Implemented CLUSTERSCAN command for topology-aware scanning

Unlike `SCAN` which is local to a single node, `CLUSTERSCAN` provides a
mechanism that helps clients iterate across slot boundaries and handles
`MOVED` redirections.

**Key details**

* Global cluster iteration via `fingerprint-{hashtag}-cursor`
* Scan one slot at a time
* Start the CLUSTERSCAN with 0
* SLOT argument for parallel scanning of multiple slots
* Re-use scanGenericCommand for the response

**Cursor format:** `fingerprint-{hashtag}-localcursor`
 - Fingerprint is a hash of the node's DB seed that identifies the
   current memory layout. On mismatch, scan restarts from cursor 0
   rather than returning an error.
 - Fingerprint 0 indicates a cross slot cursor (e.g., initial cursor
   or slot transition) where validation is skipped.
 - Hashtag encodes the target slot
 - Local cursor tracks position within the slot

**Usage:**

```
CLUSTERSCAN <cursor> [MATCH pattern] [COUNT count] [TYPE type] [SLOT number]
```

```
  CLUSTERSCAN 0                    # Start scanning from slot 0
  CLUSTERSCAN <cursor>             # Continue from cursor
  CLUSTERSCAN 0 SLOT 1000          # Start scanning specific slot
  CLUSTERSCAN <cursor> MATCH user:* COUNT 100
```

---------

Signed-off-by: nmvk <r@nmvk.com>
Signed-off-by: Raghav <r@nmvk.com>
Signed-off-by: Madelyn Olson <madelyneolson@gmail.com>
Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>
Co-authored-by: Madelyn Olson <madelyneolson@gmail.com>
Signed-off-by: Daniel Lemire <daniel@lemire.me>

This reverts commit 8a4a7b2.

Docuementation changes for the CLUSTERSCAN

valkey-io/valkey#2934

Signed-off-by: nmvk <r@nmvk.com>

- Fix release date to Mon Mar 18 2026
- Fix typos: duplicate 'load', 'keyes' -> 'keys', duplicate 'INFO'
- Remove reverted contributor (arshidkv12, valkey-io#3137)
- Add 7 new release-notes entries from upstream/unstable merge:
  CLUSTERSCAN (valkey-io#2934), MSETEX (valkey-io#3121), availability-zone (valkey-io#3156),
  stream range optimization (valkey-io#3002), RDB as AOF preamble (valkey-io#1901),
  unsigned 64-bit module config (valkey-io#1546), fast_float -> ffc (valkey-io#3329)

Signed-off-by: Madelyn Olson <madelyneolson@gmail.com>

Docuementation changes for the CLUSTERSCAN

valkey-io/valkey#2934

Signed-off-by: nmvk <r@nmvk.com>

Implemented CLUSTERSCAN command for topology-aware scanning

Unlike `SCAN` which is local to a single node, `CLUSTERSCAN` provides a
mechanism that helps clients iterate across slot boundaries and handles
`MOVED` redirections.

**Key details**

* Global cluster iteration via `fingerprint-{hashtag}-cursor`
* Scan one slot at a time
* Start the CLUSTERSCAN with 0
* SLOT argument for parallel scanning of multiple slots
* Re-use scanGenericCommand for the response

**Cursor format:** `fingerprint-{hashtag}-localcursor`
 - Fingerprint is a hash of the node's DB seed that identifies the
   current memory layout. On mismatch, scan restarts from cursor 0
   rather than returning an error.
 - Fingerprint 0 indicates a cross slot cursor (e.g., initial cursor
   or slot transition) where validation is skipped.
 - Hashtag encodes the target slot
 - Local cursor tracks position within the slot

**Usage:**

```
CLUSTERSCAN <cursor> [MATCH pattern] [COUNT count] [TYPE type] [SLOT number]
```

```
  CLUSTERSCAN 0                    # Start scanning from slot 0
  CLUSTERSCAN <cursor>             # Continue from cursor
  CLUSTERSCAN 0 SLOT 1000          # Start scanning specific slot
  CLUSTERSCAN <cursor> MATCH user:* COUNT 100
```

---------

Signed-off-by: nmvk <r@nmvk.com>
Signed-off-by: Raghav <r@nmvk.com>
Signed-off-by: Madelyn Olson <madelyneolson@gmail.com>
Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>
Co-authored-by: Madelyn Olson <madelyneolson@gmail.com>

Instead of scanning one slot at a time `CLUSTERSCAN` now scans the
entire contiguous range of slots owned by the current node.

Implementation details

* Re-sharding safe as the hash slot is updated based on the local cursor
  position.
* Fingerprint remains stable across the entire contiguous slot range
  instead of being reset per slot.
* Parsing/validation of parameters for the SCAN commands is refactored
  and moved to a separate function.

```
   > CLUSTERSCAN 0
   "0-{06S}-0"                      # start at slot 0

   > CLUSTERSCAN 0-{06S}-0
   "aBcDeF-{06S}-48"                # scanning slot 0...

   > CLUSTERSCAN aBcDeF-{06S}-48
   "aBcDeF-{1Y7}-16"                 # slot 0 done, continues to slot 6 (same node hence FP is unchanged)

   > CLUSTERSCAN aBcDeF-{1Y7}-16
   "aBcDeF-{0or}-32"                # slot 6 done, continues to slot 100  (same node hence FP is unchanged)
   ...
   > CLUSTERSCAN aBcDeF-{...}-64
   "0-{8YG}-0"                      # Current continuous slot boundary reached hence cross-node transition 
```

Follow-up of #2934

---------

Signed-off-by: nmvk <r@nmvk.com>
Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech>
Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

Instead of scanning one slot at a time `CLUSTERSCAN` now scans the
entire contiguous range of slots owned by the current node.

Implementation details

* Re-sharding safe as the hash slot is updated based on the local cursor
  position.
* Fingerprint remains stable across the entire contiguous slot range
  instead of being reset per slot.
* Parsing/validation of parameters for the SCAN commands is refactored
  and moved to a separate function.

```
   > CLUSTERSCAN 0
   "0-{06S}-0"                      # start at slot 0

   > CLUSTERSCAN 0-{06S}-0
   "aBcDeF-{06S}-48"                # scanning slot 0...

   > CLUSTERSCAN aBcDeF-{06S}-48
   "aBcDeF-{1Y7}-16"                 # slot 0 done, continues to slot 6 (same node hence FP is unchanged)

   > CLUSTERSCAN aBcDeF-{1Y7}-16
   "aBcDeF-{0or}-32"                # slot 6 done, continues to slot 100  (same node hence FP is unchanged)
   ...
   > CLUSTERSCAN aBcDeF-{...}-64
   "0-{8YG}-0"                      # Current continuous slot boundary reached hence cross-node transition 
```

Follow-up of #2934

---------

Signed-off-by: nmvk <r@nmvk.com>
Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech>
Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

Instead of scanning one slot at a time `CLUSTERSCAN` now scans the
entire contiguous range of slots owned by the current node.

Implementation details

* Re-sharding safe as the hash slot is updated based on the local cursor
  position.
* Fingerprint remains stable across the entire contiguous slot range
  instead of being reset per slot.
* Parsing/validation of parameters for the SCAN commands is refactored
  and moved to a separate function.

```
   > CLUSTERSCAN 0
   "0-{06S}-0"                      # start at slot 0

   > CLUSTERSCAN 0-{06S}-0
   "aBcDeF-{06S}-48"                # scanning slot 0...

   > CLUSTERSCAN aBcDeF-{06S}-48
   "aBcDeF-{1Y7}-16"                 # slot 0 done, continues to slot 6 (same node hence FP is unchanged)

   > CLUSTERSCAN aBcDeF-{1Y7}-16
   "aBcDeF-{0or}-32"                # slot 6 done, continues to slot 100  (same node hence FP is unchanged)
   ...
   > CLUSTERSCAN aBcDeF-{...}-64
   "0-{8YG}-0"                      # Current continuous slot boundary reached hence cross-node transition 
```

Follow-up of #2934

---------

Signed-off-by: nmvk <r@nmvk.com>
Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech>
Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>

This bug was introduced in #3366.

Before PR #3366, hash-seed config was applied directly via
hashtableSetHashFunctionSeed(), so clusterscanFingerprint() correctly
used hash_function_seed to derive the fingerprint.
```c
if (server.hash_seed != NULL) {
    memset(hashseed, 0, sizeof(hashseed));
    getHashSeedFromString(hashseed, sizeof(hashseed), server.hash_seed);
    hashtableSetHashFunctionSeed(hashseed);
}
```

PR #3366 introduced a separate configurable_hash_seed for data
hashtables and kept hash_function_seed as a random per-process value.
```c
/* Set the configured hash seed used by data hashtables (keys, sets, zsets,
 * hashes) or use the random seed if not configured. */
if (server.hash_seed) {
    uint8_t seed[16] = {0};
    getHashSeedFromString(seed, sizeof(seed), server.hash_seed);
    setConfigurableHashSeed(seed);
} else {
    setConfigurableHashSeed(hashtableGetHashFunctionSeed());
}
```

However, clusterscanFingerprint() was not updated accordingly — it
still reads hash_function_seed, which is now random on every node.
This makes fingerprints differ across nodes even when they share the
same hash-seed config, causing cursors to restart on failover.

CLUSTERSCAN was introduced in #2934.

Signed-off-by: Binbin <binloveplay1314@qq.com>

…3675)

No bug exists — all NOT_KEY commands (CLUSTERSCAN, SSUBSCRIBE,
SPUBLISH, SUNSUBSCRIBE) have NULL getkeys_proc, so doesCommandHaveKeys
returns 0 and ACL correctly skips key checks. This PR makes the
handling more explicit and defensive for future commands that may
combine getkeys_proc with NOT_KEY key-specs.

Changes:

- Refactor doesCommandHaveKeys() from a one-line ternary into clearer
  if-else branches. Add an explicit check: if a command has getkeys_proc
  but all its key-specs are NOT_KEY, treat it as having no real keys.

- Add a defensive NOT_KEY check in ACLSelectorCheckKey() to skip
  key-pattern ACL validation for NOT_KEY entries, consistent with the
  existing skip in getKeysUsingKeySpecs().

- Add tests: verify COMMAND GETKEYS/GETKEYSANDFLAGS report "no key
  arguments" for NOT_KEY commands; verify restricted ACL users can
  run CLUSTERSCAN without key-permission errors.

Related: #2934, #3699

Signed-off-by: Binbin <binloveplay1314@qq.com>