feat: introduce a new method MemHookSet (tikv#1362)

Signed-off-by: ekexium <[email protected]>

internal/unionstore/memdb.go

@@ -898,3 +898,8 @@ func (db *MemDB) SetEntrySizeLimit(entryLimit, bufferLimit uint64) {
 func (db *MemDB) setSkipMutex(skip bool) {
 	db.skipMutex = skip
 }
+
+// MemHookSet implements the MemBuffer interface.
+func (db *MemDB) MemHookSet() bool {
+	return db.allocator.memChangeHook.Load() != nil
+}

internal/unionstore/pipelined_memdb.go

@@ -525,3 +525,8 @@ func (p *PipelinedMemDB) GetFlushMetrics() FlushMetrics {
 		WaitDuration: p.flushWaitDuration,
 	}
 }
+
+// MemHookSet implements the MemBuffer interface.
+func (p *PipelinedMemDB) MemHookSet() bool {
+	return p.memChangeHook != nil
+}

internal/unionstore/union_store.go

@@ -212,6 +212,8 @@ type MemBuffer interface {
 	Dirty() bool
 	// SetMemoryFootprintChangeHook sets the hook for memory footprint change.
 	SetMemoryFootprintChangeHook(hook func(uint64))
+	// MemHookSet returns whether the memory footprint change hook is set.
+	MemHookSet() bool
 	// Mem returns the memory usage of MemBuffer.
 	Mem() uint64
 	// Len returns the count of entries in the MemBuffer.

txnkv/transaction/txn.go

@@ -1703,3 +1703,8 @@ func (txn *KVTxn) SetRequestSourceType(tp string) {
 func (txn *KVTxn) SetExplicitRequestSourceType(tp string) {
 	txn.RequestSource.SetExplicitRequestSourceType(tp)
 }
+
+// MemHookSet returns whether the mem buffer has a memory footprint change hook set.
+func (txn *KVTxn) MemHookSet() bool {
+	return txn.us.GetMemBuffer().MemHookSet()
+}