Add create/restore/release savepoint context methods to XTM

Author: knizhnik

contrib/mmts/multimaster.c

@@ -146,9 +146,12 @@ static bool MtmDetectGlobalDeadLock(PGPROC* proc);
 static void MtmAddSubtransactions(MtmTransState* ts, TransactionId* subxids, int nSubxids);
 static char const* MtmGetName(void);
 static size_t MtmGetTransactionStateSize(void);
-static void MtmSerializeTransactionState(void* ctx);
-static void MtmDeserializeTransactionState(void* ctx);
-static void MtmInitializeSequence(int64* start, int64* step);
+static void   MtmSerializeTransactionState(void* ctx);
+static void   MtmDeserializeTransactionState(void* ctx);
+static void   MtmInitializeSequence(int64* start, int64* step);
+static void*  MtmCreateSavepointContext(void);
+static void   MtmRestoreSavepointContext(void* ctx);
+static void   MtmReleaseSavepointContext(void* ctx);
 
 static void MtmCheckClusterLock(void);
 static void MtmCheckSlots(void);
@@ -197,7 +200,10 @@ static TransactionManager MtmTM =
 	MtmGetTransactionStateSize,
 	MtmSerializeTransactionState,
 	MtmDeserializeTransactionState,
-	MtmInitializeSequence
+	MtmInitializeSequence,
+	MtmCreateSavepointContext,
+	MtmRestoreSavepointContext,
+	MtmReleaseSavepointContext
 };
 
 char const* const MtmNodeStatusMnem[] = 
@@ -466,6 +472,20 @@ MtmInitializeSequence(int64* start, int64* step)
 	}
 }
 
+static void* MtmCreateSavepointContext(void)
+{
+	return (void*)(size_t)MtmTx.containsDML;
+}
+
+static void  MtmRestoreSavepointContext(void* ctx)
+{
+	MtmTx.containsDML = ctx != NULL;
+}
+
+static void  MtmReleaseSavepointContext(void* ctx)
+{
+}
+
 
 /*
  * -------------------------------------------

src/backend/access/transam/xact.c

@@ -176,6 +176,7 @@ typedef struct TransactionStateData
 	SubTransactionId subTransactionId;	/* my subxact ID */
 	char	   *name;			/* savepoint name, if any */
 	int			savepointLevel; /* savepoint level */
+	void*       savepointContext;        /* savepoint XTM context */
 	TransState	state;			/* low-level state */
 	TBlockState blockState;		/* high-level state */
 	int			nestingLevel;	/* transaction nesting depth */
@@ -4095,6 +4096,7 @@ DefineSavepoint(char *name)
 			 */
 			if (name)
 				s->name = MemoryContextStrdup(TopTransactionContext, name);
+			s->savepointContext = TM->CreateSavepointContext();
 			break;
 
 			/* These cases are invalid. */
@@ -4227,6 +4229,7 @@ ReleaseSavepoint(List *options)
 	{
 		Assert(xact->blockState == TBLOCK_SUBINPROGRESS);
 		xact->blockState = TBLOCK_SUBRELEASE;
+		TM->ReleaseSavepointContext(xact->savepointContext);
 		if (xact == target)
 			break;
 		xact = xact->parent;
@@ -4346,9 +4349,11 @@ RollbackToSavepoint(List *options)
 		else
 			elog(FATAL, "RollbackToSavepoint: unexpected state %s",
 				 BlockStateAsString(xact->blockState));
+		TM->ReleaseSavepointContext(xact->savepointContext);
 		xact = xact->parent;
 		Assert(PointerIsValid(xact));
 	}
+	TM->RestoreSavepointContext(xact->savepointContext);
 
 	/* And mark the target as "restart pending" */
 	if (xact->blockState == TBLOCK_SUBINPROGRESS)

src/backend/access/transam/xtm.c

@@ -52,13 +52,27 @@ PgDeserializeTransactionState(void* ctx)
 {
 }
 
-void PgInitializeSequence(int64* init, int64* step)
+void 
+PgInitializeSequence(int64* init, int64* step)
 {
 	*init = 1;
 	*step = 1;
 }
 
 
+void* PgCreateSavepointContext(void)
+{
+	return NULL;
+}
+
+void PgRestoreSavepointContext(void* ctx)
+{
+}
+
+void PgReleaseSavepointContext(void* ctx)
+{
+}
+
 TransactionManager PgTM = {
 	PgTransactionIdGetStatus,
 	PgTransactionIdSetTreeStatus,
@@ -73,7 +87,10 @@ TransactionManager PgTM = {
 	PgGetTransactionStateSize,
 	PgSerializeTransactionState,
 	PgDeserializeTransactionState,
-	PgInitializeSequence
+	PgInitializeSequence,
+	PgCreateSavepointContext,
+	PgRestoreSavepointContext,
+	PgReleaseSavepointContext
 };
 
 TransactionManager *TM = &PgTM;

src/include/access/xtm.h

@@ -94,6 +94,22 @@ typedef struct
 	 */
 	void        (*InitializeSequence)(int64* start, int64* step);
 
+	/*
+	 * Create custom savepoint context.
+	 * This function can be used to accociate any data with savepoint which will be used by RestoreSavepointContext function to restore context
+	 */
+	void*       (*CreateSavepointContext)(void);
+
+	/*
+	 * Restore context saved by CreateSavepointContext
+	 */
+	void        (*RestoreSavepointContext)(void* ctx);
+
+	/*
+	 * Release context saved by CreateSavepointContext
+	 */
+	void        (*ReleaseSavepointContext)(void* ctx);
+
 }	TransactionManager;
 
 /* Get pointer to transaction manager: actually returns content of TM variable */
@@ -128,6 +144,9 @@ extern size_t PgGetTransactionStateSize(void);
 extern void PgSerializeTransactionState(void* ctx);
 extern void PgDeserializeTransactionState(void* ctx);
 extern void PgInitializeSequence(int64* start, int64* step);
+extern void* PgCreateSavepointContext(void);
+extern void PgRestoreSavepointContext(void*);
+extern void PgReleaseSavepointContext(void*);
 
 
 #endif