parse_expr.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

				 * Although the parser does not ever deal with already-planned
				 * expression trees, we support SubPlan nodes in this routine
				 * for the convenience of ruleutils.c.
				 */
				SubPlan    *subplan = (SubPlan *) expr;

				if (subplan->subLinkType == EXPR_SUBLINK ||
					subplan->subLinkType == ARRAY_SUBLINK)
				{
					/* get the type of the subselect's first target column */
					TargetEntry *tent;

					tent = (TargetEntry *) linitial(subplan->plan->targetlist);
					Assert(IsA(tent, TargetEntry));
					Assert(!tent->resjunk);
					type = exprType((Node *) tent->expr);
					if (subplan->subLinkType == ARRAY_SUBLINK)
					{
						type = get_array_type(type);
						if (!OidIsValid(type))
							ereport(ERROR,
									(errcode(ERRCODE_UNDEFINED_OBJECT),
									 errmsg("could not find array type for data type %s",
							format_type_be(exprType((Node *) tent->expr)))));
					}
				}
				else
				{
					/* for all other subplan types, result is boolean */
					type = BOOLOID;
				}
			}
			break;
		case T_FieldSelect:
			type = ((FieldSelect *) expr)->resulttype;
			break;
		case T_FieldStore:
			type = ((FieldStore *) expr)->resulttype;
			break;
		case T_RelabelType:
			type = ((RelabelType *) expr)->resulttype;
			break;
		case T_ConvertRowtypeExpr:
			type = ((ConvertRowtypeExpr *) expr)->resulttype;
			break;
		case T_CaseExpr:
			type = ((CaseExpr *) expr)->casetype;
			break;
		case T_CaseWhen:
			type = exprType((Node *) ((CaseWhen *) expr)->result);
			break;
		case T_CaseTestExpr:
			type = ((CaseTestExpr *) expr)->typeId;
			break;
		case T_ArrayExpr:
			type = ((ArrayExpr *) expr)->array_typeid;
			break;
		case T_RowExpr:
			type = ((RowExpr *) expr)->row_typeid;
			break;
		case T_CoalesceExpr:
			type = ((CoalesceExpr *) expr)->coalescetype;
			break;
		case T_MinMaxExpr:
			type = ((MinMaxExpr *) expr)->minmaxtype;
			break;
		case T_NullIfExpr:
			type = exprType((Node *) linitial(((NullIfExpr *) expr)->args));
			break;
		case T_NullTest:
			type = BOOLOID;
			break;
		case T_BooleanTest:
			type = BOOLOID;
			break;
		case T_CoerceToDomain:
			type = ((CoerceToDomain *) expr)->resulttype;
			break;
		case T_CoerceToDomainValue:
			type = ((CoerceToDomainValue *) expr)->typeId;
			break;
		case T_SetToDefault:
			type = ((SetToDefault *) expr)->typeId;
			break;
		default:
			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(expr));
			type = InvalidOid;	/* keep compiler quiet */
			break;
	}
	return type;
}

/*
 *	exprTypmod -
 *	  returns the type-specific attrmod of the expression, if it can be
 *	  determined.  In most cases, it can't and we return -1.
 */
int32
exprTypmod(Node *expr)
{
	if (!expr)
		return -1;

	switch (nodeTag(expr))
	{
		case T_Var:
			return ((Var *) expr)->vartypmod;
		case T_Const:
			{
				/* Be smart about string constants... */
				Const	   *con = (Const *) expr;

				switch (con->consttype)
				{
					case BPCHAROID:
						if (!con->constisnull)
						{
							int32		len = VARSIZE(DatumGetPointer(con->constvalue)) - VARHDRSZ;

							/* if multi-byte, take len and find # characters */
							if (pg_database_encoding_max_length() > 1)
								len = pg_mbstrlen_with_len(VARDATA(DatumGetPointer(con->constvalue)), len);
							return len + VARHDRSZ;
						}
						break;
					default:
						break;
				}
			}
			break;
		case T_FuncExpr:
			{
				int32		coercedTypmod;

				/* Be smart about length-coercion functions... */
				if (exprIsLengthCoercion(expr, &coercedTypmod))
					return coercedTypmod;
			}
			break;
		case T_FieldSelect:
			return ((FieldSelect *) expr)->resulttypmod;
		case T_RelabelType:
			return ((RelabelType *) expr)->resulttypmod;
		case T_CaseExpr:
			{
				/*
				 * If all the alternatives agree on type/typmod, return that
				 * typmod, else use -1
				 */
				CaseExpr   *cexpr = (CaseExpr *) expr;
				Oid			casetype = cexpr->casetype;
				int32		typmod;
				ListCell   *arg;

				if (!cexpr->defresult)
					return -1;
				if (exprType((Node *) cexpr->defresult) != casetype)
					return -1;
				typmod = exprTypmod((Node *) cexpr->defresult);
				if (typmod < 0)
					return -1;	/* no point in trying harder */
				foreach(arg, cexpr->args)
				{
					CaseWhen   *w = (CaseWhen *) lfirst(arg);

					Assert(IsA(w, CaseWhen));
					if (exprType((Node *) w->result) != casetype)
						return -1;
					if (exprTypmod((Node *) w->result) != typmod)
						return -1;
				}
				return typmod;
			}
			break;
		case T_CaseTestExpr:
			return ((CaseTestExpr *) expr)->typeMod;
		case T_CoalesceExpr:
			{
				/*
				 * If all the alternatives agree on type/typmod, return that
				 * typmod, else use -1
				 */
				CoalesceExpr *cexpr = (CoalesceExpr *) expr;
				Oid			coalescetype = cexpr->coalescetype;
				int32		typmod;
				ListCell   *arg;

				if (exprType((Node *) linitial(cexpr->args)) != coalescetype)
					return -1;
				typmod = exprTypmod((Node *) linitial(cexpr->args));
				if (typmod < 0)
					return -1;	/* no point in trying harder */
				for_each_cell(arg, lnext(list_head(cexpr->args)))
				{
					Node	   *e = (Node *) lfirst(arg);

					if (exprType(e) != coalescetype)
						return -1;
					if (exprTypmod(e) != typmod)
						return -1;
				}
				return typmod;
			}
			break;
		case T_MinMaxExpr:
			{
				/*
				 * If all the alternatives agree on type/typmod, return that
				 * typmod, else use -1
				 */
				MinMaxExpr *mexpr = (MinMaxExpr *) expr;
				Oid			minmaxtype = mexpr->minmaxtype;
				int32		typmod;
				ListCell   *arg;

				if (exprType((Node *) linitial(mexpr->args)) != minmaxtype)
					return -1;
				typmod = exprTypmod((Node *) linitial(mexpr->args));
				if (typmod < 0)
					return -1;	/* no point in trying harder */
				for_each_cell(arg, lnext(list_head(mexpr->args)))
				{
					Node	   *e = (Node *) lfirst(arg);

					if (exprType(e) != minmaxtype)
						return -1;
					if (exprTypmod(e) != typmod)
						return -1;
				}
				return typmod;
			}
			break;
		case T_NullIfExpr:
			{
				NullIfExpr *nexpr = (NullIfExpr *) expr;

				return exprTypmod((Node *) linitial(nexpr->args));
			}
			break;
		case T_CoerceToDomain:
			return ((CoerceToDomain *) expr)->resulttypmod;
		case T_CoerceToDomainValue:
			return ((CoerceToDomainValue *) expr)->typeMod;
		case T_SetToDefault:
			return ((SetToDefault *) expr)->typeMod;
		default:
			break;
	}
	return -1;
}

/*
 * exprIsLengthCoercion
 *		Detect whether an expression tree is an application of a datatype's
 *		typmod-coercion function.  Optionally extract the result's typmod.
 *
 * If coercedTypmod is not NULL, the typmod is stored there if the expression
 * is a length-coercion function, else -1 is stored there.
 *
 * Note that a combined type-and-length coercion will be treated as a
 * length coercion by this routine.
 */
bool
exprIsLengthCoercion(Node *expr, int32 *coercedTypmod)
{
	FuncExpr   *func;
	int			nargs;
	Const	   *second_arg;

	if (coercedTypmod != NULL)
		*coercedTypmod = -1;	/* default result on failure */

	/* Is it a function-call at all? */
	if (expr == NULL || !IsA(expr, FuncExpr))
		return false;
	func = (FuncExpr *) expr;

	/*
	 * If it didn't come from a coercion context, reject.
	 */
	if (func->funcformat != COERCE_EXPLICIT_CAST &&
		func->funcformat != COERCE_IMPLICIT_CAST)
		return false;

	/*
	 * If it's not a two-argument or three-argument function with the second
	 * argument being an int4 constant, it can't have been created from a
	 * length coercion (it must be a type coercion, instead).
	 */
	nargs = list_length(func->args);
	if (nargs < 2 || nargs > 3)
		return false;

	second_arg = (Const *) lsecond(func->args);
	if (!IsA(second_arg, Const) ||
		second_arg->consttype != INT4OID ||
		second_arg->constisnull)
		return false;

	/*
	 * OK, it is indeed a length-coercion function.
	 */
	if (coercedTypmod != NULL)
		*coercedTypmod = DatumGetInt32(second_arg->constvalue);

	return true;
}

/*
 * Handle an explicit CAST construct.
 *
 * The given expr has already been transformed, but we need to lookup
 * the type name and then apply any necessary coercion function(s).
 */
static Node *
typecast_expression(ParseState *pstate, Node *expr, TypeName *typename)
{
	Oid			inputType = exprType(expr);
	Oid			targetType;

	targetType = typenameTypeId(typename);

	if (inputType == InvalidOid)
		return expr;			/* do nothing if NULL input */

	expr = coerce_to_target_type(pstate, expr, inputType,
								 targetType, typename->typmod,
								 COERCION_EXPLICIT,
								 COERCE_EXPLICIT_CAST);
	if (expr == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_CANNOT_COERCE),
				 errmsg("cannot cast type %s to %s",
						format_type_be(inputType),
						format_type_be(targetType))));

	return expr;
}

/*
 * Transform a "row op row" construct
 */
static Node *
make_row_op(ParseState *pstate, List *opname, Node *ltree, Node *rtree)
{
	Node	   *result = NULL;
	RowExpr    *lrow,
			   *rrow;
	List	   *largs,
			   *rargs;
	ListCell   *l,
			   *r;
	char	   *oprname;
	BoolExprType boolop;

	/* Inputs are untransformed RowExprs */
	lrow = (RowExpr *) transformExpr(pstate, ltree);
	rrow = (RowExpr *) transformExpr(pstate, rtree);
	Assert(IsA(lrow, RowExpr));
	Assert(IsA(rrow, RowExpr));
	largs = lrow->args;
	rargs = rrow->args;

	if (list_length(largs) != list_length(rargs))
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("unequal number of entries in row expression")));

	/*
	 * XXX it's really wrong to generate a simple AND combination for < <= >
	 * >=.	We probably need to invent a new runtime node type to handle those
	 * correctly.  For the moment, though, keep on doing this ...
	 */
	oprname = strVal(llast(opname));

	if ((strcmp(oprname, "=") == 0) ||
		(strcmp(oprname, "<") == 0) ||
		(strcmp(oprname, "<=") == 0) ||
		(strcmp(oprname, ">") == 0) ||
		(strcmp(oprname, ">=") == 0))
		boolop = AND_EXPR;
	else if (strcmp(oprname, "<>") == 0)
		boolop = OR_EXPR;
	else
	{
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("operator %s is not supported for row expressions",
						oprname)));
		boolop = 0;				/* keep compiler quiet */
	}

	forboth(l, largs, r, rargs)
	{
		Node	   *larg = (Node *) lfirst(l);
		Node	   *rarg = (Node *) lfirst(r);
		Node	   *cmp;

		cmp = (Node *) make_op(pstate, opname, larg, rarg);
		cmp = coerce_to_boolean(pstate, cmp, "row comparison");
		if (result == NULL)
			result = cmp;
		else
			result = (Node *) makeBoolExpr(boolop,
										   list_make2(result, cmp));
	}

	if (result == NULL)
	{
		/* zero-length rows?  Generate constant TRUE or FALSE */
		if (boolop == AND_EXPR)
			result = makeBoolConst(true, false);
		else
			result = makeBoolConst(false, false);
	}

	return result;
}

/*
 * Transform a "row IS DISTINCT FROM row" construct
 */
static Node *
make_row_distinct_op(ParseState *pstate, List *opname,
					 Node *ltree, Node *rtree)
{
	Node	   *result = NULL;
	RowExpr    *lrow,
			   *rrow;
	List	   *largs,
			   *rargs;
	ListCell   *l,
			   *r;

	/* Inputs are untransformed RowExprs */
	lrow = (RowExpr *) transformExpr(pstate, ltree);
	rrow = (RowExpr *) transformExpr(pstate, rtree);
	Assert(IsA(lrow, RowExpr));
	Assert(IsA(rrow, RowExpr));
	largs = lrow->args;
	rargs = rrow->args;

	if (list_length(largs) != list_length(rargs))
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("unequal number of entries in row expression")));

	forboth(l, largs, r, rargs)
	{
		Node	   *larg = (Node *) lfirst(l);
		Node	   *rarg = (Node *) lfirst(r);
		Node	   *cmp;

		cmp = (Node *) make_distinct_op(pstate, opname, larg, rarg);
		if (result == NULL)
			result = cmp;
		else
			result = (Node *) makeBoolExpr(OR_EXPR,
										   list_make2(result, cmp));
	}

	if (result == NULL)
	{
		/* zero-length rows?  Generate constant FALSE */
		result = makeBoolConst(false, false);
	}

	return result;
}

/*
 * make the node for an IS DISTINCT FROM operator
 */
static Expr *
make_distinct_op(ParseState *pstate, List *opname, Node *ltree, Node *rtree)
{
	Expr	   *result;

	result = make_op(pstate, opname, ltree, rtree);
	if (((OpExpr *) result)->opresulttype != BOOLOID)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
		   errmsg("IS DISTINCT FROM requires = operator to yield boolean")));

	/*
	 * We rely on DistinctExpr and OpExpr being same struct
	 */
	NodeSetTag(result, T_DistinctExpr);

	return result;
}