Fix XREAD returning error on empty stream with + ID by diego-ciciani01 · Pull Request #2742 · valkey-io/valkey

diego-ciciani01 · 2025-10-16T17:30:01Z

When using XREAD STREAMS + on an empty stream created with MKSTREAM, valkey returns an error instead of nil.

This heppens because is missing a check on the stream length

The fix adds the lenght check on the condition

When using XREAD STREAMS <stream> + on an empty stream created with MKSTREAM, valkey returns an error instead of nil. This heppens because is missing a check on the stream length The fix adds the lenght check on the condition Fixes valkey-io#2728 Signed-off-by: diego-ciciani01 <diego.ciciani@gmail.com>

codecov · 2025-10-17T08:18:24Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.31%. Comparing base (fa59643) to head (82d7220).
⚠️ Report is 18 commits behind head on unstable.

Additional details and impacted files

@@            Coverage Diff            @@
##           unstable    #2742   +/-   ##
=========================================
  Coverage     74.31%   74.31%           
=========================================
  Files           129      129           
  Lines         70987    70987           
=========================================
+ Hits          52751    52754    +3     
+ Misses        18236    18233    -3

Files with missing lines	Coverage Δ
src/t_stream.c	`94.41% <100.00%> (ø)`

... and 24 files with indirect coverage changes

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stockholmux

Nice work - tried it out and it behaves as expected.

I do wonder if this needs a test since there is a /* shouldn't happen */ comment when sending the the stream last element ID is 0-0 error.

I'm guessing this would also need to be a Valkey 10.0 change since it would be a behaviour change from Valkey 9.0 even if unintended.

diego-ciciani01 · 2025-10-26T22:47:27Z

Hi @stockholmux,
you're right it makes sense to have test coverage especially given the /* shouldn't happen */ comment, which indicates this was an unexpected edge case. I'll add it to the stream tests to prevent any future regressions.
I agree that targeting 10.0 is the safer approach, changing behavior in a minor version could potentially affect users.

thearchitector · 2025-11-13T21:47:43Z

is there an update on merging this?

zuiderkwast · 2026-01-13T20:50:04Z

@valkey-io/valkey-committers Does anyone want to review this one?

I'm not familiar enough with streams commands. Looking at the docs for XREAD, I can't see the special ID + mentioned there at all. If the behavior is not documented, is it then a bug? Is the + documented somewhere else?

Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

thearchitector · 2026-01-21T23:33:27Z

If the behavior is not documented, is it then a bug? Is the + documented somewhere else?

its in the redis docs, as of 7.4

https://redis.io/docs/latest/commands/xread/#the-special--id-1

im not sure at which version valkey forked, but as it stands, support for + exists even if undocumented

so imo its either

explicitly remove support for it, and document that limitation
fix it, and document it

the latter seems better and easier, based on this PR

i agree that the documentation should be updated either way, though

zuiderkwast · 2026-01-22T10:19:02Z

Valkey was forked some time between Redis 7.2 and Redis 7.4. Redis 7.2 and Valkey 7.2 are identical.

Does this bug affect also Valkey 8.1, 8.0 and 7.2?

If yes, we may want to include the fix in patch releases of these versions too.

When using XREAD STREAMS <stream> + on an empty stream created with MKSTREAM, valkey returns an error instead of nil. This happens because is missing a check on the stream length. The fix adds the length check on the condition. Fixes valkey-io#2728 Signed-off-by: diego-ciciani01 <diego.ciciani@gmail.com> Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech> Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

When using XREAD STREAMS <stream> + on an empty stream created with MKSTREAM, valkey returns an error instead of nil. This happens because is missing a check on the stream length. The fix adds the length check on the condition. Fixes #2728 Signed-off-by: diego-ciciani01 <diego.ciciani@gmail.com> Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech> Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

When using XREAD STREAMS <stream> + on an empty stream created with MKSTREAM, valkey returns an error instead of nil. This happens because is missing a check on the stream length. The fix adds the length check on the condition. Fixes valkey-io#2728 Signed-off-by: diego-ciciani01 <diego.ciciani@gmail.com> Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech> Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

When using XREAD STREAMS <stream> + on an empty stream created with MKSTREAM, valkey returns an error instead of nil. This happens because is missing a check on the stream length. The fix adds the length check on the condition. Fixes valkey-io#2728 Signed-off-by: diego-ciciani01 <diego.ciciani@gmail.com> Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech> Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech> Signed-off-by: Harkrishn Patro <bunty.hari@gmail.com>

This PR contains the following updates: | Package | Type | Update | Change | |---|---|---|---| | [docker.io/valkey/valkey](https://github.com/valkey-io/valkey) | image | patch | `9.0.1` → `9.0.4` | --- ### Release Notes <details> <summary>valkey-io/valkey (docker.io/valkey/valkey)</summary> ### [`v9.0.4`](https://github.com/valkey-io/valkey/releases/tag/9.0.4) [Compare Source](valkey-io/valkey@9.0.3...9.0.4) Upgrade urgency SECURITY: This release includes security fixes we recommend you apply as soon as possible. ##### Security fixes - (CVE-2026-23479) Use-After-Free in unblock client flow - (CVE-2026-25243) Invalid Memory Access in RESTORE command - (CVE-2026-23631) Use-after-free when full sync occurs during a yielding Lua/function execution ### [`v9.0.3`](https://github.com/valkey-io/valkey/releases/tag/9.0.3) [Compare Source](valkey-io/valkey@9.0.2...9.0.3) ##### Valkey 9.0.3 Upgrade urgency SECURITY: This release includes security fixes we recommend you apply as soon as possible. ##### Security fixes - (CVE-2025-67733) RESP Protocol Injection via Lua error\_reply - (CVE-2026-21863) Remote DoS with malformed Valkey Cluster bus message - (CVE-2026-27623) Reset request type after handling empty requests ##### Bug fixes - Avoids crash during MODULE UNLOAD when ACL rules reference a module command and subcommand ([#3160](valkey-io/valkey#3160)) - Fix server assert on ACL LOAD when current user loses permission to channels ([#3182](valkey-io/valkey#3182)) - Fix bug causing no response flush sometimes when IO threads are busy ([#3205](valkey-io/valkey#3205)) ### [`v9.0.2`](https://github.com/valkey-io/valkey/releases/tag/9.0.2) [Compare Source](valkey-io/valkey@9.0.1...9.0.2) Upgrade urgency HIGH: There are critical bugs that may affect a subset of users. #### Bug fixes - Avoid memory leak of new argv when HEXPIRE commands target only non-exiting fields ([#2973](valkey-io/valkey#2973)) - Fix HINCRBY and HINCRBYFLOAT to update volatile key tracking ([#2974](valkey-io/valkey#2974)) - Avoid empty hash object when HSETEX added no fields ([#2998](valkey-io/valkey#2998)) - Fix case-sensitive check for the FNX and FXX arguments in HSETEX ([#3000](valkey-io/valkey#3000)) - Prevent assertion in active expiration job after a hash with volatile fields is overwritten ([#3003](valkey-io/valkey#3003), [#3007](valkey-io/valkey#3007)) - Fix HRANDFIELD to return null response when no field could be found ([#3022](valkey-io/valkey#3022)) - Fix HEXPIRE to not delete items when validation rules fail and expiration is in the past ([#3023](valkey-io/valkey#3023), [#3048](valkey-io/valkey#3048)) - Fix how hash is handling overriding of expired fields overwrite ([#3060](valkey-io/valkey#3060)) - HSETEX - Always issue keyspace notifications after validation ([#3001](valkey-io/valkey#3001)) - Make zero a valid TTL for hash fields during import mode and data loading ([#3006](valkey-io/valkey#3006)) - Trigger prepareCommand on argc change in module command filters ([#2945](valkey-io/valkey#2945)) - Restrict TTL from being negative and avoid crash in import-mode ([#2944](valkey-io/valkey#2944)) - Fix chained replica crash when doing dual channel replication ([#2983](valkey-io/valkey#2983)) - Skip slot cache optimization for AOF client to prevent key duplication and data corruption ([#3004](valkey-io/valkey#3004)) - Fix used\_memory\_dataset underflow due to miscalculated used\_memory\_overhead ([#3005](valkey-io/valkey#3005)) - Avoid duplicate calculations of network-bytes-out in slot stats with copy-avoidance ([#3046](valkey-io/valkey#3046)) - Fix XREAD returning error on empty stream with + ID ([#2742](valkey-io/valkey#2742)) #### Performance/Efficiency Improvements - Track reply bytes in I/O threads if commandlog-reply-larger-than is -1 ([#3086](valkey-io/valkey#3086), [#3126](valkey-io/valkey#3126)). This makes it possible to mitigate a performance regression in 9.0.1 caused by the bug fix [#2652](valkey-io/valkey#2652). **Full Changelog**: <valkey-io/valkey@9.0.1...9.0.2> </details> --- ### Configuration 📅 **Schedule**: (UTC) - Branch creation - "before 6am" - Automerge - At any time (no schedule defined) 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Mend Renovate](https://github.com/renovatebot/renovate).

github-actions Bot assigned diego-ciciani01 Oct 16, 2025

stockholmux reviewed Oct 24, 2025

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hwware approved these changes Oct 24, 2025

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Nikhil-Manglore approved these changes Jan 13, 2026

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zuiderkwast added this to Valkey 9.0 Jan 13, 2026

zuiderkwast moved this to In Progress in Valkey 9.0 Jan 13, 2026

Merge branch 'unstable' into fix-check-empty-stream

82d7220

Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

zuiderkwast requested a review from lucasyonge January 14, 2026 22:03

zuiderkwast approved these changes Jan 22, 2026

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zuiderkwast merged commit 231a9e7 into valkey-io:unstable Jan 22, 2026
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github-project-automation Bot moved this from In Progress to To be backported in Valkey 9.0 Jan 22, 2026

zuiderkwast moved this from To be backported to 9.0.2 WIP in Valkey 9.0 Jan 30, 2026

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Fix XREAD returning error on empty stream with + ID#2742

Fix XREAD returning error on empty stream with + ID#2742
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diego-ciciani01:fix-check-empty-stream

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