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new 93b48ec6c0 docs: mention querying durable state changes by slices
(#3595)
93b48ec6c0 is described below
commit 93b48ec6c047178956f0c3cc2c9d9eddc0935550
Author: PJ Fanning <[email protected]>
AuthorDate: Fri Oct 9 05:22:36 2026 +0100
docs: mention querying durable state changes by slices (#3595)
Motivation:
The durable state Persistence Query page says the query is only based
on tags, but persistence-query also provides
DurableStateStoreBySliceQuery with changesBySlices and
currentChangesBySlices.
Modification:
Describe both ways of querying durable state changes: by tag with
DurableStateStoreQuery, and by slices with DurableStateStoreBySliceQuery
(marked @ApiMayChange), including what a slice is and the
sliceForPersistenceId/sliceRanges helpers, and link to the
EventsBySlice section. Note that support depends on the state store
plugin.
Result:
Users know the by-slices query exists.
Tests:
- Not run - docs only
References:
None - found during a review of the docs
---
docs/src/main/paradox/durable-state/persistence-query.md | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/docs/src/main/paradox/durable-state/persistence-query.md
b/docs/src/main/paradox/durable-state/persistence-query.md
index 8a68ae6337..146837cbe9 100644
--- a/docs/src/main/paradox/durable-state/persistence-query.md
+++ b/docs/src/main/paradox/durable-state/persistence-query.md
@@ -35,7 +35,18 @@ durable state is stored in a database and fetched as an
asynchronous stream to t
durable state, provided by the `DurableStateStoreQuery` interface, is used to
implement tag based searches in
Pekko Projections.
-At present the query is based on _tags_. So if you have not tagged your
objects, this query cannot be used.
+Changes to durable state can be queried in two ways, depending on which
queries the state store plugin implements:
+
+* by _tag_, with `changes` and `currentChanges` of
@apidoc[pekko.persistence.query.*.DurableStateStoreQuery].
+ If you have not tagged your objects, this query cannot be used.
+* by _slices_, with `changesBySlices` and `currentChangesBySlices` of
@apidoc[pekko.persistence.query.typed.*.DurableStateStoreBySliceQuery]
+ for a given entity type and slice range. A slice is deterministically
defined based on the persistence id, and the
+ purpose is to evenly distribute all persistence ids over the slices.
`sliceForPersistenceId` returns the slice of a
+ persistence id and `sliceRanges` splits all slices into a given number of
ranges, for example to run one query per range.
+ This is similar to
@ref:[EventsBySlice](../persistence-query.md#eventsbyslice-and-currenteventsbyslice)
for event
+ sourced entities. This API may change.
+
+Refer to the documentation of the state store plugin you are using for which
of these queries it supports.
The example below shows how to get the `DurableStateStoreQuery` from the
`DurableStateStoreRegistry` extension.
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