Encapsulate snapshot used for reading stripes in cstore_metadata_tables

cstore.h

@@ -285,6 +285,7 @@ extern void DeleteDataFileMetadataRowIfExists(Oid relfilenode);
 extern void InitCStoreDataFileMetadata(Oid relfilenode, int blockRowCount);
 extern void InsertStripeMetadataRow(Oid relfilenode, StripeMetadata *stripe);
 extern DataFileMetadata * ReadDataFileMetadata(Oid relfilenode, bool missingOk);
+extern uint64 GetHighestUsedAddress(Oid relfilenode);
 extern void SaveStripeSkipList(Oid relfilenode, uint64 stripe,
 							   StripeSkipList *stripeSkipList,
 							   TupleDesc tupleDescriptor);

cstore_metadata_tables.c

@@ -43,6 +43,7 @@ typedef struct
 	EState *estate;
 } ModifyState;
 
+static List * ReadDataFileStripeList(Oid relfilenode, Snapshot snapshot);
 static Oid CStoreStripesRelationId(void);
 static Oid CStoreStripesIndexRelationId(void);
 static Oid CStoreDataFilesRelationId(void);
@@ -345,17 +346,8 @@ InsertStripeMetadataRow(Oid relfilenode, StripeMetadata *stripe)
 DataFileMetadata *
 ReadDataFileMetadata(Oid relfilenode, bool missingOk)
 {
-	Oid cstoreStripesOid = InvalidOid;
-	Relation cstoreStripes = NULL;
-	Relation index = NULL;
-	TupleDesc tupleDescriptor = NULL;
-	ScanKeyData scanKey[1];
-	SysScanDesc scanDescriptor = NULL;
-	HeapTuple heapTuple;
-	bool found = false;
-
 	DataFileMetadata *datafileMetadata = palloc0(sizeof(DataFileMetadata));
-	found = ReadCStoreDataFiles(relfilenode, &datafileMetadata->blockRowCount);
+	bool found = ReadCStoreDataFiles(relfilenode, &datafileMetadata->blockRowCount);
 	if (!found)
 	{
 		if (!missingOk)
@@ -369,6 +361,56 @@ ReadDataFileMetadata(Oid relfilenode, bool missingOk)
 		}
 	}
 
+	datafileMetadata->stripeMetadataList =
+		ReadDataFileStripeList(relfilenode, GetTransactionSnapshot());
+
+	return datafileMetadata;
+}
+
+
+/*
+ * GetHighestUsedAddress returns the highest used address for the given
+ * relfilenode across all active and inactive transactions.
+ */
+uint64
+GetHighestUsedAddress(Oid relfilenode)
+{
+	uint64 highestUsedAddress = 0;
+	ListCell *stripeMetadataCell = NULL;
+	List *stripeMetadataList = NIL;
+
+	SnapshotData SnapshotDirty;
+	InitDirtySnapshot(SnapshotDirty);
+
+	stripeMetadataList = ReadDataFileStripeList(relfilenode, &SnapshotDirty);
+
+	foreach(stripeMetadataCell, stripeMetadataList)
+	{
+		StripeMetadata *stripe = lfirst(stripeMetadataCell);
+		uint64 lastByte = stripe->fileOffset + stripe->dataLength - 1;
+		highestUsedAddress = Max(highestUsedAddress, lastByte);
+	}
+
+	return highestUsedAddress;
+}
+
+
+/*
+ * ReadDataFileStripeList reads the stripe list for a given relfilenode
+ * in the given snapshot.
+ */
+static List *
+ReadDataFileStripeList(Oid relfilenode, Snapshot snapshot)
+{
+	List *stripeMetadataList = NIL;
+	Oid cstoreStripesOid = InvalidOid;
+	Relation cstoreStripes = NULL;
+	Relation index = NULL;
+	TupleDesc tupleDescriptor = NULL;
+	ScanKeyData scanKey[1];
+	SysScanDesc scanDescriptor = NULL;
+	HeapTuple heapTuple;
+
 	ScanKeyInit(&scanKey[0], Anum_cstore_stripes_relfilenode,
 				BTEqualStrategyNumber, F_OIDEQ, Int32GetDatum(relfilenode));
 
@@ -403,16 +445,14 @@ ReadDataFileMetadata(Oid relfilenode, bool missingOk)
 		stripeMetadata->rowCount = DatumGetInt64(
 			datumArray[Anum_cstore_stripes_row_count - 1]);
 
-		datafileMetadata->stripeMetadataList = lappend(
-			datafileMetadata->stripeMetadataList,
-			stripeMetadata);
+		stripeMetadataList = lappend(stripeMetadataList, stripeMetadata);
 	}
 
 	systable_endscan_ordered(scanDescriptor);
 	index_close(index, NoLock);
 	heap_close(cstoreStripes, NoLock);
 
-	return datafileMetadata;
+	return stripeMetadataList;
 }
 
 

cstore_tableam.c

@@ -601,6 +601,8 @@ cstore_vacuum_rel(Relation rel, VacuumParams *params,
 	/* this should have been resolved by vacuum.c until now */
 	Assert(params->truncate != VACOPT_TERNARY_DEFAULT);
 
+	LogRelationStats(rel, elevel);
+
 	/*
 	 * We don't have updates, deletes, or concurrent updates, so all we
 	 * care for now is truncating the unused space at the end of storage.
@@ -609,8 +611,6 @@ cstore_vacuum_rel(Relation rel, VacuumParams *params,
 	{
 		TruncateCStore(rel, elevel);
 	}
-
-	LogRelationStats(rel, elevel);
 }
 
 
@@ -727,8 +727,7 @@ TruncateCStore(Relation rel, int elevel)
 	PGRUsage ru0;
 	BlockNumber old_rel_pages = 0;
 	BlockNumber new_rel_pages = 0;
-	DataFileMetadata *metadata = NULL;
-	ListCell *stripeMetadataCell = NULL;
+	SmgrAddr highestPhysicalAddress;
 
 	pg_rusage_init(&ru0);
 
@@ -765,17 +764,15 @@ TruncateCStore(Relation rel, int elevel)
 	old_rel_pages = smgrnblocks(rel->rd_smgr, MAIN_FORKNUM);
 	RelationCloseSmgr(rel);
 
-	metadata = ReadDataFileMetadata(rel->rd_node.relNode, false);
-
-	/* loop over stripes and find max used block */
-	foreach(stripeMetadataCell, metadata->stripeMetadataList)
-	{
-		StripeMetadata *stripe = lfirst(stripeMetadataCell);
-		uint64 lastByte = stripe->fileOffset + stripe->dataLength - 1;
-		SmgrAddr addr = logical_to_smgr(lastByte);
-		new_rel_pages = Max(new_rel_pages, addr.blockno + 1);
-	}
+	/*
+	 * Due to the AccessExclusive lock there's no danger that
+	 * new stripes be added beyond highestPhysicalAddress while
+	 * we're truncating.
+	 */
+	highestPhysicalAddress =
+		logical_to_smgr(GetHighestUsedAddress(rel->rd_node.relNode));
 
+	new_rel_pages = highestPhysicalAddress.blockno + 1;
 	if (new_rel_pages == old_rel_pages)
 	{
 		UnlockRelation(rel, AccessExclusiveLock);

expected/am_vacuum.out

@@ -135,13 +135,13 @@ SELECT pg_size_pretty(pg_relation_size('t'));
 COMMIT;
 -- vacuum should truncate the relation to the usable space
 VACUUM VERBOSE t;
-INFO:  "t": truncated 7 to 2 pages
-DETAIL:  CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s
 INFO:  statistics for "t":
-total file size: 16384, total data size: 10754
+total file size: 57344, total data size: 10754
 total row count: 2530, stripe count: 3, average rows per stripe: 843
 block count: 3, containing data for dropped columns: 0, none compressed: 3, pglz compressed: 0
 
+INFO:  "t": truncated 7 to 2 pages
+DETAIL:  CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.00 s
 SELECT pg_size_pretty(pg_relation_size('t'));
  pg_size_pretty 
 ----------------

expected/am_vacuum_vs_insert.out

@@ -10,12 +10,12 @@ step s1-begin:
 step s1-insert: 
     INSERT INTO test_vacuum_vs_insert SELECT i, 2 * i FROM generate_series(1, 3) i;
 
-s2: INFO:  "test_vacuum_vs_insert": stopping truncate due to conflicting lock request
 s2: INFO:  statistics for "test_vacuum_vs_insert":
 total file size: 8192, total data size: 26
 total row count: 3, stripe count: 1, average rows per stripe: 3
 block count: 2, containing data for dropped columns: 0, none compressed: 2, pglz compressed: 0
 
+s2: INFO:  "test_vacuum_vs_insert": stopping truncate due to conflicting lock request
 step s2-vacuum: 
     VACUUM VERBOSE test_vacuum_vs_insert;