This release marks a significant step forward in Redis compatibility: the new redis-databases option closes the gap of SELECT command between Kvrocks and Redis. Applications that rely on Redis's multi-database model can now migrate to Kvrocks without any code changes.
Beyond that, this release expands TimeSeries and TDigest command coverage and tightens replication reliability — all while upgrading the C++ standard to C++20 and RocksDB to v10.10.1.
Highlights:
- Support SELECT database — Kvrocks can now emulate Redis's multi-database model, unblocking migrations from Redis deployments that use
SELECTto switch between logical databases - New TimeSeries commands — TS.MREVRANGE, TS.QUERYINDEX, and TS.ALTER round out the time-series API surface for analytics-heavy workloads
- New TDigest commands — TDIGEST.RANK, TDIGEST.REVRANK, TDIGEST.BYRANK, and TDIGEST.BYREVRANK enable percentile and rank queries on streaming data
Support SELECT Database
Kvrocks uses a namespace mechanism as its multi-tenancy primitive, which differs from Redis's numbered logical databases. Before this release, issuing SELECT against Kvrocks was a no-op — the command was accepted but had no effect. v2.15.0 introduces the redis-databases option (#3294) to bridge this gap and make SELECT behave as it does in Redis.
The option takes a numeric value:
redis-databases 0— default;SELECTremains a no-op (existing namespace behavior is unchanged)redis-databases N(N > 0) — enables Redis-style database switching with N logical databases; requires that no namespaces are configured
# kvrocks.conf
redis-databases 16
Once enabled, clients can issue SELECT as they would against Redis:
127.0.0.1:6666> SELECT 3
# OK
127.0.0.1:6666[3]> SET mykey "hello"
# OK — stored in database 3
New TimeSeries Commands
Kvrocks's RedisTimeSeries compatibility layer gains three commands that are essential for production time-series pipelines. TS.MREVRANGE lets you query multiple series in reverse chronological order in a single round-trip. TS.QUERYINDEX filters series by label predicates without pulling data. TS.ALTER modifies retention and label metadata on existing series without recreating them.
# Create series with labels
127.0.0.1:6666> TS.CREATE metrics:us-east:1 LABELS region us-east
127.0.0.1:6666> TS.CREATE metrics:us-east:2 LABELS region us-east
127.0.0.1:6666> TS.CREATE temperature:NYC LABELS sensor temperature location NYC
# Add samples
TS.ADD metrics:us-east:1 * 42
127.0.0.1:6666> TS.ADD metrics:us-east:2 * 87
# Query the last 10 samples across all "region=us-east" series, newest first
127.0.0.1:6666> TS.MREVRANGE - + FILTER region=us-east COUNT 10
# Find series matching a label filter (no data returned)
127.0.0.1:6666> TS.QUERYINDEX sensor=temperature location=NYC
# Change retention period on an existing series
127.0.0.1:6666> TS.ALTER temperature:NYC RETENTION 86400000
New TDigest Commands
The TDigest sketch — useful for approximate quantile computation over streaming data — now supports rank-based queries. TDIGEST.RANK returns the estimated rank of a value within the digest. TDIGEST.BYRANK returns the value at a given rank. The REV variants work in descending order. Together these four commands make it practical to answer questions like "what percentile is this latency?" or "what is the p99 value?" directly from Kvrocks.
# Create a TDigest key
127.0.0.1:6666> TDIGEST.CREATE latency
# Insert observations
127.0.0.1:6666> TDIGEST.ADD latency 120 95 200 340 88 150
# What rank is the value 150?
127.0.0.1:6666> TDIGEST.RANK latency 150
# What value sits at rank 4?
127.0.0.1:6666> TDIGEST.BYRANK latency 4
# What value sits at rank 4 counting from the top?
127.0.0.1:6666> TDIGEST.BYREVRANK latency 4
End
Except for that, this release also includes a number of bug fixes and performance improvements. For the full list of changes, please refer to changelog to see all the details. We encourage users to upgrade to v2.15.0 to take advantage of these new features and improvements. As always, we welcome feedback and contributions from the community!