*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.43 1999/07/27 03:51:04 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.44 1999/08/09 00:51:24 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
#include "utils/lsyscache.h"
-static bool fix_opid_walker(Node *node, void *context);
+static bool fix_opids_walker(Node *node, void *context);
static int is_single_func(Node *node);
else
restqual = lcons(lfirst(q), restqual);
}
- freeList(quals);
+ freeList(quals); /* XXX seems a tad risky? */
*constantQual = constqual;
return restqual;
}
if (vi == NIL)
var_list = lappend(var_list, var);
}
+ freeList(clvars);
*relids = varno_list;
*vars = var_list;
List *vars = pull_var_clause(clause);
List *var_list = NIL;
List *i;
+ int result;
foreach(i, vars)
{
var_list = lconsi(var->varno, var_list);
}
- return length(var_list);
+ result = length(var_list);
+ freeList(vars);
+ freeList(var_list);
+ return result;
}
/*
}
/*
- * fix_opid
+ * fix_opids
* Calculate opid field from opno for each Oper node in given tree.
+ * (The given tree can be anything expression_tree_walker handles.)
*
- * Returns nothing.
+ * Returns its argument, which has been modified in-place.
*/
-void
-fix_opid(Node *clause)
+List *
+fix_opids(List *clauses)
{
/* This tree walk requires no special setup, so away we go... */
- fix_opid_walker(clause, NULL);
+ fix_opids_walker((Node *) clauses, NULL);
+ return clauses;
}
static bool
-fix_opid_walker (Node *node, void *context)
+fix_opids_walker (Node *node, void *context)
{
if (node == NULL)
return false;
if (is_opclause(node))
replace_opid((Oper *) ((Expr *) node)->oper);
- return expression_tree_walker(node, fix_opid_walker, context);
-}
-
-/*
- * fix_opids
- * Calculate the opid from the opno for all the clauses...
- *
- * Returns its argument.
- *
- * XXX This could and should be merged with fix_opid.
- *
- */
-List *
-fix_opids(List *clauses)
-{
- fix_opid((Node *) clauses);
- return clauses;
+ return expression_tree_walker(node, fix_opids_walker, context);
}
/*
if (vars != NIL)
{
int funcvarno = ((Var *) lfirst(vars))->varno;
+ List *v;
/* need to check that all args of func are same relation */
- while ((vars = lnext(vars)) != NIL)
+ foreach(v, lnext(vars))
{
- if (((Var *) lfirst(vars))->varno != funcvarno)
- return 0;
+ if (((Var *) lfirst(v))->varno != funcvarno)
+ {
+ funcvarno = 0;
+ break;
+ }
}
+ freeList(vars);
return funcvarno;
}
}
/*--------------------
* CommuteClause: commute a binary operator clause
+ *
+ * XXX the clause is destructively modified!
*--------------------
*/
void
}
-/*--------------------
+/*
* Standard expression-tree walking support
*
* We used to have near-duplicate code in many different routines that
* these routines only actually care about certain node types, and don't
* care about other types except insofar as they have to recurse through
* non-primitive node types. Therefore, we now provide generic tree-walking
- * logic to consolidate the redundant "boilerplate" code.
- *
+ * logic to consolidate the redundant "boilerplate" code. There are
+ * two versions: expression_tree_walker() and expression_tree_mutator().
+ */
+
+/*--------------------
* expression_tree_walker() is designed to support routines that traverse
* a tree in a read-only fashion (although it will also work for routines
- * that modify nodes in-place but never add or delete nodes). A walker
- * routine should look like this:
+ * that modify nodes in-place but never add/delete/replace nodes).
+ * A walker routine should look like this:
*
* bool my_walker (Node *node, my_struct *context)
* {
* }
*
* The "context" argument points to a struct that holds whatever context
- * information the walker routine needs (it can be used to return data
- * gathered by the walker, too). This argument is not touched by
+ * information the walker routine needs --- it can be used to return data
+ * gathered by the walker, too. This argument is not touched by
* expression_tree_walker, but it is passed down to recursive sub-invocations
* of my_walker. The tree walk is started from a setup routine that
* fills in the appropriate context struct, calls my_walker with the top-level
break;
case T_SubLink:
/* A "bare" SubLink (note we will not come here if we found
- * a SUBPLAN_EXPR node above). Examine the lefthand side,
+ * a SUBPLAN_EXPR node above it). Examine the lefthand side,
* but not the oper list nor the subquery.
*/
return walker(((SubLink *) node)->lefthand, context);
}
return false;
}
+
+/*--------------------
+ * expression_tree_mutator() is designed to support routines that make a
+ * modified copy of an expression tree, with some nodes being added,
+ * removed, or replaced by new subtrees. The original tree is (normally)
+ * not changed. Each recursion level is responsible for returning a copy of
+ * (or appropriately modified substitute for) the subtree it is handed.
+ * A mutator routine should look like this:
+ *
+ * Node * my_mutator (Node *node, my_struct *context)
+ * {
+ * if (node == NULL)
+ * return NULL;
+ * // check for nodes that special work is required for, eg:
+ * if (IsA(node, Var))
+ * {
+ * ... create and return modified copy of Var node
+ * }
+ * else if (IsA(node, ...))
+ * {
+ * ... do special transformations of other node types
+ * }
+ * // for any node type not specially processed, do:
+ * return expression_tree_mutator(node, my_mutator, (void *) context);
+ * }
+ *
+ * The "context" argument points to a struct that holds whatever context
+ * information the mutator routine needs --- it can be used to return extra
+ * data gathered by the mutator, too. This argument is not touched by
+ * expression_tree_mutator, but it is passed down to recursive sub-invocations
+ * of my_mutator. The tree walk is started from a setup routine that
+ * fills in the appropriate context struct, calls my_mutator with the
+ * top-level node of the tree, and does any required post-processing.
+ *
+ * Each level of recursion must return an appropriately modified Node.
+ * If expression_tree_mutator() is called, it will make an exact copy
+ * of the given Node, but invoke my_mutator() to copy the sub-node(s)
+ * of that Node. In this way, my_mutator() has full control over the
+ * copying process but need not directly deal with expression trees
+ * that it has no interest in.
+ *
+ * Just as for expression_tree_walker, the node types handled by
+ * expression_tree_mutator include all those normally found in target lists
+ * and qualifier clauses during the planning stage.
+ *
+ * expression_tree_mutator will handle a SUBPLAN_EXPR node by recursing into
+ * the args and slink->oper lists (which belong to the outer plan), but it
+ * will simply copy the link to the inner plan, since that's typically what
+ * expression tree mutators want. A mutator that wants to modify the subplan
+ * can force appropriate behavior by recognizing subplan nodes and doing the
+ * right thing.
+ *
+ * Bare SubLink nodes (without a SUBPLAN_EXPR) are handled by recursing into
+ * the "lefthand" argument list only. (A bare SubLink should be seen only if
+ * the tree has not yet been processed by subselect.c.) Again, this can be
+ * overridden by the mutator, but it seems to be the most useful default
+ * behavior.
+ *--------------------
+ */
+
+Node *
+expression_tree_mutator(Node *node, Node * (*mutator) (), void *context)
+{
+ /*
+ * The mutator has already decided not to modify the current node,
+ * but we must call the mutator for any sub-nodes.
+ */
+
+#define FLATCOPY(newnode, node, nodetype) \
+ ( (newnode) = makeNode(nodetype), \
+ memcpy((newnode), (node), sizeof(nodetype)) )
+
+#define CHECKFLATCOPY(newnode, node, nodetype) \
+ ( AssertMacro(IsA((node), nodetype)), \
+ (newnode) = makeNode(nodetype), \
+ memcpy((newnode), (node), sizeof(nodetype)) )
+
+#define MUTATE(newfield, oldfield, fieldtype) \
+ ( (newfield) = (fieldtype) mutator((Node *) (oldfield), context) )
+
+ if (node == NULL)
+ return NULL;
+ switch (nodeTag(node))
+ {
+ case T_Ident:
+ case T_Const:
+ case T_Var:
+ case T_Param:
+ /* primitive node types with no subnodes */
+ return (Node *) copyObject(node);
+ case T_Expr:
+ {
+ Expr *expr = (Expr *) node;
+ Expr *newnode;
+
+ FLATCOPY(newnode, expr, Expr);
+
+ if (expr->opType == SUBPLAN_EXPR)
+ {
+ SubLink *oldsublink = ((SubPlan *) expr->oper)->sublink;
+ SubPlan *newsubplan;
+
+ /* flat-copy the oper node, which is a SubPlan */
+ CHECKFLATCOPY(newsubplan, expr->oper, SubPlan);
+ newnode->oper = (Node *) newsubplan;
+ /* likewise its SubLink node */
+ CHECKFLATCOPY(newsubplan->sublink, oldsublink, SubLink);
+ /* transform args list (params to be passed to subplan) */
+ MUTATE(newnode->args, expr->args, List *);
+ /* transform sublink's oper list as well */
+ MUTATE(newsubplan->sublink->oper, oldsublink->oper, List*);
+ /* but not the subplan itself, which is referenced as-is */
+ }
+ else
+ {
+ /* for other Expr node types, just transform args list,
+ * linking to original oper node (OK?)
+ */
+ MUTATE(newnode->args, expr->args, List *);
+ }
+ return (Node *) newnode;
+ }
+ break;
+ case T_Aggref:
+ {
+ Aggref *aggref = (Aggref *) node;
+ Aggref *newnode;
+
+ FLATCOPY(newnode, aggref, Aggref);
+ MUTATE(newnode->target, aggref->target, Node *);
+ return (Node *) newnode;
+ }
+ break;
+ case T_Iter:
+ {
+ Iter *iter = (Iter *) node;
+ Iter *newnode;
+
+ FLATCOPY(newnode, iter, Iter);
+ MUTATE(newnode->iterexpr, iter->iterexpr, Node *);
+ return (Node *) newnode;
+ }
+ break;
+ case T_ArrayRef:
+ {
+ ArrayRef *arrayref = (ArrayRef *) node;
+ ArrayRef *newnode;
+
+ FLATCOPY(newnode, arrayref, ArrayRef);
+ MUTATE(newnode->refupperindexpr, arrayref->refupperindexpr,
+ List *);
+ MUTATE(newnode->reflowerindexpr, arrayref->reflowerindexpr,
+ List *);
+ MUTATE(newnode->refexpr, arrayref->refexpr,
+ Node *);
+ MUTATE(newnode->refassgnexpr, arrayref->refassgnexpr,
+ Node *);
+ return (Node *) newnode;
+ }
+ break;
+ case T_CaseExpr:
+ {
+ CaseExpr *caseexpr = (CaseExpr *) node;
+ CaseExpr *newnode;
+
+ FLATCOPY(newnode, caseexpr, CaseExpr);
+ MUTATE(newnode->args, caseexpr->args, List *);
+ /* caseexpr->arg should be null, but we'll check it anyway */
+ MUTATE(newnode->arg, caseexpr->arg, Node *);
+ MUTATE(newnode->defresult, caseexpr->defresult, Node *);
+ return (Node *) newnode;
+ }
+ break;
+ case T_CaseWhen:
+ {
+ CaseWhen *casewhen = (CaseWhen *) node;
+ CaseWhen *newnode;
+
+ FLATCOPY(newnode, casewhen, CaseWhen);
+ MUTATE(newnode->expr, casewhen->expr, Node *);
+ MUTATE(newnode->result, casewhen->result, Node *);
+ return (Node *) newnode;
+ }
+ break;
+ case T_SubLink:
+ {
+ /* A "bare" SubLink (note we will not come here if we found
+ * a SUBPLAN_EXPR node above it). Transform the lefthand side,
+ * but not the oper list nor the subquery.
+ */
+ SubLink *sublink = (SubLink *) node;
+ SubLink *newnode;
+
+ FLATCOPY(newnode, sublink, SubLink);
+ MUTATE(newnode->lefthand, sublink->lefthand, List *);
+ return (Node *) newnode;
+ }
+ break;
+ case T_List:
+ {
+ /* We assume the mutator isn't interested in the list nodes
+ * per se, so just invoke it on each list element.
+ * NOTE: this would fail badly on a list with integer elements!
+ */
+ List *resultlist = NIL;
+ List *temp;
+
+ foreach(temp, (List *) node)
+ {
+ resultlist = lappend(resultlist,
+ mutator((Node *) lfirst(temp),
+ context));
+ }
+ return (Node *) resultlist;
+ }
+ break;
+ case T_TargetEntry:
+ {
+ /* We mutate the expression, but not the resdom, by default. */
+ TargetEntry *targetentry = (TargetEntry *) node;
+ TargetEntry *newnode;
+
+ FLATCOPY(newnode, targetentry, TargetEntry);
+ MUTATE(newnode->expr, targetentry->expr, Node *);
+ return (Node *) newnode;
+ }
+ break;
+ default:
+ elog(ERROR, "expression_tree_mutator: Unexpected node type %d",
+ nodeTag(node));
+ break;
+ }
+ /* can't get here, but keep compiler happy */
+ return NULL;
+}
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