batcheval: add range tombstone support for DeleteRange

This patch adds a parameter `UseExperimentalRangeTombstone` for
`DeleteRange`, which deletes the span using an MVCC range tombstone.
This must only be called after checking
`storage.CanUseExperimentalMVCCRangeTombstones()`, which ensures the
`ExperimentalMVCCRangeTombstones` version gate and
`COCKROACH_EXPERIMENTAL_MVCC_RANGE_TOMBSTONES` environment variable are
set.

Did I mention that MVCC range tombstones are experimental? They are
currently under active development, and are not respected by the KV or
MVCC APIs, nor are they persisted. This patch simply sets up the
plumbing for it.

Release note: None

docs/generated/settings/settings-for-tenants.txt

@@ -174,4 +174,4 @@ trace.debug.enable	boolean	false	if set, traces for recent requests can be seen
 trace.jaeger.agent	string		the address of a Jaeger agent to receive traces using the Jaeger UDP Thrift protocol, as <host>:<port>. If no port is specified, 6381 will be used.
 trace.opentelemetry.collector	string		address of an OpenTelemetry trace collector to receive traces using the otel gRPC protocol, as <host>:<port>. If no port is specified, 4317 will be used.
 trace.zipkin.collector	string		the address of a Zipkin instance to receive traces, as <host>:<port>. If no port is specified, 9411 will be used.
-version	version	21.2-62	set the active cluster version in the format '<major>.<minor>'
+version	version	21.2-64	set the active cluster version in the format '<major>.<minor>'

docs/generated/settings/settings.html

@@ -186,6 +186,6 @@
 <tr><td><code>trace.jaeger.agent</code></td><td>string</td><td><code></code></td><td>the address of a Jaeger agent to receive traces using the Jaeger UDP Thrift protocol, as <host>:<port>. If no port is specified, 6381 will be used.</td></tr>
 <tr><td><code>trace.opentelemetry.collector</code></td><td>string</td><td><code></code></td><td>address of an OpenTelemetry trace collector to receive traces using the otel gRPC protocol, as <host>:<port>. If no port is specified, 4317 will be used.</td></tr>
 <tr><td><code>trace.zipkin.collector</code></td><td>string</td><td><code></code></td><td>the address of a Zipkin instance to receive traces, as <host>:<port>. If no port is specified, 9411 will be used.</td></tr>
-<tr><td><code>version</code></td><td>version</td><td><code>21.2-62</code></td><td>set the active cluster version in the format '<major>.<minor>'</td></tr>
+<tr><td><code>version</code></td><td>version</td><td><code>21.2-64</code></td><td>set the active cluster version in the format '<major>.<minor>'</td></tr>
 </tbody>
 </table>

pkg/clusterversion/cockroach_versions.go

@@ -269,6 +269,9 @@ const (
 	DontProposeWriteTimestampForLeaseTransfers
 	// TenantSettingsTable adds the system table for tracking tenant usage.
 	TenantSettingsTable
+	// ExperimentalMVCCRangeTombstones enables the use of highly experimental MVCC
+	// range tombstones.
+	ExperimentalMVCCRangeTombstones
 
 	// *************************************************
 	// Step (1): Add new versions here.
@@ -429,6 +432,10 @@ var versionsSingleton = keyedVersions{
 		Key:     TenantSettingsTable,
 		Version: roachpb.Version{Major: 21, Minor: 2, Internal: 62},
 	},
+	{
+		Key:     ExperimentalMVCCRangeTombstones,
+		Version: roachpb.Version{Major: 21, Minor: 2, Internal: 64},
+	},
 
 	// *************************************************
 	// Step (2): Add new versions here.

pkg/kv/kvserver/batcheval/cmd_delete_range.go

@@ -19,6 +19,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/storage"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
+	"github.com/cockroachdb/errors"
 )
 
 func init() {
@@ -49,6 +50,22 @@ func DeleteRange(
 	h := cArgs.Header
 	reply := resp.(*roachpb.DeleteRangeResponse)
 
+	// Use experimental MVCC range tombstone if requested. The caller is expected
+	// to have checked storage.CanUseExperimentalMVCCRangeTombstones() first.
+	if args.UseExperimentalRangeTombstone {
+		if args.Inline {
+			return result.Result{}, errors.AssertionFailedf("Inline can't be used with range tombstones")
+		}
+		if args.ReturnKeys {
+			return result.Result{}, errors.AssertionFailedf(
+				"ReturnKeys can't be used with range tombstones")
+		}
+		maxIntents := storage.MaxIntentsPerWriteIntentError.Get(&cArgs.EvalCtx.ClusterSettings().SV)
+		err := storage.ExperimentalMVCCDeleteRangeUsingTombstone(
+			ctx, readWriter, cArgs.Stats, args.Key, args.EndKey, h.Timestamp, maxIntents)
+		return result.Result{}, err
+	}
+
 	var timestamp hlc.Timestamp
 	if !args.Inline {
 		timestamp = h.Timestamp

pkg/roachpb/api.go

@@ -1225,6 +1225,11 @@ func (*DeleteRequest) flags() flag {
 }
 
 func (drr *DeleteRangeRequest) flags() flag {
+	// DeleteRangeRequest using MVCC range tombstones cannot be transactional,
+	// and thus cannot span ranges.
+	if drr.UseExperimentalRangeTombstone {
+		return isWrite | isRange | isAlone | appliesTSCache
+	}
 	// DeleteRangeRequest has different properties if the "inline" flag is set.
 	// This flag indicates that the request is deleting inline MVCC values,
 	// which cannot be deleted transactionally - inline DeleteRange will thus

pkg/roachpb/api.proto

@@ -348,6 +348,17 @@ message DeleteRangeRequest {
   // Inline values cannot be deleted transactionally; a DeleteRange with
   // "inline" set to true will fail if it is executed within a transaction.
   bool inline = 4;
+  // If enabled, the range is deleted using an MVCC range tombstone, which is a
+  // cheap constant-time operation. This option cannot be used in a transaction,
+  // and it cannot be combined with Inline or ReturnKeys.
+  //
+  // The caller must check storage.CanUseExperimentalMVCCRangeTombstones()
+  // before enabling this parameter.
+  //
+  // This parameter is EXPERIMENTAL: range tombstones are under active
+  // development, and have severe limitations including being ignored by all
+  // KV and MVCC APIs and only being stored in memory.
+  bool use_experimental_range_tombstone = 5;
 }
 
 // A DeleteRangeResponse is the return value from the DeleteRange()

pkg/storage/mvcc.go

@@ -20,10 +20,12 @@ import (
 	"sync"
 	"time"
 
+	"github.com/cockroachdb/cockroach/pkg/clusterversion"
 	"github.com/cockroachdb/cockroach/pkg/keys"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/uncertainty"
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
 	"github.com/cockroachdb/cockroach/pkg/settings"
+	"github.com/cockroachdb/cockroach/pkg/settings/cluster"
 	"github.com/cockroachdb/cockroach/pkg/storage/enginepb"
 	"github.com/cockroachdb/cockroach/pkg/util/envutil"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
@@ -84,6 +86,19 @@ var rocksdbConcurrency = envutil.EnvOrDefaultInt(
 		return max
 	}())
 
+// CanUseExperimentalMVCCRangeTombstones returns true if MVCC range tombstones
+// are enabled. Callers must check this before using range tombstones.
+//
+// These are EXPERIMENTAL: range tombstones are under active
+// development, and have severe limitations including being ignored by all
+// KV and MVCC APIs and only being stored in memory.
+func CanUseExperimentalMVCCRangeTombstones(ctx context.Context, st *cluster.Settings) bool {
+	// TODO(erikgrinaker): Consider using a cluster setting rather than an
+	// environment variable once range tombstones are fully implemented.
+	return st.Version.IsActive(ctx, clusterversion.ExperimentalMVCCRangeTombstones) &&
+		envutil.EnvOrDefaultBool("COCKROACH_EXPERIMENTAL_MVCC_RANGE_TOMBSTONES", false)
+}
+
 // MakeValue returns the inline value.
 func MakeValue(meta enginepb.MVCCMetadata) roachpb.Value {
 	return roachpb.Value{RawBytes: meta.RawBytes}