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What changed in PostgreSQL 19
The PostgreSQL 19 Beta 1 announcement states that data checksums can be enabled or disabled online. A cluster does not need a restart or reinitialization for the change. That is the headline difference from earlier releases, where checksums were chosen when a cluster was created or changed through an offline procedure.
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The official commit announcement, published on 2026-04-03 by Daniel Gustafsson, describes the same capability in more technical terms: “This allows data checksums to be enabled, or disabled, in a running cluster without restricting access to the cluster during processing.” The phrase to note is “without restricting access.” The commit description says normal access need not be blocked while the change is processed. It does not say the change is free of cost, and it does not give a timing figure.
How this differs from pg_checksums
Readers who have used the pg_checksums utility should not assume it is the new online mechanism. It is still documented as an offline tool. The server must be shut down cleanly before it runs. When it enables checksums, it rewrites blocks in the relation files, and the manual warns that the cluster and any other program writing to its data directory must not be started while the operation runs.
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The two workflows therefore differ on three points:
| Point of comparison | PostgreSQL 19 online enablement | pg_checksums utility (offline) |
|---|---|---|
| Required server state | Running cluster, per the Beta 1 announcement | Cleanly shut down server |
| Access during the change | Need not be restricted, per the commit announcement | No other program may write to the data directory; the cluster must not be started |
| What is rewritten | Not specified in the sources reviewed | Relation-file blocks are rewritten when enabling |
| Source | PostgreSQL 19 Beta 1 announcement; commit announcement dated 2026-04-03 | Official pg_checksums documentation |
If your operations plan relies on the offline utility, nothing in the PostgreSQL 19 announcements changes that procedure. The online capability is an additional option for clusters that run the beta or a later release.
What checksums protect
When data checksums are enabled, the checksum of a data page is updated when the page is written and verified when it is read. That is the protection: a page that has been corrupted on disk can be detected when it is read back, instead of being silently returned to a query.
The scope is narrower than many administrators assume. PostgreSQL’s documentation says checksums cover data pages. They do not cover internal data structures or temporary files. The setting is also cluster-wide. You cannot turn it on for one database or one table while leaving others unchecked.
How to check the current state
Run the following statement from any SQL session to see whether checksums are active:
SHOW data_checksums;returns the checksum state for the cluster.- The setting is read-only. It reports state; it does not change it.
- PostgreSQL 19’s preset-options reference lists
data_checksumsas a boolean. Use the same check before and after any change to confirm the result.
Release status and what is not yet established
As of early October 2026, the PostgreSQL 19 release documentation showed Beta 4, announced September 24, 2026, and listed the final release date as unknown. Treat the online enablement described here as beta behavior. Final release notes and the final data-checksum documentation may change the interface details or the caveats.
Several points are not established by the official sources reviewed:
- Managed services. The announcements do not show whether managed PostgreSQL providers expose the online control to customers. Check your provider’s documentation before planning around it.
- Performance. No measured figure for processing time, I/O cost, or performance impact has been published in these sources. Plan for a test on a copy of your data before running it in production.
- Adoption. No statistic on how widely checksums are used has been established from these sources.
What is established is narrow but useful: PostgreSQL 19 can change the checksum state of a running cluster, the change does not require a restart or reinitialization, and access need not be restricted during processing. Confirm the final behavior against the release notes before you depend on it.
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