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Fix comments for ChangeVarNodes() and related functions

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The comment for ChangeVarNodes() refers to a parameter named
change_RangeTblRef, which does not exist in the code.

The comment for ChangeVarNodesExtended() contains an extra space,
while the comment for replace_relid_callback() has an awkward line
break and a typo.

This patch fixes these issues and revises some sentences for smoother
wording.

Oversights in commits ab42d643c and fc069a3a6.

Author: Richard Guo <guofenglinux@gmail.com>
Discussion: https://postgr.es/m/CAMbWs480j16HC1JtjKCgj5WshivT8ZJYkOfTyZAM0POjFomJkg@mail.gmail.com
Backpatch-through: 18
This commit is contained in:
Richard Guo
2025-11-05 12:29:31 +09:00
parent 2fc3107962
commit 59dec6c0b0
2 changed files with 17 additions and 20 deletions
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18
src/backend/optimizer/plan/analyzejoins.c
View File

@@ -1683,14 +1683,14 @@ add_non_redundant_clauses(PlannerInfo *root,
}
/*
* A custom callback for ChangeVarNodesExtended() providing
* Self-join elimination (SJE) related functionality
* 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 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() would fail to identify the nodes
* to delete.
*
* SJE also needs to change the relids within RestrictInfo's.
*/
@@ -1769,8 +1769,8 @@ replace_relid_callback(Node *node, ChangeVarNodes_context *context)
/*
* 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
* as "t1.a" is not null. We use equal() to check for such a
* case, and then we replace the qual with a check for not null
* (NullTest).
*/
if (leftOp != NULL && equal(leftOp, rightOp))

17
src/backend/rewrite/rewriteManip.c
View File

@@ -542,8 +542,6 @@ offset_relid_set(Relids relids, int offset)
* (identified by sublevels_up and rt_index), and change their varno fields
* to 'new_index'. The varnosyn fields are changed too. Also, adjust other
* nodes that contain rangetable indexes, such as RangeTblRef and JoinExpr.
* Specifying 'change_RangeTblRef' to false allows skipping RangeTblRef.
* See ChangeVarNodesExtended for details.
*
* NOTE: although this has the form of a walker, we cheat and modify the
* nodes in-place. The given expression tree should have been copied
@@ -667,14 +665,13 @@ ChangeVarNodes_walker(Node *node, ChangeVarNodes_context *context)
* ChangeVarNodesExtended - similar to ChangeVarNodes, but with an additional
* 'callback' param
*
* ChangeVarNodes changes a given node and all of its underlying nodes.
* 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.
* ChangeVarNodes changes a given node and all of its underlying nodes. 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 the 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,