In SPOP, when COUNT is greater than or equal to set's size,
we will remove the set. In dbDelete, we will do DEL or UNLINK
according to the lazy flag. This is also required for propagate.
In RESTORE, we won't store expired keys into the db, see #7472.
When used together with REPLACE, it should emit a DEL or UNLINK
according to the lazy flag.
This PR also adds tests to cover the propagation. The RESTORE
test will also cover #7472.
We check lazyfree_lazy_server_del in sunionDiffGenericCommand
to see if we need to lazyfree the temp set. Now do the same in
zunionInterDiffGenericCommand to lazyfree the temp zset.
This is a minor change, follow #5903. Also improved the comments.
Additionally, avoid creating unused zset object in ZINTERCARD,
results in some 10% performance improvement.
Optimized HRANDFIELD and ZRANDMEMBER commands as in #8444,
CASE 3 under listpack encoding. Boost optimization to CASE 2.5.
CASE 2.5 listpack only. Sampling unique elements, in non-random order.
Listpack encoded hashes / zsets are meant to be relatively small, so
HRANDFIELD_SUB_STRATEGY_MUL / ZRANDMEMBER_SUB_STRATEGY_MUL
isn't necessary and we rather not make copies of the entries. Instead, we
emit them directly to the output buffer.
Simple benchmarks shows it provides some 400% improvement in HRANDFIELD
and ZRANGESTORE both in CASE 3.
Unrelated changes: remove useless setTypeRandomElements and fix a typo.
A single SPOP with command with count argument resulted in many SPOP
commands being propagated to the replica.
This is inefficient because the key name is repeated many times, and is also
being looked-up many times.
also it results in high QPS metrics on the replica.
To solve that, we flush batches of 1024 fields per SPOP command.
Co-authored-by: zhaozhao.zz <zhaozhao.zz@alibaba-inc.com>
For sets and hashes that will eventually be stored as the hash encoding, it's much faster to immediately convert them to their hash encoding and then perform the insertions since it avoids the O(N) search and frequent reallocations. This change checks the number of arguments in the incoming command, and converts the data-structure if the number of new entries exceeds the listpack-max-entries configuration. This can cause us to over-allocate memory if their are duplicate entries in the input, which is unexpected.
unstable
Summary:
throughput summary: 805.54 requests per second
latency summary (msec):
avg min p50 p95 p99 max
61.908 25.680 68.351 73.279 75.967 79.295
hset-improvement
Summary:
throughput summary: 4701.46 requests per second
latency summary (msec):
avg min p50 p95 p99 max
10.546 0.832 11.959 12.471 13.119 14.967
If a dict has only keys, and no use of values, then a key can be stored directly in a
dict's hashtable. The key replaces the dictEntry. To distinguish between a key and
a dictEntry, we only use this optimization if the key is odd, i.e. if the key has the least
significant bit set. This is true for sds strings, since the sds header is always an odd
number of bytes.
Dict entries are used as a fallback when there is a hash collision. A special dict entry
without a value (only key and next) is used so we save one word in this case too.
This saves 24 bytes per set element for larges sets, and also gains some speed improvement
as a side effect (less allocations and cache misses).
A quick test adding 1M elements to a set using the command below resulted in memory
usage of 28.83M, compared to 46.29M on unstable.
That's 18 bytes per set element on average.
eval 'for i=1,1000000,1 do redis.call("sadd", "myset", "x"..i) end' 0
Other changes:
Allocations are ensured to have at least 8 bits alignment on all systems. This affects 32-bit
builds compiled without HAVE_MALLOC_SIZE (not jemalloc or glibc) in which Redis
stores the size of each allocation, after this change in 8 bytes instead of previously 4 bytes
per allocation. This is done so we can reliably use the 3 least significant bits in a pointer to
encode stuff.
Related to the hang reported in #11671
Currently, redis can disconnect a client due to reaching output buffer limit,
it'll also avoid feeding that output buffer with more data, but it will keep
running the loop in the command (despite the client already being marked for
disconnection)
This PR is an attempt to mitigate the problem, specifically for commands that
are easy to abuse, specifically: KEYS, HRANDFIELD, SRANDMEMBER, ZRANDMEMBER.
The RAND family of commands can take a negative COUNT argument (which is not
bound to the number of elements in the key), so it's enough to create a key
with one field, and then these commands can be used to hang redis.
For KEYS the caller can use the existing keyspace in redis (if big enough).
PR #11290 added listpack encoding for sets, but was missing two things:
1. Correct handling of MEMORY USAGE (leading to an assertion).
2. Had an uncontrolled scratch buffer size in SRANDMEMBER leading to
OOM panic (reported in #11668). Fixed by copying logic from ZRANDMEMBER.
note that both issues didn't exist in any redis release.
In #11290, we added listpack encoding for SET object.
But forgot to support it in zuiFind, causes ZINTER, ZINTERSTORE,
ZINTERCARD, ZIDFF, ZDIFFSTORE to crash.
And forgot to support it in RM_ScanKey, causes it hang.
This PR add support SET listpack in zuiFind, and in RM_ScanKey.
And add tests for related commands to cover this case.
Other changes:
- There is no reason for zuiFind to go into the internals of the SET.
It can simply use setTypeIsMember and don't care about encoding.
- Remove the `#include "intset.h"` from server.h reduce the chance of
accidental intset API use.
- Move setTypeAddAux, setTypeRemoveAux and setTypeIsMemberAux
interfaces to the header.
- In scanGenericCommand, use setTypeInitIterator and setTypeNext
to handle OBJ_SET scan.
- In RM_ScanKey, improve hash scan mode, use lpGetValue like zset,
they can share code and better performance.
The zuiFind part fixes#11578
Co-authored-by: Oran Agra <oran@redislabs.com>
Co-authored-by: Viktor Söderqvist <viktor.soderqvist@est.tech>
In most cases when a listpack or intset is converted to a dict, the conversion
is trigged when adding an element. The extra element is added after conversion
to dict (in all cases except when the conversion is triggered by
set-max-intset-entries being reached).
If set-max-listpack-entries is set to a power of two, let's say 128, when
adding the 129th element, the 128 element listpack is first converted to a dict
with a hashtable presized for 128 elements. After converting to dict, the 129th
element is added to the dict which immediately triggers incremental rehashing
to size 256.
This commit instead presizes the dict to one more element, with the assumption
that conversion to dict is followed by adding another element, so the dict
doesn't immediately need rehashing.
Co-authored-by: sundb <sundbcn@gmail.com>
Co-authored-by: Oran Agra <oran@redislabs.com>
Add a new module event `RedisModule_Event_Key`, this event is fired
when a key is removed from the keyspace.
The event includes an open key that can be used for reading the key before
it is removed. Modules can also extract the key-name, and use RM_Open
or RM_Call to access key from within that event, but shouldn't modify anything
from within this event.
The following sub events are available:
- `REDISMODULE_SUBEVENT_KEY_DELETED`
- `REDISMODULE_SUBEVENT_KEY_EXPIRED`
- `REDISMODULE_SUBEVENT_KEY_EVICTED`
- `REDISMODULE_SUBEVENT_KEY_OVERWRITE`
The data pointer can be casted to a RedisModuleKeyInfo structure
with the following fields:
```
RedisModuleKey *key; // Opened Key
```
### internals
* We also add two dict functions:
`dictTwoPhaseUnlinkFind` finds an element from the table, also get the plink of the entry.
The entry is returned if the element is found. The user should later call `dictTwoPhaseUnlinkFree`
with it in order to unlink and release it. Otherwise if the key is not found, NULL is returned.
These two functions should be used in pair. `dictTwoPhaseUnlinkFind` pauses rehash and
`dictTwoPhaseUnlinkFree` resumes rehash.
* We change `dbOverwrite` to `dbReplaceValue` which just replaces the value of the key and
doesn't fire any events. The "overwrite" part (which emits events) is just when called from `setKey`,
the other places that called dbOverwrite were ones that just update the value in-place (INCR*, SPOP,
and dbUnshareStringValue). This should not have any real impact since `moduleNotifyKeyUnlink` and
`signalDeletedKeyAsReady` wouldn't have mattered in these cases anyway (i.e. module keys and
stream keys didn't have direct calls to dbOverwrite)
* since we allow doing RM_OpenKey from withing these callbacks, we temporarily disable lazy expiry.
* We also temporarily disable lazy expiry when we are in unlink/unlink2 callback and keyspace
notification callback.
* Move special definitions to the top of redismodule.h
This is needed to resolve compilation errors with RedisModuleKeyInfoV1
that carries a RedisModuleKey member.
Co-authored-by: Oran Agra <oran@redislabs.com>
This payload produces a set with duplicate elements (listpack encoding):
```
restore _key 0 "\x14\x25\x25\x00\x00\x00\x0A\x00\x06\x01\x82\x5F\x35\x03\x04\x01\x82\x5F\x31\x03\x82\x5F\x33\x03\x00\x01\x82\x5F\x39\x03\x82\x5F\x33\x03\x08\x01\x02\x01\xFF\x0B\x00\x31\xBE\x7D\x41\x01\x03\x5B\xEC"
smembers key
1) "6"
2) "_5"
3) "4"
4) "_1"
5) "_3" ---> dup
6) "0"
7) "_9"
8) "_3" ---> dup
9) "8"
10) "2"
```
This kind of sets will cause SDIFF to hang, SDIFF generated a broken
protocol and left the client hung. (Expected ten elements, but only
got nine elements due to the duplication.)
If we set `sanitize-dump-payload` to yes, we will be able to find
the duplicate elements and report "ERR Bad data format".
Discovered and discussed in #11290.
This PR also improve prints when corrupt-dump-fuzzer hangs, it will
print the cmds and the payload, an example like:
```
Testing integration/corrupt-dump-fuzzer
[TIMEOUT]: clients state report follows.
sock6 => (SPAWNED SERVER) pid:28884
Killing still running Redis server 28884
commands caused test to hang:
SDIFF __key
payload that caused test to hang: "\x14\balabala"
```
Co-authored-by: Oran Agra <oran@redislabs.com>
Small sets with not only integer elements are listpack encoded, by default
up to 128 elements, max 64 bytes per element, new config `set-max-listpack-entries`
and `set-max-listpack-value`. This saves memory for small sets compared to using a hashtable.
Sets with only integers, even very small sets, are still intset encoded (up to 1G
limit, etc.). Larger sets are hashtable encoded.
This PR increments the RDB version, and has an effect on OBJECT ENCODING
Possible conversions when elements are added:
intset -> listpack
listpack -> hashtable
intset -> hashtable
Note: No conversion happens when elements are deleted. If all elements are
deleted and then added again, the set is deleted and recreated, thus implicitly
converted to a smaller encoding.
The PR reverts the changes made on #10969.
The reason for revert was trigger because of occasional test failure
that started after the PR was merged.
The issue is that if there is a lazy expire during the command invocation,
the `del` command is added to the replication stream after the command
placeholder. So the logical order on the primary is:
* Delete the key (lazy expiration)
* Command invocation
But the replication stream gets it the other way around:
* Command invocation (because the command is written into the placeholder)
* Delete the key (lazy expiration)
So if the command write to the key that was just lazy expired we will get
inconsistency between primary and replica.
One solution we considered is to add another lazy expire replication stream
and write all the lazy expire there. Then when replicating, we will replicate the
lazy expire replication stream first. This will solve this specific test failure but
we realize that the issues does not ends here and the more we dig the more
problems we find.One of the example we thought about (that can actually
crashes Redis) is as follow:
* User perform SINTERSTORE
* When Redis tries to fetch the second input key it triggers lazy expire
* The lazy expire trigger a module logic that deletes the first input key
* Now Redis hold the robj of the first input key that was actually freed
We believe we took the wrong approach and we will come up with another
PR that solve the problem differently, for now we revert the changes so we
will not have the tests failure.
Notice that not the entire code was revert, some parts of the PR are changes
that we would like to keep. The changes that **was** reverted are:
* Saving a placeholder for replication at the beginning of the command (`call` function)
* Order of the replication stream on active expire and eviction (we will decide how
to handle it correctly on follow up PR)
* `Spop` changes are no longer needed (because we reverted the placeholder code)
Changes that **was not** reverted:
* On expire/eviction, wrap the `del` and the notification effect in a multi exec.
* `PropagateNow` function can still accept a special dbid, -1, indicating not to replicate select.
* Keep optimisation for reusing the `alsoPropagate` array instead of allocating it each time.
Tests:
* All tests was kept and only few tests was modify to work correctly with the changes
* Test was added to verify that the revert fixes the issues.
Fix replication inconsistency on modules that uses key space notifications.
### The Problem
In general, key space notifications are invoked after the command logic was
executed (this is not always the case, we will discuss later about specific
command that do not follow this rules). For example, the `set x 1` will trigger
a `set` notification that will be invoked after the `set` logic was performed, so
if the notification logic will try to fetch `x`, it will see the new data that was written.
Consider the scenario on which the notification logic performs some write
commands. for example, the notification logic increase some counter,
`incr x{counter}`, indicating how many times `x` was changed.
The logical order by which the logic was executed is has follow:
```
set x 1
incr x{counter}
```
The issue is that the `set x 1` command is added to the replication buffer
at the end of the command invocation (specifically after the key space
notification logic was invoked and performed the `incr` command).
The replication/aof sees the commands in the wrong order:
```
incr x{counter}
set x 1
```
In this specific example the order is less important.
But if, for example, the notification would have deleted `x` then we would
end up with primary-replica inconsistency.
### The Solution
Put the command that cause the notification in its rightful place. In the
above example, the `set x 1` command logic was executed before the
notification logic, so it should be added to the replication buffer before
the commands that is invoked by the notification logic. To achieve this,
without a major code refactoring, we save a placeholder in the replication
buffer, when finishing invoking the command logic we check if the command
need to be replicated, and if it does, we use the placeholder to add it to the
replication buffer instead of appending it to the end.
To be efficient and not allocating memory on each command to save the
placeholder, the replication buffer array was modified to reuse memory
(instead of allocating it each time we want to replicate commands).
Also, to avoid saving a placeholder when not needed, we do it only for
WRITE or MAY_REPLICATE commands.
#### Additional Fixes
* Expire and Eviction notifications:
* Expire/Eviction logical order was to first perform the Expire/Eviction
and then the notification logic. The replication buffer got this in the
other way around (first notification effect and then the `del` command).
The PR fixes this issue.
* The notification effect and the `del` command was not wrap with
`multi-exec` (if needed). The PR also fix this issue.
* SPOP command:
* On spop, the `spop` notification was fired before the command logic
was executed. The change in this PR would have cause the replication
order to be change (first `spop` command and then notification `logic`)
although the logical order is first the notification logic and then the
`spop` logic. The right fix would have been to move the notification to
be fired after the command was executed (like all the other commands),
but this can be considered a breaking change. To overcome this, the PR
keeps the current behavior and changes the `spop` code to keep the right
logical order when pushing commands to the replication buffer. Another PR
will follow to fix the SPOP properly and match it to the other command (we
split it to 2 separate PR's so it will be easy to cherry-pick this PR to 7.0 if
we chose to).
#### Unhanded Known Limitations
* key miss event:
* On key miss event, if a module performed some write command on the
event (using `RM_Call`), the `dirty` counter would increase and the read
command that cause the key miss event would be replicated to the replication
and aof. This problem can also happened on a write command that open
some keys but eventually decides not to perform any action. We decided
not to handle this problem on this PR because the solution is complex
and will cause additional risks in case we will want to cherry-pick this PR.
We should decide if we want to handle it in future PR's. For now, modules
writers is advice not to perform any write commands on key miss event.
#### Testing
* We already have tests to cover cases where a notification is invoking write
commands that are also added to the replication buffer, the tests was modified
to verify that the replica gets the command in the correct logical order.
* Test was added to verify that `spop` behavior was kept unchanged.
* Test was added to verify key miss event behave as expected.
* Test was added to verify the changes do not break lazy expiration.
#### Additional Changes
* `propagateNow` function can accept a special dbid, -1, indicating not
to replicate `select`. We use this to replicate `multi/exec` on `propagatePendingCommands`
function. The side effect of this change is that now the `select` command
will appear inside the `multi/exec` block on the replication stream (instead of
outside of the `multi/exec` block). Tests was modified to match this new behavior.
Updated the comments for:
info command
lmpopCommand and blmpopCommand
sinterGenericCommand
Fix the missing "key" words in the srandmemberCommand function
For LPOS command, when rank is 0, prompt user that rank could be
positive number or negative number, and add a test for it
When user uses the same input key for SDIFF as the first one, the result must be empty, so we don't need to process the elements to test.
This method is like the one done in zset‘s `zsetChooseDiffAlgorithm`
Co-authored-by: Oran Agra <oran@redislabs.com>
Writable replicas now no longer use the values of expired keys. Expired keys are
deleted when lookupKeyWrite() is used, even on a writable replica. Previously,
writable replicas could use the value of an expired key in write commands such
as INCR, SUNIONSTORE, etc..
This commit also sorts out the mess around the functions lookupKeyRead() and
lookupKeyWrite() so they now indicate what we intend to do with the key and
are not affected by the command calling them.
Multi-key commands like SUNIONSTORE, ZUNIONSTORE, COPY and SORT with the
store option now use lookupKeyRead() for the keys they're reading from (which will
not allow reading from logically expired keys).
This commit also fixes a bug where PFCOUNT could return a value of an
expired key.
Test modules commands have their readonly and write flags updated to correctly
reflect their lookups for reading or writing. Modules are not required to
correctly reflect this in their command flags, but this change is made for
consistency since the tests serve as usage examples.
Fixes#6842. Fixes#7475.
When using SETNX and SETXX we could end up doing key lookup twice.
This presents a small inefficiency price.
Also once we have statistics of write hit and miss they'll be wrong (recording the same key hit twice)
The vulnerability involves changing the default set-max-intset-entries
configuration parameter to a very large value and constructing specially
crafted commands to manipulate sets
In the `HRANDFIELD`, `SRANDMEMBER` and `ZRANDMEMBER` commands,
There are some strategies that could in some rare cases return an unfair random.
these cases are where s small dict happens be be hashed unevenly.
Specifically when `count*ZRANDMEMBER_SUB_STRATEGY_MUL > size`,
using `dictGetRandomKey` to randomize from a dict will result in an unfair random result.
Implements the [LIMIT limit] variant of SINTERCARD/ZINTERCARD.
Now with the LIMIT, we can stop the searching when cardinality
reaching the limit, and return the cardinality ASAP.
Note that in SINTERCARD, the old synatx was: `SINTERCARD key [key ...]`
In order to add a optional parameter, we must break the old synatx.
So the new syntax of SINTERCARD will be consistent with ZINTERCARD.
New syntax: `SINTERCARD numkeys key [key ...] [LIMIT limit]`.
Note that this means that SINTERCARD has a different syntax than
SINTER and SINTERSTORE (taking numkeys argument)
As for ZINTERCARD, we can easily add a optional parameter to it.
New syntax: `ZINTERCARD numkeys key [key ...] [LIMIT limit]`
The `cmd` argument was completely unused, and all the code that bothered to pass it was unnecessary.
This is a prepartion for a future commit that treats subcommands as commands
Reduce dict struct memory overhead
on 64bit dict size goes down from jemalloc's 96 byte bin to its 56 byte bin.
summary of changes:
- Remove `privdata` from callbacks and dict creation. (this affects many files, see "Interface change" below).
- Meld `dictht` struct into the `dict` struct to eliminate struct padding. (this affects just dict.c and defrag.c)
- Eliminate the `sizemask` field, can be calculated from size when needed.
- Convert the `size` field into `size_exp` (exponent), utilizes one byte instead of 8.
Interface change: pass dict pointer to dict type call back functions.
This is instead of passing the removed privdata field. In the future if
we'd like to have private data in the callbacks we can extract it from
the dict type. We can extend dictType to include a custom dict struct
allocator and use it to allocate more data at the end of the dict
struct. This data can then be used to store private data later acccessed
by the callbacks.
Add SINTERCARD and ZINTERCARD commands that are similar to
ZINTER and SINTER but only return the cardinality with minimum
processing and memory overheads.
Co-authored-by: Oran Agra <oran@redislabs.com>
Create new module type enhanced callbacks: mem_usage2, free_effort2, unlink2, copy2.
These will be given a context point from which the module can obtain the key name and database id.
In addition the digest and defrag context can now be used to obtain the key name and database id.
SINTERSTORE would have deleted the dest key right away,
even when later on it is bound to fail on an (WRONGTYPE) error.
With this change it first picks up all the input keys, and only later
delete the dest key if one is empty.
Also add more tests for some commands.
Mainly focus on
- `wrong type error`:
expand test case (base on sinter bug) in non-store variant
add tests for store variant (although it exists in non-store variant, i think it would be better to have same tests)
- the dstkey result when we meet `non-exist key (empty set)` in *store
sdiff:
- improve test case about wrong type error (the one we found in sinter, although it is safe in sdiff)
- add test about using non-exist key (treat it like an empty set)
sdiffstore:
- according to sdiff test case, also add some tests about `wrong type error` and `non-exist key`
- the different is that in sdiffstore, we will consider the `dstkey` result
sunion/sunionstore add more tests (same as above)
sinter/sinterstore also same as above ...
SRANDMEMBER with negative count (non unique) can return the same member
multiple times, and the order of elements in the returned collection matters.
For these reasons returning a RESP3 Set type is not valid for the negative
count, but also not really valid for the positive (unique) variant either (the
command returns an array of random picks, not a set)
This PR also contains a minor optimization for SRANDMEMBER, HRANDFIELD,
and ZRANDMEMBER, to avoid the temporary dict from being rehashed while it grows.
Co-authored-by: Oran Agra <oran@redislabs.com>
New commands:
`HRANDFIELD [<count> [WITHVALUES]]`
`ZRANDMEMBER [<count> [WITHSCORES]]`
Algorithms are similar to the one in SRANDMEMBER.
Both return a simple bulk response when no arguments are given, and an array otherwise.
In case values/scores are requested, RESP2 returns a long array, and RESP3 a nested array.
note: in all 3 commands, the only option that also provides random order is the one with negative count.
Changes to SRANDMEMBER
* Optimization when count is 1, we can use the more efficient algorithm of non-unique random
* optimization: work with sds strings rather than robj
Other changes:
* zzlGetScore: when zset needs to convert string to double, we use safer memcpy (in
case the buffer is too small)
* Solve a "bug" in SRANDMEMBER test: it intended to test a positive count (case 3 or
case 4) and by accident used a negative count
Co-authored-by: xinluton <xinluton@qq.com>
Co-authored-by: Oran Agra <oran@redislabs.com>
Fix wrong server dirty increment in
* spopWithCountCommand
* hsetCommand
* ltrimCommand
* pfaddCommand
Some didn't increment the amount of fields (just one per command).
Others had excessive increments.
Syntax:
COPY <key> <new-key> [DB <dest-db>] [REPLACE]
No support for module keys yet.
Co-authored-by: tmgauss
Co-authored-by: Itamar Haber <itamar@redislabs.com>
Co-authored-by: Oran Agra <oran@redislabs.com>
Add two optional callbacks to the RedisModuleTypeMethods structure, which is `free_effort`
and `unlink`. the `free_effort` callback indicates the effort required to free a module memory.
Currently, if the effort exceeds LAZYFREE_THRESHOLD, the module memory may be released
asynchronously. the `unlink` callback indicates the key has been removed from the DB by redis, and
may soon be freed by a background thread.
Add `lazyfreed_objects` info field, which represents the number of objects that have been
lazyfreed since redis was started.
Add `RM_GetTypeMethodVersion` API, which return the current redis-server runtime value of
`REDISMODULE_TYPE_METHOD_VERSION`. You can use that when calling `RM_CreateDataType` to know
which fields of RedisModuleTypeMethods are gonna be supported and which will be ignored.
Reference the correct "case", case 4, in the comment explaining the need
for case 3, when the number of request items is too close to the
cardinality of the set. Case 4 is indeed the "natural approach"
referenced earlier in that sentence.
This is a rebased version of #3078 originally by shaharmor
with the following patches by TysonAndre made after rebasing
to work with the updated C API:
1. Add 2 more unit tests
(wrong argument count error message, integer over 64 bits)
2. Use addReplyArrayLen instead of addReplyMultiBulkLen.
3. Undo changes to src/help.h - for the ZMSCORE PR,
I heard those should instead be automatically
generated from the redis-doc repo if it gets updated
Motivations:
- Example use case: Client code to efficiently check if each element of a set
of 1000 items is a member of a set of 10 million items.
(Similar to reasons for working on #7593)
- HMGET and ZMSCORE already exist. This may lead to developers deciding
to implement functionality that's best suited to a regular set with a
data type of sorted set or hash map instead, for the multi-get support.
Currently, multi commands or lua scripting to call sismember multiple times
would almost definitely be less efficient than a native smismember
for the following reasons:
- Need to fetch the set from the string every time
instead of reusing the C pointer.
- Using pipelining or multi-commands would result in more bytes sent
and received by the client for the repeated SISMEMBER KEY sections.
- Need to specially encode the data and decode it from the client
for lua-based solutions.
- Proposed solutions using Lua or SADD/SDIFF could trigger writes to
memory, which is undesirable on a redis replica server
or when commands get replicated to replicas.
Co-Authored-By: Shahar Mor <shahar@peer5.com>
Co-Authored-By: Tyson Andre <tysonandre775@hotmail.com>
