static bool is_strict_saop(ScalarArrayOpExpr *expr, bool falseOK);
static Node *eval_const_expressions_mutator(Node *node,
eval_const_expressions_context *context);
+static bool contain_non_const_walker(Node *node, void *context);
+static bool ece_function_is_safe(Oid funcid,
+ eval_const_expressions_context *context);
static List *simplify_or_arguments(List *args,
eval_const_expressions_context *context,
bool *haveNull, bool *forceTrue);
return eval_const_expressions_mutator(node, &context);
}
+/*
+ * The generic case in eval_const_expressions_mutator is to recurse using
+ * expression_tree_mutator, which will copy the given node unchanged but
+ * const-simplify its arguments (if any) as far as possible. If the node
+ * itself does immutable processing, and each of its arguments were reduced
+ * to a Const, we can then reduce it to a Const using evaluate_expr. (Some
+ * node types need more complicated logic; for example, a CASE expression
+ * might be reducible to a constant even if not all its subtrees are.)
+ */
+#define ece_generic_processing(node) \
+ expression_tree_mutator((Node *) (node), eval_const_expressions_mutator, \
+ (void *) context)
+
+/*
+ * Check whether all arguments of the given node were reduced to Consts.
+ * By going directly to expression_tree_walker, contain_non_const_walker
+ * is not applied to the node itself, only to its children.
+ */
+#define ece_all_arguments_const(node) \
+ (!expression_tree_walker((Node *) (node), contain_non_const_walker, NULL))
+
+/* Generic macro for applying evaluate_expr */
+#define ece_evaluate_expr(node) \
+ ((Node *) evaluate_expr((Expr *) (node), \
+ exprType((Node *) (node)), \
+ exprTypmod((Node *) (node)), \
+ exprCollation((Node *) (node))))
+
+/*
+ * Recursive guts of eval_const_expressions/estimate_expression_value
+ */
static Node *
eval_const_expressions_mutator(Node *node,
eval_const_expressions_context *context)
newexpr->location = expr->location;
return (Node *) newexpr;
}
+ case T_ScalarArrayOpExpr:
+ {
+ ScalarArrayOpExpr *saop;
+
+ /* Copy the node and const-simplify its arguments */
+ saop = (ScalarArrayOpExpr *) ece_generic_processing(node);
+
+ /* Make sure we know underlying function */
+ set_sa_opfuncid(saop);
+
+ /*
+ * If all arguments are Consts, and it's a safe function, we
+ * can fold to a constant
+ */
+ if (ece_all_arguments_const(saop) &&
+ ece_function_is_safe(saop->opfuncid, context))
+ return ece_evaluate_expr(saop);
+ return (Node *) saop;
+ }
case T_BoolExpr:
{
BoolExpr *expr = (BoolExpr *) node;
}
case T_ArrayCoerceExpr:
{
- ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;
- Expr *arg;
- Expr *elemexpr;
- ArrayCoerceExpr *newexpr;
-
- /*
- * Reduce constants in the ArrayCoerceExpr's argument and
- * per-element expressions, then build a new ArrayCoerceExpr.
- */
- arg = (Expr *) eval_const_expressions_mutator((Node *) expr->arg,
- context);
- elemexpr = (Expr *) eval_const_expressions_mutator((Node *) expr->elemexpr,
- context);
+ ArrayCoerceExpr *ac;
- newexpr = makeNode(ArrayCoerceExpr);
- newexpr->arg = arg;
- newexpr->elemexpr = elemexpr;
- newexpr->resulttype = expr->resulttype;
- newexpr->resulttypmod = expr->resulttypmod;
- newexpr->resultcollid = expr->resultcollid;
- newexpr->coerceformat = expr->coerceformat;
- newexpr->location = expr->location;
+ /* Copy the node and const-simplify its arguments */
+ ac = (ArrayCoerceExpr *) ece_generic_processing(node);
/*
- * If constant argument and per-element expression is
+ * If constant argument and the per-element expression is
* immutable, we can simplify the whole thing to a constant.
* Exception: although contain_mutable_functions considers
* CoerceToDomain immutable for historical reasons, let's not
* do so here; this ensures coercion to an array-over-domain
* does not apply the domain's constraints until runtime.
*/
- if (arg && IsA(arg, Const) &&
- elemexpr && !IsA(elemexpr, CoerceToDomain) &&
- !contain_mutable_functions((Node *) elemexpr))
- return (Node *) evaluate_expr((Expr *) newexpr,
- newexpr->resulttype,
- newexpr->resulttypmod,
- newexpr->resultcollid);
-
- /* Else we must return the partially-simplified node */
- return (Node *) newexpr;
+ if (ac->arg && IsA(ac->arg, Const) &&
+ ac->elemexpr && !IsA(ac->elemexpr, CoerceToDomain) &&
+ !contain_mutable_functions((Node *) ac->elemexpr))
+ return ece_evaluate_expr(ac);
+ return (Node *) ac;
}
case T_CollateExpr:
{
else
return copyObject(node);
}
+ case T_ArrayRef:
case T_ArrayExpr:
+ case T_RowExpr:
{
- ArrayExpr *arrayexpr = (ArrayExpr *) node;
- ArrayExpr *newarray;
- bool all_const = true;
- List *newelems;
- ListCell *element;
-
- newelems = NIL;
- foreach(element, arrayexpr->elements)
- {
- Node *e;
-
- e = eval_const_expressions_mutator((Node *) lfirst(element),
- context);
- if (!IsA(e, Const))
- all_const = false;
- newelems = lappend(newelems, e);
- }
+ /*
+ * Generic handling for node types whose own processing is
+ * known to be immutable, and for which we need no smarts
+ * beyond "simplify if all inputs are constants".
+ */
- newarray = makeNode(ArrayExpr);
- newarray->array_typeid = arrayexpr->array_typeid;
- newarray->array_collid = arrayexpr->array_collid;
- newarray->element_typeid = arrayexpr->element_typeid;
- newarray->elements = newelems;
- newarray->multidims = arrayexpr->multidims;
- newarray->location = arrayexpr->location;
-
- if (all_const)
- return (Node *) evaluate_expr((Expr *) newarray,
- newarray->array_typeid,
- exprTypmod(node),
- newarray->array_collid);
-
- return (Node *) newarray;
+ /* Copy the node and const-simplify its arguments */
+ node = ece_generic_processing(node);
+ /* If all arguments are Consts, we can fold to a constant */
+ if (ece_all_arguments_const(node))
+ return ece_evaluate_expr(node);
+ return node;
}
case T_CoalesceExpr:
{
* simple Var. (This case won't be generated directly by the
* parser, because ParseComplexProjection short-circuits it.
* But it can arise while simplifying functions.) Also, we
- * can optimize field selection from a RowExpr construct.
+ * can optimize field selection from a RowExpr construct, or
+ * of course from a constant.
*
* However, replacing a whole-row Var in this way has a
* pitfall: if we've already built the rel targetlist for the
* We must also check that the declared type of the field is
* still the same as when the FieldSelect was created --- this
* can change if someone did ALTER COLUMN TYPE on the rowtype.
+ * If it isn't, we skip the optimization; the case will
+ * probably fail at runtime, but that's not our problem here.
*/
FieldSelect *fselect = (FieldSelect *) node;
FieldSelect *newfselect;
newfselect->resulttype = fselect->resulttype;
newfselect->resulttypmod = fselect->resulttypmod;
newfselect->resultcollid = fselect->resultcollid;
+ if (arg && IsA(arg, Const))
+ {
+ Const *con = (Const *) arg;
+
+ if (rowtype_field_matches(con->consttype,
+ newfselect->fieldnum,
+ newfselect->resulttype,
+ newfselect->resulttypmod,
+ newfselect->resultcollid))
+ return ece_evaluate_expr(newfselect);
+ }
return (Node *) newfselect;
}
case T_NullTest:
}
case T_BooleanTest:
{
+ /*
+ * This case could be folded into the generic handling used
+ * for ArrayRef etc. But because the simplification logic is
+ * so trivial, applying evaluate_expr() to perform it would be
+ * a heavy overhead. BooleanTest is probably common enough to
+ * justify keeping this bespoke implementation.
+ */
BooleanTest *btest = (BooleanTest *) node;
BooleanTest *newbtest;
Node *arg;
}
/*
- * For any node type not handled above, we recurse using
- * expression_tree_mutator, which will copy the node unchanged but try to
- * simplify its arguments (if any) using this routine. For example: we
- * cannot eliminate an ArrayRef node, but we might be able to simplify
- * constant expressions in its subscripts.
+ * For any node type not handled above, copy the node unchanged but
+ * const-simplify its subexpressions. This is the correct thing for node
+ * types whose behavior might change between planning and execution, such
+ * as CoerceToDomain. It's also a safe default for new node types not
+ * known to this routine.
*/
- return expression_tree_mutator(node, eval_const_expressions_mutator,
- (void *) context);
+ return ece_generic_processing(node);
+}
+
+/*
+ * Subroutine for eval_const_expressions: check for non-Const nodes.
+ *
+ * We can abort recursion immediately on finding a non-Const node. This is
+ * critical for performance, else eval_const_expressions_mutator would take
+ * O(N^2) time on non-simplifiable trees. However, we do need to descend
+ * into List nodes since expression_tree_walker sometimes invokes the walker
+ * function directly on List subtrees.
+ */
+static bool
+contain_non_const_walker(Node *node, void *context)
+{
+ if (node == NULL)
+ return false;
+ if (IsA(node, Const))
+ return false;
+ if (IsA(node, List))
+ return expression_tree_walker(node, contain_non_const_walker, context);
+ /* Otherwise, abort the tree traversal and return true */
+ return true;
+}
+
+/*
+ * Subroutine for eval_const_expressions: check if a function is OK to evaluate
+ */
+static bool
+ece_function_is_safe(Oid funcid, eval_const_expressions_context *context)
+{
+ char provolatile = func_volatile(funcid);
+
+ /*
+ * Ordinarily we are only allowed to simplify immutable functions. But for
+ * purposes of estimation, we consider it okay to simplify functions that
+ * are merely stable; the risk that the result might change from planning
+ * time to execution time is worth taking in preference to not being able
+ * to estimate the value at all.
+ */
+ if (provolatile == PROVOLATILE_IMMUTABLE)
+ return true;
+ if (context->estimate && provolatile == PROVOLATILE_STABLE)
+ return true;
+ return false;
}
/*
projects / postgresql / commitdiff