chore: add migrate operation interface (#387)

Please see inline comments

cmd/signozschemamigrator/schema_migrator/op.go

@@ -0,0 +1,35 @@
+package schemamigrator
+
+// Operation is the interface that all operations must implement.
+// An Operation that is not mutation, idempotent and lightweight is expected
+// to complete almost immediately given there are no blocking items in the
+// distributed_ddl_queue.
+// Such operations are completed synchronously and allow the release upgrade
+// to proceed.
+// All other operations are run asynchronously in the background and do not
+// block the release upgrade.
+type Operation interface {
+ // ToSQL returns the SQL for the alter operation
+ ToSQL() string
+ // IsMutation returns true if the operation is a mutation
+ IsMutation() bool
+ // IsIdempotent returns true if the operation is idempotent
+ // This is used to determine if the operation can be retried in case of a
+ // failure.
+ IsIdempotent() bool
+ // IsLightweight returns true if the operation is lightweight
+ // The lightweight operations are the ones that either modify the metadata or
+ // drop the delete from disk as opposed to the ones that re-write the whole
+ // data parts.
+ IsLightweight() bool
+
+ // OnCluster returns a new operation with the cluster name set
+ // This is used when the operation is run on a specific cluster
+ OnCluster(string) Operation
+
+ // WithReplication returns a new operation with the replication set
+ WithReplication() Operation
+
+ // ShouldWaitForDistributionQueue returns true if the operation should wait for the distribution queue to be empty
+ ShouldWaitForDistributionQueue() (bool, string, string)
+}