parse_expr.c

关系型数据库 Postgresql 6.5.2

						 */
						c->casetype = ptype;
					}
					else if (can_coerce_type(1, &c->casetype, &ptype))
					{
						c->defresult = coerce_type(pstate, c->defresult,
												 c->casetype, ptype, -1);
						c->casetype = ptype;
					}
					else
					{
						elog(ERROR, "CASE/ELSE unable to convert to type %s",
							 typeidTypeName(ptype));
					}
				}

				/* Convert when clauses, if not null and if necessary */
				foreach(args, c->args)
				{
					Oid			wtype;

					w = lfirst(args);
					wtype = exprType(w->result);

					/*
					 * only bother with conversion if not NULL and
					 * different type...
					 */
					if (wtype && (wtype != UNKNOWNOID)
						&& (wtype != ptype))
					{
						if (can_coerce_type(1, &wtype, &ptype))
						{
							w->result = coerce_type(pstate, w->result, wtype,
													ptype, -1);
						}
						else
						{
							elog(ERROR, "CASE/WHEN unable to convert to type %s",
								 typeidTypeName(ptype));
						}
					}
				}

				result = expr;
				break;
			}

		case T_CaseWhen:
			{
				CaseWhen   *w = (CaseWhen *) expr;

				w->expr = transformExpr(pstate, (Node *) w->expr, precedence);
				if (exprType(w->expr) != BOOLOID)
					elog(ERROR, "WHEN clause must have a boolean result");

				/*
				 * result is NULL for NULLIF() construct - thomas
				 * 1998-11-11
				 */
				if (w->result == NULL)
				{
					A_Const    *n = makeNode(A_Const);

					n->val.type = T_Null;
					w->result = (Node *) n;
				}
				w->result = transformExpr(pstate, (Node *) w->result, precedence);
				result = expr;
				break;
			}

/* Some nodes do _not_ come from the original parse tree,
 *	but result from parser transformation in this phase.
 * At least one construct (BETWEEN/AND) puts the same nodes
 *	into two branches of the parse tree; hence, some nodes
 *	are transformed twice.
 * Another way it can happen is that coercion of an operator or
 *	function argument to the required type (via coerce_type())
 *	can apply transformExpr to an already-transformed subexpression.
 *	An example here is "SELECT count(*) + 1.0 FROM table".
 * Thus, we can see node types in this routine that do not appear in the
 *	original parse tree.  Assume they are already transformed, and just
 *	pass them through.
 * Do any other node types need to be accepted?  For now we are taking
 *	a conservative approach, and only accepting node types that are
 *	demonstrably necessary to accept.
 */
		case T_Expr:
		case T_Var:
		case T_Const:
		case T_Param:
		case T_Aggref:
		case T_ArrayRef:
			{
				result = (Node *) expr;
				break;
			}
		default:
			/* should not reach here */
			elog(ERROR, "transformExpr: does not know how to transform node %d",
				 nodeTag(expr));
			break;
	}

	return result;
}

static Node *
transformIdent(ParseState *pstate, Node *expr, int precedence)
{
	Ident	   *ident = (Ident *) expr;
	RangeTblEntry *rte;
	Node	   *column_result,
			   *relation_result,
			   *result;

	column_result = relation_result = result = 0;
	/* try to find the ident as a column */
	if ((rte = colnameRangeTableEntry(pstate, ident->name)) != NULL)
	{
		Attr	   *att = makeNode(Attr);

		/* we add the relation name for them */
		att->relname = rte->refname;
		att->attrs = lcons(makeString(ident->name), NIL);
		column_result = (Node *) ParseNestedFuncOrColumn(pstate, att,
									  &pstate->p_last_resno, precedence);
	}

	/* try to find the ident as a relation */
	if (refnameRangeTableEntry(pstate, ident->name) != NULL)
	{
		ident->isRel = TRUE;
		relation_result = (Node *) ident;
	}

	/* choose the right result based on the precedence */
	if (precedence == EXPR_COLUMN_FIRST)
	{
		if (column_result)
			result = column_result;
		else
			result = relation_result;
	}
	else
	{
		if (relation_result)
			result = relation_result;
		else
			result = column_result;
	}

	if (result == NULL)
		elog(ERROR, "attribute '%s' not found", ident->name);

	return result;
}

/*
 *	exprType -
 *	  returns the Oid of the type of the expression. (Used for typechecking.)
 */
Oid
exprType(Node *expr)
{
	Oid			type = (Oid) 0;

	if (!expr)
		return type;

	switch (nodeTag(expr))
	{
		case T_Func:
			type = ((Func *) expr)->functype;
			break;
		case T_Iter:
			type = ((Iter *) expr)->itertype;
			break;
		case T_Var:
			type = ((Var *) expr)->vartype;
			break;
		case T_Expr:
			type = ((Expr *) expr)->typeOid;
			break;
		case T_Const:
			type = ((Const *) expr)->consttype;
			break;
		case T_ArrayRef:
			type = ((ArrayRef *) expr)->refelemtype;
			break;
		case T_Aggref:
			type = ((Aggref *) expr)->aggtype;
			break;
		case T_Param:
			type = ((Param *) expr)->paramtype;
			break;
		case T_SubLink:
			{
				SubLink    *sublink = (SubLink *) expr;

				if (sublink->subLinkType == EXPR_SUBLINK)
				{
					/* return the result type of the combining operator */
					Expr	   *op_expr = (Expr *) lfirst(sublink->oper);

					type = op_expr->typeOid;
				}
				else
				{
					/* for all other sublink types, result is boolean */
					type = BOOLOID;
				}
			}
			break;
		case T_CaseExpr:
			type = ((CaseExpr *) expr)->casetype;
			break;
		case T_CaseWhen:
			type = exprType(((CaseWhen *) expr)->result);
			break;
		case T_Ident:
			/* is this right? */
			type = UNKNOWNOID;
			break;
		default:
			elog(ERROR, "exprType: don't know how to get type for %d node",
				 nodeTag(expr));
			break;
	}
	return type;
}

static Node *
parser_typecast(Value *expr, TypeName *typename, int32 atttypmod)
{
	/* check for passing non-ints */
	Const	   *adt;
	Datum		lcp;
	Type		tp;
	char		type_string[NAMEDATALEN];
	int32		len;
	char	   *cp = NULL;
	char	   *const_string = NULL;
	bool		string_palloced = false;

	switch (nodeTag(expr))
	{
		case T_String:
			const_string = DatumGetPointer(expr->val.str);
			break;
		case T_Integer:
			string_palloced = true;
			const_string = int4out(expr->val.ival);
			break;
		case T_Float:
			string_palloced = true;
			const_string = float8out(&expr->val.dval);
			break;
		default:
			elog(ERROR,
			 "parser_typecast: cannot cast this expression to type '%s'",
				 typename->name);
	}

	if (typename->arrayBounds != NIL)
	{
		sprintf(type_string, "_%s", typename->name);
		tp = (Type) typenameType(type_string);
	}
	else
		tp = (Type) typenameType(typename->name);

	len = typeLen(tp);

	cp = stringTypeString(tp, const_string, atttypmod);

	if (!typeByVal(tp))
		lcp = PointerGetDatum(cp);
	else
	{
		switch (len)
		{
			case 1:
				lcp = Int8GetDatum(cp);
				break;
			case 2:
				lcp = Int16GetDatum(cp);
				break;
			case 4:
				lcp = Int32GetDatum(cp);
				break;
			default:
				lcp = PointerGetDatum(cp);
				break;
		}
	}

	adt = makeConst(typeTypeId(tp),
					len,
					(Datum) lcp,
					false,
					typeByVal(tp),
					false,		/* not a set */
					true /* is cast */ );

	if (string_palloced)
		pfree(const_string);

	return (Node *) adt;
}


/* parser_typecast2()
 * Convert (only) constants to specified type.
 */
Node *
parser_typecast2(Node *expr, Oid exprType, Type tp, int32 atttypmod)
{
	/* check for passing non-ints */
	Const	   *adt;
	Datum		lcp;
	int32		len = typeLen(tp);
	char	   *cp = NULL;

	char	   *const_string = NULL;
	bool		string_palloced = false;

	Assert(IsA(expr, Const));

	switch (exprType)
	{
		case 0:			/* NULL */
			break;
		case INT4OID:			/* int4 */
			const_string = (char *) palloc(256);
			string_palloced = true;
			sprintf(const_string, "%d",
					(int) ((Const *) expr)->constvalue);
			break;
		case NAMEOID:			/* name */
			const_string = (char *) palloc(256);
			string_palloced = true;
			sprintf(const_string, "%s",
					(char *) ((Const *) expr)->constvalue);
			break;
		case CHAROID:			/* char */
			const_string = (char *) palloc(256);
			string_palloced = true;
			sprintf(const_string, "%c",
					(char) ((Const *) expr)->constvalue);
			break;
		case FLOAT4OID: /* float4 */
			{
				float32		floatVal = DatumGetFloat32(((Const *) expr)->constvalue);

				const_string = (char *) palloc(256);
				string_palloced = true;
				sprintf(const_string, "%f", *floatVal);
				break;
			}
		case FLOAT8OID: /* float8 */
			{
				float64		floatVal = DatumGetFloat64(((Const *) expr)->constvalue);

				const_string = (char *) palloc(256);
				string_palloced = true;
				sprintf(const_string, "%f", *floatVal);
				break;
			}
		case CASHOID:			/* money */
			const_string = (char *) palloc(256);
			string_palloced = true;
			sprintf(const_string, "%ld",
					(long) ((Const *) expr)->constvalue);
			break;
		case TEXTOID:			/* text */
			const_string = DatumGetPointer(((Const *) expr)->constvalue);
			const_string = (char *) textout((struct varlena *) const_string);
			break;
		case UNKNOWNOID:		/* unknown */
			const_string = DatumGetPointer(((Const *) expr)->constvalue);
			const_string = (char *) textout((struct varlena *) const_string);
			break;
		default:
			elog(ERROR, "unknown type %u", exprType);
	}

	if (!exprType)
	{
		adt = makeConst(typeTypeId(tp),
						(Size) 0,
						(Datum) NULL,
						true,	/* isnull */
						false,	/* was omitted */
						false,	/* not a set */
						true /* is cast */ );
		return (Node *) adt;
	}

	cp = stringTypeString(tp, const_string, atttypmod);

	if (!typeByVal(tp))
		lcp = PointerGetDatum(cp);
	else
	{
		switch (len)
		{
			case 1:
				lcp = Int8GetDatum(cp);
				break;
			case 2:
				lcp = Int16GetDatum(cp);
				break;
			case 4:
				lcp = Int32GetDatum(cp);
				break;
			default:
				lcp = PointerGetDatum(cp);
				break;
		}
	}

	adt = makeConst(typeTypeId(tp),
					(Size) len,
					(Datum) lcp,
					false,
					typeByVal(tp),
					false,		/* not a set */
					true /* is cast */ );

	/*
	 * printf("adt %s : %u %d %d\n",CString(expr),typeTypeId(tp) ,
	 * len,cp);
	 */
	if (string_palloced)
		pfree(const_string);

	return (Node *) adt;
}