storage: add RevertRange

pkg/roachpb/api.go

@@ -477,6 +477,9 @@ func (*DeleteRangeRequest) Method() Method { return DeleteRange }
 // Method implements the Request interface.
 func (*ClearRangeRequest) Method() Method { return ClearRange }
 
+// Method implements the Request interface.
+func (*RevertRangeRequest) Method() Method { return RevertRange }
+
 // Method implements the Request interface.
 func (*ScanRequest) Method() Method { return Scan }
 
@@ -630,6 +633,12 @@ func (crr *ClearRangeRequest) ShallowCopy() Request {
 	return &shallowCopy
 }
 
+// ShallowCopy implements the Request interface.
+func (crr *RevertRangeRequest) ShallowCopy() Request {
+	shallowCopy := *crr
+	return &shallowCopy
+}
+
 // ShallowCopy implements the Request interface.
 func (sr *ScanRequest) ShallowCopy() Request {
 	shallowCopy := *sr
@@ -1027,7 +1036,12 @@ func (drr *DeleteRangeRequest) flags() int {
 // Note that ClearRange commands cannot be part of a transaction as
 // they clear all MVCC versions.
 func (*ClearRangeRequest) flags() int { return isWrite | isRange | isAlone }
-func (*ScanRequest) flags() int       { return isRead | isRange | isTxn | updatesReadTSCache | needsRefresh }
+
+// Note that RevertRange commands cannot be part of a transaction as
+// they clear all MVCC versions above their target time.
+func (*RevertRangeRequest) flags() int { return isWrite | isRange | isAlone }
+
+func (*ScanRequest) flags() int { return isRead | isRange | isTxn | updatesReadTSCache | needsRefresh }
 func (*ReverseScanRequest) flags() int {
 	return isRead | isRange | isReverse | isTxn | updatesReadTSCache | needsRefresh
 }

pkg/roachpb/api.proto

@@ -293,6 +293,33 @@ message ClearRangeResponse {
   ResponseHeader header = 1 [(gogoproto.nullable) = false, (gogoproto.embed) = true];
 }
 
+
+// A RevertRangeRequest specifies a range of keys in which to clear all MVCC
+// revisions more recent than some TargetTime from the underlying engine, thus
+// reverting the range (from the perspective of an MVCC scan) to that time.
+//
+// Note: if a more recent MVCC revision of a key has caused an earlier revision
+// to be GC'ed, it is no longer possible to revert to that earlier revision and
+// instead clearing the more recent revision would simply delete that key. It is
+// up to the caller to consider if this is applicable to their usage and if so,
+// take steps to avoid it. Some future work could add the concept of a
+// gc.revert_ttl to prevent GC until the newer revision meets an age threshold.
+message RevertRangeRequest {
+  option (gogoproto.equal) = true;
+
+  RequestHeader header = 1 [(gogoproto.nullable) = false, (gogoproto.embed) = true];
+
+  // TargetTime specifies a the time to which to "revert" the range by clearing any
+  // MVCC key with a strictly higher timestamp.
+  util.hlc.Timestamp target_time = 2 [(gogoproto.nullable) = false];
+}
+
+// A RevertRangeResponse is the return value from the RevertRange() method.
+message RevertRangeResponse {
+  ResponseHeader header = 1 [(gogoproto.nullable) = false, (gogoproto.embed) = true];
+}
+
+
 // ScanOptions is a collection of options for a batch of scans. The options
 // apply to all the scans in the batch.
 //
@@ -1549,6 +1576,7 @@ message RequestUnion {
     DeleteRequest delete = 5;
     DeleteRangeRequest delete_range = 6;
     ClearRangeRequest clear_range = 38;
+    RevertRangeRequest revert_range = 48;
     ScanRequest scan = 7;
     BeginTransactionRequest begin_transaction = 8;
     EndTransactionRequest end_transaction = 9;
@@ -1600,6 +1628,7 @@ message ResponseUnion {
     DeleteResponse delete = 5;
     DeleteRangeResponse delete_range = 6;
     ClearRangeResponse clear_range = 38;
+    RevertRangeResponse revert_range = 48;
     ScanResponse scan = 7;
     BeginTransactionResponse begin_transaction = 8;
     EndTransactionResponse end_transaction = 9;