Function make_const

src/backend/parser/parse_node.c:351–468

* make_const * * Convert a Value 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. * * For string literals we produce a constant of type UNKNOWN ---- whose * representation is the same as cstring, but it indicates to la

 *	too many examples that fail if we try.
 */
Const *
make_const(ParseState *pstate, Value *value, int location)
{
	Const	   *con;
	Datum		val;
	int64		val64;
	Oid			typeid;
	int			typelen;
	bool		typebyval;
	ParseCallbackState pcbstate;

	switch (nodeTag(value))
	{
		case T_Integer:
			val = Int32GetDatum(intVal(value));

			typeid = INT4OID;
			typelen = sizeof(int32);
			typebyval = true;
			break;

		case T_Float:
			/* could be an oversize integer as well as a float ... */
			if (scanint8(strVal(value), true, &val64))
			{
				/*
				 * It might actually fit in int32. Probably only INT_MIN can
				 * occur, but we'll code the test generally just to be sure.
				 */
				int32		val32 = (int32) val64;

				if (val64 == (int64) val32)
				{
					val = Int32GetDatum(val32);

					typeid = INT4OID;
					typelen = sizeof(int32);
					typebyval = true;
				}
				else
				{
					val = Int64GetDatum(val64);

					typeid = INT8OID;
					typelen = sizeof(int64);
					typebyval = FLOAT8PASSBYVAL;	/* int8 and float8 alike */
				}
			}
			else
			{
				/* arrange to report location if numeric_in() fails */
				setup_parser_errposition_callback(&pcbstate, pstate, location);
				val = DirectFunctionCall3(numeric_in,
										  CStringGetDatum(strVal(value)),
										  ObjectIdGetDatum(InvalidOid),
										  Int32GetDatum(-1));
				cancel_parser_errposition_callback(&pcbstate);