greenplumn joinrels 源码
greenplumn joinrels 代码
文件路径：/src/backend/optimizer/path/joinrels.c
/*-------------------------------------------------------------------------
*
* joinrels.c
* Routines to determine which relations should be joined
*
* Portions Copyright (c) 2006-2008, Greenplum inc
* Portions Copyright (c) 2012-Present VMware, Inc. or its affiliates.
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/optimizer/path/joinrels.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "miscadmin.h"
#include "optimizer/appendinfo.h"
#include "optimizer/joininfo.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "partitioning/partbounds.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
static void make_rels_by_clause_joins(PlannerInfo *root,
RelOptInfo *old_rel,
ListCell *other_rels);
static void make_rels_by_clauseless_joins(PlannerInfo *root,
RelOptInfo *old_rel,
ListCell *other_rels);
static bool has_join_restriction(PlannerInfo *root, RelOptInfo *rel);
static bool has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel);
static bool restriction_is_constant_false(List *restrictlist,
RelOptInfo *joinrel,
bool only_pushed_down);
static void populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
RelOptInfo *rel2, RelOptInfo *joinrel,
SpecialJoinInfo *sjinfo, List *restrictlist);
static void try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1,
RelOptInfo *rel2, RelOptInfo *joinrel,
SpecialJoinInfo *parent_sjinfo,
List *parent_restrictlist);
static SpecialJoinInfo *build_child_join_sjinfo(PlannerInfo *root,
SpecialJoinInfo *parent_sjinfo,
Relids left_relids, Relids right_relids);
static int match_expr_to_partition_keys(Expr *expr, RelOptInfo *rel,
bool strict_op);
/*
* join_search_one_level
* Consider ways to produce join relations containing exactly 'level'
* jointree items. (This is one step of the dynamic-programming method
* embodied in standard_join_search.) Join rel nodes for each feasible
* combination of lower-level rels are created and returned in a list.
* Implementation paths are created for each such joinrel, too.
*
* level: level of rels we want to make this time
* root->join_rel_level[j], 1 <= j < level, is a list of rels containing j items
*
* The result is returned in root->join_rel_level[level].
*/
void
join_search_one_level(PlannerInfo *root, int level)
{
List **joinrels = root->join_rel_level;
ListCell *r;
int k;
/*
* There should not be any joins on this level yet, unless we're retrying
* with all plan types enabled, after failing to find any joins that
* satisfy the current enable_*=false restrictions.
*/
Assert(joinrels[level] == NIL);
/* Set join_cur_level so that new joinrels are added to proper list */
root->join_cur_level = level;
/*
* First, consider left-sided and right-sided plans, in which rels of
* exactly level-1 member relations are joined against initial relations.
* We prefer to join using join clauses, but if we find a rel of level-1
* members that has no join clauses, we will generate Cartesian-product
* joins against all initial rels not already contained in it.
*/
foreach(r, joinrels[level - 1])
{
RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
if (old_rel->joininfo != NIL || old_rel->has_eclass_joins ||
has_join_restriction(root, old_rel))
{
/*
* There are join clauses or join order restrictions relevant to
* this rel, so consider joins between this rel and (only) those
* initial rels it is linked to by a clause or restriction.
*
* At level 2 this condition is symmetric, so there is no need to
* look at initial rels before this one in the list; we already
* considered such joins when we were at the earlier rel. (The
* mirror-image joins are handled automatically by make_join_rel.)
* In later passes (level > 2), we join rels of the previous level
* to each initial rel they don't already include but have a join
* clause or restriction with.
*/
ListCell *other_rels;
if (level == 2) /* consider remaining initial rels */
other_rels = lnext(r);
else /* consider all initial rels */
other_rels = list_head(joinrels[1]);
make_rels_by_clause_joins(root,
old_rel,
other_rels);
}
else
{
/*
* Oops, we have a relation that is not joined to any other
* relation, either directly or by join-order restrictions.
* Cartesian product time.
*
* We consider a cartesian product with each not-already-included
* initial rel, whether it has other join clauses or not. At
* level 2, if there are two or more clauseless initial rels, we
* will redundantly consider joining them in both directions; but
* such cases aren't common enough to justify adding complexity to
* avoid the duplicated effort.
*/
make_rels_by_clauseless_joins(root,
old_rel,
list_head(joinrels[1]));
}
}
/*
* Now, consider "bushy plans" in which relations of k initial rels are
* joined to relations of level-k initial rels, for 2 <= k <= level-2.
*
* We only consider bushy-plan joins for pairs of rels where there is a
* suitable join clause (or join order restriction), in order to avoid
* unreasonable growth of planning time.
*/
for (k = 2;; k++)
{
int other_level = level - k;
/*
* Since make_join_rel(x, y) handles both x,y and y,x cases, we only
* need to go as far as the halfway point.
*/
if (k > other_level)
break;
foreach(r, joinrels[k])
{
RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
ListCell *other_rels;
ListCell *r2;
/*
* We can ignore relations without join clauses here, unless they
* participate in join-order restrictions --- then we might have
* to force a bushy join plan.
*/
if (old_rel->joininfo == NIL && !old_rel->has_eclass_joins &&
!has_join_restriction(root, old_rel))
continue;
if (k == other_level)
other_rels = lnext(r); /* only consider remaining rels */
else
other_rels = list_head(joinrels[other_level]);
for_each_cell(r2, other_rels)
{
RelOptInfo *new_rel = (RelOptInfo *) lfirst(r2);
if (!bms_overlap(old_rel->relids, new_rel->relids))
{
/*
* OK, we can build a rel of the right level from this
* pair of rels. Do so if there is at least one relevant
* join clause or join order restriction.
*/
if (have_relevant_joinclause(root, old_rel, new_rel) ||
have_join_order_restriction(root, old_rel, new_rel))
{
(void) make_join_rel(root, old_rel, new_rel);
}
}
}
}
}
/*----------
* Last-ditch effort: if we failed to find any usable joins so far, force
* a set of cartesian-product joins to be generated. This handles the
* special case where all the available rels have join clauses but we
* cannot use any of those clauses yet. This can only happen when we are
* considering a join sub-problem (a sub-joinlist) and all the rels in the
* sub-problem have only join clauses with rels outside the sub-problem.
* An example is
*
* SELECT ... FROM a INNER JOIN b ON TRUE, c, d, ...
* WHERE a.w = c.x and b.y = d.z;
*
* If the "a INNER JOIN b" sub-problem does not get flattened into the
* upper level, we must be willing to make a cartesian join of a and b;
* but the code above will not have done so, because it thought that both
* a and b have joinclauses. We consider only left-sided and right-sided
* cartesian joins in this case (no bushy).
*----------
*/
if (joinrels[level] == NIL)
{
/*
* This loop is just like the first one, except we always call
* make_rels_by_clauseless_joins().
*/
foreach(r, joinrels[level - 1])
{
RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
make_rels_by_clauseless_joins(root,
old_rel,
list_head(joinrels[1]));
}
/*----------
* When special joins are involved, there may be no legal way
* to make an N-way join for some values of N. For example consider
*
* SELECT ... FROM t1 WHERE
* x IN (SELECT ... FROM t2,t3 WHERE ...) AND
* y IN (SELECT ... FROM t4,t5 WHERE ...)
*
* We will flatten this query to a 5-way join problem, but there are
* no 4-way joins that join_is_legal() will consider legal. We have
* to accept failure at level 4 and go on to discover a workable
* bushy plan at level 5.
*
* However, if there are no special joins and no lateral references
* then join_is_legal() should never fail, and so the following sanity
* check is useful.
*----------
*/
if (joinrels[level] == NIL &&
root->join_info_list == NIL &&
!root->hasLateralRTEs)
elog(ERROR, "failed to build any %d-way joins", level);
}
}
/*
* make_rels_by_clause_joins
* Build joins between the given relation 'old_rel' and other relations
* that participate in join clauses that 'old_rel' also participates in
* (or participate in join-order restrictions with it).
* The join rels are returned in root->join_rel_level[join_cur_level].
*
* Note: at levels above 2 we will generate the same joined relation in
* multiple ways --- for example (a join b) join c is the same RelOptInfo as
* (b join c) join a, though the second case will add a different set of Paths
* to it. This is the reason for using the join_rel_level mechanism, which
* automatically ensures that each new joinrel is only added to the list once.
*
* 'old_rel' is the relation entry for the relation to be joined
* 'other_rels': the first cell in a linked list containing the other
* rels to be considered for joining
*
* Currently, this is only used with initial rels in other_rels, but it
* will work for joining to joinrels too.
*/
static void
make_rels_by_clause_joins(PlannerInfo *root,
RelOptInfo *old_rel,
ListCell *other_rels)
{
ListCell *l;
for_each_cell(l, other_rels)
{
RelOptInfo *other_rel = (RelOptInfo *) lfirst(l);
if (!bms_overlap(old_rel->relids, other_rel->relids) &&
(have_relevant_joinclause(root, old_rel, other_rel) ||
have_join_order_restriction(root, old_rel, other_rel)))
{
(void) make_join_rel(root, old_rel, other_rel);
}
}
}
/*
* make_rels_by_clauseless_joins
* Given a relation 'old_rel' and a list of other relations
* 'other_rels', create a join relation between 'old_rel' and each
* member of 'other_rels' that isn't already included in 'old_rel'.
* The join rels are returned in root->join_rel_level[join_cur_level].
*
* 'old_rel' is the relation entry for the relation to be joined
* 'other_rels': the first cell of a linked list containing the
* other rels to be considered for joining
*
* Currently, this is only used with initial rels in other_rels, but it would
* work for joining to joinrels too.
*/
static void
make_rels_by_clauseless_joins(PlannerInfo *root,
RelOptInfo *old_rel,
ListCell *other_rels)
{
ListCell *l;
for_each_cell(l, other_rels)
{
RelOptInfo *other_rel = (RelOptInfo *) lfirst(l);
if (!bms_overlap(other_rel->relids, old_rel->relids))
{
(void) make_join_rel(root, old_rel, other_rel);
}
}
}
/*
* join_is_legal
* Determine whether a proposed join is legal given the query's
* join order constraints; and if it is, determine the join type.
*
* Caller must supply not only the two rels, but the union of their relids.
* (We could simplify the API by computing joinrelids locally, but this
* would be redundant work in the normal path through make_join_rel.)
*
* On success, *sjinfo_p is set to NULL if this is to be a plain inner join,
* else it's set to point to the associated SpecialJoinInfo node. Also,
* *reversed_p is set true if the given relations need to be swapped to
* match the SpecialJoinInfo node.
*/
static bool
join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
Relids joinrelids,
SpecialJoinInfo **sjinfo_p, bool *reversed_p)
{
SpecialJoinInfo *match_sjinfo;
bool reversed;
bool unique_ified;
bool must_be_leftjoin;
ListCell *l;
/*
* Ensure output params are set on failure return. This is just to
* suppress uninitialized-variable warnings from overly anal compilers.
*/
*sjinfo_p = NULL;
*reversed_p = false;
/*
* If we have any special joins, the proposed join might be illegal; and
* in any case we have to determine its join type. Scan the join info
* list for matches and conflicts.
*/
match_sjinfo = NULL;
reversed = false;
unique_ified = false;
must_be_leftjoin = false;
foreach(l, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
/*
* This special join is not relevant unless its RHS overlaps the
* proposed join. (Check this first as a fast path for dismissing
* most irrelevant SJs quickly.)
*/
if (!bms_overlap(sjinfo->min_righthand, joinrelids))
continue;
/*
* Also, not relevant if proposed join is fully contained within RHS
* (ie, we're still building up the RHS).
*/
if (bms_is_subset(joinrelids, sjinfo->min_righthand))
continue;
/*
* Also, not relevant if SJ is already done within either input.
*/
if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
bms_is_subset(sjinfo->min_righthand, rel1->relids))
continue;
if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
bms_is_subset(sjinfo->min_righthand, rel2->relids))
continue;
/*
* If it's a semijoin and we already joined the RHS to any other rels
* within either input, then we must have unique-ified the RHS at that
* point (see below). Therefore the semijoin is no longer relevant in
* this join path.
*/
if (sjinfo->jointype == JOIN_SEMI)
{
if (bms_is_subset(sjinfo->syn_righthand, rel1->relids) &&
!bms_equal(sjinfo->syn_righthand, rel1->relids))
continue;
if (bms_is_subset(sjinfo->syn_righthand, rel2->relids) &&
!bms_equal(sjinfo->syn_righthand, rel2->relids))
continue;
}
/*
* If one input contains min_lefthand and the other contains
* min_righthand, then we can perform the SJ at this join.
*
* Reject if we get matches to more than one SJ; that implies we're
* considering something that's not really valid.
*/
if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
bms_is_subset(sjinfo->min_righthand, rel2->relids))
{
if (match_sjinfo)
return false; /* invalid join path */
match_sjinfo = sjinfo;
reversed = false;
}
else if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
bms_is_subset(sjinfo->min_righthand, rel1->relids))
{
if (match_sjinfo)
return false; /* invalid join path */
match_sjinfo = sjinfo;
reversed = true;
}
else if (sjinfo->jointype == JOIN_SEMI &&
bms_equal(sjinfo->syn_righthand, rel2->relids) &&
create_unique_path(root, rel2, rel2->cheapest_total_path,
sjinfo) != NULL)
{
/*----------
* For a semijoin, we can join the RHS to anything else by
* unique-ifying the RHS (if the RHS can be unique-ified).
* We will only get here if we have the full RHS but less
* than min_lefthand on the LHS.
*
* The reason to consider such a join path is exemplified by
* SELECT ... FROM a,b WHERE (a.x,b.y) IN (SELECT c1,c2 FROM c)
* If we insist on doing this as a semijoin we will first have
* to form the cartesian product of A*B. But if we unique-ify
* C then the semijoin becomes a plain innerjoin and we can join
* in any order, eg C to A and then to B. When C is much smaller
* than A and B this can be a huge win. So we allow C to be
* joined to just A or just B here, and then make_join_rel has
* to handle the case properly.
*
* Note that actually we'll allow unique-ified C to be joined to
* some other relation D here, too. That is legal, if usually not
* very sane, and this routine is only concerned with legality not
* with whether the join is good strategy.
*----------
*/
if (match_sjinfo)
return false; /* invalid join path */
match_sjinfo = sjinfo;
reversed = false;
unique_ified = true;
}
else if (sjinfo->jointype == JOIN_SEMI &&
bms_equal(sjinfo->syn_righthand, rel1->relids) &&
create_unique_path(root, rel1, rel1->cheapest_total_path,
sjinfo) != NULL)
{
/* Reversed semijoin case */
if (match_sjinfo)
return false; /* invalid join path */
match_sjinfo = sjinfo;
reversed = true;
unique_ified = true;
}
else
{
/*
* Otherwise, the proposed join overlaps the RHS but isn't a valid
* implementation of this SJ. But don't panic quite yet: the RHS
* violation might have occurred previously, in one or both input
* relations, in which case we must have previously decided that
* it was OK to commute some other SJ with this one. If we need
* to perform this join to finish building up the RHS, rejecting
* it could lead to not finding any plan at all. (This can occur
* because of the heuristics elsewhere in this file that postpone
* clauseless joins: we might not consider doing a clauseless join
* within the RHS until after we've performed other, validly
* commutable SJs with one or both sides of the clauseless join.)
* This consideration boils down to the rule that if both inputs
* overlap the RHS, we can allow the join --- they are either
* fully within the RHS, or represent previously-allowed joins to
* rels outside it.
*/
if (bms_overlap(rel1->relids, sjinfo->min_righthand) &&
bms_overlap(rel2->relids, sjinfo->min_righthand))
continue; /* assume valid previous violation of RHS */
/*
* The proposed join could still be legal, but only if we're
* allowed to associate it into the RHS of this SJ. That means
* this SJ must be a LEFT join (not SEMI, ANTI or LASJ, and certainly
* not FULL) and the proposed join must not overlap the LHS.
*/
if (sjinfo->jointype != JOIN_LEFT ||
bms_overlap(joinrelids, sjinfo->min_lefthand))
return false; /* invalid join path */
/*
* To be valid, the proposed join must be a LEFT join; otherwise
* it can't associate into this SJ's RHS. But we may not yet have
* found the SpecialJoinInfo matching the proposed join, so we
* can't test that yet. Remember the requirement for later.
*/
must_be_leftjoin = true;
}
}
/*
* Fail if violated any SJ's RHS and didn't match to a LEFT SJ: the
* proposed join can't associate into an SJ's RHS.
*
* Also, fail if the proposed join's predicate isn't strict; we're
* essentially checking to see if we can apply outer-join identity 3, and
* that's a requirement. (This check may be redundant with checks in
* make_outerjoininfo, but I'm not quite sure, and it's cheap to test.)
*/
if (must_be_leftjoin &&
(match_sjinfo == NULL ||
match_sjinfo->jointype != JOIN_LEFT ||
!match_sjinfo->lhs_strict))
return false; /* invalid join path */
/*
* We also have to check for constraints imposed by LATERAL references.
*/
if (root->hasLateralRTEs)
{
bool lateral_fwd;
bool lateral_rev;
Relids join_lateral_rels;
/*
* The proposed rels could each contain lateral references to the
* other, in which case the join is impossible. If there are lateral
* references in just one direction, then the join has to be done with
* a nestloop with the lateral referencer on the inside. If the join
* matches an SJ that cannot be implemented by such a nestloop, the
* join is impossible.
*
* Also, if the lateral reference is only indirect, we should reject
* the join; whatever rel(s) the reference chain goes through must be
* joined to first.
*
* Another case that might keep us from building a valid plan is the
* implementation restriction described by have_dangerous_phv().
*/
lateral_fwd = bms_overlap(rel1->relids, rel2->lateral_relids);
lateral_rev = bms_overlap(rel2->relids, rel1->lateral_relids);
if (lateral_fwd && lateral_rev)
return false; /* have lateral refs in both directions */
if (lateral_fwd)
{
/* has to be implemented as nestloop with rel1 on left */
if (match_sjinfo &&
(reversed ||
unique_ified ||
match_sjinfo->jointype == JOIN_FULL))
return false; /* not implementable as nestloop */
/* check there is a direct reference from rel2 to rel1 */
if (!bms_overlap(rel1->relids, rel2->direct_lateral_relids))
return false; /* only indirect refs, so reject */
/* check we won't have a dangerous PHV */
if (have_dangerous_phv(root, rel1->relids, rel2->lateral_relids))
return false; /* might be unable to handle required PHV */
}
else if (lateral_rev)
{
/* has to be implemented as nestloop with rel2 on left */
if (match_sjinfo &&
(!reversed ||
unique_ified ||
match_sjinfo->jointype == JOIN_FULL))
return false; /* not implementable as nestloop */
/* check there is a direct reference from rel1 to rel2 */
if (!bms_overlap(rel2->relids, rel1->direct_lateral_relids))
return false; /* only indirect refs, so reject */
/* check we won't have a dangerous PHV */
if (have_dangerous_phv(root, rel2->relids, rel1->lateral_relids))
return false; /* might be unable to handle required PHV */
}
/*
* LATERAL references could also cause problems later on if we accept
* this join: if the join's minimum parameterization includes any rels
* that would have to be on the inside of an outer join with this join
* rel, then it's never going to be possible to build the complete
* query using this join. We should reject this join not only because
* it'll save work, but because if we don't, the clauseless-join
* heuristics might think that legality of this join means that some
* other join rel need not be formed, and that could lead to failure
* to find any plan at all. We have to consider not only rels that
* are directly on the inner side of an OJ with the joinrel, but also
* ones that are indirectly so, so search to find all such rels.
*/
join_lateral_rels = min_join_parameterization(root, joinrelids,
rel1, rel2);
if (join_lateral_rels)
{
Relids join_plus_rhs = bms_copy(joinrelids);
bool more;
do
{
more = false;
foreach(l, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
/* ignore full joins --- their ordering is predetermined */
if (sjinfo->jointype == JOIN_FULL)
continue;
if (bms_overlap(sjinfo->min_lefthand, join_plus_rhs) &&
!bms_is_subset(sjinfo->min_righthand, join_plus_rhs))
{
join_plus_rhs = bms_add_members(join_plus_rhs,
sjinfo->min_righthand);
more = true;
}
}
} while (more);
if (bms_overlap(join_plus_rhs, join_lateral_rels))
return false; /* will not be able to join to some RHS rel */
}
}
/* Otherwise, it's a valid join */
*sjinfo_p = match_sjinfo;
*reversed_p = reversed;
return true;
}
/*
* make_join_rel
* Find or create a join RelOptInfo that represents the join of
* the two given rels, and add to it path information for paths
* created with the two rels as outer and inner rel.
* (The join rel may already contain paths generated from other
* pairs of rels that add up to the same set of base rels.)
*
* NB: will return NULL if attempted join is not valid. This can happen
* when working with outer joins, or with IN or EXISTS clauses that have been
* turned into joins.
*/
RelOptInfo *
make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
{
Relids joinrelids;
SpecialJoinInfo *sjinfo;
bool reversed;
SpecialJoinInfo sjinfo_data;
RelOptInfo *joinrel;
List *restrictlist;
/* This is a convenient place to check for query cancel. */
CHECK_FOR_INTERRUPTS();
Assert(rel1 &&
rel2 &&
rel1->cheapest_total_path &&
rel2->cheapest_total_path);
/* We should never try to join two overlapping sets of rels. */
Assert(!bms_overlap(rel1->relids, rel2->relids));
/* Construct Relids set that identifies the joinrel. */
joinrelids = bms_union(rel1->relids, rel2->relids);
/* Check validity and determine join type. */
if (!join_is_legal(root, rel1, rel2, joinrelids,
&sjinfo, &reversed))
{
/* invalid join path */
bms_free(joinrelids);
return NULL;
}
/* Swap rels if needed to match the join info. */
if (reversed)
{
RelOptInfo *trel = rel1;
rel1 = rel2;
rel2 = trel;
}
/*
* If it's a plain inner join, then we won't have found anything in
* join_info_list. Make up a SpecialJoinInfo so that selectivity
* estimation functions will know what's being joined.
*/
if (sjinfo == NULL)
{
sjinfo = &sjinfo_data;
sjinfo->type = T_SpecialJoinInfo;
sjinfo->min_lefthand = rel1->relids;
sjinfo->min_righthand = rel2->relids;
sjinfo->syn_lefthand = rel1->relids;
sjinfo->syn_righthand = rel2->relids;
sjinfo->jointype = JOIN_INNER;
/* we don't bother trying to make the remaining fields valid */
sjinfo->lhs_strict = false;
sjinfo->delay_upper_joins = false;
sjinfo->semi_can_btree = false;
sjinfo->semi_can_hash = false;
sjinfo->semi_operators = NIL;
sjinfo->semi_rhs_exprs = NIL;
}
/*
* Find or build the join RelOptInfo, and compute the restrictlist that
* goes with this particular joining.
*/
joinrel = build_join_rel(root, joinrelids, rel1, rel2, sjinfo,
&restrictlist);
/*
* If we've already proven this join is empty, we needn't consider any
* more paths for it.
*/
if (is_dummy_rel(joinrel))
{
bms_free(joinrelids);
return joinrel;
}
/* Add paths to the join relation. */
populate_joinrel_with_paths(root, rel1, rel2, joinrel, sjinfo,
restrictlist);
bms_free(joinrelids);
return joinrel;
}
/*
* populate_joinrel_with_paths
* Add paths to the given joinrel for given pair of joining relations. The
* SpecialJoinInfo provides details about the join and the restrictlist
* contains the join clauses and the other clauses applicable for given pair
* of the joining relations.
*/
static void
populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
RelOptInfo *rel2, RelOptInfo *joinrel,
SpecialJoinInfo *sjinfo, List *restrictlist)
{
/*
* Consider paths using each rel as both outer and inner. Depending on
* the join type, a provably empty outer or inner rel might mean the join
* is provably empty too; in which case throw away any previously computed
* paths and mark the join as dummy. (We do it this way since it's
* conceivable that dummy-ness of a multi-element join might only be
* noticeable for certain construction paths.)
*
* Also, a provably constant-false join restriction typically means that
* we can skip evaluating one or both sides of the join. We do this by
* marking the appropriate rel as dummy. For outer joins, a
* constant-false restriction that is pushed down still means the whole
* join is dummy, while a non-pushed-down one means that no inner rows
* will join so we can treat the inner rel as dummy.
*
* We need only consider the jointypes that appear in join_info_list, plus
* JOIN_INNER.
*/
switch (sjinfo->jointype)
{
case JOIN_INNER:
if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
restriction_is_constant_false(restrictlist, joinrel, false))
{
mark_dummy_rel(root, joinrel);
break;
}
add_paths_to_joinrel(root, joinrel, rel1, rel2,
JOIN_INNER, sjinfo,
restrictlist);
add_paths_to_joinrel(root, joinrel, rel2, rel1,
JOIN_INNER, sjinfo,
restrictlist);
break;
case JOIN_LEFT:
if (is_dummy_rel(rel1) ||
restriction_is_constant_false(restrictlist, joinrel, true))
{
mark_dummy_rel(root, joinrel);
break;
}
if (restriction_is_constant_false(restrictlist, joinrel, false) &&
bms_is_subset(rel2->relids, sjinfo->syn_righthand))
mark_dummy_rel(root, rel2);
add_paths_to_joinrel(root, joinrel, rel1, rel2,
JOIN_LEFT, sjinfo,
restrictlist);
add_paths_to_joinrel(root, joinrel, rel2, rel1,
JOIN_RIGHT, sjinfo,
restrictlist);
break;
case JOIN_FULL:
if ((is_dummy_rel(rel1) && is_dummy_rel(rel2)) ||
restriction_is_constant_false(restrictlist, joinrel, true))
{
mark_dummy_rel(root, joinrel);
break;
}
add_paths_to_joinrel(root, joinrel, rel1, rel2,
JOIN_FULL, sjinfo,
restrictlist);
add_paths_to_joinrel(root, joinrel, rel2, rel1,
JOIN_FULL, sjinfo,
restrictlist);
/*
* If there are join quals that aren't mergeable or hashable, we
* may not be able to build any valid plan. Complain here so that
* we can give a somewhat-useful error message. (Since we have no
* flexibility of planning for a full join, there's no chance of
* succeeding later with another pair of input rels.)
*/
if (joinrel->pathlist == NIL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("FULL JOIN is only supported with merge-joinable or hash-joinable join conditions")));
break;
case JOIN_SEMI:
/*
* We might have a normal semijoin, or a case where we don't have
* enough rels to do the semijoin but can unique-ify the RHS and
* then do an innerjoin (see comments in join_is_legal). In the
* latter case we can't apply JOIN_SEMI joining.
*/
if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
bms_is_subset(sjinfo->min_righthand, rel2->relids))
{
if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
restriction_is_constant_false(restrictlist, joinrel, false))
{
mark_dummy_rel(root, joinrel);
break;
}
add_paths_to_joinrel(root, joinrel, rel1, rel2,
JOIN_SEMI, sjinfo,
restrictlist);
/*
* In GPDB, also try a path, where we perform a normal inner
* join, and eliminate duplicates afterwards.
*/
add_paths_to_joinrel(root, joinrel, rel1, rel2,
JOIN_DEDUP_SEMI, sjinfo,
restrictlist);
add_paths_to_joinrel(root, joinrel, rel2, rel1,
JOIN_DEDUP_SEMI_REVERSE, sjinfo,
restrictlist);
}
/*
* If we know how to unique-ify the RHS and one input rel is
* exactly the RHS (not a superset) we can consider unique-ifying
* it and then doing a regular join. (The create_unique_path
* check here is probably redundant with what join_is_legal did,
* but if so the check is cheap because it's cached. So test
* anyway to be sure.)
*/
if (bms_equal(sjinfo->syn_righthand, rel2->relids) &&
create_unique_path(root, rel2, rel2->cheapest_total_path,
sjinfo) != NULL)
{
if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
restriction_is_constant_false(restrictlist, joinrel, false))
{
mark_dummy_rel(root, joinrel);
break;
}
add_paths_to_joinrel(root, joinrel, rel1, rel2,
JOIN_UNIQUE_INNER, sjinfo,
restrictlist);
add_paths_to_joinrel(root, joinrel, rel2, rel1,
JOIN_UNIQUE_OUTER, sjinfo,
restrictlist);
}
break;
case JOIN_ANTI:
case JOIN_LASJ_NOTIN:
if (is_dummy_rel(rel1) ||
restriction_is_constant_false(restrictlist, joinrel, true))
{
mark_dummy_rel(root, joinrel);
break;
}
if (restriction_is_constant_false(restrictlist, joinrel, false) &&
bms_is_subset(rel2->relids, sjinfo->syn_righthand))
mark_dummy_rel(root, rel2);
add_paths_to_joinrel(root, joinrel, rel1, rel2,
sjinfo->jointype, sjinfo,
restrictlist);
break;
default:
/* other values not expected here */
elog(ERROR, "unrecognized join type: %d", (int) sjinfo->jointype);
break;
}
/* Apply partitionwise join technique, if possible. */
try_partitionwise_join(root, rel1, rel2, joinrel, sjinfo, restrictlist);
}
/*
* have_join_order_restriction
* Detect whether the two relations should be joined to satisfy
* a join-order restriction arising from special or lateral joins.
*
* In practice this is always used with have_relevant_joinclause(), and so
* could be merged with that function, but it seems clearer to separate the
* two concerns. We need this test because there are degenerate cases where
* a clauseless join must be performed to satisfy join-order restrictions.
* Also, if one rel has a lateral reference to the other, or both are needed
* to compute some PHV, we should consider joining them even if the join would
* be clauseless.
*
* Note: this is only a problem if one side of a degenerate outer join
* contains multiple rels, or a clauseless join is required within an
* IN/EXISTS RHS; else we will find a join path via the "last ditch" case in
* join_search_one_level(). We could dispense with this test if we were
* willing to try bushy plans in the "last ditch" case, but that seems much
* less efficient.
*/
bool
have_join_order_restriction(PlannerInfo *root,
RelOptInfo *rel1, RelOptInfo *rel2)
{
bool result = false;
ListCell *l;
/*
* If either side has a direct lateral reference to the other, attempt the
* join regardless of outer-join considerations.
*/
if (bms_overlap(rel1->relids, rel2->direct_lateral_relids) ||
bms_overlap(rel2->relids, rel1->direct_lateral_relids))
return true;
/*
* Likewise, if both rels are needed to compute some PlaceHolderVar,
* attempt the join regardless of outer-join considerations. (This is not
* very desirable, because a PHV with a large eval_at set will cause a lot
* of probably-useless joins to be considered, but failing to do this can
* cause us to fail to construct a plan at all.)
*/
foreach(l, root->placeholder_list)
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
if (bms_is_subset(rel1->relids, phinfo->ph_eval_at) &&
bms_is_subset(rel2->relids, phinfo->ph_eval_at))
return true;
}
/*
* Likewise, if both rels are needed to compute some PlaceHolderVar,
* attempt the join regardless of outer-join considerations. (This is not
* very desirable, because a PHV with a large eval_at set will cause a lot
* of probably-useless joins to be considered, but failing to do this can
* cause us to fail to construct a plan at all.)
*/
foreach(l, root->placeholder_list)
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
if (bms_is_subset(rel1->relids, phinfo->ph_eval_at) &&
bms_is_subset(rel2->relids, phinfo->ph_eval_at))
return true;
}
/*
* It's possible that the rels correspond to the left and right sides of a
* degenerate outer join, that is, one with no joinclause mentioning the
* non-nullable side; in which case we should force the join to occur.
*
* Also, the two rels could represent a clauseless join that has to be
* completed to build up the LHS or RHS of an outer join.
*/
foreach(l, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
/* ignore full joins --- other mechanisms handle them */
if (sjinfo->jointype == JOIN_FULL)
continue;
/* Can we perform the SJ with these rels? */
if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
bms_is_subset(sjinfo->min_righthand, rel2->relids))
{
result = true;
break;
}
if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
bms_is_subset(sjinfo->min_righthand, rel1->relids))
{
result = true;
break;
}
/*
* Might we need to join these rels to complete the RHS? We have to
* use "overlap" tests since either rel might include a lower SJ that
* has been proven to commute with this one.
*/
if (bms_overlap(sjinfo->min_righthand, rel1->relids) &&
bms_overlap(sjinfo->min_righthand, rel2->relids))
{
result = true;
break;
}
/* Likewise for the LHS. */
if (bms_overlap(sjinfo->min_lefthand, rel1->relids) &&
bms_overlap(sjinfo->min_lefthand, rel2->relids))
{
result = true;
break;
}
}
/*
* We do not force the join to occur if either input rel can legally
* be joined to anything else using joinclauses. This essentially
* means that clauseless bushy joins are put off as long as possible.
* The reason is that when there is a join order restriction high up
* in the join tree (that is, with many rels inside the LHS or RHS),
* we would otherwise expend lots of effort considering very stupid
* join combinations within its LHS or RHS.
*/
if (result)
{
if (has_legal_joinclause(root, rel1) ||
has_legal_joinclause(root, rel2))
result = false;
}
return result;
}
/*
* has_join_restriction
* Detect whether the specified relation has join-order restrictions,
* due to being inside an outer join or an IN (sub-SELECT),
* or participating in any LATERAL references or multi-rel PHVs.
*
* Essentially, this tests whether have_join_order_restriction() could
* succeed with this rel and some other one. It's OK if we sometimes
* say "true" incorrectly. (Therefore, we don't bother with the relatively
* expensive has_legal_joinclause test.)
*/
static bool
has_join_restriction(PlannerInfo *root, RelOptInfo *rel)
{
ListCell *l;
if (rel->lateral_relids != NULL || rel->lateral_referencers != NULL)
return true;
foreach(l, root->placeholder_list)
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
if (bms_is_subset(rel->relids, phinfo->ph_eval_at) &&
!bms_equal(rel->relids, phinfo->ph_eval_at))
return true;
}
foreach(l, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
/* ignore full joins --- other mechanisms preserve their ordering */
if (sjinfo->jointype == JOIN_FULL)
continue;
/* ignore if SJ is already contained in rel */
if (bms_is_subset(sjinfo->min_lefthand, rel->relids) &&
bms_is_subset(sjinfo->min_righthand, rel->relids))
continue;
/* restricted if it overlaps LHS or RHS, but doesn't contain SJ */
if (bms_overlap(sjinfo->min_lefthand, rel->relids) ||
bms_overlap(sjinfo->min_righthand, rel->relids))
return true;
}
return false;
}
/*
* has_legal_joinclause
* Detect whether the specified relation can legally be joined
* to any other rels using join clauses.
*
* We consider only joins to single other relations in the current
* initial_rels list. This is sufficient to get a "true" result in most real
* queries, and an occasional erroneous "false" will only cost a bit more
* planning time. The reason for this limitation is that considering joins to
* other joins would require proving that the other join rel can legally be
* formed, which seems like too much trouble for something that's only a
* heuristic to save planning time. (Note: we must look at initial_rels
* and not all of the query, since when we are planning a sub-joinlist we
* may be forced to make clauseless joins within initial_rels even though
* there are join clauses linking to other parts of the query.)
*/
static bool
has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel)
{
ListCell *lc;
foreach(lc, root->initial_rels)
{
RelOptInfo *rel2 = (RelOptInfo *) lfirst(lc);
/* ignore rels that are already in "rel" */
if (bms_overlap(rel->relids, rel2->relids))
continue;
if (have_relevant_joinclause(root, rel, rel2))
{
Relids joinrelids;
SpecialJoinInfo *sjinfo;
bool reversed;
/* join_is_legal needs relids of the union */
joinrelids = bms_union(rel->relids, rel2->relids);
if (join_is_legal(root, rel, rel2, joinrelids,
&sjinfo, &reversed))
{
/* Yes, this will work */
bms_free(joinrelids);
return true;
}
bms_free(joinrelids);
}
}
return false;
}
/*
* There's a pitfall for creating parameterized nestloops: suppose the inner
* rel (call it A) has a parameter that is a PlaceHolderVar, and that PHV's
* minimum eval_at set includes the outer rel (B) and some third rel (C).
* We might think we could create a B/A nestloop join that's parameterized by
* C. But we would end up with a plan in which the PHV's expression has to be
* evaluated as a nestloop parameter at the B/A join; and the executor is only
* set up to handle simple Vars as NestLoopParams. Rather than add complexity
* and overhead to the executor for such corner cases, it seems better to
* forbid the join. (Note that we can still make use of A's parameterized
* path with pre-joined B+C as the outer rel. have_join_order_restriction()
* ensures that we will consider making such a join even if there are not
* other reasons to do so.)
*
* So we check whether any PHVs used in the query could pose such a hazard.
* We don't have any simple way of checking whether a risky PHV would actually
* be used in the inner plan, and the case is so unusual that it doesn't seem
* worth working very hard on it.
*
* This needs to be checked in two places. If the inner rel's minimum
* parameterization would trigger the restriction, then join_is_legal() should
* reject the join altogether, because there will be no workable paths for it.
* But joinpath.c has to check again for every proposed nestloop path, because
* the inner path might have more than the minimum parameterization, causing
* some PHV to be dangerous for it that otherwise wouldn't be.
*/
bool
have_dangerous_phv(PlannerInfo *root,
Relids outer_relids, Relids inner_params)
{
ListCell *lc;
foreach(lc, root->placeholder_list)
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
if (!bms_is_subset(phinfo->ph_eval_at, inner_params))
continue; /* ignore, could not be a nestloop param */
if (!bms_overlap(phinfo->ph_eval_at, outer_relids))
continue; /* ignore, not relevant to this join */
if (bms_is_subset(phinfo->ph_eval_at, outer_relids))
continue; /* safe, it can be eval'd within outerrel */
/* Otherwise, it's potentially unsafe, so reject the join */
return true;
}
/* OK to perform the join */
return false;
}
/*
* is_dummy_rel --- has relation been proven empty?
*/
bool
is_dummy_rel(RelOptInfo *rel)
{
Path *path;
/*
* A rel that is known dummy will have just one path that is a childless
* Append. (Even if somehow it has more paths, a childless Append will
* have cost zero and hence should be at the front of the pathlist.)
*/
if (rel->pathlist == NIL)
return false;
path = (Path *) linitial(rel->pathlist);
/*
* Initially, a dummy path will just be a childless Append. But in later
* planning stages we might stick a ProjectSetPath and/or ProjectionPath
* on top, since Append can't project. Rather than make assumptions about
* which combinations can occur, just descend through whatever we find.
*/
for (;;)
{
if (IsA(path, ProjectionPath))
path = ((ProjectionPath *) path)->subpath;
else if (IsA(path, ProjectSetPath))
path = ((ProjectSetPath *) path)->subpath;
else
break;
}
if (IS_DUMMY_APPEND(path))
return true;
return false;
}
/*
* Mark a relation as proven empty.
*
* During GEQO planning, this can get invoked more than once on the same
* baserel struct, so it's worth checking to see if the rel is already marked
* dummy.
*
* Also, when called during GEQO join planning, we are in a short-lived
* memory context. We must make sure that the dummy path attached to a
* baserel survives the GEQO cycle, else the baserel is trashed for future
* GEQO cycles. On the other hand, when we are marking a joinrel during GEQO,
* we don't want the dummy path to clutter the main planning context. Upshot
* is that the best solution is to explicitly make the dummy path in the same
* context the given RelOptInfo is in.
*/
void
mark_dummy_rel(PlannerInfo *root, RelOptInfo *rel)
{
MemoryContext oldcontext;
/* Already marked? */
if (is_dummy_rel(rel))
return;
/* No, so choose correct context to make the dummy path in */
oldcontext = MemoryContextSwitchTo(GetMemoryChunkContext(rel));
/* Set dummy size estimate */
rel->rows = 0;
/* Evict any previously chosen paths */
rel->pathlist = NIL;
rel->partial_pathlist = NIL;
/* Set up the dummy path */
add_path(rel, (Path *) create_append_path(root, rel, NIL, NIL,
NIL, rel->lateral_relids,
0, false, NIL, -1));
/* Set or update cheapest_total_path */
set_cheapest(rel);
MemoryContextSwitchTo(oldcontext);
}
/*
* restriction_is_constant_false --- is a restrictlist just false?
*
* In cases where a qual is provably constant false, eval_const_expressions
* will generally have thrown away anything that's ANDed with it. In outer
* join situations this will leave us computing cartesian products only to
* decide there's no match for an outer row, which is pretty stupid. So,
* we need to detect the case.
*
* If only_pushed_down is true, then consider only quals that are pushed-down
* from the point of view of the joinrel.
*/
static bool
restriction_is_constant_false(List *restrictlist,
RelOptInfo *joinrel,
bool only_pushed_down)
{
ListCell *lc;
/*
* Despite the above comment, the restriction list we see here might
* possibly have other members besides the FALSE constant, since other
* quals could get "pushed down" to the outer join level. So we check
* each member of the list.
*/
foreach(lc, restrictlist)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
if (only_pushed_down && !RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids))
continue;
if (rinfo->clause && IsA(rinfo->clause, Const))
{
Const *con = (Const *) rinfo->clause;
/* constant NULL is as good as constant FALSE for our purposes */
if (con->constisnull)
return true;
if (!DatumGetBool(con->constvalue))
return true;
}
}
return false;
}
/*
* Assess whether join between given two partitioned relations can be broken
* down into joins between matching partitions; a technique called
* "partitionwise join"
*
* Partitionwise join is possible when a. Joining relations have same
* partitioning scheme b. There exists an equi-join between the partition keys
* of the two relations.
*
* Partitionwise join is planned as follows (details: optimizer/README.)
*
* 1. Create the RelOptInfos for joins between matching partitions i.e
* child-joins and add paths to them.
*
* 2. Construct Append or MergeAppend paths across the set of child joins.
* This second phase is implemented by generate_partitionwise_join_paths().
*
* The RelOptInfo, SpecialJoinInfo and restrictlist for each child join are
* obtained by translating the respective parent join structures.
*/
static void
try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
RelOptInfo *joinrel, SpecialJoinInfo *parent_sjinfo,
List *parent_restrictlist)
{
bool rel1_is_simple = IS_SIMPLE_REL(rel1);
bool rel2_is_simple = IS_SIMPLE_REL(rel2);
int nparts;
int cnt_parts;
/* Guard against stack overflow due to overly deep partition hierarchy. */
check_stack_depth();
/* Nothing to do, if the join relation is not partitioned. */
if (!IS_PARTITIONED_REL(joinrel))
return;
/* The join relation should have consider_partitionwise_join set. */
Assert(joinrel->consider_partitionwise_join);
/*
* Since this join relation is partitioned, all the base relations
* participating in this join must be partitioned and so are all the
* intermediate join relations.
*/
Assert(IS_PARTITIONED_REL(rel1) && IS_PARTITIONED_REL(rel2));
Assert(REL_HAS_ALL_PART_PROPS(rel1) && REL_HAS_ALL_PART_PROPS(rel2));
/* The joining relations should have consider_partitionwise_join set. */
Assert(rel1->consider_partitionwise_join &&
rel2->consider_partitionwise_join);
/*
* The partition scheme of the join relation should match that of the
* joining relations.
*/
Assert(joinrel->part_scheme == rel1->part_scheme &&
joinrel->part_scheme == rel2->part_scheme);
/*
* Since we allow partitionwise join only when the partition bounds of the
* joining relations exactly match, the partition bounds of the join
* should match those of the joining relations.
*/
Assert(partition_bounds_equal(joinrel->part_scheme->partnatts,
joinrel->part_scheme->parttyplen,
joinrel->part_scheme->parttypbyval,
joinrel->boundinfo, rel1->boundinfo));
Assert(partition_bounds_equal(joinrel->part_scheme->partnatts,
joinrel->part_scheme->parttyplen,
joinrel->part_scheme->parttypbyval,
joinrel->boundinfo, rel2->boundinfo));
nparts = joinrel->nparts;
/*
* Create child-join relations for this partitioned join, if those don't
* exist. Add paths to child-joins for a pair of child relations
* corresponding to the given pair of parent relations.
*/
for (cnt_parts = 0; cnt_parts < nparts; cnt_parts++)
{
RelOptInfo *child_rel1 = rel1->part_rels[cnt_parts];
RelOptInfo *child_rel2 = rel2->part_rels[cnt_parts];
bool rel1_empty = (child_rel1 == NULL ||
IS_DUMMY_REL(child_rel1));
bool rel2_empty = (child_rel2 == NULL ||
IS_DUMMY_REL(child_rel2));
SpecialJoinInfo *child_sjinfo;
List *child_restrictlist;
RelOptInfo *child_joinrel;
Relids child_joinrelids;
AppendRelInfo **appinfos;
int nappinfos;
/*
* Check for cases where we can prove that this segment of the join
* returns no rows, due to one or both inputs being empty (including
* inputs that have been pruned away entirely). If so just ignore it.
* These rules are equivalent to populate_joinrel_with_paths's rules
* for dummy input relations.
*/
switch (parent_sjinfo->jointype)
{
case JOIN_INNER:
case JOIN_SEMI:
if (rel1_empty || rel2_empty)
continue; /* ignore this join segment */
break;
case JOIN_LEFT:
case JOIN_ANTI:
if (rel1_empty)
continue; /* ignore this join segment */
break;
case JOIN_FULL:
if (rel1_empty && rel2_empty)
continue; /* ignore this join segment */
break;
default:
/* other values not expected here */
elog(ERROR, "unrecognized join type: %d",
(int) parent_sjinfo->jointype);
break;
}
/*
* If a child has been pruned entirely then we can't generate paths
* for it, so we have to reject partitionwise joining unless we were
* able to eliminate this partition above.
*/
if (child_rel1 == NULL || child_rel2 == NULL)
{
/*
* Mark the joinrel as unpartitioned so that later functions treat
* it correctly.
*/
joinrel->nparts = 0;
return;
}
/*
* If a leaf relation has consider_partitionwise_join=false, it means
* that it's a dummy relation for which we skipped setting up tlist
* expressions and adding EC members in set_append_rel_size(), so
* again we have to fail here.
*/
if (rel1_is_simple && !child_rel1->consider_partitionwise_join)
{
Assert(child_rel1->reloptkind == RELOPT_OTHER_MEMBER_REL);
Assert(IS_DUMMY_REL(child_rel1));
joinrel->nparts = 0;
return;
}
if (rel2_is_simple && !child_rel2->consider_partitionwise_join)
{
Assert(child_rel2->reloptkind == RELOPT_OTHER_MEMBER_REL);
Assert(IS_DUMMY_REL(child_rel2));
joinrel->nparts = 0;
return;
}
/* We should never try to join two overlapping sets of rels. */
Assert(!bms_overlap(child_rel1->relids, child_rel2->relids));
child_joinrelids = bms_union(child_rel1->relids, child_rel2->relids);
appinfos = find_appinfos_by_relids(root, child_joinrelids, &nappinfos);
/*
* Construct SpecialJoinInfo from parent join relations's
* SpecialJoinInfo.
*/
child_sjinfo = build_child_join_sjinfo(root, parent_sjinfo,
child_rel1->relids,
child_rel2->relids);
/*
* Construct restrictions applicable to the child join from those
* applicable to the parent join.
*/
child_restrictlist =
(List *) adjust_appendrel_attrs(root,
(Node *) parent_restrictlist,
nappinfos, appinfos);
pfree(appinfos);
child_joinrel = joinrel->part_rels[cnt_parts];
if (!child_joinrel)
{
child_joinrel = build_child_join_rel(root, child_rel1, child_rel2,
joinrel, child_restrictlist,
child_sjinfo,
child_sjinfo->jointype);
joinrel->part_rels[cnt_parts] = child_joinrel;
}
Assert(bms_equal(child_joinrel->relids, child_joinrelids));
populate_joinrel_with_paths(root, child_rel1, child_rel2,
child_joinrel, child_sjinfo,
child_restrictlist);
}
}
/*
* Construct the SpecialJoinInfo for a child-join by translating
* SpecialJoinInfo for the join between parents. left_relids and right_relids
* are the relids of left and right side of the join respectively.
*/
static SpecialJoinInfo *
build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo,
Relids left_relids, Relids right_relids)
{
SpecialJoinInfo *sjinfo = makeNode(SpecialJoinInfo);
AppendRelInfo **left_appinfos;
int left_nappinfos;
AppendRelInfo **right_appinfos;
int right_nappinfos;
memcpy(sjinfo, parent_sjinfo, sizeof(SpecialJoinInfo));
left_appinfos = find_appinfos_by_relids(root, left_relids,
&left_nappinfos);
right_appinfos = find_appinfos_by_relids(root, right_relids,
&right_nappinfos);
sjinfo->min_lefthand = adjust_child_relids(sjinfo->min_lefthand,
left_nappinfos, left_appinfos);
sjinfo->min_righthand = adjust_child_relids(sjinfo->min_righthand,
right_nappinfos,
right_appinfos);
sjinfo->syn_lefthand = adjust_child_relids(sjinfo->syn_lefthand,
left_nappinfos, left_appinfos);
sjinfo->syn_righthand = adjust_child_relids(sjinfo->syn_righthand,
right_nappinfos,
right_appinfos);
sjinfo->semi_rhs_exprs = (List *) adjust_appendrel_attrs(root,
(Node *) sjinfo->semi_rhs_exprs,
right_nappinfos,
right_appinfos);
pfree(left_appinfos);
pfree(right_appinfos);
return sjinfo;
}
/*
* Returns true if there exists an equi-join condition for each pair of
* partition keys from given relations being joined.
*/
bool
have_partkey_equi_join(RelOptInfo *joinrel,
RelOptInfo *rel1, RelOptInfo *rel2,
JoinType jointype, List *restrictlist)
{
PartitionScheme part_scheme = rel1->part_scheme;
ListCell *lc;
int cnt_pks;
bool pk_has_clause[PARTITION_MAX_KEYS];
bool strict_op;
/*
* This function should be called when the joining relations have same
* partitioning scheme.
*/
Assert(rel1->part_scheme == rel2->part_scheme);
Assert(part_scheme);
memset(pk_has_clause, 0, sizeof(pk_has_clause));
foreach(lc, restrictlist)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
OpExpr *opexpr;
Expr *expr1;
Expr *expr2;
int ipk1;
int ipk2;
/* If processing an outer join, only use its own join clauses. */
if (IS_OUTER_JOIN(jointype) &&
RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids))
continue;
/* Skip clauses which can not be used for a join. */
if (!rinfo->can_join)
continue;
/* Skip clauses which are not equality conditions. */
if (!rinfo->mergeopfamilies && !OidIsValid(rinfo->hashjoinoperator))
continue;
opexpr = castNode(OpExpr, rinfo->clause);
/*
* The equi-join between partition keys is strict if equi-join between
* at least one partition key is using a strict operator. See
* explanation about outer join reordering identity 3 in
* optimizer/README
*/
strict_op = op_strict(opexpr->opno);
/* Match the operands to the relation. */
if (bms_is_subset(rinfo->left_relids, rel1->relids) &&
bms_is_subset(rinfo->right_relids, rel2->relids))
{
expr1 = linitial(opexpr->args);
expr2 = lsecond(opexpr->args);
}
else if (bms_is_subset(rinfo->left_relids, rel2->relids) &&
bms_is_subset(rinfo->right_relids, rel1->relids))
{
expr1 = lsecond(opexpr->args);
expr2 = linitial(opexpr->args);
}
else
continue;
/*
* Only clauses referencing the partition keys are useful for
* partitionwise join.
*/
ipk1 = match_expr_to_partition_keys(expr1, rel1, strict_op);
if (ipk1 < 0)
continue;
ipk2 = match_expr_to_partition_keys(expr2, rel2, strict_op);
if (ipk2 < 0)
continue;
/*
* If the clause refers to keys at different ordinal positions, it can
* not be used for partitionwise join.
*/
if (ipk1 != ipk2)
continue;
/*
* The clause allows partitionwise join if only it uses the same
* operator family as that specified by the partition key.
*/
if (rel1->part_scheme->strategy == PARTITION_STRATEGY_HASH)
{
if (!op_in_opfamily(rinfo->hashjoinoperator,
part_scheme->partopfamily[ipk1]))
continue;
}
else if (!list_member_oid(rinfo->mergeopfamilies,
part_scheme->partopfamily[ipk1]))
continue;
/* Mark the partition key as having an equi-join clause. */
pk_has_clause[ipk1] = true;
}
/* Check whether every partition key has an equi-join condition. */
for (cnt_pks = 0; cnt_pks < part_scheme->partnatts; cnt_pks++)
{
if (!pk_has_clause[cnt_pks])
return false;
}
return true;
}
/*
* Find the partition key from the given relation matching the given
* expression. If found, return the index of the partition key, else return -1.
*/
static int
match_expr_to_partition_keys(Expr *expr, RelOptInfo *rel, bool strict_op)
{
int cnt;
/* This function should be called only for partitioned relations. */
Assert(rel->part_scheme);
/* Remove any relabel decorations. */
while (IsA(expr, RelabelType))
expr = (Expr *) (castNode(RelabelType, expr))->arg;
for (cnt = 0; cnt < rel->part_scheme->partnatts; cnt++)
{
ListCell *lc;
Assert(rel->partexprs);
foreach(lc, rel->partexprs[cnt])
{
if (equal(lfirst(lc), expr))
return cnt;
}
if (!strict_op)
continue;
/*
* If it's a strict equi-join a NULL partition key on one side will
* not join a NULL partition key on the other side. So, rows with NULL
* partition key from a partition on one side can not join with those
* from a non-matching partition on the other side. So, search the
* nullable partition keys as well.
*/
Assert(rel->nullable_partexprs);
foreach(lc, rel->nullable_partexprs[cnt])
{
if (equal(lfirst(lc), expr))
return cnt;
}
}
return -1;
}
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