ParseState *pstate, Value *value, int location)
 	bool		typebyval;
 	ParseCallbackState pcbstate;
 
-	switch (nodeTag(value))
+	if (aconst->isnull)
+	{
+		/* return a null const */
+		con = makeConst(UNKNOWNOID,
+						-1,
+						InvalidOid,
+						-2,
+						(Datum) 0,
+						true,
+						false);
+		con->location = aconst->location;
+		return con;
+	}
+
+	switch (nodeTag(&aconst->val))
 	{
 		case T_Integer:
-			val = Int32GetDatum(intVal(value));
+			val = Int32GetDatum(aconst->val.ival.val);
 
 			typeid = INT4OID;
 			typelen = sizeof(int32);
@@ -371,7 +385,7 @@ make_const(ParseState *pstate, Value *value, int location)
 
 		case T_Float:
 			/* could be an oversize integer as well as a float ... */
-			if (scanint8(strVal(value), true, &val64))
+			if (scanint8(aconst->val.fval.val, true, &val64))
 			{
 				/*
 				 * It might actually fit in int32. Probably only INT_MIN can
@@ -399,9 +413,9 @@ make_const(ParseState *pstate, Value *value, int location)
 			else
 			{
 				/* arrange to report location if numeric_in() fails */
-				setup_parser_errposition_callback(&pcbstate, pstate, location);
+				setup_parser_errposition_callback(&pcbstate, pstate, aconst->location);
 				val = DirectFunctionCall3(numeric_in,
-										  CStringGetDatum(strVal(value)),
+										  CStringGetDatum(aconst->val.fval.val),
 										  ObjectIdGetDatum(InvalidOid),
 										  Int32GetDatum(-1));
 				cancel_parser_errposition_callback(&pcbstate);
@@ -418,7 +432,7 @@ make_const(ParseState *pstate, Value *value, int location)
 			 * We assume here that UNKNOWN's internal representation is the
 			 * same as CSTRING
 			 */
-			val = CStringGetDatum(strVal(value));
+			val = CStringGetDatum(aconst->val.sval.val);
 
 			typeid = UNKNOWNOID;	/* will be coerced later */
 			typelen = -2;		/* cstring-style varwidth type */
@@ -427,9 +441,9 @@ make_const(ParseState *pstate, Value *value, int location)
 
 		case T_BitString:
 			/* arrange to report location if bit_in() fails */
-			setup_parser_errposition_callback(&pcbstate, pstate, location);
+			setup_parser_errposition_callback(&pcbstate, pstate, aconst->location);
 			val = DirectFunctionCall3(bit_in,
-									  CStringGetDatum(strVal(value)),
+									  CStringGetDatum(aconst->val.bsval.val),
 									  ObjectIdGetDatum(InvalidOid),
 									  Int32GetDatum(-1));
 			cancel_parser_errposition_callback(&pcbstate);
@@ -438,20 +452,8 @@ make_const(ParseState *pstate, Value *value, int location)
 			typebyval = false;
 			break;
 
-		case T_Null:
-			/* return a null const */
-			con = makeConst(UNKNOWNOID,
-							-1,
-							InvalidOid,
-							-2,
-							(Datum) 0,
-							true,
-							false);
-			con->location = location;
-			return con;
-
 		default:
-			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(value));
+			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(&aconst->val));
 			return NULL;		/* keep compiler quiet */
 	}
 
@@ -462,7 +464,7 @@ make_const(ParseState *pstate, Value *value, int location)
 					val,
 					false,
 					typebyval);
-	con->location = location;
+	con->location = aconst->location;
 
 	return con;
 }