v26.47.0 release notes - #39891

Release notes for the v26.47.0 train. One commit was added per snapshot; the final snapshot sets the real dates. All six snapshots (rc.1–rc.5, final) are now applied — this branch is complete and ready for review.

• Content: 2 Feature sections (TRY_CAST, EXCLUDE ALL NOT NULL CONSTRAINTS), 7 Improvements, 13 Bug Fixes — rc.1 contributed all of it except the top four Bug Fixes: rc.2 added two, and rc.3 and rc.4 one each. rc.5 added no new entries; it amended rc.4's probe-port Bug Fix instead (see below). final adds nothing at all — its tracking issue holds only the unassociated release: bump to version v26.47.0 commit (bed23494d), and the v26.47.0-rc.5 and v26.47.0 tags are 14h28m apart with that bump the only thing between them. Its commit is empty and exists to record on the branch that the snapshot was applied.
• Dates (final, no longer provisional): Cloud 2026-10-22, Self-Managed 2026-10-23. Every RC estimated this same pair from the v26.47.0-rc.1 tag, and the real dates confirmed it — the five RCs compressed into one week rather than pushing the train out — so no published date text changed in the final commit. ⚠️ One thing worth a last look before merge: 2026-10-22 is a Wednesday, one day off the usual Thursday Cloud date (2026-10-23 is the normal Friday Self-Managed day). That is the supplied value and it stands, but if the release owner expected Thursday 2026-10-23 / Friday 2026-10-24, this branch is where to correct it.
• Operator compatibility: row added for v26.47, release date 2026-10-23.
• Branch base: main, whose newest section is ## v26.45.1 — v26.46.0's section is still on its own unmerged branch (v26.46.0 release notes #39690). Expect a top-of-list conflict when both merge; v26.47.0 goes above v26.46.0.

✅ Corrections already on this branch — a final verification pass over the whole assembled section confirmed these and deliberately left them alone:

• rc.1 named a syntax that does not exist. It published "CREATE TABLE ... FROM SOURCE now accepts an ALL COLUMNS NULLABLE option", taking the name from #39680's title and body. At the v26.47.0 tag the option is EXCLUDE ALL NOT NULL CONSTRAINTS (TableFromSourceOptionName::ExcludeAllNotNullConstraints), and NULLABLE is not a lexer keyword at all, so the published syntax would have been a parse error for anyone who copied it. A human editor caught this and replaced the bullet with the {#v26.47-exclude-not-null-constraints} feature section now on the branch. The rc.1 snapshot directory in mz-skills still carries the wrong wording — snapshot directories are the record of what was reviewed at the time and are left untouched.
• rc.5's cross-snapshot rewrite is applied once, including the "Deployments using password, SASL, or OIDC authentication have no separate internal SQL port and continue to be probed on the external one" clause.
• PR citations are stripped from all entries as a deliberate house-style edit, matching how published sections read. PR links remain available in the mz-skills snapshot drafts linked below.

⚠️ Open questions for the release owner — none of these were resolved by final; this branch is the last place to act on them

• Was any rc.4 artifact handed to a customer or used for an upgrade rehearsal? This decides a published entry. #40036 (published as a Bug Fix by rc.4) made the operator probe environmentd's internal SQL port unconditionally, which crashloops deployments using Password, SASL, or OIDC authentication — they have no internal SQL port. #40046 fixed that roughly seven hours later, inside this same unreleased train, so no shipped build (v26.46.1 probes the external port unconditionally) could have hit it. It is therefore recorded as Borderline rather than published as a Bug Fix of its own, and its substance folded into rc.4's bullet as a scoping clause. If an rc.4 build did reach anyone, the crashloop was reachable and #40046 should be published in its own right. Note the author wrote an explicit positive release-note line for it, which is why this is flagged rather than quietly dropped.
• GA announcements — the largest judgment call in this train. Three docs PRs remove preview markers: #39831 (source versioning, CREATE TABLE ... FROM SOURCE), #39836 (replacement materialized views), #39830 (Kafka sink headers, noted as "GA in v26.47"). None changes code, so all three were held; drafted wording for each is in omitted.md. Which are actually GA in v26.47.0 and should be announced? Note v26.46.0 published Kafka sink message attribution as private preview — if the header goes GA here, this release should say so rather than repeat the preview framing.
• GCS blob read throughput (#39906, held in rc.2): restores the read throughput GCS deployments lost when #39351 — already shipped — forced HTTP/2 and collapsed per-request connections into one. It is selected by persist_blob_http_pool, verified to default to off at the v26.47.0-rc.2 tag, and the author notes "the default should eventually be 'GCS-only'". Is persist_blob_http_pool being set to gcs for v26.47.0? If so this is a clear win to publish for GCP users, who carry the regression today; drafted wording is in rc.2's omitted.md.
• SUBSCRIBE soft assertions (#37611, #39764, both held): drafted as Bug Fixes, then pulled back. Both failures come from soft_assert_or_log!, which panics only where soft assertions are enabled and otherwise logs; neither PR says what a release build does. Are soft assertions on in the environments customers run? If yes, both are publishable as drafted in omitted.md.
• Console Freshness page (#39340, held): a complete new Monitoring > Freshness page, gated behind freshness-page-CNS164, off in both Cloud and self-managed, and the LaunchDarkly flag is not yet created. If it is turned on for v26.47.0, this likely deserves a Feature heading.
• PostgreSQL sources ingesting during a snapshot (#39419, #39479, held): adding a large table to an existing source would no longer stall the tables already hydrated — but storage_persist_sink_description_lookahead is Duration::ZERO at the tag. Publish if the lookahead is being enabled.
• Coalesced materialized-view sink batches (#37591, held): measures ~67% fewer blob writes and ~54% smaller state diffs, at ~10 ms added p50 latency on small writes, but compute_mv_sink_shared_batch_max_bytes is 0 at the tag. Publish (with the latency cost stated) if the staged rollout reaches customers in this release.
• MCP 2026-07-28 conformance checks (#39694, #39695, held): enable_mcp_protocol_2026_07_28 is false at the tag. If the revision is being served, these belong together as one Improvement.
• Refresh strategy columns (#39597, published as an Improvement): this renames aligned_to → aligned_to_expression and at → at_expression and changes their type. It is a breaking change for anyone selecting them, in a schema documented as unstable — it may warrant more prominence than a bullet.
• Retained input after ALTER SINK ... SET FROM (from rc.3's #37653): the PR records a pre-existing gap it does not fix — after SET FROM, the old upstream relation stays held, and therefore un-compactable, until the sink is dropped or environmentd restarts. It is not something this release changed, so it is out of these notes, but it is a real footgun for the blue/green pattern that sql/alter-sink.md recommends SET FROM for. Should the ALTER SINK page or the blue/green guide call it out?
• Operator upgrade shows pending changes (from rc.4's #40036): the probe-port change alters the generated environmentd StatefulSet, so after upgrading the operator, existing environments report pending changes and pick up the new port on their next rollout — they are not restarted on their own. That is an upgrade consequence rather than something the release changed, so it is out of the notes, but a Self-Managed operator who cannot account for the pending-changes state may read it as a problem. The v26.47 upgrade guide looks like the right venue.

Snapshot drafts (with PR links) in mz-skills:

• rc.1: release_notes.md / omitted.md
• rc.2: release_notes.md / omitted.md
• rc.3: release_notes.md / omitted.md
• rc.4: release_notes.md / omitted.md
• rc.5: release_notes.md / omitted.md
• final: release_notes.md / omitted.md

Borderline PRs omitted: rc.1: 14 — omitted.md#borderline, rc.2: 2 — omitted.md#borderline, rc.3: 0 — omitted.md#borderline, rc.4: 0 — omitted.md#borderline, rc.5: 1 — omitted.md#borderline, final: 0 — omitted.md#borderline

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