Fix obtaning snashot though DTMD

knizhnik · knizhnik · commit 536d5562e7b1 · 2015-09-09T22:48:46.000+03:00
diff --git a/contrib/pg_xtm/libdtm.c b/contrib/pg_xtm/libdtm.c
@@ -163,6 +163,30 @@ bool DtmGlobalStartTransaction(DTMConn dtm, GlobalTransactionId *gtid) {
 	return ok;
 }
 
+void DtmInitSnapshot(Snapshot snapshot)
+{
+	if (snapshot->xip == NULL)
+	{
+		/*
+		 * First call for this snapshot. Snapshot is same size whether or not
+		 * we are in recovery, see later comments.
+		 */
+		snapshot->xip = (TransactionId *)
+			malloc(GetMaxSnapshotXidCount() * sizeof(TransactionId));
+		if (snapshot->xip == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_OUT_OF_MEMORY),
+					 errmsg("out of memory")));
+		Assert(snapshot->subxip == NULL);
+		snapshot->subxip = (TransactionId *)
+			malloc(GetMaxSnapshotSubxidCount() * sizeof(TransactionId));
+		if (snapshot->subxip == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_OUT_OF_MEMORY),
+					 errmsg("out of memory")));
+	}
+}
+
 // Asks DTM for a fresh snapshot. Returns 'true' on success, or 'false'
 // otherwise.
 bool DtmGlobalGetSnapshot(DTMConn dtm, NodeId nodeid, TransactionId xid, Snapshot s) {
@@ -191,8 +215,7 @@ bool DtmGlobalGetSnapshot(DTMConn dtm, NodeId nodeid, TransactionId xid, Snapsho
 	s->xcnt = number;
 	Assert(s->xcnt == number); // the number should definitely fit into xcnt field size
 
-	if (s->xip) free(s->xip);
-	s->xip = malloc(s->xcnt * sizeof(TransactionId));
+	DtmInitSnapshot(s);
 	for (i = 0; i < s->xcnt; i++) {
 		if (!dtm_read_hex16(dtm, &number)) return false;
 		s->xip[i] = number;
diff --git a/contrib/pg_xtm/libdtm.h b/contrib/pg_xtm/libdtm.h
@@ -3,6 +3,7 @@
 
 #include "postgres.h"
 #include "utils/snapmgr.h"
+#include "storage/procarray.h"
 #include "access/clog.h"
 
 #define INVALID_XID 0
@@ -19,6 +20,8 @@ DTMConn DtmConnect(char *host, int port);
 // bad things will happen.
 void DtmDisconnect(DTMConn dtm);
 
+void DtmInitSnapshot(Snapshot snapshot);
+
 typedef struct {
     TransactionId* xids;
     NodeId* nodes;
diff --git a/contrib/pg_xtm/pg_dtm.c b/contrib/pg_xtm/pg_dtm.c
@@ -37,6 +37,7 @@ void _PG_fini(void);
 
 static void DtmEnsureConnection(void);
 static Snapshot DtmGetSnapshot(Snapshot snapshot);
+static void DtmCopySnapshot(Snapshot dst, Snapshot src);
 static XidStatus DtmGetTransactionStatus(TransactionId xid, XLogRecPtr *lsn);
 static void DtmSetTransactionStatus(TransactionId xid, int nsubxids, TransactionId *subxids, XidStatus status, XLogRecPtr lsn);
 static bool DtmTransactionIsRunning(TransactionId xid);
@@ -58,12 +59,21 @@ static void DtmEnsureConnection(void)
     }
 }
 
-extern SnapshotData CatalogSnapshotData;
+static void DtmCopySnapshot(Snapshot dst, Snapshot src)
+{
+    DtmInitSnapshot(dst);
+    memcpy(dst->xip, src->xip, src->xcnt*sizeof(TransactionId));
+    dst->xmax = src->xmax;
+    dst->xmin = src->xmin;
+    dst->xcnt = src->xcnt;
+    dst->curcid = src->curcid;
+}
 
 static Snapshot DtmGetSnapshot(Snapshot snapshot)
 {
-    if (DtmHasSnapshot && snapshot->satisfies == HeapTupleSatisfiesMVCC) { 
-        return &DtmSnapshot;
+    if (DtmHasSnapshot) { 
+        CopyDtmSnapshot(snapshot, &DtmSnapshot);
+        return snapshot;
     }
     return GetLocalSnapshotData(snapshot);
 }

Original file line number	Diff line number	Diff line change
`@@ -37,6 +37,7 @@ void _PG_fini(void);`
`37`	`37`
`38`	`38`	`static void DtmEnsureConnection(void);`
`39`	`39`	`static Snapshot DtmGetSnapshot(Snapshot snapshot);`
	`40`	`+static void DtmCopySnapshot(Snapshot dst, Snapshot src);`
`40`	`41`	`static XidStatus DtmGetTransactionStatus(TransactionId xid, XLogRecPtr *lsn);`
`41`	`42`	`static void DtmSetTransactionStatus(TransactionId xid, int nsubxids, TransactionId *subxids, XidStatus status, XLogRecPtr lsn);`
`42`	`43`	`static bool DtmTransactionIsRunning(TransactionId xid);`
`@@ -58,12 +59,21 @@ static void DtmEnsureConnection(void)`
`58`	`59`	`}`
`59`	`60`	`}`
`60`	`61`
`61`		`-extern SnapshotData CatalogSnapshotData;`
	`62`	`+static void DtmCopySnapshot(Snapshot dst, Snapshot src)`
	`63`	`+{`
	`64`	`+ DtmInitSnapshot(dst);`
	`65`	`+ memcpy(dst->xip, src->xip, src->xcnt*sizeof(TransactionId));`
	`66`	`+ dst->xmax = src->xmax;`
	`67`	`+ dst->xmin = src->xmin;`
	`68`	`+ dst->xcnt = src->xcnt;`
	`69`	`+ dst->curcid = src->curcid;`
	`70`	`+}`
`62`	`71`
`63`	`72`	`static Snapshot DtmGetSnapshot(Snapshot snapshot)`
`64`	`73`	`{`
`65`		`- if (DtmHasSnapshot && snapshot->satisfies == HeapTupleSatisfiesMVCC) {`
`66`		`- return &DtmSnapshot;`
	`74`	`+ if (DtmHasSnapshot) {`
	`75`	`+ CopyDtmSnapshot(snapshot, &DtmSnapshot);`
	`76`	`+ return snapshot;`
`67`	`77`	`}`
`68`	`78`	`return GetLocalSnapshotData(snapshot);`
`69`	`79`	`}`