From c457804fad3732f827506b530b00d8c796b9d916 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=9B=D0=B5=D0=BE=D0=BD=D0=B8=D0=B4=20=D0=AE=D1=80=D1=8C?=
 =?UTF-8?q?=D0=B5=D0=B2=20=28Leonid=20Yuriev=29?= <leo@yuriev.ru>
Date: Thu, 20 Mar 2025 01:46:13 +0300
Subject: [PATCH] =?UTF-8?q?mdbx:=20=D0=B8=D1=81=D0=BF=D1=80=D0=B0=D0=B2?=
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---
 src/api-cursor.c |  6 ++----
 src/cursor.c     | 13 ++++++++++---
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/src/api-cursor.c b/src/api-cursor.c
index 18396299..f5f09c20 100644
--- a/src/api-cursor.c
+++ b/src/api-cursor.c
@@ -690,11 +690,9 @@ MDBX_txn *mdbx_cursor_txn(const MDBX_cursor *mc) {
   if (unlikely(!mc || mc->signature != cur_signature_live))
     return nullptr;
   MDBX_txn *txn = mc->txn;
-  if (unlikely(!txn || txn->signature != txn_signature))
+  if (unlikely(!txn || txn->signature != txn_signature || (txn->flags & MDBX_TXN_FINISHED)))
     return nullptr;
-  if (unlikely(txn->flags & MDBX_TXN_FINISHED))
-    return nullptr;
-  return txn;
+  return (txn->flags & MDBX_TXN_HAS_CHILD) ? txn->env->txn : txn;
 }
 
 MDBX_dbi mdbx_cursor_dbi(const MDBX_cursor *mc) {
diff --git a/src/cursor.c b/src/cursor.c
index 8a96387d..b313a78f 100644
--- a/src/cursor.c
+++ b/src/cursor.c
@@ -2347,14 +2347,21 @@ int cursor_check(const MDBX_cursor *mc, int txn_bad_bits) {
                                         (char *)mc - stack_top < (ptrdiff_t)globals.sys_pagesize * 4));
 
   if (txn_bad_bits) {
-    int rc = check_txn(mc->txn, txn_bad_bits);
+    int rc = check_txn(mc->txn, txn_bad_bits & ~MDBX_TXN_HAS_CHILD);
     if (unlikely(rc != MDBX_SUCCESS)) {
       cASSERT(mc, rc != MDBX_RESULT_TRUE);
       return rc;
     }
 
-    if (unlikely(cursor_dbi_changed(mc)))
-      return MDBX_BAD_DBI;
+    if (likely((mc->txn->flags & MDBX_TXN_HAS_CHILD) == 0))
+      return likely(!cursor_dbi_changed(mc)) ? MDBX_SUCCESS : MDBX_BAD_DBI;
+
+    cASSERT(mc, (mc->txn->flags & MDBX_TXN_RDONLY) == 0 && mc->txn != mc->txn->env->txn && mc->txn->env->txn);
+    rc = dbi_check(mc->txn->env->txn, cursor_dbi(mc));
+    if (unlikely(rc != MDBX_SUCCESS))
+      return rc;
+
+    cASSERT(mc, (mc->txn->flags & MDBX_TXN_RDONLY) == 0 && mc->txn == mc->txn->env->txn);
   }
 
   return MDBX_SUCCESS;