Clickhouse just turned postgres's wal into its own pipeline. walshadow, out september 10, consumes…
clickhouse just turned postgres's wal into its own pipeline. walshadow, out september 10, consumes the physical wal stream directly and turns clickhouse into an analytical standby with sub-second lag.
the replication debate skipped logical decoding.
Context
ClickHouse's blog post of September 10, 2026 introduces WalShadow, an open-source engine that replicates Postgres data to ClickHouse directly from physical WAL. It does not use Postgres logical replication or slots, and it consumes the physical WAL stream outside the source, decodes it and writes ClickHouse-native blocks, which the post calls effectively turning ClickHouse into an analytical physical standby. It covers initial load, continuous replication, schema evolution, restart recovery and planned switchover. A managed version is in private preview on ClickHouse Managed Postgres. The post reports commit-to-visible latency of around 200 ms against about 50 ms for a Postgres physical replica and about 10 seconds for PeerDB, and 289K rows per second sustained.
The latency and throughput numbers are ClickHouse's own and vendor-reported, and the test setup and hardware were not itemized in the text read. The post says most managed Postgres services do not expose physical WAL to customers, so self-managed access or ClickHouse Managed Postgres is needed. The replication debate skipped logical decoding is the author's take.
Watch next
- General availability of the managed preview and independent latency tests.
Sources
- ClickHouse: introducing WalShadow (September 10, 2026)clickhouse.com
Provenance
The note above is reproduced unedited from the original post, first published on Threads on 23 September 2026 at 02:17 IST. Sources are the papers and datasets the note draws on.
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