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Restore comments in ChangeVarNodesExtended()
authorAlexander Korotkov <akorotkov@postgresql.org>
Mon, 28 Apr 2025 08:20:22 +0000 (11:20 +0300)
committerAlexander Korotkov <akorotkov@postgresql.org>
Mon, 28 Apr 2025 08:20:22 +0000 (11:20 +0300)
This commit restores comments in ChangeVarNodesExtended(), which were
accidentally removed by fc069a3a6319.

Reported-by: Richard Guo <guofenglinux@gmail.com>
Discussion: https://postgr.es/m/CAMbWs49PE3CvnV8vrQ0Dr%3DHqgZZmX0tdNbzVNJxqc8yg-8kDQQ%40mail.gmail.com

src/backend/rewrite/rewriteManip.c patch | blob | blame | history

diff --git a/src/backend/rewrite/rewriteManip.c b/src/backend/rewrite/rewriteManip.c
index 1c61085a0a7641769526be08e24c93bf7839ed0f..e190f169fb3e08ce628524a3c8e27687dafe4aaf 100644 (file)
--- a/src/backend/rewrite/rewriteManip.c
+++ b/src/backend/rewrite/rewriteManip.c
@@ -758,10 +758,23 @@ ChangeVarNodesExtended(Node *node, int rt_index, int new_index,
    context.sublevels_up = sublevels_up;
    context.change_RangeTblRef = change_RangeTblRef;
 
+   /*
+    * Must be prepared to start with a Query or a bare expression tree; if
+    * it's a Query, go straight to query_tree_walker to make sure that
+    * sublevels_up doesn't get incremented prematurely.
+    */
    if (node && IsA(node, Query))
    {
        Query      *qry = (Query *) node;
 
+       /*
+        * If we are starting at a Query, and sublevels_up is zero, then we
+        * must also fix rangetable indexes in the Query itself --- namely
+        * resultRelation, mergeTargetRelation, exclRelIndex  and rowMarks
+        * entries.  sublevels_up cannot be zero when recursing into a
+        * subquery, so there's no need to have the same logic inside
+        * ChangeVarNodes_walker.
+        */
        if (sublevels_up == 0)
        {
            ListCell   *l;
@@ -772,6 +785,7 @@ ChangeVarNodesExtended(Node *node, int rt_index, int new_index,
            if (qry->mergeTargetRelation == rt_index)
                qry->mergeTargetRelation = new_index;
 
+           /* this is unlikely to ever be used, but ... */
            if (qry->onConflict && qry->onConflict->exclRelIndex == rt_index)
                qry->onConflict->exclRelIndex = new_index;
 
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