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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
2025-05-03 22:30:52 +03:00
parent fb21ed6c38
commit 250a718aad
4 changed files with 192 additions and 124 deletions
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138
src/backend/rewrite/rewriteManip.c
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@@ -550,19 +550,15 @@ offset_relid_set(Relids relids, int offset)
* earlier to ensure that no unwanted side-effects occur!
*/
typedef struct
{
int rt_index;
int new_index;
int sublevels_up;
bool change_RangeTblRef;
} ChangeVarNodes_context;
static bool
ChangeVarNodes_walker(Node *node, ChangeVarNodes_context *context)
{
if (node == NULL)
return false;
if (context->callback && context->callback(node, context))
return false;
if (IsA(node, Var))
{
Var *var = (Var *) node;
@@ -588,7 +584,7 @@ ChangeVarNodes_walker(Node *node, ChangeVarNodes_context *context)
cexpr->cvarno = context->new_index;
return false;
}
if (IsA(node, RangeTblRef) && context->change_RangeTblRef)
if (IsA(node, RangeTblRef))
{
RangeTblRef *rtr = (RangeTblRef *) node;
@@ -635,95 +631,6 @@ ChangeVarNodes_walker(Node *node, ChangeVarNodes_context *context)
}
return false;
}
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;
expression_tree_walker((Node *) rinfo->clause, ChangeVarNodes_walker, (void *) context);
expression_tree_walker((Node *) rinfo->orclause, ChangeVarNodes_walker, (void *) 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 false;
}
if (IsA(node, AppendRelInfo))
{
AppendRelInfo *appinfo = (AppendRelInfo *) node;
@@ -757,26 +664,28 @@ ChangeVarNodes_walker(Node *node, ChangeVarNodes_context *context)
}
/*
* ChangeVarNodesExtended - similar to ChangeVarNodes, but has additional
* 'change_RangeTblRef' param
* ChangeVarNodesExtended - similar to ChangeVarNodes, but with an additional
* 'callback' param
*
* ChangeVarNodes changes a given node and all of its underlying nodes.
* However, self-join elimination (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.
* This version of function additionally takes a callback, which has a
* chance to process a node before ChangeVarNodes_walker. A callback
* returns a boolean value indicating if given node should be skipped from
* further processing by ChangeVarNodes_walker. The callback is called
* only for expressions and other children nodes of a Query processed by
* a walker. Initial processing of the root Query doesn't involve the
* callback.
*/
void
ChangeVarNodesExtended(Node *node, int rt_index, int new_index,
int sublevels_up, bool change_RangeTblRef)
int sublevels_up, ChangeVarNodes_callback callback)
{
ChangeVarNodes_context context;
context.rt_index = rt_index;
context.new_index = new_index;
context.sublevels_up = sublevels_up;
context.change_RangeTblRef = change_RangeTblRef;
context.callback = callback;
/*
* Must be prepared to start with a Query or a bare expression tree; if
@@ -826,7 +735,20 @@ ChangeVarNodesExtended(Node *node, int rt_index, int new_index,
void
ChangeVarNodes(Node *node, int rt_index, int new_index, int sublevels_up)
{
ChangeVarNodesExtended(node, rt_index, new_index, sublevels_up, true);
ChangeVarNodesExtended(node, rt_index, new_index, sublevels_up, NULL);
}
/*
* ChangeVarNodesWalkExpression - process expression within the custom
* callback provided to the
* ChangeVarNodesExtended.
*/
bool
ChangeVarNodesWalkExpression(Node *node, ChangeVarNodes_context *context)
{
return expression_tree_walker(node,
ChangeVarNodes_walker,
(void *) context);
}
/*