viirya commented on a change in pull request #26935:
URL: https://github.com/apache/spark/pull/26935#discussion_r491747706
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/StateStore.scala
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@@ -81,6 +74,42 @@ trait StateStore {
iterator()
}
+ /**
+ * Return an iterator containing all the key-value pairs in the StateStore.
Implementations must
+ * ensure that updates (puts, removes) can be made while iterating over this
iterator.
+ */
+ def iterator(): Iterator[UnsafeRowPair]
+
+ /**
+ * Clean up the resource.
+ *
+ * The method name is to respect backward compatibility on [[StateStore]].
+ */
+ def abort(): Unit
+}
+
+/**
+ * Base trait for a versioned key-value store. Each instance of a `StateStore`
represents a specific
+ * version of state data, and such instances are created through a
[[StateStoreProvider]].
+ *
+ * Unlike [[ReadOnlyStateStore]], `abort` method may not be called if the
`commit` method succeeds
+ * to commit the change. (`hasCommitted` returns `true`.) Otherwise, `abort`
method will be called.
+ * Implementation should deal with resource cleanup in both methods, but also
need to guard with
+ * double resource cleanup.
+ */
+trait StateStore extends ReadOnlyStateStore {
Review comment:
So if we need to check if an instance of state store is read-only, we
can only check if it is `StateStore` but not `ReadOnlyStateStore`? I agree that
enforcing read-only behavior at interface level sounds good. Just it looks a
bit weird that an instance of `StateStore` is also `ReadOnlyStateStore`.
Maybe `ReadStateStore` or `StateStoreForRead` instead of
`ReadOnlyStateStore`? Just suggestion.
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