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Refactor ChangeVarNodesExtended() using the custom callback

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fc069a3a63 implemented Self-Join Elimination (SJE) and put related logic
to ChangeVarNodes_walker().  This commit provides refactoring to remove the
SJE-related logic from ChangeVarNodes_walker() but adds a custom callback to
ChangeVarNodesExtended(), which has a chance to process a node before
ChangeVarNodes_walker().  Passing this callback to ChangeVarNodesExtended()
allows SJE-related node handling to be kept within the analyzejoins.c.

Reported-by: Richard Guo <guofenglinux@gmail.com>
Discussion: https://postgr.es/m/CAMbWs49PE3CvnV8vrQ0Dr%3DHqgZZmX0tdNbzVNJxqc8yg-8kDQQ%40mail.gmail.com
Author: Andrei Lepikhov <lepihov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
This commit is contained in:
Alexander Korotkov
2025-05-07 11:10:16 +03:00
parent 2448c7a9e0
commit ab42d643c1
4 changed files with 192 additions and 124 deletions
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160
src/backend/optimizer/plan/analyzejoins.c
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@@ -74,6 +74,8 @@ static bool is_innerrel_unique_for(PlannerInfo *root,
List *restrictlist,
List **extra_clauses);
static int self_join_candidates_cmp(const void *a, const void *b);
static bool replace_relid_callback(Node *node,
ChangeVarNodes_context *context);
/*
@@ -397,7 +399,8 @@ remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel,
{
Assert(subst > 0);
ChangeVarNodes((Node *) sjinf->semi_rhs_exprs, relid, subst, 0);
ChangeVarNodesExtended((Node *) sjinf->semi_rhs_exprs, relid, subst,
0, replace_relid_callback);
}
}
@@ -469,7 +472,8 @@ remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel,
sjinfo->ojrelid, subst);
Assert(!bms_is_empty(phv->phrels));
ChangeVarNodes((Node *) phv->phexpr, relid, subst, 0);
ChangeVarNodesExtended((Node *) phv->phexpr, relid, subst, 0,
replace_relid_callback);
Assert(phv->phnullingrels == NULL); /* no need to adjust */
}
@@ -523,7 +527,8 @@ remove_rel_from_query(PlannerInfo *root, RelOptInfo *rel,
}
if (subst > 0)
ChangeVarNodes((Node *) otherrel->lateral_vars, relid, subst, 0);
ChangeVarNodesExtended((Node *) otherrel->lateral_vars, relid,
subst, 0, replace_relid_callback);
}
}
@@ -757,7 +762,8 @@ remove_rel_from_eclass(EquivalenceClass *ec, SpecialJoinInfo *sjinfo,
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
if (sjinfo == NULL)
ChangeVarNodes((Node *) rinfo, relid, subst, 0);
ChangeVarNodesExtended((Node *) rinfo, relid, subst, 0,
replace_relid_callback);
else
remove_rel_from_restrictinfo(rinfo, relid, sjinfo->ojrelid);
}
@@ -1548,7 +1554,8 @@ update_eclasses(EquivalenceClass *ec, int from, int to)
em->em_jdomain->jd_relids = adjust_relid_set(em->em_jdomain->jd_relids, from, to);
/* We only process inner joins */
ChangeVarNodes((Node *) em->em_expr, from, to, 0);
ChangeVarNodesExtended((Node *) em->em_expr, from, to, 0,
replace_relid_callback);
foreach_node(EquivalenceMember, other, new_members)
{
@@ -1582,7 +1589,8 @@ update_eclasses(EquivalenceClass *ec, int from, int to)
continue;
}
ChangeVarNodes((Node *) rinfo, from, to, 0);
ChangeVarNodesExtended((Node *) rinfo, from, to, 0,
replace_relid_callback);
/*
* After switching the clause to the remaining relation, check it for
@@ -1677,6 +1685,118 @@ add_non_redundant_clauses(PlannerInfo *root,
}
}
/*
* A custom callback for ChangeVarNodesExtended() providing
* Self-join elimination (SJE) related functionality
*
* SJE needs to skip the RangeTblRef node
* type. During SJE's last step, remove_rel_from_joinlist() removes
* remaining RangeTblRefs with target relid. If ChangeVarNodes() replaces
* the target relid before, remove_rel_from_joinlist() fails to identify
* the nodes to delete.
*
* SJE also needs to change the relids within RestrictInfo's.
*/
static bool
replace_relid_callback(Node *node, ChangeVarNodes_context *context)
{
if (IsA(node, RangeTblRef))
{
return true;
}
else if (IsA(node, RestrictInfo))
{
RestrictInfo *rinfo = (RestrictInfo *) node;
int relid = -1;
bool is_req_equal =
(rinfo->required_relids == rinfo->clause_relids);
bool clause_relids_is_multiple =
(bms_membership(rinfo->clause_relids) == BMS_MULTIPLE);
/*
* Recurse down into clauses if the target relation is present in
* clause_relids or required_relids. We must check required_relids
* because the relation not present in clause_relids might still be
* present somewhere in orclause.
*/
if (bms_is_member(context->rt_index, rinfo->clause_relids) ||
bms_is_member(context->rt_index, rinfo->required_relids))
{
Relids new_clause_relids;
ChangeVarNodesWalkExpression((Node *) rinfo->clause, context);
ChangeVarNodesWalkExpression((Node *) rinfo->orclause, context);
new_clause_relids = adjust_relid_set(rinfo->clause_relids,
context->rt_index,
context->new_index);
/*
* Incrementally adjust num_base_rels based on the change of
* clause_relids, which could contain both base relids and
* outer-join relids. This operation is legal until we remove
* only baserels.
*/
rinfo->num_base_rels -= bms_num_members(rinfo->clause_relids) -
bms_num_members(new_clause_relids);
rinfo->clause_relids = new_clause_relids;
rinfo->left_relids =
adjust_relid_set(rinfo->left_relids, context->rt_index, context->new_index);
rinfo->right_relids =
adjust_relid_set(rinfo->right_relids, context->rt_index, context->new_index);
}
if (is_req_equal)
rinfo->required_relids = rinfo->clause_relids;
else
rinfo->required_relids =
adjust_relid_set(rinfo->required_relids, context->rt_index, context->new_index);
rinfo->outer_relids =
adjust_relid_set(rinfo->outer_relids, context->rt_index, context->new_index);
rinfo->incompatible_relids =
adjust_relid_set(rinfo->incompatible_relids, context->rt_index, context->new_index);
if (rinfo->mergeopfamilies &&
bms_get_singleton_member(rinfo->clause_relids, &relid) &&
clause_relids_is_multiple &&
relid == context->new_index && IsA(rinfo->clause, OpExpr))
{
Expr *leftOp;
Expr *rightOp;
leftOp = (Expr *) get_leftop(rinfo->clause);
rightOp = (Expr *) get_rightop(rinfo->clause);
/*
* For self-join elimination, changing varnos could transform
* "t1.a = t2.a" into "t1.a = t1.a". That is always true as long
* as "t1.a" is not null. We use qual() to check for such a case,
* and then we replace the qual for a check for not null
* (NullTest).
*/
if (leftOp != NULL && equal(leftOp, rightOp))
{
NullTest *ntest = makeNode(NullTest);
ntest->arg = leftOp;
ntest->nulltesttype = IS_NOT_NULL;
ntest->argisrow = false;
ntest->location = -1;
rinfo->clause = (Expr *) ntest;
rinfo->mergeopfamilies = NIL;
rinfo->left_em = NULL;
rinfo->right_em = NULL;
}
Assert(rinfo->orclause == NULL);
}
return true;
}
return false;
}
/*
* Remove a relation after we have proven that it participates only in an
* unneeded unique self-join.
@@ -1725,7 +1845,8 @@ remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
foreach_node(RestrictInfo, rinfo, joininfos)
{
remove_join_clause_from_rels(root, rinfo, rinfo->required_relids);
ChangeVarNodes((Node *) rinfo, toRemove->relid, toKeep->relid, 0);
ChangeVarNodesExtended((Node *) rinfo, toRemove->relid, toKeep->relid,
0, replace_relid_callback);
if (bms_membership(rinfo->required_relids) == BMS_MULTIPLE)
jinfo_candidates = lappend(jinfo_candidates, rinfo);
@@ -1743,7 +1864,8 @@ remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
restrictlist);
foreach_node(RestrictInfo, rinfo, toRemove->baserestrictinfo)
{
ChangeVarNodes((Node *) rinfo, toRemove->relid, toKeep->relid, 0);
ChangeVarNodesExtended((Node *) rinfo, toRemove->relid, toKeep->relid,
0, replace_relid_callback);
if (bms_membership(rinfo->required_relids) == BMS_MULTIPLE)
jinfo_candidates = lappend(jinfo_candidates, rinfo);
@@ -1785,7 +1907,8 @@ remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
{
Node *node = lfirst(lc);
ChangeVarNodes(node, toRemove->relid, toKeep->relid, 0);
ChangeVarNodesExtended(node, toRemove->relid, toKeep->relid, 0,
replace_relid_callback);
if (!list_member(toKeep->reltarget->exprs, node))
toKeep->reltarget->exprs = lappend(toKeep->reltarget->exprs, node);
}
@@ -1829,14 +1952,18 @@ remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
* Replace varno in all the query structures, except nodes RangeTblRef
* otherwise later remove_rel_from_joinlist will yield errors.
*/
ChangeVarNodesExtended((Node *) root->parse, toRemove->relid, toKeep->relid, 0, false);
ChangeVarNodesExtended((Node *) root->parse, toRemove->relid, toKeep->relid,
0, replace_relid_callback);
/* Replace links in the planner info */
remove_rel_from_query(root, toRemove, toKeep->relid, NULL, NULL);
/* At last, replace varno in root targetlist and HAVING clause */
ChangeVarNodes((Node *) root->processed_tlist, toRemove->relid, toKeep->relid, 0);
ChangeVarNodes((Node *) root->processed_groupClause, toRemove->relid, toKeep->relid, 0);
ChangeVarNodesExtended((Node *) root->processed_tlist, toRemove->relid,
toKeep->relid, 0, replace_relid_callback);
ChangeVarNodesExtended((Node *) root->processed_groupClause,
toRemove->relid, toKeep->relid, 0,
replace_relid_callback);
adjust_relid_set(root->all_result_relids, toRemove->relid, toKeep->relid);
adjust_relid_set(root->leaf_result_relids, toRemove->relid, toKeep->relid);
@@ -1919,8 +2046,10 @@ split_selfjoin_quals(PlannerInfo *root, List *joinquals, List **selfjoinquals,
* when we have cast of the same var to different (but compatible)
* types.
*/
ChangeVarNodes(rightexpr, bms_singleton_member(rinfo->right_relids),
bms_singleton_member(rinfo->left_relids), 0);
ChangeVarNodesExtended(rightexpr,
bms_singleton_member(rinfo->right_relids),
bms_singleton_member(rinfo->left_relids), 0,
replace_relid_callback);
if (equal(leftexpr, rightexpr))
sjoinquals = lappend(sjoinquals, rinfo);
@@ -1956,7 +2085,8 @@ match_unique_clauses(PlannerInfo *root, RelOptInfo *outer, List *uclauses,
bms_is_empty(rinfo->right_relids));
clause = (Expr *) copyObject(rinfo->clause);
ChangeVarNodes((Node *) clause, relid, outer->relid, 0);
ChangeVarNodesExtended((Node *) clause, relid, outer->relid, 0,
replace_relid_callback);
iclause = bms_is_empty(rinfo->left_relids) ? get_rightop(clause) :
get_leftop(clause);