*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.61 2000/03/12 19:32:06 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.62 2000/03/19 18:20:38 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
check_subplans_for_ungrouped_vars_context *context);
static int is_single_func(Node *node);
static Node *eval_const_expressions_mutator (Node *node, void *context);
+static Expr *simplify_op_or_func(Expr *expr, List *args);
Expr *
{
case OP_EXPR:
case FUNC_EXPR:
- {
- /*
- * For an operator or function, we cannot simplify
- * unless all the inputs are constants. (XXX possible
- * future improvement: if the op/func is strict and
- * at least one input is NULL, we could simplify to NULL.
- * But we do not currently have any way to know if the
- * op/func is strict or not. For now, a NULL input is
- * treated the same as any other constant node.)
- */
- bool args_all_const = true;
- List *arg;
- Oid funcid;
- Oid result_typeid;
- HeapTuple func_tuple;
- Form_pg_proc funcform;
- Type resultType;
- Datum const_val;
- bool const_is_null;
- bool isDone;
-
- foreach(arg, args)
- {
- if (! IsA(lfirst(arg), Const))
- {
- args_all_const = false;
- break;
- }
- }
- if (! args_all_const)
- break;
- /*
- * Get the function procedure's OID and look to see
- * whether it is marked proiscachable.
- */
- if (expr->opType == OP_EXPR)
- {
- Oper *oper = (Oper *) expr->oper;
-
- replace_opid(oper);
- funcid = oper->opid;
- result_typeid = oper->opresulttype;
- }
- else
- {
- Func *func = (Func *) expr->oper;
-
- funcid = func->funcid;
- result_typeid = func->functype;
- }
- /* Someday lsyscache.c might provide a function for this */
- func_tuple = SearchSysCacheTuple(PROCOID,
- ObjectIdGetDatum(funcid),
- 0, 0, 0);
- if (!HeapTupleIsValid(func_tuple))
- elog(ERROR, "Function OID %u does not exist", funcid);
- funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
- if (! funcform->proiscachable)
- break;
- /*
- * Also check to make sure it doesn't return a set.
- *
- * XXX would it be better to take the result type from the
- * pg_proc tuple, rather than the Oper or Func node?
- */
- if (funcform->proretset)
- break;
- /*
- * OK, looks like we can simplify this operator/function.
- * We use the executor's routine ExecEvalExpr() to avoid
- * duplication of code and ensure we get the same result
- * as the executor would get.
- *
- * Build a new Expr node containing the already-simplified
- * arguments. The only other setup needed here is the
- * replace_opid() that we already did for the OP_EXPR case.
- */
- newexpr = makeNode(Expr);
- newexpr->typeOid = expr->typeOid;
- newexpr->opType = expr->opType;
- newexpr->oper = expr->oper;
- newexpr->args = args;
- /*
- * It is OK to pass econtext = NULL because none of the
- * ExecEvalExpr() code used in this situation will use
- * econtext. That might seem fortuitous, but it's not
- * so unreasonable --- a constant expression does not
- * depend on context, by definition, n'est ce pas?
- */
- const_val = ExecEvalExpr((Node *) newexpr, NULL,
- &const_is_null, &isDone);
- Assert(isDone); /* if this isn't set, we blew it... */
- pfree(newexpr);
/*
- * Make the constant result node.
+ * Code for op/func case is pretty bulky, so split it out
+ * as a separate function.
*/
- resultType = typeidType(result_typeid);
- return (Node *) makeConst(result_typeid, typeLen(resultType),
- const_val, const_is_null,
- typeByVal(resultType),
- false, false);
- }
+ newexpr = simplify_op_or_func(expr, args);
+ if (newexpr) /* successfully simplified it */
+ return (Node *) newexpr;
+ /* else fall out to build new Expr node with simplified args */
+ break;
case OR_EXPR:
{
/*
/*
* If we can simplify the input to a constant, then we don't need
* the RelabelType node anymore: just change the type field of
- * the Const node. Otherwise keep the RelabelType node.
- *
- * XXX if relabel has a nondefault resulttypmod, do we need to
- * keep it to show that? At present I don't think so.
+ * the Const node. Otherwise, copy the RelabelType node.
*/
RelabelType *relabel = (RelabelType *) node;
Node *arg;
Const *con = (Const *) arg;
con->consttype = relabel->resulttype;
+ /*
+ * relabel's resulttypmod is discarded, which is OK for now;
+ * if the type actually needs a runtime length coercion then
+ * there should be a function call to do it just above this node.
+ */
return (Node *) con;
}
else
(void *) context);
}
+/*
+ * Subroutine for eval_const_expressions: try to evaluate an op or func
+ *
+ * Inputs are the op or func Expr node, and the pre-simplified argument list.
+ * Returns a simplified expression if successful, or NULL if cannot
+ * simplify the op/func.
+ *
+ * XXX Possible future improvement: if the func is SQL-language, and its
+ * definition is simply "SELECT expression", we could parse and substitute
+ * the expression here. This would avoid much runtime overhead, and perhaps
+ * expose opportunities for constant-folding within the expression even if
+ * not all the func's input args are constants. It'd be appropriate to do
+ * here, and not in the parser, since we wouldn't want it to happen until
+ * after rule substitution/rewriting.
+ */
+static Expr *
+simplify_op_or_func(Expr *expr, List *args)
+{
+ List *arg;
+ Oid funcid;
+ Oid result_typeid;
+ HeapTuple func_tuple;
+ Form_pg_proc funcform;
+ Type resultType;
+ Expr *newexpr;
+ Datum const_val;
+ bool const_is_null;
+ bool isDone;
+
+ /*
+ * For an operator or function, we cannot simplify unless all the inputs
+ * are constants. (XXX possible future improvement: if the op/func is
+ * strict and at least one input is NULL, we could simplify to NULL.
+ * But we do not currently have any way to know if the op/func is strict
+ * or not. For now, a NULL input is treated the same as any other
+ * constant node.)
+ */
+ foreach(arg, args)
+ {
+ if (! IsA(lfirst(arg), Const))
+ return NULL;
+ }
+ /*
+ * Get the function procedure's OID and look to see
+ * whether it is marked proiscachable.
+ */
+ if (expr->opType == OP_EXPR)
+ {
+ Oper *oper = (Oper *) expr->oper;
+
+ replace_opid(oper); /* OK to scribble on input to this extent */
+ funcid = oper->opid;
+ result_typeid = oper->opresulttype;
+ }
+ else
+ {
+ Func *func = (Func *) expr->oper;
+
+ funcid = func->funcid;
+ result_typeid = func->functype;
+ }
+ /* Someday lsyscache.c might provide a function for this */
+ func_tuple = SearchSysCacheTuple(PROCOID,
+ ObjectIdGetDatum(funcid),
+ 0, 0, 0);
+ if (!HeapTupleIsValid(func_tuple))
+ elog(ERROR, "Function OID %u does not exist", funcid);
+ funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
+ if (! funcform->proiscachable)
+ return NULL;
+ /*
+ * Also check to make sure it doesn't return a set.
+ */
+ if (funcform->proretset)
+ return NULL;
+ /*
+ * OK, looks like we can simplify this operator/function.
+ *
+ * We use the executor's routine ExecEvalExpr() to avoid duplication of
+ * code and ensure we get the same result as the executor would get.
+ *
+ * Build a new Expr node containing the already-simplified arguments.
+ * The only other setup needed here is the replace_opid() that we already
+ * did for the OP_EXPR case.
+ */
+ newexpr = makeNode(Expr);
+ newexpr->typeOid = expr->typeOid;
+ newexpr->opType = expr->opType;
+ newexpr->oper = expr->oper;
+ newexpr->args = args;
+ /*
+ * It is OK to pass econtext = NULL because none of the ExecEvalExpr()
+ * code used in this situation will use econtext. That might seem
+ * fortuitous, but it's not so unreasonable --- a constant expression does
+ * not depend on context, by definition, n'est ce pas?
+ */
+ const_val = ExecEvalExpr((Node *) newexpr, NULL,
+ &const_is_null, &isDone);
+ Assert(isDone); /* if this isn't set, we blew it... */
+ pfree(newexpr);
+ /*
+ * Make the constant result node.
+ *
+ * XXX would it be better to take the result type from the
+ * pg_proc tuple, rather than the Oper or Func node?
+ */
+ resultType = typeidType(result_typeid);
+ return (Expr *) makeConst(result_typeid, typeLen(resultType),
+ const_val, const_is_null,
+ typeByVal(resultType),
+ false, false);
+}
+
+
/*
* Standard expression-tree walking support
*
projects / users / c2main / postgres.git / commitdiff