/*-------------------------------------------------------------------------
*
* planner.c
* The query optimizer external interface.
*
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.132 2002/11/29 21:39:11 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <limits.h>
#include "catalog/pg_operator.h"
#include "catalog/pg_type.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#ifdef OPTIMIZER_DEBUG
#include "nodes/print.h"
#endif
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/planner.h"
#include "optimizer/prep.h"
#include "optimizer/subselect.h"
#include "optimizer/tlist.h"
#include "optimizer/var.h"
#include "parser/analyze.h"
#include "parser/parsetree.h"
#include "parser/parse_expr.h"
#include "parser/parse_oper.h"
#include "rewrite/rewriteManip.h"
#include "utils/lsyscache.h"
#include "utils/selfuncs.h"
#include "utils/syscache.h"
/* Expression kind codes for preprocess_expression */
#define EXPRKIND_TARGET 0
#define EXPRKIND_WHERE 1
#define EXPRKIND_HAVING 2
static Node *pull_up_subqueries(Query *parse, Node *jtnode,
bool below_outer_join);
static bool is_simple_subquery(Query *subquery);
static bool has_nullable_targetlist(Query *subquery);
static void resolvenew_in_jointree(Node *jtnode, int varno, List *subtlist);
static Node *preprocess_jointree(Query *parse, Node *jtnode);
static Node *preprocess_expression(Query *parse, Node *expr, int kind);
static void preprocess_qual_conditions(Query *parse, Node *jtnode);
static Plan *inheritance_planner(Query *parse, List *inheritlist);
static Plan *grouping_planner(Query *parse, double tuple_fraction);
static bool hash_safe_grouping(Query *parse);
static List *make_subplanTargetList(Query *parse, List *tlist,
AttrNumber **groupColIdx);
static Plan *make_groupsortplan(Query *parse,
List *groupClause,
AttrNumber *grpColIdx,
Plan *subplan);
static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
/*****************************************************************************
*
* Query optimizer entry point
*
*****************************************************************************/
Plan *
planner(Query *parse)
{
Plan *result_plan;
Index save_PlannerQueryLevel;
List *save_PlannerParamVar;
/*
* The planner can be called recursively (an example is when
* eval_const_expressions tries to pre-evaluate an SQL function). So,
* these global state variables must be saved and restored.
*
* These vars cannot be moved into the Query structure since their whole
* purpose is communication across multiple sub-Queries.
*
* Note we do NOT save and restore PlannerPlanId: it exists to assign
* unique IDs to SubPlan nodes, and we want those IDs to be unique for
* the life of a backend. Also, PlannerInitPlan is saved/restored in
* subquery_planner, not here.
*/
save_PlannerQueryLevel = PlannerQueryLevel;
save_PlannerParamVar = PlannerParamVar;
/* Initialize state for handling outer-level references and params */
PlannerQueryLevel = 0; /* will be 1 in top-level subquery_planner */
PlannerParamVar = NIL;
/* primary planning entry point (may recurse for subqueries) */
result_plan = subquery_planner(parse, -1.0 /* default case */ );
Assert(PlannerQueryLevel == 0);
/* executor wants to know total number of Params used overall */
result_plan->nParamExec = length(PlannerParamVar);
/* final cleanup of the plan */
set_plan_references(result_plan, parse->rtable);
/* restore state for outer planner, if any */
PlannerQueryLevel = save_PlannerQueryLevel;
PlannerParamVar = save_PlannerParamVar;
return result_plan;
}
/*--------------------
* subquery_planner
* Invokes the planner on a subquery. We recurse to here for each
* sub-SELECT found in the query tree.
*
* parse is the querytree produced by the parser & rewriter.
* tuple_fraction is the fraction of tuples we expect will be retrieved.
* tuple_fraction is interpreted as explained for grouping_planner, below.
*
* Basically, this routine does the stuff that should only be done once
* per Query object. It then calls grouping_planner. At one time,
* grouping_planner could be invoked recursively on the same Query object;
* that's not currently true, but we keep the separation between the two
* routines anyway, in case we need it again someday.
*
* subquery_planner will be called recursively to handle sub-Query nodes
* found within the query's expressions and rangetable.
*
* Returns a query plan.
*--------------------
*/
Plan *
subquery_planner(Query *parse, double tuple_fraction)
{
List *saved_initplan = PlannerInitPlan;
int saved_planid = PlannerPlanId;
Plan *plan;
List *newHaving;
List *lst;
/* Set up for a new level of subquery */
PlannerQueryLevel++;
PlannerInitPlan = NIL;
/*
* Check to see if any subqueries in the rangetable can be merged into
* this query.
*/
parse->jointree = (FromExpr *)
pull_up_subqueries(parse, (Node *) parse->jointree, false);
/*
* If so, we may have created opportunities to simplify the jointree.
*/
parse->jointree = (FromExpr *)
preprocess_jointree(parse, (Node *) parse->jointree);
/*
* Detect whether any rangetable entries are RTE_JOIN kind; if not,
* we can avoid the expense of doing flatten_join_alias_vars().
* This must be done after we have done pull_up_subqueries, of course.
*/
parse->hasJoinRTEs = false;
foreach(lst, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(lst);
if (rte->rtekind == RTE_JOIN)
{
parse->hasJoinRTEs = true;
break;
}
}
/*
* Do expression preprocessing on targetlist and quals.
*/
parse->targetList = (List *)
preprocess_expression(parse, (Node *) parse->targetList,
EXPRKIND_TARGET);
preprocess_qual_conditions(parse, (Node *) parse->jointree);
parse->havingQual = preprocess_expression(parse, parse->havingQual,
EXPRKIND_HAVING);
/* Also need to preprocess expressions for function RTEs */
foreach(lst, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(lst);
if (rte->rtekind == RTE_FUNCTION)
rte->funcexpr = preprocess_expression(parse, rte->funcexpr,
EXPRKIND_TARGET);
/* These are not targetlist items, but close enough... */
}
/*
* Check for ungrouped variables passed to subplans in targetlist and
* HAVING clause (but not in WHERE or JOIN/ON clauses, since those are
* evaluated before grouping). We can't do this any earlier because
* we must use the preprocessed targetlist for comparisons of grouped
* expressions.
*/
if (parse->hasSubLinks &&
(parse->groupClause != NIL || parse->hasAggs))
check_subplans_for_ungrouped_vars(parse);
/*
* A HAVING clause without aggregates is equivalent to a WHERE clause
* (except it can only refer to grouped fields). Transfer any
* agg-free clauses of the HAVING qual into WHERE. This may seem like
* wasting cycles to cater to stupidly-written queries, but there are
* other reasons for doing it. Firstly, if the query contains no aggs
* at all, then we aren't going to generate an Agg plan node, and so
* there'll be no place to execute HAVING conditions; without this
* transfer, we'd lose the HAVING condition entirely, which is wrong.
* Secondly, when we push down a qual condition into a sub-query, it's
* easiest to push the qual into HAVING always, in case it contains
* aggs, and then let this code sort it out.
*
* Note that both havingQual and parse->jointree->quals are in
* implicitly-ANDed-list form at this point, even though they are
* declared as Node *. Also note that contain_agg_clause does not
* recurse into sub-selects, which is exactly what we need here.
*/
newHaving = NIL;
foreach(lst, (List *) parse->havingQual)
{
Node *havingclause = (Node *) lfirst(lst);
if (contain_agg_clause(havingclause))
newHaving = lappend(newHaving, havingclause);
else
parse->jointree->quals = (Node *)
lappend((List *) parse->jointree->quals, havingclause);
}
parse->havingQual = (Node *) newHaving;
/*
* Do the main planning. If we have an inherited target relation,
* that needs special processing, else go straight to
* grouping_planner.
*/
if (parse->resultRelation &&
(lst = expand_inherted_rtentry(parse, parse->resultRelation, false))
!= NIL)
plan = inheritance_planner(parse, lst);
else
plan = grouping_planner(parse, tuple_fraction);
/*
* If any subplans were generated, or if we're inside a subplan, build
* subPlan, extParam and locParam lists for plan nodes.
*/
if (PlannerPlanId != saved_planid || PlannerQueryLevel > 1)
{
(void) SS_finalize_plan(plan, parse->rtable);
/*
* At the moment, SS_finalize_plan doesn't handle initPlans and so
* we assign them to the topmost plan node.
*/
plan->initPlan = PlannerInitPlan;
/* Must add the initPlans' extParams to the topmost node's, too */
foreach(lst, plan->initPlan)
{
SubPlan *subplan = (SubPlan *) lfirst(lst);
plan->extParam = set_unioni(plan->extParam,
subplan->plan->extParam);
}
}
/* Return to outer subquery context */
PlannerQueryLevel--;
PlannerInitPlan = saved_initplan;
/* we do NOT restore PlannerPlanId; that's not an oversight! */
return plan;
}
/*
* pull_up_subqueries
* Look for subqueries in the rangetable that can be pulled up into
* the parent query. If the subquery has no special features like
* grouping/aggregation then we can merge it into the parent's jointree.
*
* below_outer_join is true if this jointree node is within the nullable
* side of an outer join. This restricts what we can do.
*
* A tricky aspect of this code is that if we pull up a subquery we have
* to replace Vars that reference the subquery's outputs throughout the
* parent query, including quals attached to jointree nodes above the one
* we are currently processing! We handle this by being careful not to
* change the jointree structure while recursing: no nodes other than
* subquery RangeTblRef entries will be replaced. Also, we can't turn
* ResolveNew loose on the whole jointree, because it'll return a mutated
* copy of the tree; we have to invoke it just on the quals, instead.
*/
static Node *
pull_up_subqueries(Query *parse, Node *jtnode, bool below_outer_join)
{
if (jtnode == NULL)
return NULL;
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
RangeTblEntry *rte = rt_fetch(varno, parse->rtable);
Query *subquery = rte->subquery;
/*
* Is this a subquery RTE, and if so, is the subquery simple
* enough to pull up? (If not, do nothing at this node.)
*
* If we are inside an outer join, only pull up subqueries whose
* targetlists are nullable --- otherwise substituting their tlist
* entries for upper Var references would do the wrong thing (the
* results wouldn't become NULL when they're supposed to). XXX
* This could be improved by generating pseudo-variables for such
* expressions; we'd have to figure out how to get the pseudo-
* variables evaluated at the right place in the modified plan
* tree. Fix it someday.
*
* Note: even if the subquery itself is simple enough, we can't pull
* it up if there is a reference to its whole tuple result.
* Perhaps a pseudo-variable is the answer here too.
*/
if (rte->rtekind == RTE_SUBQUERY && is_simple_subquery(subquery) &&
(!below_outer_join || has_nullable_targetlist(subquery)) &&
!contain_whole_tuple_var((Node *) parse, varno, 0))
{
int rtoffset;
List *subtlist;
List *rt;
/*
* First, recursively pull up the subquery's subqueries, so
* that this routine's processing is complete for its jointree
* and rangetable. NB: if the same subquery is referenced
* from multiple jointree items (which can't happen normally,
* but might after rule rewriting), then we will invoke this
* processing multiple times on that subquery. OK because
* nothing will happen after the first time. We do have to be
* careful to copy everything we pull up, however, or risk
* having chunks of structure multiply linked.
*/
subquery->jointree = (FromExpr *)
pull_up_subqueries(subquery, (Node *) subquery->jointree,
below_outer_join);
/*
* Now make a modifiable copy of the subquery that we can run
* OffsetVarNodes and IncrementVarSublevelsUp on.
*/
subquery = copyObject(subquery);
/*
* Adjust level-0 varnos in subquery so that we can append its
* rangetable to upper query's.
*/
rtoffset = length(parse->rtable);
OffsetVarNodes((Node *) subquery, rtoffset, 0);
/*
* Upper-level vars in subquery are now one level closer to their
* parent than before.
*/
IncrementVarSublevelsUp((Node *) subquery, -1, 1);
/*
* Replace all of the top query's references to the subquery's
* outputs with copies of the adjusted subtlist items, being
* careful not to replace any of the jointree structure.
* (This'd be a lot cleaner if we could use
* query_tree_mutator.)
*/
subtlist = subquery->targetList;
parse->targetList = (List *)
ResolveNew((Node *) parse->targetList,
varno, 0, subtlist, CMD_SELECT, 0);
resolvenew_in_jointree((Node *) parse->jointree, varno, subtlist);
Assert(parse->setOperations == NULL);
parse->havingQual =
ResolveNew(parse->havingQual,
varno, 0, subtlist, CMD_SELECT, 0);
foreach(rt, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(rt);
if (rte->rtekind == RTE_JOIN)
rte->joinaliasvars = (List *)
ResolveNew((Node *) rte->joinaliasvars,
varno, 0, subtlist, CMD_SELECT, 0);
}
/*
* Now append the adjusted rtable entries to upper query. (We
* hold off until after fixing the upper rtable entries; no
* point in running that code on the subquery ones too.)
*/
parse->rtable = nconc(parse->rtable, subquery->rtable);
/*
* Pull up any FOR UPDATE markers, too. (OffsetVarNodes
* already adjusted the marker values, so just nconc the
* list.)
*/
parse->rowMarks = nconc(parse->rowMarks, subquery->rowMarks);
/*
* Miscellaneous housekeeping.
*/
parse->hasSubLinks |= subquery->hasSubLinks;
/* subquery won't be pulled up if it hasAggs, so no work there */
/*
* Return the adjusted subquery jointree to replace the
* RangeTblRef entry in my jointree.
*/
return (Node *) subquery->jointree;
}
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
List *l;
foreach(l, f->fromlist)
lfirst(l) = pull_up_subqueries(parse, lfirst(l),
below_outer_join);
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
/* Recurse, being careful to tell myself when inside outer join */
switch (j->jointype)
{
case JOIN_INNER:
j->larg = pull_up_subqueries(parse, j->larg,
below_outer_join);
j->rarg = pull_up_subqueries(parse, j->rarg,
below_outer_join);
break;
case JOIN_LEFT:
j->larg = pull_up_subqueries(parse, j->larg,
below_outer_join);
j->rarg = pull_up_subqueries(parse, j->rarg,
true);
break;
case JOIN_FULL:
j->larg = pull_up_subqueries(parse, j->larg,
true);
j->rarg = pull_up_subqueries(parse, j->rarg,
true);
break;
case JOIN_RIGHT:
j->larg = pull_up_subqueries(parse, j->larg,
true);
j->rarg = pull_up_subqueries(parse, j->rarg,
below_outer_join);
break;
case JOIN_UNION:
/*
* This is where we fail if upper levels of planner
* haven't rewritten UNION JOIN as an Append ...
*/
elog(ERROR, "UNION JOIN is not implemented yet");
break;
default:
elog(ERROR, "pull_up_subqueries: unexpected join type %d",
j->jointype);
break;
}
}
else
elog(ERROR, "pull_up_subqueries: unexpected node type %d",
nodeTag(jtnode));
return jtnode;
}
/*
* is_simple_subquery
* Check a subquery in the range table to see if it's simple enough
* to pull up into the parent query.
*/
static bool
is_simple_subquery(Query *subquery)
{
/*
* Let's just make sure it's a valid subselect ...
*/
if (!IsA(subquery, Query) ||
subquery->commandType != CMD_SELECT ||
subquery->resultRelation != 0 ||
subquery->into != NULL ||
subquery->isPortal)
elog(ERROR, "is_simple_subquery: subquery is bogus");
/*
* Can't currently pull up a query with setops. Maybe after querytree
* redesign...
*/
if (subquery->setOperations)
return false;
/*
* Can't pull up a subquery involving grouping, aggregation, sorting,
* or limiting.
*/
if (subquery->hasAggs ||
subquery->groupClause ||
subquery->havingQual ||
subquery->sortClause ||
subquery->distinctClause ||
subquery->limitOffset ||
subquery->limitCount)
return false;
/*
* Don't pull up a subquery that has any set-returning functions in
* its targetlist. Otherwise we might well wind up inserting
* set-returning functions into places where they mustn't go, such as
* quals of higher queries.
*/
if (expression_returns_set((Node *) subquery->targetList))
return false;
/*
* Hack: don't try to pull up a subquery with an empty jointree.
* query_planner() will correctly generate a Result plan for a
* jointree that's totally empty, but I don't think the right things
* happen if an empty FromExpr appears lower down in a jointree. Not
* worth working hard on this, just to collapse SubqueryScan/Result
* into Result...
*/
if (subquery->jointree->fromlist == NIL)
return false;
return true;
}
/*
* has_nullable_targetlist
* Check a subquery in the range table to see if all the non-junk
* targetlist items are simple variables (and, hence, will correctly
* go to NULL when examined above the point of an outer join).
*
* A possible future extension is to accept strict functions of simple
* variables, eg, "x + 1".
*/
static bool
has_nullable_targetlist(Query *subquery)
{
List *l;
foreach(l, subquery->targetList)
{
TargetEntry *tle = (TargetEntry *) lfirst(l);
/* ignore resjunk columns */
if (tle->resdom->resjunk)
continue;
/* Okay if tlist item is a simple Var */
if (tle->expr && IsA(tle->expr, Var))
continue;
return false;
}
return true;
}
/*
* Helper routine for pull_up_subqueries: do ResolveNew on every expression
* in the jointree, without changing the jointree structure itself. Ugly,
* but there's no other way...
*/
static void
resolvenew_in_jointree(Node *jtnode, int varno, List *subtlist)
{
if (jtnode == NULL)
return;
if (IsA(jtnode, RangeTblRef))
{
/* nothing to do here */
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
List *l;
foreach(l, f->fromlist)
resolvenew_in_jointree(lfirst(l), varno, subtlist);
f->quals = ResolveNew(f->quals,
varno, 0, subtlist, CMD_SELECT, 0);
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
resolvenew_in_jointree(j->larg, varno, subtlist);
resolvenew_in_jointree(j->rarg, varno, subtlist);
j->quals = ResolveNew(j->quals,
varno, 0, subtlist, CMD_SELECT, 0);
/*
* We don't bother to update the colvars list, since it won't be
* used again ...
*/
}
else
elog(ERROR, "resolvenew_in_jointree: unexpected node type %d",
nodeTag(jtnode));
}
/*
* preprocess_jointree
* Attempt to simplify a query's jointree.
*
* If we succeed in pulling up a subquery then we might form a jointree
* in which a FromExpr is a direct child of another FromExpr. In that
* case we can consider collapsing the two FromExprs into one. This is
* an optional conversion, since the planner will work correctly either
* way. But we may find a better plan (at the cost of more planning time)
* if we merge the two nodes.
*
* NOTE: don't try to do this in the same jointree scan that does subquery
* pullup! Since we're changing the jointree structure here, that wouldn't
* work reliably --- see comments for pull_up_subqueries().
*/
static Node *
preprocess_jointree(Query *parse, Node *jtnode)
{
if (jtnode == NULL)
return NULL;
if (IsA(jtnode, RangeTblRef))
{
/* nothing to do here... */
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
List *newlist = NIL;
List *l;
foreach(l, f->fromlist)
{
Node *child = (Node *) lfirst(l);
/* Recursively simplify the child... */
child = preprocess_jointree(parse, child);
/* Now, is it a FromExpr? */
if (child && IsA(child, FromExpr))
{
/*
* Yes, so do we want to merge it into parent? Always do
* so if child has just one element (since that doesn't
* make the parent's list any longer). Otherwise we have
* to be careful about the increase in planning time
* caused by combining the two join search spaces into
* one. Our heuristic is to merge if the merge will
* produce a join list no longer than GEQO_RELS/2.
* (Perhaps need an additional user parameter?)
*/
FromExpr *subf = (FromExpr *) child;
int childlen = length(subf->fromlist);
int myothers = length(newlist) + length(lnext(l));
if (childlen <= 1 || (childlen + myothers) <= geqo_rels / 2)
{
newlist = nconc(newlist, subf->fromlist);
f->quals = make_and_qual(subf->quals, f->quals);
}
else
newlist = lappend(newlist, child);
}
else
newlist = lappend(newlist, child);
}
f->fromlist = newlist;
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
/* Can't usefully change the JoinExpr, but recurse on children */
j->larg = preprocess_jointree(parse, j->larg);
j->rarg = preprocess_jointree(parse, j->rarg);
}
else
elog(ERROR, "preprocess_jointree: unexpected node type %d",
nodeTag(jtnode));
return jtnode;
}
/*
* preprocess_expression
* Do subquery_planner's preprocessing work for an expression,
* which can be a targetlist, a WHERE clause (including JOIN/ON
* conditions), or a HAVING clause.
*/
static Node *
preprocess_expression(Query *parse, Node *expr, int kind)
{
/*
* Simplify constant expressions.
*
* Note that at this point quals have not yet been converted to
* implicit-AND form, so we can apply eval_const_expressions directly.
*/
expr = eval_const_expressions(expr);
/*
* If it's a qual or havingQual, canonicalize it, and convert it to
* implicit-AND format.
*
* XXX Is there any value in re-applying eval_const_expressions after
* canonicalize_qual?
*/
if (kind != EXPRKIND_TARGET)
{
expr = (Node *) canonicalize_qual((Expr *) expr, true);
#ifdef OPTIMIZER_DEBUG
printf("After canonicalize_qual()\n");
pprint(expr);
#endif
}
/* Expand SubLinks to SubPlans */
if (parse->hasSubLinks)
expr = SS_process_sublinks(expr);
/* Replace uplevel vars with Param nodes */
if (PlannerQueryLevel > 1)
expr = SS_replace_correlation_vars(expr);
/*
* If the query has any join RTEs, try to replace join alias variables
* with base-relation variables, to allow quals to be pushed down. We
* must do this after sublink processing, since it does not recurse
* into sublinks.
*/
if (parse->hasJoinRTEs)
expr = flatten_join_alias_vars(expr, parse->rtable, false);
return expr;
}
/*
* preprocess_qual_conditions
* Recursively scan the query's jointree and do subquery_planner's
* preprocessing work on each qual condition found therein.
*/
static void
preprocess_qual_conditions(Query *parse, Node *jtnode)
{
if (jtnode == NULL)
return;
if (IsA(jtnode, RangeTblRef))
{
/* nothing to do here */
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
List *l;
foreach(l, f->fromlist)
preprocess_qual_conditions(parse, lfirst(l));
f->quals = preprocess_expression(parse, f->quals, EXPRKIND_WHERE);
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
preprocess_qual_conditions(parse, j->larg);
preprocess_qual_conditions(parse, j->rarg);
j->quals = preprocess_expression(parse, j->quals, EXPRKIND_WHERE);
}
else
elog(ERROR, "preprocess_qual_conditions: unexpected node type %d",
nodeTag(jtnode));
}
/*--------------------
* inheritance_planner
* Generate a plan in the case where the result relation is an
* inheritance set.
*
* We have to handle this case differently from cases where a source
* relation is an inheritance set. Source inheritance is expanded at
* the bottom of the plan tree (see allpaths.c), but target inheritance
* has to be expanded at the top. The reason is that for UPDATE, each
* target relation needs a different targetlist matching its own column
* set. (This is not so critical for DELETE, but for simplicity we treat
* inherited DELETE the same way.) Fortunately, the UPDATE/DELETE target
* can never be the nullable side of an outer join, so it's OK to generate
* the plan this way.
*
* parse is the querytree produced by the parser & rewriter.
* inheritlist is an integer list of RT indexes for the result relation set.
*
* Returns a query plan.
*--------------------
*/
static Plan *
inheritance_planner(Query *parse, List *inheritlist)
{
int parentRTindex = parse->resultRelation;
Oid parentOID = getrelid(parentRTindex, parse->rtable);
List *subplans = NIL;
List *tlist = NIL;
List *l;
foreach(l, inheritlist)
{
int childRTindex = lfirsti(l);
Oid childOID = getrelid(childRTindex, parse->rtable);
Query *subquery;
Plan *subplan;
/* Generate modified query with this rel as target */
subquery = (Query *) adjust_inherited_attrs((Node *) parse,
parentRTindex, parentOID,
childRTindex, childOID);
/* Generate plan */
subplan = grouping_planner(subquery, 0.0 /* retrieve all tuples */ );
subplans = lappend(subplans, subplan);
/* Save preprocessed tlist from first rel for use in Append */
if (tlist == NIL)
tlist = subplan->targetlist;
}
/* Save the target-relations list for the executor, too */
parse->resultRelations = inheritlist;
return (Plan *) make_append(subplans, true, tlist);
}
/*--------------------
* grouping_planner
* Perform planning steps related to grouping, aggregation, etc.
* This primarily means adding top-level processing to the basic
* query plan produced by query_planner.
*
* parse is the querytree produced by the parser & rewriter.
* tuple_fraction is the fraction of tuples we expect will be retrieved
*
* tuple_fraction is interpreted as follows:
* < 0: determine fraction by inspection of query (normal case)
* 0: expect all tuples to be retrieved
* 0 < tuple_fraction < 1: expect the given fraction of tuples available
* from the plan to be retrieved
* tuple_fraction >= 1: tuple_fraction is the absolute number of tuples
* expected to be retrieved (ie, a LIMIT specification)
* The normal case is to pass -1, but some callers pass values >= 0 to
* override this routine's determination of the appropriate fraction.
*
* Returns a query plan.
*--------------------
*/
static Plan *
grouping_planner(Query *parse, double tuple_fraction)
{
List *tlist = parse->targetList;
Plan *result_plan;
List *current_pathkeys;
List *sort_pathkeys;
if (parse->setOperations)
{
/*
* Construct the plan for set operations. The result will not
* need any work except perhaps a top-level sort and/or LIMIT.
*/
result_plan = plan_set_operations(parse);
/*
* We should not need to call preprocess_targetlist, since we must
* be in a SELECT query node. Instead, use the targetlist
* returned by plan_set_operations (since this tells whether it
* returned any resjunk columns!), and transfer any sort key
* information from the original tlist.
*/
Assert(parse->commandType == CMD_SELECT);
tlist = postprocess_setop_tlist(result_plan->targetlist, tlist);
/*
* Can't handle FOR UPDATE here (parser should have checked
* already, but let's make sure).
*/
if (parse->rowMarks)
elog(ERROR, "SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT");
/*
* We set current_pathkeys NIL indicating we do not know sort
* order. This is correct when the top set operation is UNION
* ALL, since the appended-together results are unsorted even if
* the subplans were sorted. For other set operations we could be
* smarter --- room for future improvement!
*/
current_pathkeys = NIL;
/*
* Calculate pathkeys that represent ordering requirements
*/
sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
tlist);
sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
}
else
{
/* No set operations, do regular planning */
List *sub_tlist;
List *group_pathkeys;
AttrNumber *groupColIdx = NULL;
double sub_tuple_fraction;
Path *cheapest_path;
Path *sorted_path;
double dNumGroups = 0;
long numGroups = 0;
int numAggs = 0;
int numGroupCols = length(parse->groupClause);
bool use_hashed_grouping = false;
/* Preprocess targetlist in case we are inside an INSERT/UPDATE. */
tlist = preprocess_targetlist(tlist,
parse->commandType,
parse->resultRelation,
parse->rtable);
/*
* Add TID targets for rels selected FOR UPDATE (should this be
* done in preprocess_targetlist?). The executor uses the TID to
* know which rows to lock, much as for UPDATE or DELETE.
*/
if (parse->rowMarks)
{
List *l;
/*
* We've got trouble if the FOR UPDATE appears inside
* grouping, since grouping renders a reference to individual
* tuple CTIDs invalid. This is also checked at parse time,
* but that's insufficient because of rule substitution, query
* pullup, etc.
*/
CheckSelectForUpdate(parse);
/*
* Currently the executor only supports FOR UPDATE at top
* level
*/
if (PlannerQueryLevel > 1)
elog(ERROR, "SELECT FOR UPDATE is not allowed in subselects");
foreach(l, parse->rowMarks)
{
Index rti = lfirsti(l);
char *resname;
Resdom *resdom;
Var *var;
TargetEntry *ctid;
resname = (char *) palloc(32);
snprintf(resname, 32, "ctid%u", rti);
resdom = makeResdom(length(tlist) + 1,
TIDOID,
-1,
resname,
true);
var = makeVar(rti,
SelfItemPointerAttributeNumber,
TIDOID,
-1,
0);
ctid = makeTargetEntry(resdom, (Node *) var);
tlist = lappend(tlist, ctid);
}
}
/*
* Generate appropriate target list for subplan; may be different
* from tlist if grouping or aggregation is needed.
*/
sub_tlist = make_subplanTargetList(parse, tlist, &groupColIdx);
/*
* Calculate pathkeys that represent grouping/ordering
* requirements
*/
group_pathkeys = make_pathkeys_for_sortclauses(parse->groupClause,
tlist);
sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
tlist);
/*
* Will need actual number of aggregates for estimating costs.
* Also, it's possible that optimization has eliminated all
* aggregates, and we may as well check for that here.
*/
if (parse->hasAggs)
{
numAggs = length(pull_agg_clause((Node *) tlist)) +
length(pull_agg_clause(parse->havingQual));
if (numAggs == 0)
parse->hasAggs = false;
}
/*
* Figure out whether we need a sorted result from query_planner.
*
* If we have a GROUP BY clause, then we want a result sorted
* properly for grouping. Otherwise, if there is an ORDER BY
* clause, we want to sort by the ORDER BY clause. (Note: if we
* have both, and ORDER BY is a superset of GROUP BY, it would be
* tempting to request sort by ORDER BY --- but that might just
* leave us failing to exploit an available sort order at all.
* Needs more thought...)
*/
if (parse->groupClause)
parse->query_pathkeys = group_pathkeys;
else if (parse->sortClause)
parse->query_pathkeys = sort_pathkeys;
else
parse->query_pathkeys = NIL;
/*
* Figure out whether we expect to retrieve all the tuples that
* the plan can generate, or to stop early due to outside factors
* such as a cursor. If the caller passed a value >= 0, believe
* that value, else do our own examination of the query context.
*/
if (tuple_fraction < 0.0)
{
/* Initial assumption is we need all the tuples */
tuple_fraction = 0.0;
/*
* Check for retrieve-into-portal, ie DECLARE CURSOR.
*
* We have no real idea how many tuples the user will ultimately
* FETCH from a cursor, but it seems a good bet that he
* doesn't want 'em all. Optimize for 10% retrieval (you
* gotta better number? Should this be a SETtable parameter?)
*/
if (parse->isPortal)
tuple_fraction = 0.10;
}
/*
* Adjust tuple_fraction if we see that we are going to apply
* limiting/grouping/aggregation/etc. This is not overridable by
* the caller, since it reflects plan actions that this routine
* will certainly take, not assumptions about context.
*/
if (parse->limitCount != NULL)
{
/*
* A LIMIT clause limits the absolute number of tuples
* returned. However, if it's not a constant LIMIT then we
* have to punt; for lack of a better idea, assume 10% of the
* plan's result is wanted.
*/
double limit_fraction = 0.0;
if (IsA(parse->limitCount, Const))
{
Const *limitc = (Const *) parse->limitCount;
int32 count = DatumGetInt32(limitc->constvalue);
/*
* A NULL-constant LIMIT represents "LIMIT ALL", which we
* treat the same as no limit (ie, expect to retrieve all
* the tuples).
*/
if (!limitc->constisnull && count > 0)
{
limit_fraction = (double) count;
/* We must also consider the OFFSET, if present */
if (parse->limitOffset != NULL)
{
if (IsA(parse->limitOffset, Const))
{
int32 offset;
limitc = (Const *) parse->limitOffset;
offset = DatumGetInt32(limitc->constvalue);
if (!limitc->constisnull && offset > 0)
limit_fraction += (double) offset;
}
else
{
/* OFFSET is an expression ... punt ... */
limit_fraction = 0.10;
}
}
}
}
else
{
/* LIMIT is an expression ... punt ... */
limit_fraction = 0.10;
}
if (limit_fraction > 0.0)
{
/*
* If we have absolute limits from both caller and LIMIT,
* use the smaller value; if one is fractional and the
* other absolute, treat the fraction as a fraction of the
* absolute value; else we can multiply the two fractions
* together.
*/
if (tuple_fraction >= 1.0)
{
if (limit_fraction >= 1.0)
{
/* both absolute */
tuple_fraction = Min(tuple_fraction, limit_fraction);
}
else
{
/* caller absolute, limit fractional */
tuple_fraction *= limit_fraction;
if (tuple_fraction < 1.0)
tuple_fraction = 1.0;
}
}
else if (tuple_fraction > 0.0)
{
if (limit_fraction >= 1.0)
{
/* caller fractional, limit absolute */
tuple_fraction *= limit_fraction;
if (tuple_fraction < 1.0)
tuple_fraction = 1.0;
}
else
{
/* both fractional */
tuple_fraction *= limit_fraction;
}
}
else
{
/* no info from caller, just use limit */
tuple_fraction = limit_fraction;
}
}
}
/*
* With grouping or aggregation, the tuple fraction to pass to
* query_planner() may be different from what it is at top level.
*/
sub_tuple_fraction = tuple_fraction;
if (parse->groupClause)
{
/*
* In GROUP BY mode, we have the little problem that we don't
* really know how many input tuples will be needed to make a
* group, so we can't translate an output LIMIT count into an
* input count. For lack of a better idea, assume 25% of the
* input data will be processed if there is any output limit.
* However, if the caller gave us a fraction rather than an
* absolute count, we can keep using that fraction (which
* amounts to assuming that all the groups are about the same
* size).
*/
if (sub_tuple_fraction >= 1.0)
sub_tuple_fraction = 0.25;
/*
* If both GROUP BY and ORDER BY are specified, we will need
* two levels of sort --- and, therefore, certainly need to
* read all the input tuples --- unless ORDER BY is a subset
* of GROUP BY. (We have not yet canonicalized the pathkeys,
* so must use the slower noncanonical comparison method.)
*/
if (parse->groupClause && parse->sortClause &&
!noncanonical_pathkeys_contained_in(sort_pathkeys,
group_pathkeys))
sub_tuple_fraction = 0.0;
}
else if (parse->hasAggs)
{
/*
* Ungrouped aggregate will certainly want all the input
* tuples.
*/
sub_tuple_fraction = 0.0;
}
else if (parse->distinctClause)
{
/*
* SELECT DISTINCT, like GROUP, will absorb an unpredictable
* number of input tuples per output tuple. Handle the same
* way.
*/
if (sub_tuple_fraction >= 1.0)
sub_tuple_fraction = 0.25;
}
/*
* Generate the best unsorted and presorted paths for this Query
* (but note there may not be any presorted path).
*/
query_planner(parse, sub_tlist, sub_tuple_fraction,
&cheapest_path, &sorted_path);
/*
* We couldn't canonicalize group_pathkeys and sort_pathkeys before
* running query_planner(), so do it now.
*/
group_pathkeys = canonicalize_pathkeys(parse, group_pathkeys);
sort_pathkeys = canonicalize_pathkeys(parse, sort_pathkeys);
/*
* Consider whether we might want to use hashed grouping.
*/
if (parse->groupClause)
{
/*
* Always estimate the number of groups. We can't do this until
* after running query_planner(), either.
*/
dNumGroups = estimate_num_groups(parse,
parse->groupClause,
cheapest_path->parent->rows);
/* Also want it as a long int --- but 'ware overflow! */
numGroups = (long) Min(dNumGroups, (double) LONG_MAX);
/*
* Check can't-do-it conditions, including whether the grouping
* operators are hashjoinable.
*
* Executor doesn't support hashed aggregation with DISTINCT
* aggregates. (Doing so would imply storing *all* the input
* values in the hash table, which seems like a certain loser.)
*/
if (!enable_hashagg || !hash_safe_grouping(parse))
use_hashed_grouping = false;
else if (parse->hasAggs &&
(contain_distinct_agg_clause((Node *) tlist) ||
contain_distinct_agg_clause(parse->havingQual)))
use_hashed_grouping = false;
else
{
/*
* Use hashed grouping if (a) we think we can fit the
* hashtable into SortMem, *and* (b) the estimated cost
* is no more than doing it the other way. While avoiding
* the need for sorted input is usually a win, the fact
* that the output won't be sorted may be a loss; so we
* need to do an actual cost comparison.
*
* In most cases we have no good way to estimate the size of
* the transition value needed by an aggregate; arbitrarily
* assume it is 100 bytes. Also set the overhead per hashtable
* entry at 64 bytes.
*/
int hashentrysize = cheapest_path->parent->width + 64 +
numAggs * 100;
if (hashentrysize * dNumGroups <= SortMem * 1024L)
{
/*
* Okay, do the cost comparison. We need to consider
* cheapest_path + hashagg [+ final sort]
* versus either
* cheapest_path [+ sort] + group or agg [+ final sort]
* or
* presorted_path + group or agg [+ final sort]
* where brackets indicate a step that may not be needed.
* We assume query_planner() will have returned a
* presorted path only if it's a winner compared to
* cheapest_path for this purpose.
*
* These path variables are dummies that just hold cost
* fields; we don't make actual Paths for these steps.
*/
Path hashed_p;
Path sorted_p;
cost_agg(&hashed_p, parse,
AGG_HASHED, numAggs,
numGroupCols, dNumGroups,
cheapest_path->startup_cost,
cheapest_path->total_cost,
cheapest_path->parent->rows);
/* Result of hashed agg is always unsorted */
if (sort_pathkeys)
cost_sort(&hashed_p, parse, sort_pathkeys,
hashed_p.total_cost,
dNumGroups,
cheapest_path->parent->width);
if (sorted_path)
{
sorted_p.startup_cost = sorted_path->startup_cost;
sorted_p.total_cost = sorted_path->total_cost;
current_pathkeys = sorted_path->pathkeys;
}
else
{
sorted_p.startup_cost = cheapest_path->startup_cost;
sorted_p.total_cost = cheapest_path->total_cost;
current_pathkeys = cheapest_path->pathkeys;
}
if (!pathkeys_contained_in(group_pathkeys,
current_pathkeys))
{
cost_sort(&sorted_p, parse, group_pathkeys,
sorted_p.total_cost,
cheapest_path->parent->rows,
cheapest_path->parent->width);
current_pathkeys = group_pathkeys;
}
if (parse->hasAggs)
cost_agg(&sorted_p, parse,
AGG_SORTED, numAggs,
numGroupCols, dNumGroups,
sorted_p.startup_cost,
sorted_p.total_cost,
cheapest_path->parent->rows);
else
cost_group(&sorted_p, parse,
numGroupCols, dNumGroups,
sorted_p.startup_cost,
sorted_p.total_cost,
cheapest_path->parent->rows);
/* The Agg or Group node will preserve ordering */
if (sort_pathkeys &&
!pathkeys_contained_in(sort_pathkeys,
current_pathkeys))
{
cost_sort(&sorted_p, parse, sort_pathkeys,
sorted_p.total_cost,
dNumGroups,
cheapest_path->parent->width);
}
/*
* Now make the decision using the top-level tuple
* fraction. First we have to convert an absolute
* count (LIMIT) into fractional form.
*/
if (tuple_fraction >= 1.0)
tuple_fraction /= dNumGroups;
if (compare_fractional_path_costs(&hashed_p, &sorted_p,
tuple_fraction) <= 0)
{
/* Hashed is cheaper, so use it */
use_hashed_grouping = true;
}
}
}
}
/*
* Select the best path and create a plan to execute it.
*
* If we are doing hashed grouping, we will always read all the
* input tuples, so use the cheapest-total path. Otherwise,
* trust query_planner's decision about which to use.
*/
if (sorted_path && !use_hashed_grouping)
{
result_plan = create_plan(parse, sorted_path);
current_pathkeys = sorted_path->pathkeys;
}
else
{
result_plan = create_plan(parse, cheapest_path);
current_pathkeys = cheapest_path->pathkeys;
}
/*
* create_plan() returns a plan with just a "flat" tlist of required
* Vars. We want to insert the sub_tlist as the tlist of the top
* plan node. If the top-level plan node is one that cannot do
* expression evaluation, we must insert a Result node to project the
* desired tlist.
* Currently, the only plan node we might see here that falls into
* that category is Append.
*/
if (IsA(result_plan, Append))
{
result_plan = (Plan *) make_result(sub_tlist, NULL, result_plan);
}
else
{
/*
* Otherwise, just replace the flat tlist with the desired tlist.
*/
result_plan->targetlist = sub_tlist;
}
/*
* Insert AGG or GROUP node if needed, plus an explicit sort step
* if necessary.
*
* HAVING clause, if any, becomes qual of the Agg node
*/
if (use_hashed_grouping)
{
/* Hashed aggregate plan --- no sort needed */
result_plan = (Plan *) make_agg(parse,
tlist,
(List *) parse->havingQual,
AGG_HASHED,
numGroupCols,
groupColIdx,
numGroups,
numAggs,
result_plan);
/* Hashed aggregation produces randomly-ordered results */
current_pathkeys = NIL;
}
else if (parse->hasAggs)
{
/* Plain aggregate plan --- sort if needed */
AggStrategy aggstrategy;
if (parse->groupClause)
{
if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
{
result_plan = make_groupsortplan(parse,
parse->groupClause,
groupColIdx,
result_plan);
current_pathkeys = group_pathkeys;
}
aggstrategy = AGG_SORTED;
/*
* The AGG node will not change the sort ordering of its
* groups, so current_pathkeys describes the result too.
*/
}
else
{
aggstrategy = AGG_PLAIN;
/* Result will be only one row anyway; no sort order */
current_pathkeys = NIL;
}
result_plan = (Plan *) make_agg(parse,
tlist,
(List *) parse->havingQual,
aggstrategy,
numGroupCols,
groupColIdx,
numGroups,
numAggs,
result_plan);
}
else
{
/*
* If there are no Aggs, we shouldn't have any HAVING qual anymore
*/
Assert(parse->havingQual == NULL);
/*
* If we have a GROUP BY clause, insert a group node (plus the
* appropriate sort node, if necessary).
*/
if (parse->groupClause)
{
/*
* Add an explicit sort if we couldn't make the path come out
* the way the GROUP node needs it.
*/
if (!pathkeys_contained_in(group_pathkeys, current_pathkeys))
{
result_plan = make_groupsortplan(parse,
parse->groupClause,
groupColIdx,
result_plan);
current_pathkeys = group_pathkeys;
}
result_plan = (Plan *) make_group(parse,
tlist,
numGroupCols,
groupColIdx,
dNumGroups,
result_plan);
/* The Group node won't change sort ordering */
}
}
} /* end of if (setOperations) */
/*
* If we were not able to make the plan come out in the right order,
* add an explicit sort step.
*/
if (parse->sortClause)
{
if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
result_plan = make_sortplan(parse, tlist, result_plan,
parse->sortClause);
}
/*
* If there is a DISTINCT clause, add the UNIQUE node.
*/
if (parse->distinctClause)
{
result_plan = (Plan *) make_unique(tlist, result_plan,
parse->distinctClause);
/*
* If there was grouping or aggregation, leave plan_rows as-is
* (ie, assume the result was already mostly unique). If not,
* it's reasonable to assume the UNIQUE filter has effects
* comparable to GROUP BY.
*/
if (!parse->groupClause && !parse->hasAggs)
result_plan->plan_rows = estimate_num_groups(parse,
parse->distinctClause,
result_plan->plan_rows);
}
/*
* Finally, if there is a LIMIT/OFFSET clause, add the LIMIT node.
*/
if (parse->limitOffset || parse->limitCount)
{
result_plan = (Plan *) make_limit(tlist, result_plan,
parse->limitOffset,
parse->limitCount);
}
return result_plan;
}
/*
* hash_safe_grouping - are grouping operators hashable?
*
* We assume hashed aggregation will work if the datatype's equality operator
* is marked hashjoinable.
*/
static bool
hash_safe_grouping(Query *parse)
{
List *gl;
foreach(gl, parse->groupClause)
{
GroupClause *grpcl = (GroupClause *) lfirst(gl);
TargetEntry *tle = get_sortgroupclause_tle(grpcl, parse->targetList);
Operator optup;
bool oprcanhash;
optup = equality_oper(tle->resdom->restype, false);
oprcanhash = ((Form_pg_operator) GETSTRUCT(optup))->oprcanhash;
ReleaseSysCache(optup);
if (!oprcanhash)
return false;
}
return true;
}
/*---------------
* make_subplanTargetList
* Generate appropriate target list when grouping is required.
*
* When grouping_planner inserts Aggregate or Group plan nodes above
* the result of query_planner, we typically want to pass a different
* target list to query_planner than the outer plan nodes should have.
* This routine generates the correct target list for the subplan.
*
* The initial target list passed from the parser already contains entries
* for all ORDER BY and GROUP BY expressions, but it will not have entries
* for variables used only in HAVING clauses; so we need to add those
* variables to the subplan target list. Also, if we are doing either
* grouping or aggregation, we flatten all expressions except GROUP BY items
* into their component variables; the other expressions will be computed by
* the inserted nodes rather than by the subplan. For example,
* given a query like
* SELECT a+b,SUM(c+d) FROM table GROUP BY a+b;
* we want to pass this targetlist to the subplan:
* a,b,c,d,a+b
* where the a+b target will be used by the Sort/Group steps, and the
* other targets will be used for computing the final results. (In the
* above example we could theoretically suppress the a and b targets and
* pass down only c,d,a+b, but it's not really worth the trouble to
* eliminate simple var references from the subplan. We will avoid doing
* the extra computation to recompute a+b at the outer level; see
* replace_vars_with_subplan_refs() in setrefs.c.)
*
* 'parse' is the query being processed.
* 'tlist' is the query's target list.
* 'groupColIdx' receives an array of column numbers for the GROUP BY
* expressions (if there are any) in the subplan's target list.
*
* The result is the targetlist to be passed to the subplan.
*---------------
*/
static List *
make_subplanTargetList(Query *parse,
List *tlist,
AttrNumber **groupColIdx)
{
List *sub_tlist;
List *extravars;
int numCols;
*groupColIdx = NULL;
/*
* If we're not grouping or aggregating, nothing to do here;
* query_planner should receive the unmodified target list.
*/
if (!parse->hasAggs && !parse->groupClause && !parse->havingQual)
return tlist;
/*
* Otherwise, start with a "flattened" tlist (having just the vars
* mentioned in the targetlist and HAVING qual --- but not upper-
* level Vars; they will be replaced by Params later on).
*/
sub_tlist = flatten_tlist(tlist);
extravars = pull_var_clause(parse->havingQual, false);
sub_tlist = add_to_flat_tlist(sub_tlist, extravars);
freeList(extravars);
/*
* If grouping, create sub_tlist entries for all GROUP BY expressions
* (GROUP BY items that are simple Vars should be in the list
* already), and make an array showing where the group columns are in
* the sub_tlist.
*/
numCols = length(parse->groupClause);
if (numCols > 0)
{
int keyno = 0;
AttrNumber *grpColIdx;
List *gl;
grpColIdx = (AttrNumber *) palloc(sizeof(AttrNumber) * numCols);
*groupColIdx = grpColIdx;
foreach(gl, parse->groupClause)
{
GroupClause *grpcl = (GroupClause *) lfirst(gl);
Node *groupexpr = get_sortgroupclause_expr(grpcl, tlist);
TargetEntry *te = NULL;
List *sl;
/* Find or make a matching sub_tlist entry */
foreach(sl, sub_tlist)
{
te = (TargetEntry *) lfirst(sl);
if (equal(groupexpr, te->expr))
break;
}
if (!sl)
{
te = makeTargetEntry(makeResdom(length(sub_tlist) + 1,
exprType(groupexpr),
exprTypmod(groupexpr),
NULL,
false),
groupexpr);
sub_tlist = lappend(sub_tlist, te);
}
/* and save its resno */
grpColIdx[keyno++] = te->resdom->resno;
}
}
return sub_tlist;
}
/*
* make_groupsortplan
* Add a Sort node to explicitly sort according to the GROUP BY clause.
*
* Note: the Sort node always just takes a copy of the subplan's tlist
* plus ordering information. (This might seem inefficient if the
* subplan contains complex GROUP BY expressions, but in fact Sort
* does not evaluate its targetlist --- it only outputs the same
* tuples in a new order. So the expressions we might be copying
* are just dummies with no extra execution cost.)
*/
static Plan *
make_groupsortplan(Query *parse,
List *groupClause,
AttrNumber *grpColIdx,
Plan *subplan)
{
List *sort_tlist = new_unsorted_tlist(subplan->targetlist);
int keyno = 0;
List *gl;
foreach(gl, groupClause)
{
GroupClause *grpcl = (GroupClause *) lfirst(gl);
TargetEntry *te = nth(grpColIdx[keyno] - 1, sort_tlist);
Resdom *resdom = te->resdom;
/*
* Check for the possibility of duplicate group-by clauses ---
* the parser should have removed 'em, but the Sort executor
* will get terribly confused if any get through!
*/
if (resdom->reskey == 0)
{
/* OK, insert the ordering info needed by the executor. */
resdom->reskey = ++keyno;
resdom->reskeyop = grpcl->sortop;
}
}
Assert(keyno > 0);
return (Plan *) make_sort(parse, sort_tlist, subplan, keyno);
}
/*
* make_sortplan
* Add a Sort node to implement an explicit ORDER BY clause.
*/
Plan *
make_sortplan(Query *parse, List *tlist, Plan *plannode, List *sortcls)
{
List *sort_tlist;
List *i;
int keyno = 0;
/*
* First make a copy of the tlist so that we don't corrupt the
* original.
*/
sort_tlist = new_unsorted_tlist(tlist);
foreach(i, sortcls)
{
SortClause *sortcl = (SortClause *) lfirst(i);
TargetEntry *tle = get_sortgroupclause_tle(sortcl, sort_tlist);
Resdom *resdom = tle->resdom;
/*
* Check for the possibility of duplicate order-by clauses --- the
* parser should have removed 'em, but the executor will get
* terribly confused if any get through!
*/
if (resdom->reskey == 0)
{
/* OK, insert the ordering info needed by the executor. */
resdom->reskey = ++keyno;
resdom->reskeyop = sortcl->sortop;
}
}
Assert(keyno > 0);
return (Plan *) make_sort(parse, sort_tlist, plannode, keyno);
}
/*
* postprocess_setop_tlist
* Fix up targetlist returned by plan_set_operations().
*
* We need to transpose sort key info from the orig_tlist into new_tlist.
* NOTE: this would not be good enough if we supported resjunk sort keys
* for results of set operations --- then, we'd need to project a whole
* new tlist to evaluate the resjunk columns. For now, just elog if we
* find any resjunk columns in orig_tlist.
*/
static List *
postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
{
List *l;
foreach(l, new_tlist)
{
TargetEntry *new_tle = (TargetEntry *) lfirst(l);
TargetEntry *orig_tle;
/* ignore resjunk columns in setop result */
if (new_tle->resdom->resjunk)
continue;
Assert(orig_tlist != NIL);
orig_tle = (TargetEntry *) lfirst(orig_tlist);
orig_tlist = lnext(orig_tlist);
if (orig_tle->resdom->resjunk)
elog(ERROR, "postprocess_setop_tlist: resjunk output columns not implemented");
Assert(new_tle->resdom->resno == orig_tle->resdom->resno);
Assert(new_tle->resdom->restype == orig_tle->resdom->restype);
new_tle->resdom->ressortgroupref = orig_tle->resdom->ressortgroupref;
}
if (orig_tlist != NIL)
elog(ERROR, "postprocess_setop_tlist: resjunk output columns not implemented");
return new_tlist;
}