From d20c6cd50cfd2fb90c61c809ad9a8b60b9443825 Mon Sep 17 00:00:00 2001
From: erhan1209 <82086267+erhan1209@users.noreply.github.com>
Date: Wed, 15 Apr 2026 15:44:14 +0300
Subject: [PATCH] Fix KEYSIZES histogram after HGETEX deletes the last hash
 fields

`HGETEX` could delete the last remaining fields in a hash and remove the key, but still update the KEYSIZES histogram as if an empty hash still existed. That left `INFO KEYSIZES` with a stale hash entry even though the key had already been deleted.

This patch makes `hgetexCommand` treat a zero-length post-operation hash as a removed key when updating the KEYSIZES histogram. Concretely, it reports the new size as `-1` for histogram accounting before deleting the key. A regression test was also added to verify that when `HGETEX PXAT 1` expires all fields in a hash, the corresponding KEYSIZES hash bucket disappears.

Testing:
- Added a regression test in `tests/unit/info-keysizes.tcl` covering `HGETEX` deleting the last hash fields and verifying the histogram entry is removed
- Not tested
---
 src/t_hash.c                 | 6 ++++--
 tests/unit/info-keysizes.tcl | 6 ++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/t_hash.c b/src/t_hash.c
index e258eb71f..db08ac62a 100644
--- a/src/t_hash.c
+++ b/src/t_hash.c
@@ -2914,10 +2914,12 @@ void hgetexCommand(client *c) {
     }
 
     /* Key may become empty due to lazy expiry in addHashFieldToReply()
-     * or the new expiration time is in the past.*/
+     * or the new expiration time is in the past. Keep the KEYSIZES
+     * histogram aligned with the fact that an empty hash key is removed. */
     newlen = hashTypeLength(o, 0);
+    int64_t hist_newlen = (newlen == 0) ? -1 : newlen;
 
-    updateKeysizesHist(c->db, OBJ_HASH, oldlen, newlen);
+    updateKeysizesHist(c->db, OBJ_HASH, oldlen, hist_newlen);
     if (newlen == 0) {
         dbDelete(c->db, c->argv[1]);
         notifyKeyspaceEvent(NOTIFY_GENERIC, "del", c->argv[1], c->db->id);
diff --git a/tests/unit/info-keysizes.tcl b/tests/unit/info-keysizes.tcl
index 065e3ee41..07ab2e04d 100644
--- a/tests/unit/info-keysizes.tcl
+++ b/tests/unit/info-keysizes.tcl
@@ -753,6 +753,12 @@ proc test_all_keysizes { {replMode 0} } {
         run_cmd_verify_hist {$server DEBUG RELOAD} {db0_STR:8=1}
     } {} {cluster:skip needs:debug}
 
+    test "KEYSIZES - HGETEX deleting the last hash fields removes the histogram entry $suffixRepl" {
+        run_cmd_verify_hist {$server FLUSHALL} {}
+        run_cmd_verify_hist {$server HSET myhash f1 v1 f2 v2 f3 v3} {db0_HASH:2=1}
+        run_cmd_verify_hist {$server HGETEX myhash PXAT 1 FIELDS 3 f1 f2 f3} {}
+    } {} {cluster:skip}
+
     test "KEYSIZES - Test RDB $suffixRepl" {
         run_cmd_verify_hist {$server FLUSHALL} {}
         # Write list, set and zset to db0