unified-storage: implement sqlkv Save method (#115458)

* unified-storage: sqlkv save method

pkg/storage/unified/sql/rvmanager/rv_manager.go

@@ -21,6 +21,19 @@ import (
 	"github.com/grafana/grafana/pkg/storage/unified/sql/sqltemplate"
 )
 
+type contextKey string
+
+const txKey contextKey = "rvmanager_db_tx"
+
+func ContextWithTx(ctx context.Context, tx db.Tx) context.Context {
+	return context.WithValue(ctx, txKey, tx)
+}
+
+func TxFromCtx(ctx context.Context) (db.Tx, bool) {
+	tx, ok := ctx.Value(txKey).(db.Tx)
+	return tx, ok
+}
+
 var tracer = otel.Tracer("github.com/grafana/grafana/pkg/storage/unified/sql/rvmanager")
 
 var (
@@ -294,7 +307,7 @@ func (m *ResourceVersionManager) execBatch(ctx context.Context, group, resource
 		// Allocate the RVs
 		for i, guid := range guids {
 			guidToRV[guid] = rv
-			guidToSnowflakeRV[guid] = snowflakeFromRv(rv)
+			guidToSnowflakeRV[guid] = SnowflakeFromRv(rv)
 			rvs[i] = rv
 			rv++
 		}
@@ -353,10 +366,20 @@ func (m *ResourceVersionManager) execBatch(ctx context.Context, group, resource
 
 // takes a unix microsecond rv and transforms into a snowflake format. The timestamp is converted from microsecond to
 // millisecond (the integer division) and the remainder is saved in the stepbits section. machine id is always 0
-func snowflakeFromRv(rv int64) int64 {
+func SnowflakeFromRv(rv int64) int64 {
 	return (((rv / 1000) - snowflake.Epoch) << (snowflake.NodeBits + snowflake.StepBits)) + (rv % 1000)
 }
 
+// helper utility to compare two RVs. The first RV must be in snowflake format. Will convert rv2 to snowflake and retry
+// if comparison fails
+func IsRvEqual(rv1, rv2 int64) bool {
+	if rv1 == rv2 {
+		return true
+	}
+
+	return rv1 == SnowflakeFromRv(rv2)
+}
+
 // Lock locks the resource version for the given key
 func (m *ResourceVersionManager) Lock(ctx context.Context, x db.ContextExecer, group, resource string) (nextRV int64, err error) {
 	// 1. Lock the row and prevent concurrent updates until the transaction is committed