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postgres/src/backend/optimizer/util/pathnode.c
Tom Lane 101fd9349e Add a GetForeignUpperPaths callback function for FDWs. 
This is basically like the just-added create_upper_paths_hook, but
control is funneled only to the FDW responsible for all the baserels
of the current query; so providing such a callback is much less likely
to add useless overhead than using the hook function is.

The documentation is a bit sketchy.  We'll likely want to improve it,
and/or adjust the call conventions, when we get some experience with
actually using this callback.  Hopefully somebody will find time to
experiment with it before 9.6 feature freeze.
2016-03-14 20:04:48 -04:00

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/*-------------------------------------------------------------------------
*
* pathnode.c
* Routines to manipulate pathlists and create path nodes
*
* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/optimizer/util/pathnode.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <math.h>
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
#include "utils/lsyscache.h"
#include "utils/selfuncs.h"
typedef enum
{
COSTS_EQUAL, /* path costs are fuzzily equal */
COSTS_BETTER1, /* first path is cheaper than second */
COSTS_BETTER2, /* second path is cheaper than first */
COSTS_DIFFERENT /* neither path dominates the other on cost */
} PathCostComparison;
/*
* STD_FUZZ_FACTOR is the normal fuzz factor for compare_path_costs_fuzzily.
* XXX is it worth making this user-controllable? It provides a tradeoff
* between planner runtime and the accuracy of path cost comparisons.
*/
#define STD_FUZZ_FACTOR 1.01
static List *translate_sub_tlist(List *tlist, int relid);
/*****************************************************************************
* MISC. PATH UTILITIES
*****************************************************************************/
/*
* compare_path_costs
* Return -1, 0, or +1 according as path1 is cheaper, the same cost,
* or more expensive than path2 for the specified criterion.
*/
int
compare_path_costs(Path *path1, Path *path2, CostSelector criterion)
{
if (criterion == STARTUP_COST)
{
if (path1->startup_cost < path2->startup_cost)
return -1;
if (path1->startup_cost > path2->startup_cost)
return +1;
/*
* If paths have the same startup cost (not at all unlikely), order
* them by total cost.
*/
if (path1->total_cost < path2->total_cost)
return -1;
if (path1->total_cost > path2->total_cost)
return +1;
}
else
{
if (path1->total_cost < path2->total_cost)
return -1;
if (path1->total_cost > path2->total_cost)
return +1;
/*
* If paths have the same total cost, order them by startup cost.
*/
if (path1->startup_cost < path2->startup_cost)
return -1;
if (path1->startup_cost > path2->startup_cost)
return +1;
}
return 0;
}
/*
* compare_path_fractional_costs
* Return -1, 0, or +1 according as path1 is cheaper, the same cost,
* or more expensive than path2 for fetching the specified fraction
* of the total tuples.
*
* If fraction is <= 0 or > 1, we interpret it as 1, ie, we select the
* path with the cheaper total_cost.
*/
int
compare_fractional_path_costs(Path *path1, Path *path2,
double fraction)
{
Cost cost1,
cost2;
if (fraction <= 0.0 || fraction >= 1.0)
return compare_path_costs(path1, path2, TOTAL_COST);
cost1 = path1->startup_cost +
fraction * (path1->total_cost - path1->startup_cost);
cost2 = path2->startup_cost +
fraction * (path2->total_cost - path2->startup_cost);
if (cost1 < cost2)
return -1;
if (cost1 > cost2)
return +1;
return 0;
}
/*
* compare_path_costs_fuzzily
* Compare the costs of two paths to see if either can be said to
* dominate the other.
*
* We use fuzzy comparisons so that add_path() can avoid keeping both of
* a pair of paths that really have insignificantly different cost.
*
* The fuzz_factor argument must be 1.0 plus delta, where delta is the
* fraction of the smaller cost that is considered to be a significant
* difference. For example, fuzz_factor = 1.01 makes the fuzziness limit
* be 1% of the smaller cost.
*
* The two paths are said to have "equal" costs if both startup and total
* costs are fuzzily the same. Path1 is said to be better than path2 if
* it has fuzzily better startup cost and fuzzily no worse total cost,
* or if it has fuzzily better total cost and fuzzily no worse startup cost.
* Path2 is better than path1 if the reverse holds. Finally, if one path
* is fuzzily better than the other on startup cost and fuzzily worse on
* total cost, we just say that their costs are "different", since neither
* dominates the other across the whole performance spectrum.
*
* This function also enforces a policy rule that paths for which the relevant
* one of parent->consider_startup and parent->consider_param_startup is false
* cannot survive comparisons solely on the grounds of good startup cost, so
* we never return COSTS_DIFFERENT when that is true for the total-cost loser.
* (But if total costs are fuzzily equal, we compare startup costs anyway,
* in hopes of eliminating one path or the other.)
*/
static PathCostComparison
compare_path_costs_fuzzily(Path *path1, Path *path2, double fuzz_factor)
{
#define CONSIDER_PATH_STARTUP_COST(p) \
((p)->param_info == NULL ? (p)->parent->consider_startup : (p)->parent->consider_param_startup)
/*
* Check total cost first since it's more likely to be different; many
* paths have zero startup cost.
*/
if (path1->total_cost > path2->total_cost * fuzz_factor)
{
/* path1 fuzzily worse on total cost */
if (CONSIDER_PATH_STARTUP_COST(path1) &&
path2->startup_cost > path1->startup_cost * fuzz_factor)
{
/* ... but path2 fuzzily worse on startup, so DIFFERENT */
return COSTS_DIFFERENT;
}
/* else path2 dominates */
return COSTS_BETTER2;
}
if (path2->total_cost > path1->total_cost * fuzz_factor)
{
/* path2 fuzzily worse on total cost */
if (CONSIDER_PATH_STARTUP_COST(path2) &&
path1->startup_cost > path2->startup_cost * fuzz_factor)
{
/* ... but path1 fuzzily worse on startup, so DIFFERENT */
return COSTS_DIFFERENT;
}
/* else path1 dominates */
return COSTS_BETTER1;
}
/* fuzzily the same on total cost ... */
if (path1->startup_cost > path2->startup_cost * fuzz_factor)
{
/* ... but path1 fuzzily worse on startup, so path2 wins */
return COSTS_BETTER2;
}
if (path2->startup_cost > path1->startup_cost * fuzz_factor)
{
/* ... but path2 fuzzily worse on startup, so path1 wins */
return COSTS_BETTER1;
}
/* fuzzily the same on both costs */
return COSTS_EQUAL;
#undef CONSIDER_PATH_STARTUP_COST
}
/*
* set_cheapest
* Find the minimum-cost paths from among a relation's paths,
* and save them in the rel's cheapest-path fields.
*
* cheapest_total_path is normally the cheapest-total-cost unparameterized
* path; but if there are no unparameterized paths, we assign it to be the
* best (cheapest least-parameterized) parameterized path. However, only
* unparameterized paths are considered candidates for cheapest_startup_path,
* so that will be NULL if there are no unparameterized paths.
*
* The cheapest_parameterized_paths list collects all parameterized paths
* that have survived the add_path() tournament for this relation. (Since
* add_path ignores pathkeys for a parameterized path, these will be paths
* that have best cost or best row count for their parameterization. We
* may also have both a parallel-safe and a non-parallel-safe path in some
* cases for the same parameterization in some cases, but this should be
* relatively rare since, most typically, all paths for the same relation
* will be parallel-safe or none of them will.)
*
* cheapest_parameterized_paths always includes the cheapest-total
* unparameterized path, too, if there is one; the users of that list find
* it more convenient if that's included.
*
* This is normally called only after we've finished constructing the path
* list for the rel node.
*/
void
set_cheapest(RelOptInfo *parent_rel)
{
Path *cheapest_startup_path;
Path *cheapest_total_path;
Path *best_param_path;
List *parameterized_paths;
ListCell *p;
Assert(IsA(parent_rel, RelOptInfo));
if (parent_rel->pathlist == NIL)
elog(ERROR, "could not devise a query plan for the given query");
cheapest_startup_path = cheapest_total_path = best_param_path = NULL;
parameterized_paths = NIL;
foreach(p, parent_rel->pathlist)
{
Path *path = (Path *) lfirst(p);
int cmp;
if (path->param_info)
{
/* Parameterized path, so add it to parameterized_paths */
parameterized_paths = lappend(parameterized_paths, path);
/*
* If we have an unparameterized cheapest-total, we no longer care
* about finding the best parameterized path, so move on.
*/
if (cheapest_total_path)
continue;
/*
* Otherwise, track the best parameterized path, which is the one
* with least total cost among those of the minimum
* parameterization.
*/
if (best_param_path == NULL)
best_param_path = path;
else
{
switch (bms_subset_compare(PATH_REQ_OUTER(path),
PATH_REQ_OUTER(best_param_path)))
{
case BMS_EQUAL:
/* keep the cheaper one */
if (compare_path_costs(path, best_param_path,
TOTAL_COST) < 0)
best_param_path = path;
break;
case BMS_SUBSET1:
/* new path is less-parameterized */
best_param_path = path;
break;
case BMS_SUBSET2:
/* old path is less-parameterized, keep it */
break;
case BMS_DIFFERENT:
/*
* This means that neither path has the least possible
* parameterization for the rel. We'll sit on the old
* path until something better comes along.
*/
break;
}
}
}
else
{
/* Unparameterized path, so consider it for cheapest slots */
if (cheapest_total_path == NULL)
{
cheapest_startup_path = cheapest_total_path = path;
continue;
}
/*
* If we find two paths of identical costs, try to keep the
* better-sorted one. The paths might have unrelated sort
* orderings, in which case we can only guess which might be
* better to keep, but if one is superior then we definitely
* should keep that one.
*/
cmp = compare_path_costs(cheapest_startup_path, path, STARTUP_COST);
if (cmp > 0 ||
(cmp == 0 &&
compare_pathkeys(cheapest_startup_path->pathkeys,
path->pathkeys) == PATHKEYS_BETTER2))
cheapest_startup_path = path;
cmp = compare_path_costs(cheapest_total_path, path, TOTAL_COST);
if (cmp > 0 ||
(cmp == 0 &&
compare_pathkeys(cheapest_total_path->pathkeys,
path->pathkeys) == PATHKEYS_BETTER2))
cheapest_total_path = path;
}
}
/* Add cheapest unparameterized path, if any, to parameterized_paths */
if (cheapest_total_path)
parameterized_paths = lcons(cheapest_total_path, parameterized_paths);
/*
* If there is no unparameterized path, use the best parameterized path as
* cheapest_total_path (but not as cheapest_startup_path).
*/
if (cheapest_total_path == NULL)
cheapest_total_path = best_param_path;
Assert(cheapest_total_path != NULL);
parent_rel->cheapest_startup_path = cheapest_startup_path;
parent_rel->cheapest_total_path = cheapest_total_path;
parent_rel->cheapest_unique_path = NULL; /* computed only if needed */
parent_rel->cheapest_parameterized_paths = parameterized_paths;
}
/*
* add_path
* Consider a potential implementation path for the specified parent rel,
* and add it to the rel's pathlist if it is worthy of consideration.
* A path is worthy if it has a better sort order (better pathkeys) or
* cheaper cost (on either dimension), or generates fewer rows, than any
* existing path that has the same or superset parameterization rels.
* We also consider parallel-safe paths more worthy than others.
*
* We also remove from the rel's pathlist any old paths that are dominated
* by new_path --- that is, new_path is cheaper, at least as well ordered,
* generates no more rows, requires no outer rels not required by the old
* path, and is no less parallel-safe.
*
* In most cases, a path with a superset parameterization will generate
* fewer rows (since it has more join clauses to apply), so that those two
* figures of merit move in opposite directions; this means that a path of
* one parameterization can seldom dominate a path of another. But such
* cases do arise, so we make the full set of checks anyway.
*
* There are two policy decisions embedded in this function, along with
* its sibling add_path_precheck. First, we treat all parameterized paths
* as having NIL pathkeys, so that they cannot win comparisons on the
* basis of sort order. This is to reduce the number of parameterized
* paths that are kept; see discussion in src/backend/optimizer/README.
*
* Second, we only consider cheap startup cost to be interesting if
* parent_rel->consider_startup is true for an unparameterized path, or
* parent_rel->consider_param_startup is true for a parameterized one.
* Again, this allows discarding useless paths sooner.
*
* The pathlist is kept sorted by total_cost, with cheaper paths
* at the front. Within this routine, that's simply a speed hack:
* doing it that way makes it more likely that we will reject an inferior
* path after a few comparisons, rather than many comparisons.
* However, add_path_precheck relies on this ordering to exit early
* when possible.
*
* NOTE: discarded Path objects are immediately pfree'd to reduce planner
* memory consumption. We dare not try to free the substructure of a Path,
* since much of it may be shared with other Paths or the query tree itself;
* but just recycling discarded Path nodes is a very useful savings in
* a large join tree. We can recycle the List nodes of pathlist, too.
*
* BUT: we do not pfree IndexPath objects, since they may be referenced as
* children of BitmapHeapPaths as well as being paths in their own right.
*
* 'parent_rel' is the relation entry to which the path corresponds.
* 'new_path' is a potential path for parent_rel.
*
* Returns nothing, but modifies parent_rel->pathlist.
*/
void
add_path(RelOptInfo *parent_rel, Path *new_path)
{
bool accept_new = true; /* unless we find a superior old path */
ListCell *insert_after = NULL; /* where to insert new item */
List *new_path_pathkeys;
ListCell *p1;
ListCell *p1_prev;
ListCell *p1_next;
/*
* This is a convenient place to check for query cancel --- no part of the
* planner goes very long without calling add_path().
*/
CHECK_FOR_INTERRUPTS();
/* Pretend parameterized paths have no pathkeys, per comment above */
new_path_pathkeys = new_path->param_info ? NIL : new_path->pathkeys;
/*
* Loop to check proposed new path against old paths. Note it is possible
* for more than one old path to be tossed out because new_path dominates
* it.
*
* We can't use foreach here because the loop body may delete the current
* list cell.
*/
p1_prev = NULL;
for (p1 = list_head(parent_rel->pathlist); p1 != NULL; p1 = p1_next)
{
Path *old_path = (Path *) lfirst(p1);
bool remove_old = false; /* unless new proves superior */
PathCostComparison costcmp;
PathKeysComparison keyscmp;
BMS_Comparison outercmp;
p1_next = lnext(p1);
/*
* Do a fuzzy cost comparison with standard fuzziness limit.
*/
costcmp = compare_path_costs_fuzzily(new_path, old_path,
STD_FUZZ_FACTOR);
/*
* If the two paths compare differently for startup and total cost,
* then we want to keep both, and we can skip comparing pathkeys and
* required_outer rels. If they compare the same, proceed with the
* other comparisons. Row count is checked last. (We make the tests
* in this order because the cost comparison is most likely to turn
* out "different", and the pathkeys comparison next most likely. As
* explained above, row count very seldom makes a difference, so even
* though it's cheap to compare there's not much point in checking it
* earlier.)
*/
if (costcmp != COSTS_DIFFERENT)
{
/* Similarly check to see if either dominates on pathkeys */
List *old_path_pathkeys;
old_path_pathkeys = old_path->param_info ? NIL : old_path->pathkeys;
keyscmp = compare_pathkeys(new_path_pathkeys,
old_path_pathkeys);
if (keyscmp != PATHKEYS_DIFFERENT)
{
switch (costcmp)
{
case COSTS_EQUAL:
outercmp = bms_subset_compare(PATH_REQ_OUTER(new_path),
PATH_REQ_OUTER(old_path));
if (keyscmp == PATHKEYS_BETTER1)
{
if ((outercmp == BMS_EQUAL ||
outercmp == BMS_SUBSET1) &&
new_path->rows <= old_path->rows &&
new_path->parallel_safe >= old_path->parallel_safe)
remove_old = true; /* new dominates old */
}
else if (keyscmp == PATHKEYS_BETTER2)
{
if ((outercmp == BMS_EQUAL ||
outercmp == BMS_SUBSET2) &&
new_path->rows >= old_path->rows &&
new_path->parallel_safe <= old_path->parallel_safe)
accept_new = false; /* old dominates new */
}
else /* keyscmp == PATHKEYS_EQUAL */
{
if (outercmp == BMS_EQUAL)
{
/*
* Same pathkeys and outer rels, and fuzzily
* the same cost, so keep just one; to decide
* which, first check parallel-safety, then
* rows, then do a fuzzy cost comparison with
* very small fuzz limit. (We used to do an
* exact cost comparison, but that results in
* annoying platform-specific plan variations
* due to roundoff in the cost estimates.) If
* things are still tied, arbitrarily keep
* only the old path. Notice that we will
* keep only the old path even if the
* less-fuzzy comparison decides the startup
* and total costs compare differently.
*/
if (new_path->parallel_safe >
old_path->parallel_safe)
remove_old = true; /* new dominates old */
else if (new_path->parallel_safe <
old_path->parallel_safe)
accept_new = false; /* old dominates new */
else if (new_path->rows < old_path->rows)
remove_old = true; /* new dominates old */
else if (new_path->rows > old_path->rows)
accept_new = false; /* old dominates new */
else if (compare_path_costs_fuzzily(new_path,
old_path,
1.0000000001) == COSTS_BETTER1)
remove_old = true; /* new dominates old */
else
accept_new = false; /* old equals or
* dominates new */
}
else if (outercmp == BMS_SUBSET1 &&
new_path->rows <= old_path->rows &&
new_path->parallel_safe >= old_path->parallel_safe)
remove_old = true; /* new dominates old */
else if (outercmp == BMS_SUBSET2 &&
new_path->rows >= old_path->rows &&
new_path->parallel_safe <= old_path->parallel_safe)
accept_new = false; /* old dominates new */
/* else different parameterizations, keep both */
}
break;
case COSTS_BETTER1:
if (keyscmp != PATHKEYS_BETTER2)
{
outercmp = bms_subset_compare(PATH_REQ_OUTER(new_path),
PATH_REQ_OUTER(old_path));
if ((outercmp == BMS_EQUAL ||
outercmp == BMS_SUBSET1) &&
new_path->rows <= old_path->rows &&
new_path->parallel_safe >= old_path->parallel_safe)
remove_old = true; /* new dominates old */
}
break;
case COSTS_BETTER2:
if (keyscmp != PATHKEYS_BETTER1)
{
outercmp = bms_subset_compare(PATH_REQ_OUTER(new_path),
PATH_REQ_OUTER(old_path));
if ((outercmp == BMS_EQUAL ||
outercmp == BMS_SUBSET2) &&
new_path->rows >= old_path->rows &&
new_path->parallel_safe <= old_path->parallel_safe)
accept_new = false; /* old dominates new */
}
break;
case COSTS_DIFFERENT:
/*
* can't get here, but keep this case to keep compiler
* quiet
*/
break;
}
}
}
/*
* Remove current element from pathlist if dominated by new.
*/
if (remove_old)
{
parent_rel->pathlist = list_delete_cell(parent_rel->pathlist,
p1, p1_prev);
/*
* Delete the data pointed-to by the deleted cell, if possible
*/
if (!IsA(old_path, IndexPath))
pfree(old_path);
/* p1_prev does not advance */
}
else
{
/* new belongs after this old path if it has cost >= old's */
if (new_path->total_cost >= old_path->total_cost)
insert_after = p1;
/* p1_prev advances */
p1_prev = p1;
}
/*
* If we found an old path that dominates new_path, we can quit
* scanning the pathlist; we will not add new_path, and we assume
* new_path cannot dominate any other elements of the pathlist.
*/
if (!accept_new)
break;
}
if (accept_new)
{
/* Accept the new path: insert it at proper place in pathlist */
if (insert_after)
lappend_cell(parent_rel->pathlist, insert_after, new_path);
else
parent_rel->pathlist = lcons(new_path, parent_rel->pathlist);
}
else
{
/* Reject and recycle the new path */
if (!IsA(new_path, IndexPath))
pfree(new_path);
}
}
/*
* add_path_precheck
* Check whether a proposed new path could possibly get accepted.
* We assume we know the path's pathkeys and parameterization accurately,
* and have lower bounds for its costs.
*
* Note that we do not know the path's rowcount, since getting an estimate for
* that is too expensive to do before prechecking. We assume here that paths
* of a superset parameterization will generate fewer rows; if that holds,
* then paths with different parameterizations cannot dominate each other
* and so we can simply ignore existing paths of another parameterization.
* (In the infrequent cases where that rule of thumb fails, add_path will
* get rid of the inferior path.)
*
* At the time this is called, we haven't actually built a Path structure,
* so the required information has to be passed piecemeal.
*/
bool
add_path_precheck(RelOptInfo *parent_rel,
Cost startup_cost, Cost total_cost,
List *pathkeys, Relids required_outer)
{
List *new_path_pathkeys;
bool consider_startup;
ListCell *p1;
/* Pretend parameterized paths have no pathkeys, per add_path policy */
new_path_pathkeys = required_outer ? NIL : pathkeys;
/* Decide whether new path's startup cost is interesting */
consider_startup = required_outer ? parent_rel->consider_param_startup : parent_rel->consider_startup;
foreach(p1, parent_rel->pathlist)
{
Path *old_path = (Path *) lfirst(p1);
PathKeysComparison keyscmp;
/*
* We are looking for an old_path with the same parameterization (and
* by assumption the same rowcount) that dominates the new path on
* pathkeys as well as both cost metrics. If we find one, we can
* reject the new path.
*
* Cost comparisons here should match compare_path_costs_fuzzily.
*/
if (total_cost > old_path->total_cost * STD_FUZZ_FACTOR)
{
/* new path can win on startup cost only if consider_startup */
if (startup_cost > old_path->startup_cost * STD_FUZZ_FACTOR ||
!consider_startup)
{
/* new path loses on cost, so check pathkeys... */
List *old_path_pathkeys;
old_path_pathkeys = old_path->param_info ? NIL : old_path->pathkeys;
keyscmp = compare_pathkeys(new_path_pathkeys,
old_path_pathkeys);
if (keyscmp == PATHKEYS_EQUAL ||
keyscmp == PATHKEYS_BETTER2)
{
/* new path does not win on pathkeys... */
if (bms_equal(required_outer, PATH_REQ_OUTER(old_path)))
{
/* Found an old path that dominates the new one */
return false;
}
}
}
}
else
{
/*
* Since the pathlist is sorted by total_cost, we can stop looking
* once we reach a path with a total_cost larger than the new
* path's.
*/
break;
}
}
return true;
}
/*
* add_partial_path
* Like add_path, our goal here is to consider whether a path is worthy
* of being kept around, but the considerations here are a bit different.
* A partial path is one which can be executed in any number of workers in
* parallel such that each worker will generate a subset of the path's
* overall result.
*
* We don't generate parameterized partial paths for several reasons. Most
* importantly, they're not safe to execute, because there's nothing to
* make sure that a parallel scan within the parameterized portion of the
* plan is running with the same value in every worker at the same time.
* Fortunately, it seems unlikely to be worthwhile anyway, because having
* each worker scan the entire outer relation and a subset of the inner
* relation will generally be a terrible plan. The inner (parameterized)
* side of the plan will be small anyway. There could be rare cases where
* this wins big - e.g. if join order constraints put a 1-row relation on
* the outer side of the topmost join with a parameterized plan on the inner
* side - but we'll have to be content not to handle such cases until somebody
* builds an executor infrastructure that can cope with them.
*
* Because we don't consider parameterized paths here, we also don't
* need to consider the row counts as a measure of quality: every path will
* produce the same number of rows. Neither do we need to consider startup
* costs: parallelism is only used for plans that will be run to completion.
* Therefore, this routine is much simpler than add_path: it needs to
* consider only pathkeys and total cost.
*/
void
add_partial_path(RelOptInfo *parent_rel, Path *new_path)
{
bool accept_new = true; /* unless we find a superior old path */
ListCell *insert_after = NULL; /* where to insert new item */
ListCell *p1;
ListCell *p1_prev;
ListCell *p1_next;
/* Check for query cancel. */
CHECK_FOR_INTERRUPTS();
/*
* As in add_path, throw out any paths which are dominated by the new
* path, but throw out the new path if some existing path dominates it.
*/
p1_prev = NULL;
for (p1 = list_head(parent_rel->partial_pathlist); p1 != NULL;
p1 = p1_next)
{
Path *old_path = (Path *) lfirst(p1);
bool remove_old = false; /* unless new proves superior */
PathKeysComparison keyscmp;
p1_next = lnext(p1);
/* Compare pathkeys. */
keyscmp = compare_pathkeys(new_path->pathkeys, old_path->pathkeys);
/* Unless pathkeys are incompable, keep just one of the two paths. */
if (keyscmp != PATHKEYS_DIFFERENT)
{
if (new_path->total_cost > old_path->total_cost * STD_FUZZ_FACTOR)
{
/* New path costs more; keep it only if pathkeys are better. */
if (keyscmp != PATHKEYS_BETTER1)
accept_new = false;
}
else if (old_path->total_cost > new_path->total_cost
* STD_FUZZ_FACTOR)
{
/* Old path costs more; keep it only if pathkeys are better. */
if (keyscmp != PATHKEYS_BETTER2)
remove_old = true;
}
else if (keyscmp == PATHKEYS_BETTER1)
{
/* Costs are about the same, new path has better pathkeys. */
remove_old = true;
}
else if (keyscmp == PATHKEYS_BETTER2)
{
/* Costs are about the same, old path has better pathkeys. */
accept_new = false;
}
else if (old_path->total_cost > new_path->total_cost * 1.0000000001)
{
/* Pathkeys are the same, and the old path costs more. */
remove_old = true;
}
else
{
/*
* Pathkeys are the same, and new path isn't materially
* cheaper.
*/
accept_new = false;
}
}
/*
* Remove current element from partial_pathlist if dominated by new.
*/
if (remove_old)
{
parent_rel->partial_pathlist =
list_delete_cell(parent_rel->partial_pathlist, p1, p1_prev);
/* add_path has a special case for IndexPath; we don't need it */
Assert(!IsA(old_path, IndexPath));
pfree(old_path);
/* p1_prev does not advance */
}
else
{
/* new belongs after this old path if it has cost >= old's */
if (new_path->total_cost >= old_path->total_cost)
insert_after = p1;
/* p1_prev advances */
p1_prev = p1;
}
/*
* If we found an old path that dominates new_path, we can quit
* scanning the partial_pathlist; we will not add new_path, and we
* assume new_path cannot dominate any later path.
*/
if (!accept_new)
break;
}
if (accept_new)
{
/* Accept the new path: insert it at proper place */
if (insert_after)
lappend_cell(parent_rel->partial_pathlist, insert_after, new_path);
else
parent_rel->partial_pathlist =
lcons(new_path, parent_rel->partial_pathlist);
}
else
{
/* add_path has a special case for IndexPath; we don't need it */
Assert(!IsA(new_path, IndexPath));
/* Reject and recycle the new path */
pfree(new_path);
}
}
/*
* add_partial_path_precheck
* Check whether a proposed new partial path could possibly get accepted.
*
* Unlike add_path_precheck, we can ignore startup cost and parameterization,
* since they don't matter for partial paths (see add_partial_path). But
* we do want to make sure we don't add a partial path if there's already
* a complete path that dominates it, since in that case the proposed path
* is surely a loser.
*/
bool
add_partial_path_precheck(RelOptInfo *parent_rel, Cost total_cost,
List *pathkeys)
{
ListCell *p1;
/*
* Our goal here is twofold. First, we want to find out whether this path
* is clearly inferior to some existing partial path. If so, we want to
* reject it immediately. Second, we want to find out whether this path
* is clearly superior to some existing partial path -- at least, modulo
* final cost computations. If so, we definitely want to consider it.
*
* Unlike add_path(), we always compare pathkeys here. This is because we
* expect partial_pathlist to be very short, and getting a definitive
* answer at this stage avoids the need to call add_path_precheck.
*/
foreach(p1, parent_rel->partial_pathlist)
{
Path *old_path = (Path *) lfirst(p1);
PathKeysComparison keyscmp;
keyscmp = compare_pathkeys(pathkeys, old_path->pathkeys);
if (keyscmp != PATHKEYS_DIFFERENT)
{
if (total_cost > old_path->total_cost * STD_FUZZ_FACTOR &&
keyscmp != PATHKEYS_BETTER1)
return false;
if (old_path->total_cost > total_cost * STD_FUZZ_FACTOR &&
keyscmp != PATHKEYS_BETTER2)
return true;
}
}
/*
* This path is neither clearly inferior to an existing partial path nor
* clearly good enough that it might replace one. Compare it to
* non-parallel plans. If it loses even before accounting for the cost of
* the Gather node, we should definitely reject it.
*
* Note that we pass the total_cost to add_path_precheck twice. This is
* because it's never advantageous to consider the startup cost of a
* partial path; the resulting plans, if run in parallel, will be run to
* completion.
*/
if (!add_path_precheck(parent_rel, total_cost, total_cost, pathkeys,
NULL))
return false;
return true;
}
/*****************************************************************************
* PATH NODE CREATION ROUTINES
*****************************************************************************/
/*
* create_seqscan_path
* Creates a path corresponding to a sequential scan, returning the
* pathnode.
*/
Path *
create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer, int parallel_degree)
{
Path *pathnode = makeNode(Path);
pathnode->pathtype = T_SeqScan;
pathnode->parent = rel;
pathnode->pathtarget = rel->reltarget;
pathnode->param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->parallel_aware = parallel_degree > 0 ? true : false;
pathnode->parallel_safe = rel->consider_parallel;
pathnode->parallel_degree = parallel_degree;
pathnode->pathkeys = NIL; /* seqscan has unordered result */
cost_seqscan(pathnode, root, rel, pathnode->param_info);
return pathnode;
}
/*
* create_samplescan_path
* Creates a path node for a sampled table scan.
*/
Path *
create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
{
Path *pathnode = makeNode(Path);
pathnode->pathtype = T_SampleScan;
pathnode->parent = rel;
pathnode->pathtarget = rel->reltarget;
pathnode->param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->parallel_aware = false;
pathnode->parallel_safe = rel->consider_parallel;
pathnode->parallel_degree = 0;
pathnode->pathkeys = NIL; /* samplescan has unordered result */
cost_samplescan(pathnode, root, rel, pathnode->param_info);
return pathnode;
}
/*
* create_index_path
* Creates a path node for an index scan.
*
* 'index' is a usable index.
* 'indexclauses' is a list of RestrictInfo nodes representing clauses
* to be used as index qual conditions in the scan.
* 'indexclausecols' is an integer list of index column numbers (zero based)
* the indexclauses can be used with.
* 'indexorderbys' is a list of bare expressions (no RestrictInfos)
* to be used as index ordering operators in the scan.
* 'indexorderbycols' is an integer list of index column numbers (zero based)
* the ordering operators can be used with.
* 'pathkeys' describes the ordering of the path.
* 'indexscandir' is ForwardScanDirection or BackwardScanDirection
* for an ordered index, or NoMovementScanDirection for
* an unordered index.
* 'indexonly' is true if an index-only scan is wanted.
* 'required_outer' is the set of outer relids for a parameterized path.
* 'loop_count' is the number of repetitions of the indexscan to factor into
* estimates of caching behavior.
*
* Returns the new path node.
*/
IndexPath *
create_index_path(PlannerInfo *root,
IndexOptInfo *index,
List *indexclauses,
List *indexclausecols,
List *indexorderbys,
List *indexorderbycols,
List *pathkeys,
ScanDirection indexscandir,
bool indexonly,
Relids required_outer,
double loop_count)
{
IndexPath *pathnode = makeNode(IndexPath);
RelOptInfo *rel = index->rel;
List *indexquals,
*indexqualcols;
pathnode->path.pathtype = indexonly ? T_IndexOnlyScan : T_IndexScan;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_degree = 0;
pathnode->path.pathkeys = pathkeys;
/* Convert clauses to indexquals the executor can handle */
expand_indexqual_conditions(index, indexclauses, indexclausecols,
&indexquals, &indexqualcols);
/* Fill in the pathnode */
pathnode->indexinfo = index;
pathnode->indexclauses = indexclauses;
pathnode->indexquals = indexquals;
pathnode->indexqualcols = indexqualcols;
pathnode->indexorderbys = indexorderbys;
pathnode->indexorderbycols = indexorderbycols;
pathnode->indexscandir = indexscandir;
cost_index(pathnode, root, loop_count);
return pathnode;
}
/*
* create_bitmap_heap_path
* Creates a path node for a bitmap scan.
*
* 'bitmapqual' is a tree of IndexPath, BitmapAndPath, and BitmapOrPath nodes.
* 'required_outer' is the set of outer relids for a parameterized path.
* 'loop_count' is the number of repetitions of the indexscan to factor into
* estimates of caching behavior.
*
* loop_count should match the value used when creating the component
* IndexPaths.
*/
BitmapHeapPath *
create_bitmap_heap_path(PlannerInfo *root,
RelOptInfo *rel,
Path *bitmapqual,
Relids required_outer,
double loop_count)
{
BitmapHeapPath *pathnode = makeNode(BitmapHeapPath);
pathnode->path.pathtype = T_BitmapHeapScan;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_degree = 0;
pathnode->path.pathkeys = NIL; /* always unordered */
pathnode->bitmapqual = bitmapqual;
cost_bitmap_heap_scan(&pathnode->path, root, rel,
pathnode->path.param_info,
bitmapqual, loop_count);
return pathnode;
}
/*
* create_bitmap_and_path
* Creates a path node representing a BitmapAnd.
*/
BitmapAndPath *
create_bitmap_and_path(PlannerInfo *root,
RelOptInfo *rel,
List *bitmapquals)
{
BitmapAndPath *pathnode = makeNode(BitmapAndPath);
pathnode->path.pathtype = T_BitmapAnd;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = NULL; /* not used in bitmap trees */
/*
* Currently, a BitmapHeapPath, BitmapAndPath, or BitmapOrPath will be
* parallel-safe if and only if rel->consider_parallel is set. So, we can
* set the flag for this path based only on the relation-level flag,
* without actually iterating over the list of children.
*/
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_degree = 0;
pathnode->path.pathkeys = NIL; /* always unordered */
pathnode->bitmapquals = bitmapquals;
/* this sets bitmapselectivity as well as the regular cost fields: */
cost_bitmap_and_node(pathnode, root);
return pathnode;
}
/*
* create_bitmap_or_path
* Creates a path node representing a BitmapOr.
*/
BitmapOrPath *
create_bitmap_or_path(PlannerInfo *root,
RelOptInfo *rel,
List *bitmapquals)
{
BitmapOrPath *pathnode = makeNode(BitmapOrPath);
pathnode->path.pathtype = T_BitmapOr;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = NULL; /* not used in bitmap trees */
/*
* Currently, a BitmapHeapPath, BitmapAndPath, or BitmapOrPath will be
* parallel-safe if and only if rel->consider_parallel is set. So, we can
* set the flag for this path based only on the relation-level flag,
* without actually iterating over the list of children.
*/
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_degree = 0;
pathnode->path.pathkeys = NIL; /* always unordered */
pathnode->bitmapquals = bitmapquals;
/* this sets bitmapselectivity as well as the regular cost fields: */
cost_bitmap_or_node(pathnode, root);
return pathnode;
}
/*
* create_tidscan_path
* Creates a path corresponding to a scan by TID, returning the pathnode.
*/
TidPath *
create_tidscan_path(PlannerInfo *root, RelOptInfo *rel, List *tidquals,
Relids required_outer)
{
TidPath *pathnode = makeNode(TidPath);
pathnode->path.pathtype = T_TidScan;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_degree = 0;
pathnode->path.pathkeys = NIL; /* always unordered */
pathnode->tidquals = tidquals;
cost_tidscan(&pathnode->path, root, rel, tidquals,
pathnode->path.param_info);
return pathnode;
}
/*
* create_append_path
* Creates a path corresponding to an Append plan, returning the
* pathnode.
*
* Note that we must handle subpaths = NIL, representing a dummy access path.
*/
AppendPath *
create_append_path(RelOptInfo *rel, List *subpaths, Relids required_outer,
int parallel_degree)
{
AppendPath *pathnode = makeNode(AppendPath);
ListCell *l;
pathnode->path.pathtype = T_Append;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = get_appendrel_parampathinfo(rel,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_degree = parallel_degree;
pathnode->path.pathkeys = NIL; /* result is always considered
* unsorted */
pathnode->subpaths = subpaths;
/*
* We don't bother with inventing a cost_append(), but just do it here.
*
* Compute rows and costs as sums of subplan rows and costs. We charge
* nothing extra for the Append itself, which perhaps is too optimistic,
* but since it doesn't do any selection or projection, it is a pretty
* cheap node.
*/
pathnode->path.rows = 0;
pathnode->path.startup_cost = 0;
pathnode->path.total_cost = 0;
foreach(l, subpaths)
{
Path *subpath = (Path *) lfirst(l);
pathnode->path.rows += subpath->rows;
if (l == list_head(subpaths)) /* first node? */
pathnode->path.startup_cost = subpath->startup_cost;
pathnode->path.total_cost += subpath->total_cost;
pathnode->path.parallel_safe = pathnode->path.parallel_safe &&
subpath->parallel_safe;
/* All child paths must have same parameterization */
Assert(bms_equal(PATH_REQ_OUTER(subpath), required_outer));
}
return pathnode;
}
/*
* create_merge_append_path
* Creates a path corresponding to a MergeAppend plan, returning the
* pathnode.
*/
MergeAppendPath *
create_merge_append_path(PlannerInfo *root,
RelOptInfo *rel,
List *subpaths,
List *pathkeys,
Relids required_outer)
{
MergeAppendPath *pathnode = makeNode(MergeAppendPath);
Cost input_startup_cost;
Cost input_total_cost;
ListCell *l;
pathnode->path.pathtype = T_MergeAppend;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = get_appendrel_parampathinfo(rel,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_degree = 0;
pathnode->path.pathkeys = pathkeys;
pathnode->subpaths = subpaths;
/*
* Apply query-wide LIMIT if known and path is for sole base relation.
* (Handling this at this low level is a bit klugy.)
*/
if (bms_equal(rel->relids, root->all_baserels))
pathnode->limit_tuples = root->limit_tuples;
else
pathnode->limit_tuples = -1.0;
/*
* Add up the sizes and costs of the input paths.
*/
pathnode->path.rows = 0;
input_startup_cost = 0;
input_total_cost = 0;
foreach(l, subpaths)
{
Path *subpath = (Path *) lfirst(l);
pathnode->path.rows += subpath->rows;
pathnode->path.parallel_safe = pathnode->path.parallel_safe &&
subpath->parallel_safe;
if (pathkeys_contained_in(pathkeys, subpath->pathkeys))
{
/* Subpath is adequately ordered, we won't need to sort it */
input_startup_cost += subpath->startup_cost;
input_total_cost += subpath->total_cost;
}
else
{
/* We'll need to insert a Sort node, so include cost for that */
Path sort_path; /* dummy for result of cost_sort */
cost_sort(&sort_path,
root,
pathkeys,
subpath->total_cost,
subpath->parent->tuples,
subpath->pathtarget->width,
0.0,
work_mem,
pathnode->limit_tuples);
input_startup_cost += sort_path.startup_cost;
input_total_cost += sort_path.total_cost;
}
/* All child paths must have same parameterization */
Assert(bms_equal(PATH_REQ_OUTER(subpath), required_outer));
}
/* Now we can compute total costs of the MergeAppend */
cost_merge_append(&pathnode->path, root,
pathkeys, list_length(subpaths),
input_startup_cost, input_total_cost,
rel->tuples);
return pathnode;
}
/*
* create_result_path
* Creates a path representing a Result-and-nothing-else plan.
*
* This is only used for degenerate cases, such as a query with an empty
* jointree.
*/
ResultPath *
create_result_path(PlannerInfo *root, RelOptInfo *rel,
PathTarget *target, List *resconstantqual)
{
ResultPath *pathnode = makeNode(ResultPath);
pathnode->path.pathtype = T_Result;
pathnode->path.parent = rel;
pathnode->path.pathtarget = target;
pathnode->path.param_info = NULL; /* there are no other rels... */
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_degree = 0;
pathnode->path.pathkeys = NIL;
pathnode->quals = resconstantqual;
/* Hardly worth defining a cost_result() function ... just do it */
pathnode->path.rows = 1;
pathnode->path.startup_cost = target->cost.startup;
pathnode->path.total_cost = target->cost.startup +
cpu_tuple_cost + target->cost.per_tuple;
if (resconstantqual)
{
QualCost qual_cost;
cost_qual_eval(&qual_cost, resconstantqual, root);
/* resconstantqual is evaluated once at startup */
pathnode->path.startup_cost += qual_cost.startup + qual_cost.per_tuple;
pathnode->path.total_cost += qual_cost.startup + qual_cost.per_tuple;
}
return pathnode;
}
/*
* create_material_path
* Creates a path corresponding to a Material plan, returning the
* pathnode.
*/
MaterialPath *
create_material_path(RelOptInfo *rel, Path *subpath)
{
MaterialPath *pathnode = makeNode(MaterialPath);
Assert(subpath->parent == rel);
pathnode->path.pathtype = T_Material;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = subpath->param_info;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
pathnode->path.pathkeys = subpath->pathkeys;
pathnode->subpath = subpath;
cost_material(&pathnode->path,
subpath->startup_cost,
subpath->total_cost,
subpath->rows,
subpath->pathtarget->width);
return pathnode;
}
/*
* create_unique_path
* Creates a path representing elimination of distinct rows from the
* input data. Distinct-ness is defined according to the needs of the
* semijoin represented by sjinfo. If it is not possible to identify
* how to make the data unique, NULL is returned.
*
* If used at all, this is likely to be called repeatedly on the same rel;
* and the input subpath should always be the same (the cheapest_total path
* for the rel). So we cache the result.
*/
UniquePath *
create_unique_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
SpecialJoinInfo *sjinfo)
{
UniquePath *pathnode;
Path sort_path; /* dummy for result of cost_sort */
Path agg_path; /* dummy for result of cost_agg */
MemoryContext oldcontext;
int numCols;
/* Caller made a mistake if subpath isn't cheapest_total ... */
Assert(subpath == rel->cheapest_total_path);
Assert(subpath->parent == rel);
/* ... or if SpecialJoinInfo is the wrong one */
Assert(sjinfo->jointype == JOIN_SEMI);
Assert(bms_equal(rel->relids, sjinfo->syn_righthand));
/* If result already cached, return it */
if (rel->cheapest_unique_path)
return (UniquePath *) rel->cheapest_unique_path;
/* If it's not possible to unique-ify, return NULL */
if (!(sjinfo->semi_can_btree || sjinfo->semi_can_hash))
return NULL;
/*
* We must ensure path struct and subsidiary data are allocated in main
* planning context; otherwise GEQO memory management causes trouble.
*/
oldcontext = MemoryContextSwitchTo(root->planner_cxt);
pathnode = makeNode(UniquePath);
pathnode->path.pathtype = T_Unique;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = subpath->param_info;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
/*
* Assume the output is unsorted, since we don't necessarily have pathkeys
* to represent it. (This might get overridden below.)
*/
pathnode->path.pathkeys = NIL;
pathnode->subpath = subpath;
pathnode->in_operators = sjinfo->semi_operators;
pathnode->uniq_exprs = sjinfo->semi_rhs_exprs;
/*
* If the input is a relation and it has a unique index that proves the
* semi_rhs_exprs are unique, then we don't need to do anything. Note
* that relation_has_unique_index_for automatically considers restriction
* clauses for the rel, as well.
*/
if (rel->rtekind == RTE_RELATION && sjinfo->semi_can_btree &&
relation_has_unique_index_for(root, rel, NIL,
sjinfo->semi_rhs_exprs,
sjinfo->semi_operators))
{
pathnode->umethod = UNIQUE_PATH_NOOP;
pathnode->path.rows = rel->rows;
pathnode->path.startup_cost = subpath->startup_cost;
pathnode->path.total_cost = subpath->total_cost;
pathnode->path.pathkeys = subpath->pathkeys;
rel->cheapest_unique_path = (Path *) pathnode;
MemoryContextSwitchTo(oldcontext);
return pathnode;
}
/*
* If the input is a subquery whose output must be unique already, then we
* don't need to do anything. The test for uniqueness has to consider
* exactly which columns we are extracting; for example "SELECT DISTINCT
* x,y" doesn't guarantee that x alone is distinct. So we cannot check for
* this optimization unless semi_rhs_exprs consists only of simple Vars
* referencing subquery outputs. (Possibly we could do something with
* expressions in the subquery outputs, too, but for now keep it simple.)
*/
if (rel->rtekind == RTE_SUBQUERY)
{
RangeTblEntry *rte = planner_rt_fetch(rel->relid, root);
if (query_supports_distinctness(rte->subquery))
{
List *sub_tlist_colnos;
sub_tlist_colnos = translate_sub_tlist(sjinfo->semi_rhs_exprs,
rel->relid);
if (sub_tlist_colnos &&
query_is_distinct_for(rte->subquery,
sub_tlist_colnos,
sjinfo->semi_operators))
{
pathnode->umethod = UNIQUE_PATH_NOOP;
pathnode->path.rows = rel->rows;
pathnode->path.startup_cost = subpath->startup_cost;
pathnode->path.total_cost = subpath->total_cost;
pathnode->path.pathkeys = subpath->pathkeys;
rel->cheapest_unique_path = (Path *) pathnode;
MemoryContextSwitchTo(oldcontext);
return pathnode;
}
}
}
/* Estimate number of output rows */
pathnode->path.rows = estimate_num_groups(root,
sjinfo->semi_rhs_exprs,
rel->rows,
NULL);
numCols = list_length(sjinfo->semi_rhs_exprs);
if (sjinfo->semi_can_btree)
{
/*
* Estimate cost for sort+unique implementation
*/
cost_sort(&sort_path, root, NIL,
subpath->total_cost,
rel->rows,
subpath->pathtarget->width,
0.0,
work_mem,
-1.0);
/*
* Charge one cpu_operator_cost per comparison per input tuple. We
* assume all columns get compared at most of the tuples. (XXX
* probably this is an overestimate.) This should agree with
* create_upper_unique_path.
*/
sort_path.total_cost += cpu_operator_cost * rel->rows * numCols;
}
if (sjinfo->semi_can_hash)
{
/*
* Estimate the overhead per hashtable entry at 64 bytes (same as in
* planner.c).
*/
int hashentrysize = subpath->pathtarget->width + 64;
if (hashentrysize * pathnode->path.rows > work_mem * 1024L)
{
/*
* We should not try to hash. Hack the SpecialJoinInfo to
* remember this, in case we come through here again.
*/
sjinfo->semi_can_hash = false;
}
else
cost_agg(&agg_path, root,
AGG_HASHED, NULL,
numCols, pathnode->path.rows,
subpath->startup_cost,
subpath->total_cost,
rel->rows);
}
if (sjinfo->semi_can_btree && sjinfo->semi_can_hash)
{
if (agg_path.total_cost < sort_path.total_cost)
pathnode->umethod = UNIQUE_PATH_HASH;
else
pathnode->umethod = UNIQUE_PATH_SORT;
}
else if (sjinfo->semi_can_btree)
pathnode->umethod = UNIQUE_PATH_SORT;
else if (sjinfo->semi_can_hash)
pathnode->umethod = UNIQUE_PATH_HASH;
else
{
/* we can get here only if we abandoned hashing above */
MemoryContextSwitchTo(oldcontext);
return NULL;
}
if (pathnode->umethod == UNIQUE_PATH_HASH)
{
pathnode->path.startup_cost = agg_path.startup_cost;
pathnode->path.total_cost = agg_path.total_cost;
}
else
{
pathnode->path.startup_cost = sort_path.startup_cost;
pathnode->path.total_cost = sort_path.total_cost;
}
rel->cheapest_unique_path = (Path *) pathnode;
MemoryContextSwitchTo(oldcontext);
return pathnode;
}
/*
* translate_sub_tlist - get subquery column numbers represented by tlist
*
* The given targetlist usually contains only Vars referencing the given relid.
* Extract their varattnos (ie, the column numbers of the subquery) and return
* as an integer List.
*
* If any of the tlist items is not a simple Var, we cannot determine whether
* the subquery's uniqueness condition (if any) matches ours, so punt and
* return NIL.
*/
static List *
translate_sub_tlist(List *tlist, int relid)
{
List *result = NIL;
ListCell *l;
foreach(l, tlist)
{
Var *var = (Var *) lfirst(l);
if (!var || !IsA(var, Var) ||
var->varno != relid)
return NIL; /* punt */
result = lappend_int(result, var->varattno);
}
return result;
}
/*
* create_gather_path
* Creates a path corresponding to a gather scan, returning the
* pathnode.
*/
GatherPath *
create_gather_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
Relids required_outer)
{
GatherPath *pathnode = makeNode(GatherPath);
Assert(subpath->parallel_safe);
pathnode->path.pathtype = T_Gather;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = false;
pathnode->path.parallel_degree = subpath->parallel_degree;
pathnode->path.pathkeys = NIL; /* Gather has unordered result */
pathnode->subpath = subpath;
pathnode->single_copy = false;
if (pathnode->path.parallel_degree == 0)
{
pathnode->path.parallel_degree = 1;
pathnode->path.pathkeys = subpath->pathkeys;
pathnode->single_copy = true;
}
cost_gather(pathnode, root, rel, pathnode->path.param_info);
return pathnode;
}
/*
* create_subqueryscan_path
* Creates a path corresponding to a scan of a subquery,
* returning the pathnode.
*/
SubqueryScanPath *
create_subqueryscan_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
List *pathkeys, Relids required_outer)
{
SubqueryScanPath *pathnode = makeNode(SubqueryScanPath);
pathnode->path.pathtype = T_SubqueryScan;
pathnode->path.parent = rel;
pathnode->path.pathtarget = rel->reltarget;
pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
pathnode->path.pathkeys = pathkeys;
pathnode->subpath = subpath;
cost_subqueryscan(pathnode, root, rel, pathnode->path.param_info);
return pathnode;
}
/*
* create_functionscan_path
* Creates a path corresponding to a sequential scan of a function,
* returning the pathnode.
*/
Path *
create_functionscan_path(PlannerInfo *root, RelOptInfo *rel,
List *pathkeys, Relids required_outer)
{
Path *pathnode = makeNode(Path);
pathnode->pathtype = T_FunctionScan;
pathnode->parent = rel;
pathnode->pathtarget = rel->reltarget;
pathnode->param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->parallel_aware = false;
pathnode->parallel_safe = rel->consider_parallel;
pathnode->parallel_degree = 0;
pathnode->pathkeys = pathkeys;
cost_functionscan(pathnode, root, rel, pathnode->param_info);
return pathnode;
}
/*
* create_valuesscan_path
* Creates a path corresponding to a scan of a VALUES list,
* returning the pathnode.
*/
Path *
create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer)
{
Path *pathnode = makeNode(Path);
pathnode->pathtype = T_ValuesScan;
pathnode->parent = rel;
pathnode->pathtarget = rel->reltarget;
pathnode->param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->parallel_aware = false;
pathnode->parallel_safe = rel->consider_parallel;
pathnode->parallel_degree = 0;
pathnode->pathkeys = NIL; /* result is always unordered */
cost_valuesscan(pathnode, root, rel, pathnode->param_info);
return pathnode;
}
/*
* create_ctescan_path
* Creates a path corresponding to a scan of a non-self-reference CTE,
* returning the pathnode.
*/
Path *
create_ctescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
{
Path *pathnode = makeNode(Path);
pathnode->pathtype = T_CteScan;
pathnode->parent = rel;
pathnode->pathtarget = rel->reltarget;
pathnode->param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->parallel_aware = false;
pathnode->parallel_safe = rel->consider_parallel;
pathnode->parallel_degree = 0;
pathnode->pathkeys = NIL; /* XXX for now, result is always unordered */
cost_ctescan(pathnode, root, rel, pathnode->param_info);
return pathnode;
}
/*
* create_worktablescan_path
* Creates a path corresponding to a scan of a self-reference CTE,
* returning the pathnode.
*/
Path *
create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer)
{
Path *pathnode = makeNode(Path);
pathnode->pathtype = T_WorkTableScan;
pathnode->parent = rel;
pathnode->pathtarget = rel->reltarget;
pathnode->param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->parallel_aware = false;
pathnode->parallel_safe = rel->consider_parallel;
pathnode->parallel_degree = 0;
pathnode->pathkeys = NIL; /* result is always unordered */
/* Cost is the same as for a regular CTE scan */
cost_ctescan(pathnode, root, rel, pathnode->param_info);
return pathnode;
}
/*
* create_foreignscan_path
* Creates a path corresponding to a scan of a foreign table, foreign join,
* or foreign upper-relation processing, returning the pathnode.
*
* This function is never called from core Postgres; rather, it's expected
* to be called by the GetForeignPaths, GetForeignJoinPaths, or
* GetForeignUpperPaths function of a foreign data wrapper. We make the FDW
* supply all fields of the path, since we do not have any way to calculate
* them in core. However, there is a usually-sane default for the pathtarget
* (rel->reltarget), so we let a NULL for "target" select that.
*/
ForeignPath *
create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel,
PathTarget *target,
double rows, Cost startup_cost, Cost total_cost,
List *pathkeys,
Relids required_outer,
Path *fdw_outerpath,
List *fdw_private)
{
ForeignPath *pathnode = makeNode(ForeignPath);
pathnode->path.pathtype = T_ForeignScan;
pathnode->path.parent = rel;
pathnode->path.pathtarget = target ? target : rel->reltarget;
pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
required_outer);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel;
pathnode->path.parallel_degree = 0;
pathnode->path.rows = rows;
pathnode->path.startup_cost = startup_cost;
pathnode->path.total_cost = total_cost;
pathnode->path.pathkeys = pathkeys;
pathnode->fdw_outerpath = fdw_outerpath;
pathnode->fdw_private = fdw_private;
return pathnode;
}
/*
* calc_nestloop_required_outer
* Compute the required_outer set for a nestloop join path
*
* Note: result must not share storage with either input
*/
Relids
calc_nestloop_required_outer(Path *outer_path, Path *inner_path)
{
Relids outer_paramrels = PATH_REQ_OUTER(outer_path);
Relids inner_paramrels = PATH_REQ_OUTER(inner_path);
Relids required_outer;
/* inner_path can require rels from outer path, but not vice versa */
Assert(!bms_overlap(outer_paramrels, inner_path->parent->relids));
/* easy case if inner path is not parameterized */
if (!inner_paramrels)
return bms_copy(outer_paramrels);
/* else, form the union ... */
required_outer = bms_union(outer_paramrels, inner_paramrels);
/* ... and remove any mention of now-satisfied outer rels */
required_outer = bms_del_members(required_outer,
outer_path->parent->relids);
/* maintain invariant that required_outer is exactly NULL if empty */
if (bms_is_empty(required_outer))
{
bms_free(required_outer);
required_outer = NULL;
}
return required_outer;
}
/*
* calc_non_nestloop_required_outer
* Compute the required_outer set for a merge or hash join path
*
* Note: result must not share storage with either input
*/
Relids
calc_non_nestloop_required_outer(Path *outer_path, Path *inner_path)
{
Relids outer_paramrels = PATH_REQ_OUTER(outer_path);
Relids inner_paramrels = PATH_REQ_OUTER(inner_path);
Relids required_outer;
/* neither path can require rels from the other */
Assert(!bms_overlap(outer_paramrels, inner_path->parent->relids));
Assert(!bms_overlap(inner_paramrels, outer_path->parent->relids));
/* form the union ... */
required_outer = bms_union(outer_paramrels, inner_paramrels);
/* we do not need an explicit test for empty; bms_union gets it right */
return required_outer;
}
/*
* create_nestloop_path
* Creates a pathnode corresponding to a nestloop join between two
* relations.
*
* 'joinrel' is the join relation.
* 'jointype' is the type of join required
* 'workspace' is the result from initial_cost_nestloop
* 'sjinfo' is extra info about the join for selectivity estimation
* 'semifactors' contains valid data if jointype is SEMI or ANTI
* 'outer_path' is the outer path
* 'inner_path' is the inner path
* 'restrict_clauses' are the RestrictInfo nodes to apply at the join
* 'pathkeys' are the path keys of the new join path
* 'required_outer' is the set of required outer rels
*
* Returns the resulting path node.
*/
NestPath *
create_nestloop_path(PlannerInfo *root,
RelOptInfo *joinrel,
JoinType jointype,
JoinCostWorkspace *workspace,
SpecialJoinInfo *sjinfo,
SemiAntiJoinFactors *semifactors,
Path *outer_path,
Path *inner_path,
List *restrict_clauses,
List *pathkeys,
Relids required_outer)
{
NestPath *pathnode = makeNode(NestPath);
Relids inner_req_outer = PATH_REQ_OUTER(inner_path);
/*
* If the inner path is parameterized by the outer, we must drop any
* restrict_clauses that are due to be moved into the inner path. We have
* to do this now, rather than postpone the work till createplan time,
* because the restrict_clauses list can affect the size and cost
* estimates for this path.
*/
if (bms_overlap(inner_req_outer, outer_path->parent->relids))
{
Relids inner_and_outer = bms_union(inner_path->parent->relids,
inner_req_outer);
List *jclauses = NIL;
ListCell *lc;
foreach(lc, restrict_clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
if (!join_clause_is_movable_into(rinfo,
inner_path->parent->relids,
inner_and_outer))
jclauses = lappend(jclauses, rinfo);
}
restrict_clauses = jclauses;
}
pathnode->path.pathtype = T_NestLoop;
pathnode->path.parent = joinrel;
pathnode->path.pathtarget = joinrel->reltarget;
pathnode->path.param_info =
get_joinrel_parampathinfo(root,
joinrel,
outer_path,
inner_path,
sjinfo,
required_outer,
&restrict_clauses);
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = joinrel->consider_parallel &&
outer_path->parallel_safe && inner_path->parallel_safe;
/* This is a foolish way to estimate parallel_degree, but for now... */
pathnode->path.parallel_degree = outer_path->parallel_degree;
pathnode->path.pathkeys = pathkeys;
pathnode->jointype = jointype;
pathnode->outerjoinpath = outer_path;
pathnode->innerjoinpath = inner_path;
pathnode->joinrestrictinfo = restrict_clauses;
final_cost_nestloop(root, pathnode, workspace, sjinfo, semifactors);
return pathnode;
}
/*
* create_mergejoin_path
* Creates a pathnode corresponding to a mergejoin join between
* two relations
*
* 'joinrel' is the join relation
* 'jointype' is the type of join required
* 'workspace' is the result from initial_cost_mergejoin
* 'sjinfo' is extra info about the join for selectivity estimation
* 'outer_path' is the outer path
* 'inner_path' is the inner path
* 'restrict_clauses' are the RestrictInfo nodes to apply at the join
* 'pathkeys' are the path keys of the new join path
* 'required_outer' is the set of required outer rels
* 'mergeclauses' are the RestrictInfo nodes to use as merge clauses
* (this should be a subset of the restrict_clauses list)
* 'outersortkeys' are the sort varkeys for the outer relation
* 'innersortkeys' are the sort varkeys for the inner relation
*/
MergePath *
create_mergejoin_path(PlannerInfo *root,
RelOptInfo *joinrel,
JoinType jointype,
JoinCostWorkspace *workspace,
SpecialJoinInfo *sjinfo,
Path *outer_path,
Path *inner_path,
List *restrict_clauses,
List *pathkeys,
Relids required_outer,
List *mergeclauses,
List *outersortkeys,
List *innersortkeys)
{
MergePath *pathnode = makeNode(MergePath);
pathnode->jpath.path.pathtype = T_MergeJoin;
pathnode->jpath.path.parent = joinrel;
pathnode->jpath.path.pathtarget = joinrel->reltarget;
pathnode->jpath.path.param_info =
get_joinrel_parampathinfo(root,
joinrel,
outer_path,
inner_path,
sjinfo,
required_outer,
&restrict_clauses);
pathnode->jpath.path.parallel_aware = false;
pathnode->jpath.path.parallel_safe = joinrel->consider_parallel &&
outer_path->parallel_safe && inner_path->parallel_safe;
/* This is a foolish way to estimate parallel_degree, but for now... */
pathnode->jpath.path.parallel_degree = outer_path->parallel_degree;
pathnode->jpath.path.pathkeys = pathkeys;
pathnode->jpath.jointype = jointype;
pathnode->jpath.outerjoinpath = outer_path;
pathnode->jpath.innerjoinpath = inner_path;
pathnode->jpath.joinrestrictinfo = restrict_clauses;
pathnode->path_mergeclauses = mergeclauses;
pathnode->outersortkeys = outersortkeys;
pathnode->innersortkeys = innersortkeys;
/* pathnode->materialize_inner will be set by final_cost_mergejoin */
final_cost_mergejoin(root, pathnode, workspace, sjinfo);
return pathnode;
}
/*
* create_hashjoin_path
* Creates a pathnode corresponding to a hash join between two relations.
*
* 'joinrel' is the join relation
* 'jointype' is the type of join required
* 'workspace' is the result from initial_cost_hashjoin
* 'sjinfo' is extra info about the join for selectivity estimation
* 'semifactors' contains valid data if jointype is SEMI or ANTI
* 'outer_path' is the cheapest outer path
* 'inner_path' is the cheapest inner path
* 'restrict_clauses' are the RestrictInfo nodes to apply at the join
* 'required_outer' is the set of required outer rels
* 'hashclauses' are the RestrictInfo nodes to use as hash clauses
* (this should be a subset of the restrict_clauses list)
*/
HashPath *
create_hashjoin_path(PlannerInfo *root,
RelOptInfo *joinrel,
JoinType jointype,
JoinCostWorkspace *workspace,
SpecialJoinInfo *sjinfo,
SemiAntiJoinFactors *semifactors,
Path *outer_path,
Path *inner_path,
List *restrict_clauses,
Relids required_outer,
List *hashclauses)
{
HashPath *pathnode = makeNode(HashPath);
pathnode->jpath.path.pathtype = T_HashJoin;
pathnode->jpath.path.parent = joinrel;
pathnode->jpath.path.pathtarget = joinrel->reltarget;
pathnode->jpath.path.param_info =
get_joinrel_parampathinfo(root,
joinrel,
outer_path,
inner_path,
sjinfo,
required_outer,
&restrict_clauses);
pathnode->jpath.path.parallel_aware = false;
pathnode->jpath.path.parallel_safe = joinrel->consider_parallel &&
outer_path->parallel_safe && inner_path->parallel_safe;
/* This is a foolish way to estimate parallel_degree, but for now... */
pathnode->jpath.path.parallel_degree = outer_path->parallel_degree;
/*
* A hashjoin never has pathkeys, since its output ordering is
* unpredictable due to possible batching. XXX If the inner relation is
* small enough, we could instruct the executor that it must not batch,
* and then we could assume that the output inherits the outer relation's
* ordering, which might save a sort step. However there is considerable
* downside if our estimate of the inner relation size is badly off. For
* the moment we don't risk it. (Note also that if we wanted to take this
* seriously, joinpath.c would have to consider many more paths for the
* outer rel than it does now.)
*/
pathnode->jpath.path.pathkeys = NIL;
pathnode->jpath.jointype = jointype;
pathnode->jpath.outerjoinpath = outer_path;
pathnode->jpath.innerjoinpath = inner_path;
pathnode->jpath.joinrestrictinfo = restrict_clauses;
pathnode->path_hashclauses = hashclauses;
/* final_cost_hashjoin will fill in pathnode->num_batches */
final_cost_hashjoin(root, pathnode, workspace, sjinfo, semifactors);
return pathnode;
}
/*
* create_projection_path
* Creates a pathnode that represents performing a projection.
*
* 'rel' is the parent relation associated with the result
* 'subpath' is the path representing the source of data
* 'target' is the PathTarget to be computed
*/
ProjectionPath *
create_projection_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
PathTarget *target)
{
ProjectionPath *pathnode = makeNode(ProjectionPath);
pathnode->path.pathtype = T_Result;
pathnode->path.parent = rel;
pathnode->path.pathtarget = target;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
/* Projection does not change the sort order */
pathnode->path.pathkeys = subpath->pathkeys;
pathnode->subpath = subpath;
/*
* The Result node's cost is cpu_tuple_cost per row, plus the cost of
* evaluating the tlist. There is no qual to worry about.
*/
pathnode->path.rows = subpath->rows;
pathnode->path.startup_cost = subpath->startup_cost + target->cost.startup;
pathnode->path.total_cost = subpath->total_cost + target->cost.startup +
(cpu_tuple_cost + target->cost.per_tuple) * subpath->rows;
return pathnode;
}
/*
* apply_projection_to_path
* Add a projection step, or just apply the target directly to given path.
*
* Most plan types include ExecProject, so we can implement a new projection
* without an extra plan node: just replace the given path's pathtarget with
* the desired one. If the given path can't project, add a ProjectionPath.
*
* We can also short-circuit cases where the targetlist expressions are
* actually equal; this is not an uncommon case, since it may arise from
* trying to apply a PathTarget with sortgroupref labeling to a derived
* path without such labeling.
*
* This requires knowing that the source path won't be referenced for other
* purposes (e.g., other possible paths), since we modify it in-place. Note
* also that we mustn't change the source path's parent link; so when it is
* add_path'd to "rel" things will be a bit inconsistent. So far that has
* not caused any trouble.
*
* 'rel' is the parent relation associated with the result
* 'path' is the path representing the source of data
* 'target' is the PathTarget to be computed
*/
Path *
apply_projection_to_path(PlannerInfo *root,
RelOptInfo *rel,
Path *path,
PathTarget *target)
{
QualCost oldcost;
/* Make a separate ProjectionPath if needed */
if (!is_projection_capable_path(path) &&
!equal(path->pathtarget->exprs, target->exprs))
return (Path *) create_projection_path(root, rel, path, target);
/*
* We can just jam the desired tlist into the existing path, being sure to
* update its cost estimates appropriately.
*/
oldcost = path->pathtarget->cost;
path->pathtarget = target;
path->startup_cost += target->cost.startup - oldcost.startup;
path->total_cost += target->cost.startup - oldcost.startup +
(target->cost.per_tuple - oldcost.per_tuple) * path->rows;
return path;
}
/*
* create_sort_path
* Creates a pathnode that represents performing an explicit sort.
*
* 'rel' is the parent relation associated with the result
* 'subpath' is the path representing the source of data
* 'pathkeys' represents the desired sort order
* 'limit_tuples' is the estimated bound on the number of output tuples,
* or -1 if no LIMIT or couldn't estimate
*/
SortPath *
create_sort_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
List *pathkeys,
double limit_tuples)
{
SortPath *pathnode = makeNode(SortPath);
pathnode->path.pathtype = T_Sort;
pathnode->path.parent = rel;
/* Sort doesn't project, so use source path's pathtarget */
pathnode->path.pathtarget = subpath->pathtarget;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
pathnode->path.pathkeys = pathkeys;
pathnode->subpath = subpath;
cost_sort(&pathnode->path, root, pathkeys,
subpath->total_cost,
subpath->rows,
subpath->pathtarget->width,
0.0, /* XXX comparison_cost shouldn't be 0? */
work_mem, limit_tuples);
return pathnode;
}
/*
* create_group_path
* Creates a pathnode that represents performing grouping of presorted input
*
* 'rel' is the parent relation associated with the result
* 'subpath' is the path representing the source of data
* 'target' is the PathTarget to be computed
* 'groupClause' is a list of SortGroupClause's representing the grouping
* 'qual' is the HAVING quals if any
* 'numGroups' is the estimated number of groups
*/
GroupPath *
create_group_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
PathTarget *target,
List *groupClause,
List *qual,
double numGroups)
{
GroupPath *pathnode = makeNode(GroupPath);
pathnode->path.pathtype = T_Group;
pathnode->path.parent = rel;
pathnode->path.pathtarget = target;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
/* Group doesn't change sort ordering */
pathnode->path.pathkeys = subpath->pathkeys;
pathnode->subpath = subpath;
pathnode->groupClause = groupClause;
pathnode->qual = qual;
cost_group(&pathnode->path, root,
list_length(groupClause),
numGroups,
subpath->startup_cost, subpath->total_cost,
subpath->rows);
/* add tlist eval cost for each output row */
pathnode->path.startup_cost += target->cost.startup;
pathnode->path.total_cost += target->cost.startup +
target->cost.per_tuple * pathnode->path.rows;
return pathnode;
}
/*
* create_upper_unique_path
* Creates a pathnode that represents performing an explicit Unique step
* on presorted input.
*
* This produces a Unique plan node, but the use-case is so different from
* create_unique_path that it doesn't seem worth trying to merge the two.
*
* 'rel' is the parent relation associated with the result
* 'subpath' is the path representing the source of data
* 'numCols' is the number of grouping columns
* 'numGroups' is the estimated number of groups
*
* The input path must be sorted on the grouping columns, plus possibly
* additional columns; so the first numCols pathkeys are the grouping columns
*/
UpperUniquePath *
create_upper_unique_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
int numCols,
double numGroups)
{
UpperUniquePath *pathnode = makeNode(UpperUniquePath);
pathnode->path.pathtype = T_Unique;
pathnode->path.parent = rel;
/* Unique doesn't project, so use source path's pathtarget */
pathnode->path.pathtarget = subpath->pathtarget;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
/* Unique doesn't change the input ordering */
pathnode->path.pathkeys = subpath->pathkeys;
pathnode->subpath = subpath;
pathnode->numkeys = numCols;
/*
* Charge one cpu_operator_cost per comparison per input tuple. We assume
* all columns get compared at most of the tuples. (XXX probably this is
* an overestimate.)
*/
pathnode->path.startup_cost = subpath->startup_cost;
pathnode->path.total_cost = subpath->total_cost +
cpu_operator_cost * subpath->rows * numCols;
pathnode->path.rows = numGroups;
return pathnode;
}
/*
* create_agg_path
* Creates a pathnode that represents performing aggregation/grouping
*
* 'rel' is the parent relation associated with the result
* 'subpath' is the path representing the source of data
* 'target' is the PathTarget to be computed
* 'aggstrategy' is the Agg node's basic implementation strategy
* 'groupClause' is a list of SortGroupClause's representing the grouping
* 'qual' is the HAVING quals if any
* 'aggcosts' contains cost info about the aggregate functions to be computed
* 'numGroups' is the estimated number of groups (1 if not grouping)
*/
AggPath *
create_agg_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
PathTarget *target,
AggStrategy aggstrategy,
List *groupClause,
List *qual,
const AggClauseCosts *aggcosts,
double numGroups)
{
AggPath *pathnode = makeNode(AggPath);
pathnode->path.pathtype = T_Agg;
pathnode->path.parent = rel;
pathnode->path.pathtarget = target;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
if (aggstrategy == AGG_SORTED)
pathnode->path.pathkeys = subpath->pathkeys; /* preserves order */
else
pathnode->path.pathkeys = NIL; /* output is unordered */
pathnode->subpath = subpath;
pathnode->aggstrategy = aggstrategy;
pathnode->numGroups = numGroups;
pathnode->groupClause = groupClause;
pathnode->qual = qual;
cost_agg(&pathnode->path, root,
aggstrategy, aggcosts,
list_length(groupClause), numGroups,
subpath->startup_cost, subpath->total_cost,
subpath->rows);
/* add tlist eval cost for each output row */
pathnode->path.startup_cost += target->cost.startup;
pathnode->path.total_cost += target->cost.startup +
target->cost.per_tuple * pathnode->path.rows;
return pathnode;
}
/*
* create_groupingsets_path
* Creates a pathnode that represents performing GROUPING SETS aggregation
*
* GroupingSetsPath represents sorted grouping with one or more grouping sets.
* The input path's result must be sorted to match the last entry in
* rollup_groupclauses.
*
* 'rel' is the parent relation associated with the result
* 'subpath' is the path representing the source of data
* 'target' is the PathTarget to be computed
* 'having_qual' is the HAVING quals if any
* 'rollup_lists' is a list of grouping sets
* 'rollup_groupclauses' is a list of grouping clauses for grouping sets
* 'agg_costs' contains cost info about the aggregate functions to be computed
* 'numGroups' is the estimated number of groups
*/
GroupingSetsPath *
create_groupingsets_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
PathTarget *target,
List *having_qual,
List *rollup_lists,
List *rollup_groupclauses,
const AggClauseCosts *agg_costs,
double numGroups)
{
GroupingSetsPath *pathnode = makeNode(GroupingSetsPath);
int numGroupCols;
/* The topmost generated Plan node will be an Agg */
pathnode->path.pathtype = T_Agg;
pathnode->path.parent = rel;
pathnode->path.pathtarget = target;
pathnode->path.param_info = subpath->param_info;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
pathnode->subpath = subpath;
/*
* Output will be in sorted order by group_pathkeys if, and only if, there
* is a single rollup operation on a non-empty list of grouping
* expressions.
*/
if (list_length(rollup_groupclauses) == 1 &&
((List *) linitial(rollup_groupclauses)) != NIL)
pathnode->path.pathkeys = root->group_pathkeys;
else
pathnode->path.pathkeys = NIL;
pathnode->rollup_groupclauses = rollup_groupclauses;
pathnode->rollup_lists = rollup_lists;
pathnode->qual = having_qual;
Assert(rollup_lists != NIL);
Assert(list_length(rollup_lists) == list_length(rollup_groupclauses));
/* Account for cost of the topmost Agg node */
numGroupCols = list_length((List *) linitial((List *) llast(rollup_lists)));
cost_agg(&pathnode->path, root,
(numGroupCols > 0) ? AGG_SORTED : AGG_PLAIN,
agg_costs,
numGroupCols,
numGroups,
subpath->startup_cost,
subpath->total_cost,
subpath->rows);
/*
* Add in the costs and output rows of the additional sorting/aggregation
* steps, if any. Only total costs count, since the extra sorts aren't
* run on startup.
*/
if (list_length(rollup_lists) > 1)
{
ListCell *lc;
foreach(lc, rollup_lists)
{
List *gsets = (List *) lfirst(lc);
Path sort_path; /* dummy for result of cost_sort */
Path agg_path; /* dummy for result of cost_agg */
/* We must iterate over all but the last rollup_lists element */
if (lnext(lc) == NULL)
break;
/* Account for cost of sort, but don't charge input cost again */
cost_sort(&sort_path, root, NIL,
0.0,
subpath->rows,
subpath->pathtarget->width,
0.0,
work_mem,
-1.0);
/* Account for cost of aggregation */
numGroupCols = list_length((List *) linitial(gsets));
cost_agg(&agg_path, root,
AGG_SORTED,
agg_costs,
numGroupCols,
numGroups, /* XXX surely not right for all steps? */
sort_path.startup_cost,
sort_path.total_cost,
sort_path.rows);
pathnode->path.total_cost += agg_path.total_cost;
pathnode->path.rows += agg_path.rows;
}
}
/* add tlist eval cost for each output row */
pathnode->path.startup_cost += target->cost.startup;
pathnode->path.total_cost += target->cost.startup +
target->cost.per_tuple * pathnode->path.rows;
return pathnode;
}
/*
* create_minmaxagg_path
* Creates a pathnode that represents computation of MIN/MAX aggregates
*
* 'rel' is the parent relation associated with the result
* 'target' is the PathTarget to be computed
* 'mmaggregates' is a list of MinMaxAggInfo structs
* 'quals' is the HAVING quals if any
*/
MinMaxAggPath *
create_minmaxagg_path(PlannerInfo *root,
RelOptInfo *rel,
PathTarget *target,
List *mmaggregates,
List *quals)
{
MinMaxAggPath *pathnode = makeNode(MinMaxAggPath);
Cost initplan_cost;
ListCell *lc;
/* The topmost generated Plan node will be a Result */
pathnode->path.pathtype = T_Result;
pathnode->path.parent = rel;
pathnode->path.pathtarget = target;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
/* A MinMaxAggPath implies use of subplans, so cannot be parallel-safe */
pathnode->path.parallel_safe = false;
pathnode->path.parallel_degree = 0;
/* Result is one unordered row */
pathnode->path.rows = 1;
pathnode->path.pathkeys = NIL;
pathnode->mmaggregates = mmaggregates;
pathnode->quals = quals;
/* Calculate cost of all the initplans ... */
initplan_cost = 0;
foreach(lc, mmaggregates)
{
MinMaxAggInfo *mminfo = (MinMaxAggInfo *) lfirst(lc);
initplan_cost += mminfo->pathcost;
}
/* add tlist eval cost for each output row, plus cpu_tuple_cost */
pathnode->path.startup_cost = initplan_cost + target->cost.startup;
pathnode->path.total_cost = initplan_cost + target->cost.startup +
target->cost.per_tuple + cpu_tuple_cost;
return pathnode;
}
/*
* create_windowagg_path
* Creates a pathnode that represents computation of window functions
*
* 'rel' is the parent relation associated with the result
* 'subpath' is the path representing the source of data
* 'target' is the PathTarget to be computed
* 'windowFuncs' is a list of WindowFunc structs
* 'winclause' is a WindowClause that is common to all the WindowFuncs
* 'winpathkeys' is the pathkeys for the PARTITION keys + ORDER keys
*
* The actual sort order of the input must match winpathkeys, but might
* have additional keys after those.
*/
WindowAggPath *
create_windowagg_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
PathTarget *target,
List *windowFuncs,
WindowClause *winclause,
List *winpathkeys)
{
WindowAggPath *pathnode = makeNode(WindowAggPath);
pathnode->path.pathtype = T_WindowAgg;
pathnode->path.parent = rel;
pathnode->path.pathtarget = target;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
/* WindowAgg preserves the input sort order */
pathnode->path.pathkeys = subpath->pathkeys;
pathnode->subpath = subpath;
pathnode->winclause = winclause;
pathnode->winpathkeys = winpathkeys;
/*
* For costing purposes, assume that there are no redundant partitioning
* or ordering columns; it's not worth the trouble to deal with that
* corner case here. So we just pass the unmodified list lengths to
* cost_windowagg.
*/
cost_windowagg(&pathnode->path, root,
windowFuncs,
list_length(winclause->partitionClause),
list_length(winclause->orderClause),
subpath->startup_cost,
subpath->total_cost,
subpath->rows);
/* add tlist eval cost for each output row */
pathnode->path.startup_cost += target->cost.startup;
pathnode->path.total_cost += target->cost.startup +
target->cost.per_tuple * pathnode->path.rows;
return pathnode;
}
/*
* create_setop_path
* Creates a pathnode that represents computation of INTERSECT or EXCEPT
*
* 'rel' is the parent relation associated with the result
* 'subpath' is the path representing the source of data
* 'cmd' is the specific semantics (INTERSECT or EXCEPT, with/without ALL)
* 'strategy' is the implementation strategy (sorted or hashed)
* 'distinctList' is a list of SortGroupClause's representing the grouping
* 'flagColIdx' is the column number where the flag column will be, if any
* 'firstFlag' is the flag value for the first input relation when hashing;
* or -1 when sorting
* 'numGroups' is the estimated number of distinct groups
* 'outputRows' is the estimated number of output rows
*/
SetOpPath *
create_setop_path(PlannerInfo *root,
RelOptInfo *rel,
Path *subpath,
SetOpCmd cmd,
SetOpStrategy strategy,
List *distinctList,
AttrNumber flagColIdx,
int firstFlag,
double numGroups,
double outputRows)
{
SetOpPath *pathnode = makeNode(SetOpPath);
pathnode->path.pathtype = T_SetOp;
pathnode->path.parent = rel;
/* SetOp doesn't project, so use source path's pathtarget */
pathnode->path.pathtarget = subpath->pathtarget;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
/* SetOp preserves the input sort order if in sort mode */
pathnode->path.pathkeys =
(strategy == SETOP_SORTED) ? subpath->pathkeys : NIL;
pathnode->subpath = subpath;
pathnode->cmd = cmd;
pathnode->strategy = strategy;
pathnode->distinctList = distinctList;
pathnode->flagColIdx = flagColIdx;
pathnode->firstFlag = firstFlag;
pathnode->numGroups = numGroups;
/*
* Charge one cpu_operator_cost per comparison per input tuple. We assume
* all columns get compared at most of the tuples.
*/
pathnode->path.startup_cost = subpath->startup_cost;
pathnode->path.total_cost = subpath->total_cost +
cpu_operator_cost * subpath->rows * list_length(distinctList);
pathnode->path.rows = outputRows;
return pathnode;
}
/*
* create_recursiveunion_path
* Creates a pathnode that represents a recursive UNION node
*
* 'rel' is the parent relation associated with the result
* 'leftpath' is the source of data for the non-recursive term
* 'rightpath' is the source of data for the recursive term
* 'target' is the PathTarget to be computed
* 'distinctList' is a list of SortGroupClause's representing the grouping
* 'wtParam' is the ID of Param representing work table
* 'numGroups' is the estimated number of groups
*
* For recursive UNION ALL, distinctList is empty and numGroups is zero
*/
RecursiveUnionPath *
create_recursiveunion_path(PlannerInfo *root,
RelOptInfo *rel,
Path *leftpath,
Path *rightpath,
PathTarget *target,
List *distinctList,
int wtParam,
double numGroups)
{
RecursiveUnionPath *pathnode = makeNode(RecursiveUnionPath);
pathnode->path.pathtype = T_RecursiveUnion;
pathnode->path.parent = rel;
pathnode->path.pathtarget = target;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
leftpath->parallel_safe && rightpath->parallel_safe;
/* Foolish, but we'll do it like joins for now: */
pathnode->path.parallel_degree = leftpath->parallel_degree;
/* RecursiveUnion result is always unsorted */
pathnode->path.pathkeys = NIL;
pathnode->leftpath = leftpath;
pathnode->rightpath = rightpath;
pathnode->distinctList = distinctList;
pathnode->wtParam = wtParam;
pathnode->numGroups = numGroups;
cost_recursive_union(&pathnode->path, leftpath, rightpath);
return pathnode;
}
/*
* create_lockrows_path
* Creates a pathnode that represents acquiring row locks
*
* 'rel' is the parent relation associated with the result
* 'subpath' is the path representing the source of data
* 'rowMarks' is a list of PlanRowMark's
* 'epqParam' is the ID of Param for EvalPlanQual re-eval
*/
LockRowsPath *
create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath, List *rowMarks, int epqParam)
{
LockRowsPath *pathnode = makeNode(LockRowsPath);
pathnode->path.pathtype = T_LockRows;
pathnode->path.parent = rel;
/* LockRows doesn't project, so use source path's pathtarget */
pathnode->path.pathtarget = subpath->pathtarget;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = false;
pathnode->path.parallel_degree = 0;
pathnode->path.rows = subpath->rows;
/*
* The result cannot be assumed sorted, since locking might cause the sort
* key columns to be replaced with new values.
*/
pathnode->path.pathkeys = NIL;
pathnode->subpath = subpath;
pathnode->rowMarks = rowMarks;
pathnode->epqParam = epqParam;
/*
* We should charge something extra for the costs of row locking and
* possible refetches, but it's hard to say how much. For now, use
* cpu_tuple_cost per row.
*/
pathnode->path.startup_cost = subpath->startup_cost;
pathnode->path.total_cost = subpath->total_cost +
cpu_tuple_cost * subpath->rows;
return pathnode;
}
/*
* create_modifytable_path
* Creates a pathnode that represents performing INSERT/UPDATE/DELETE mods
*
* 'rel' is the parent relation associated with the result
* 'operation' is the operation type
* 'canSetTag' is true if we set the command tag/es_processed
* 'nominalRelation' is the parent RT index for use of EXPLAIN
* 'resultRelations' is an integer list of actual RT indexes of target rel(s)
* 'subpaths' is a list of Path(s) producing source data (one per rel)
* 'subroots' is a list of PlannerInfo structs (one per rel)
* 'withCheckOptionLists' is a list of WCO lists (one per rel)
* 'returningLists' is a list of RETURNING tlists (one per rel)
* 'rowMarks' is a list of PlanRowMarks (non-locking only)
* 'onconflict' is the ON CONFLICT clause, or NULL
* 'epqParam' is the ID of Param for EvalPlanQual re-eval
*/
ModifyTablePath *
create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
CmdType operation, bool canSetTag,
Index nominalRelation,
List *resultRelations, List *subpaths,
List *subroots,
List *withCheckOptionLists, List *returningLists,
List *rowMarks, OnConflictExpr *onconflict,
int epqParam)
{
ModifyTablePath *pathnode = makeNode(ModifyTablePath);
double total_size;
ListCell *lc;
Assert(list_length(resultRelations) == list_length(subpaths));
Assert(list_length(resultRelations) == list_length(subroots));
Assert(withCheckOptionLists == NIL ||
list_length(resultRelations) == list_length(withCheckOptionLists));
Assert(returningLists == NIL ||
list_length(resultRelations) == list_length(returningLists));
pathnode->path.pathtype = T_ModifyTable;
pathnode->path.parent = rel;
/* pathtarget is not interesting, just make it minimally valid */
pathnode->path.pathtarget = rel->reltarget;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = false;
pathnode->path.parallel_degree = 0;
pathnode->path.pathkeys = NIL;
/*
* Compute cost & rowcount as sum of subpath costs & rowcounts.
*
* Currently, we don't charge anything extra for the actual table
* modification work, nor for the WITH CHECK OPTIONS or RETURNING
* expressions if any. It would only be window dressing, since
* ModifyTable is always a top-level node and there is no way for the
* costs to change any higher-level planning choices. But we might want
* to make it look better sometime.
*/
pathnode->path.startup_cost = 0;
pathnode->path.total_cost = 0;
pathnode->path.rows = 0;
total_size = 0;
foreach(lc, subpaths)
{
Path *subpath = (Path *) lfirst(lc);
if (lc == list_head(subpaths)) /* first node? */
pathnode->path.startup_cost = subpath->startup_cost;
pathnode->path.total_cost += subpath->total_cost;
pathnode->path.rows += subpath->rows;
total_size += subpath->pathtarget->width * subpath->rows;
}
/*
* Set width to the average width of the subpath outputs. XXX this is
* totally wrong: we should report zero if no RETURNING, else an average
* of the RETURNING tlist widths. But it's what happened historically,
* and improving it is a task for another day.
*/
if (pathnode->path.rows > 0)
total_size /= pathnode->path.rows;
pathnode->path.pathtarget->width = rint(total_size);
pathnode->operation = operation;
pathnode->canSetTag = canSetTag;
pathnode->nominalRelation = nominalRelation;
pathnode->resultRelations = resultRelations;
pathnode->subpaths = subpaths;
pathnode->subroots = subroots;
pathnode->withCheckOptionLists = withCheckOptionLists;
pathnode->returningLists = returningLists;
pathnode->rowMarks = rowMarks;
pathnode->onconflict = onconflict;
pathnode->epqParam = epqParam;
return pathnode;
}
/*
* create_limit_path
* Creates a pathnode that represents performing LIMIT/OFFSET
*
* In addition to providing the actual OFFSET and LIMIT expressions,
* the caller must provide estimates of their values for costing purposes.
* The estimates are as computed by preprocess_limit(), ie, 0 represents
* the clause not being present, and -1 means it's present but we could
* not estimate its value.
*
* 'rel' is the parent relation associated with the result
* 'subpath' is the path representing the source of data
* 'limitOffset' is the actual OFFSET expression, or NULL
* 'limitCount' is the actual LIMIT expression, or NULL
* 'offset_est' is the estimated value of the OFFSET expression
* 'count_est' is the estimated value of the LIMIT expression
*/
LimitPath *
create_limit_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath,
Node *limitOffset, Node *limitCount,
int64 offset_est, int64 count_est)
{
LimitPath *pathnode = makeNode(LimitPath);
pathnode->path.pathtype = T_Limit;
pathnode->path.parent = rel;
/* Limit doesn't project, so use source path's pathtarget */
pathnode->path.pathtarget = subpath->pathtarget;
/* For now, assume we are above any joins, so no parameterization */
pathnode->path.param_info = NULL;
pathnode->path.parallel_aware = false;
pathnode->path.parallel_safe = rel->consider_parallel &&
subpath->parallel_safe;
pathnode->path.parallel_degree = subpath->parallel_degree;
pathnode->path.rows = subpath->rows;
pathnode->path.startup_cost = subpath->startup_cost;
pathnode->path.total_cost = subpath->total_cost;
pathnode->path.pathkeys = subpath->pathkeys;
pathnode->subpath = subpath;
pathnode->limitOffset = limitOffset;
pathnode->limitCount = limitCount;
/*
* Adjust the output rows count and costs according to the offset/limit.
* This is only a cosmetic issue if we are at top level, but if we are
* building a subquery then it's important to report correct info to the
* outer planner.
*
* When the offset or count couldn't be estimated, use 10% of the
* estimated number of rows emitted from the subpath.
*
* XXX we don't bother to add eval costs of the offset/limit expressions
* themselves to the path costs. In theory we should, but in most cases
* those expressions are trivial and it's just not worth the trouble.
*/
if (offset_est != 0)
{
double offset_rows;
if (offset_est > 0)
offset_rows = (double) offset_est;
else
offset_rows = clamp_row_est(subpath->rows * 0.10);
if (offset_rows > pathnode->path.rows)
offset_rows = pathnode->path.rows;
if (subpath->rows > 0)
pathnode->path.startup_cost +=
(subpath->total_cost - subpath->startup_cost)
* offset_rows / subpath->rows;
pathnode->path.rows -= offset_rows;
if (pathnode->path.rows < 1)
pathnode->path.rows = 1;
}
if (count_est != 0)
{
double count_rows;
if (count_est > 0)
count_rows = (double) count_est;
else
count_rows = clamp_row_est(subpath->rows * 0.10);
if (count_rows > pathnode->path.rows)
count_rows = pathnode->path.rows;
if (subpath->rows > 0)
pathnode->path.total_cost = pathnode->path.startup_cost +
(subpath->total_cost - subpath->startup_cost)
* count_rows / subpath->rows;
pathnode->path.rows = count_rows;
if (pathnode->path.rows < 1)
pathnode->path.rows = 1;
}
return pathnode;
}
/*
* reparameterize_path
* Attempt to modify a Path to have greater parameterization
*
* We use this to attempt to bring all child paths of an appendrel to the
* same parameterization level, ensuring that they all enforce the same set
* of join quals (and thus that that parameterization can be attributed to
* an append path built from such paths). Currently, only a few path types
* are supported here, though more could be added at need. We return NULL
* if we can't reparameterize the given path.
*
* Note: we intentionally do not pass created paths to add_path(); it would
* possibly try to delete them on the grounds of being cost-inferior to the
* paths they were made from, and we don't want that. Paths made here are
* not necessarily of general-purpose usefulness, but they can be useful
* as members of an append path.
*/
Path *
reparameterize_path(PlannerInfo *root, Path *path,
Relids required_outer,
double loop_count)
{
RelOptInfo *rel = path->parent;
/* Can only increase, not decrease, path's parameterization */
if (!bms_is_subset(PATH_REQ_OUTER(path), required_outer))
return NULL;
switch (path->pathtype)
{
case T_SeqScan:
return create_seqscan_path(root, rel, required_outer, 0);
case T_SampleScan:
return (Path *) create_samplescan_path(root, rel, required_outer);
case T_IndexScan:
case T_IndexOnlyScan:
{
IndexPath *ipath = (IndexPath *) path;
IndexPath *newpath = makeNode(IndexPath);
/*
* We can't use create_index_path directly, and would not want
* to because it would re-compute the indexqual conditions
* which is wasted effort. Instead we hack things a bit:
* flat-copy the path node, revise its param_info, and redo
* the cost estimate.
*/
memcpy(newpath, ipath, sizeof(IndexPath));
newpath->path.param_info =
get_baserel_parampathinfo(root, rel, required_outer);
cost_index(newpath, root, loop_count);
return (Path *) newpath;
}
case T_BitmapHeapScan:
{
BitmapHeapPath *bpath = (BitmapHeapPath *) path;
return (Path *) create_bitmap_heap_path(root,
rel,
bpath->bitmapqual,
required_outer,
loop_count);
}
case T_SubqueryScan:
{
SubqueryScanPath *spath = (SubqueryScanPath *) path;
return (Path *) create_subqueryscan_path(root,
rel,
spath->subpath,
spath->path.pathkeys,
required_outer);
}
default:
break;
}
return NULL;
}
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