lostluck commented on a change in pull request #15639:
URL: https://github.com/apache/beam/pull/15639#discussion_r720610725
##########
File path: sdks/go/pkg/beam/core/runtime/harness/statecache/statecache.go
##########
@@ -21,25 +21,45 @@
package statecache
import (
+ "io"
"sync"
+ "github.com/apache/beam/sdks/v2/go/pkg/beam/core/typex"
"github.com/apache/beam/sdks/v2/go/pkg/beam/internal/errors"
fnpb "github.com/apache/beam/sdks/v2/go/pkg/beam/model/fnexecution_v1"
)
type token string
-// ReusableInput is a resettable value, notably used to unwind iterators
cheaply
-// and cache materialized side input across invocations.
+// FullValue represents the full runtime value for a data element, incl. the
+// implicit context. The result of a GBK or CoGBK is not a single FullValue.
+// The consumer is responsible for converting the values to the correct type.
+// To represent a nested KV with FullValues, assign a *FullValue to Elm/Elm2.
//
-// Redefined from exec's input.go to avoid a cyclical dependency.
-type ReusableInput interface {
- // Init initializes the value before use.
- Init() error
- // Value returns the side input value.
- Value() interface{}
- // Reset resets the value after use.
- Reset() error
+// Copied from exec/fullvalue.go to avoid cyclical dependencies.
+type FullValue struct {
+ Elm interface{} // Element or KV key.
+ Elm2 interface{} // KV value, if not invalid
+
+ Timestamp typex.EventTime
+ Windows []typex.Window
+ Pane typex.PaneInfo
+}
+
+// Stream is a FullValue reader. It returns io.EOF when complete, but can be
+// prematurely closed.
+//
+// Copied from exec/fullvalue.go to prevent cyclical dependencies.
+type Stream interface {
+ io.Closer
+ Read() (*FullValue, error)
Review comment:
Copying this from exec will not work since exec.FullValue and
statecache.FullValue are different types., so version of Stream won't match the
exec.Stream version. Go doesn't have any co- or contra-variance in it's type
system. (See
https://en.wikipedia.org/wiki/Covariance_and_contravariance_(computer_science))
Instead this package should depend on the exec package, and if the exec
package needs to interact with a cache-like object, it uses an interface on
it's end instead. Afterall, that's how the SideInputAdapters, and state reader
and similar work.
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