Refactor COPY to accept a generic tuple source

src/backend/distributed/commands/multi_copy.c

@@ -8,9 +8,9 @@
  * COPY ... FROM commands on distributed tables. CitusCopyFrom parses the input
  * from stdin, a program, or a file, and decides to copy new rows to existing
  * shards or new shards based on the partition method of the distributed table.
- * If copy is run a worker node, CitusCopyFrom calls CopyFromWorkerNode which
+ * If copy is run a worker node, CitusCopyFrom calls LocalCopyFromWorkerNode
- * parses the master node copy options and handles communication with the master
+ * which parses the master node copy options and handles communication with
- * node.
+ * the master node.
  *
  * It opens a new connection for every shard placement and uses the PQputCopyData
  * function to copy the data. Because PQputCopyData transmits data, asynchronously,
@@ -128,6 +128,15 @@
 #include "utils/memutils.h"
 
 
+/* struct type to use a local COPY .. FROM statement as a tuple source */
+typedef struct LocalCopyContext
+{
+	CopyStmt *copyStatement;
+	CopyState copyState;
+	EState *executorState;
+} LocalCopyContext;
+
+
 /* constant used in binary protocol */
 static const char BinarySignature[11] = "PGCOPY\n\377\r\n\0";
 
@@ -136,21 +145,28 @@ static PGconn *masterConnection = NULL;
 
 
 /* Local functions forward declarations */
-static void CopyFromWorkerNode(CopyStmt *copyStatement, char *completionTag);
+static CopyTupleSource * CreateLocalCopyTupleSource(CopyStmt *copyStatement);
-static void CopyToExistingShards(CopyStmt *copyStatement, char *completionTag);
+static void LocalCopyOpen(void *context, Relation relation,
-static void CopyToNewShards(CopyStmt *copyStatement, char *completionTag, Oid relationId);
+						  ErrorContextCallback *errorCallback);
+static bool LocalCopyNextTuple(void *context, Datum *columnValues, bool *columnNulls);
+static void LocalCopyClose(void *context);
+static uint64 LocalCopyFromWorkerNode(CopyStmt *copyStatement);
+static uint64 CopyToExistingShards(CopyTupleSource *tupleSource, RangeVar *relation);
+static uint64 CopyToNewShards(CopyTupleSource *tupleSource, RangeVar *relation,
+							  Oid relationId);
 static char MasterPartitionMethod(RangeVar *relation);
 static void RemoveMasterOptions(CopyStmt *copyStatement);
-static void OpenCopyTransactions(CopyStmt *copyStatement,
+static void OpenCopyTransactions(RangeVar *relation, ShardConnections *shardConnections,
-								 ShardConnections *shardConnections, bool stopOnFailure,
+								 bool stopOnFailure, bool useBinaryCopyFormat);
-								 bool useBinaryCopyFormat);
+static CopyOutState CreateCopyOutState(TupleDesc tupleDescriptor,
+									   MemoryContext rowContext);
 static bool CanUseBinaryCopyFormat(TupleDesc tupleDescription,
 								   CopyOutState rowOutputState);
 static List * MasterShardPlacementList(uint64 shardId);
 static List * RemoteFinalizedShardPlacementList(uint64 shardId);
 static void SendCopyBinaryHeaders(CopyOutState copyOutState, List *connectionList);
 static void SendCopyBinaryFooters(CopyOutState copyOutState, List *connectionList);
-static StringInfo ConstructCopyStatement(CopyStmt *copyStatement, int64 shardId,
+static StringInfo ConstructCopyStatement(RangeVar *relation, int64 shardId,
 										 bool useBinaryCopyFormat);
 static void SendCopyDataToAll(StringInfo dataBuffer, List *connectionList);
 static void SendCopyDataToPlacement(StringInfo dataBuffer, PGconn *connection,
@@ -158,8 +174,8 @@ static void SendCopyDataToPlacement(StringInfo dataBuffer, PGconn *connection,
 static void EndRemoteCopy(List *connectionList, bool stopOnFailure);
 static void ReportCopyError(PGconn *connection, PGresult *result);
 static uint32 AvailableColumnCount(TupleDesc tupleDescriptor);
-static void StartCopyToNewShard(ShardConnections *shardConnections,
+static void StartCopyToNewShard(RangeVar *relation, ShardConnections *shardConnections,
-								CopyStmt *copyStatement, bool useBinaryCopyFormat);
+								bool useBinaryCopyFormat);
 static int64 MasterCreateEmptyShard(char *relationName);
 static int64 CreateEmptyShard(char *relationName);
 static int64 RemoteCreateEmptyShard(char *relationName);
@@ -186,6 +202,7 @@ void
 CitusCopyFrom(CopyStmt *copyStatement, char *completionTag)
 {
 	bool isCopyFromWorker = false;
+	uint64 processedRowCount = 0;
 
 	/* disallow COPY to/from file or program except for superusers */
 	if (copyStatement->filename != NULL && !superuser())
@@ -211,30 +228,140 @@ CitusCopyFrom(CopyStmt *copyStatement, char *completionTag)
 	isCopyFromWorker = IsCopyFromWorker(copyStatement);
 	if (isCopyFromWorker)
 	{
-		CopyFromWorkerNode(copyStatement, completionTag);
+		processedRowCount = LocalCopyFromWorkerNode(copyStatement);
 	}
 	else
 	{
-		Oid relationId = RangeVarGetRelid(copyStatement->relation, NoLock, false);
+		CopyTupleSource *tupleSource = CreateLocalCopyTupleSource(copyStatement);
+		RangeVar *relation = copyStatement->relation;
+
+		processedRowCount = CopyTupleSourceToShards(tupleSource, relation);
+	}
+
+	if (completionTag != NULL)
+	{
+		snprintf(completionTag, COMPLETION_TAG_BUFSIZE,
+				 "COPY " UINT64_FORMAT, processedRowCount);
+	}
+
+	XactModificationLevel = XACT_MODIFICATION_DATA;
+}
+
+
+/*
+ * CopyTupleSourceToShards copies the tuples provided by tupleSource to
+ * the shards of the given relation. For hash- and range-distributed
+ * tables it copies to the existing shards and for append-distributed
+ * tables it adds a new shard.
+ */
+uint64
+CopyTupleSourceToShards(CopyTupleSource *tupleSource, RangeVar *relation)
+{
+	uint64 processedRowCount = 0;
+
+	Oid relationId = RangeVarGetRelid(relation, NoLock, false);
 	char partitionMethod = PartitionMethod(relationId);
 
-		if (partitionMethod == DISTRIBUTE_BY_HASH || partitionMethod ==
+	if (partitionMethod == DISTRIBUTE_BY_HASH || partitionMethod == DISTRIBUTE_BY_RANGE)
-			DISTRIBUTE_BY_RANGE)
 	{
-			CopyToExistingShards(copyStatement, completionTag);
+		processedRowCount = CopyToExistingShards(tupleSource, relation);
 	}
 	else if (partitionMethod == DISTRIBUTE_BY_APPEND)
 	{
-			CopyToNewShards(copyStatement, completionTag, relationId);
+		processedRowCount = CopyToNewShards(tupleSource, relation, relationId);
 	}
 	else
 	{
 		ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 						errmsg("unsupported partition method")));
 	}
+
+	return processedRowCount;
 }
 
-	XactModificationLevel = XACT_MODIFICATION_DATA;
+
+/*
+ * CreateLocalCopyTupleSource creates and returns a tuple source for a local
+ * COPY .. FROM command.
+ */
+static CopyTupleSource *
+CreateLocalCopyTupleSource(CopyStmt *copyStatement)
+{
+	LocalCopyContext *localCopyContext = palloc0(sizeof(LocalCopyContext));
+	CopyTupleSource *tupleSource = palloc0(sizeof(CopyTupleSource));
+	EState *executorState = CreateExecutorState();
+
+	localCopyContext->copyStatement = copyStatement;
+	localCopyContext->copyState = NULL;
+	localCopyContext->executorState = executorState;
+
+	tupleSource->context = localCopyContext;
+	tupleSource->rowContext = GetPerTupleMemoryContext(executorState);
+	tupleSource->Open = LocalCopyOpen;
+	tupleSource->NextTuple = LocalCopyNextTuple;
+	tupleSource->Close = LocalCopyClose;
+
+	return tupleSource;
+}
+
+
+/*
+ * LocalCopyOpen opens the COPY input for copying into the given relation.
+ */
+static void
+LocalCopyOpen(void *context, Relation relation, ErrorContextCallback *errorCallback)
+{
+	LocalCopyContext *localCopyContext = (LocalCopyContext *) context;
+
+	CopyStmt *copyStatement = localCopyContext->copyStatement;
+	CopyState copyState = NULL;
+
+	copyState = BeginCopyFrom(relation,
+							  copyStatement->filename,
+							  copyStatement->is_program,
+							  copyStatement->attlist,
+							  copyStatement->options);
+
+	localCopyContext->copyState = copyState;
+
+	errorCallback->callback = CopyFromErrorCallback;
+	errorCallback->arg = (void *) copyState;
+	errorCallback->previous = error_context_stack;
+}
+
+
+/*
+ * LocalCopyNextTuple reads a tuple from the COPY input. columnValeus
+ * will contain values for all columns, using the default values for
+ * columns that were not provided by the COPY command. columnNulls
+ * is true for columns that contain NULL. LocalCopyNextTuple returns
+ * if the end of the input is reached and true otherwise.
+ */
+static bool
+LocalCopyNextTuple(void *context, Datum *columnValues, bool *columnNulls)
+{
+	LocalCopyContext *localCopyContext = (LocalCopyContext *) context;
+
+	CopyState copyState = localCopyContext->copyState;
+	EState *executorState = localCopyContext->executorState;
+	ExprContext *expressionContext = GetPerTupleExprContext(executorState);
+
+	bool nextRowFound = NextCopyFrom(copyState, expressionContext, columnValues,
+									 columnNulls, NULL);
+
+	return nextRowFound;
+}
+
+
+/*
+ * LocalCopyClose closes the COPY input.
+ */
+static void
+LocalCopyClose(void *context)
+{
+	LocalCopyContext *localCopyContext = (LocalCopyContext *) context;
+
+	EndCopyFrom(localCopyContext->copyState);
 }
 
 
@@ -259,16 +386,17 @@ IsCopyFromWorker(CopyStmt *copyStatement)
 
 
 /*
- * CopyFromWorkerNode implements the COPY table_name FROM ... from worker nodes
+ * LocalCopyFromWorkerNode implements the COPY table_name FROM ... from worker
- * for append-partitioned tables.
+ * nodes for append-partitioned tables.
  */
-static void
+static uint64
-CopyFromWorkerNode(CopyStmt *copyStatement, char *completionTag)
+LocalCopyFromWorkerNode(CopyStmt *copyStatement)
 {
 	NodeAddress *masterNodeAddress = MasterNodeAddress(copyStatement);
 	char *nodeName = masterNodeAddress->nodeName;
 	int32 nodePort = masterNodeAddress->nodePort;
 	char *nodeUser = CurrentUserName();
+	uint64 processedRowCount = 0;
 
 	if (XactModificationLevel > XACT_MODIFICATION_NONE)
 	{
@@ -285,17 +413,19 @@ CopyFromWorkerNode(CopyStmt *copyStatement, char *completionTag)
 		PGresult *queryResult = NULL;
 		Oid relationId = InvalidOid;
 		char partitionMethod = 0;
+		CopyTupleSource *tupleSource = NULL;
 
 		/* strip schema name for local reference */
-		char *schemaName = copyStatement->relation->schemaname;
+		RangeVar *relation = copyStatement->relation;
-		copyStatement->relation->schemaname = NULL;
+		char *schemaName = relation->schemaname;
+		relation->schemaname = NULL;
 
-		relationId = RangeVarGetRelid(copyStatement->relation, NoLock, false);
+		relationId = RangeVarGetRelid(relation, NoLock, false);
 
 		/* put schema name back */
-		copyStatement->relation->schemaname = schemaName;
+		relation->schemaname = schemaName;
 
-		partitionMethod = MasterPartitionMethod(copyStatement->relation);
+		partitionMethod = MasterPartitionMethod(relation);
 		if (partitionMethod != DISTRIBUTE_BY_APPEND)
 		{
 			ereport(ERROR, (errmsg("copy from worker nodes is only supported "
@@ -317,7 +447,9 @@ CopyFromWorkerNode(CopyStmt *copyStatement, char *completionTag)
 		 */
 		RemoveMasterOptions(copyStatement);
 
-		CopyToNewShards(copyStatement, completionTag, relationId);
+		tupleSource = CreateLocalCopyTupleSource(copyStatement);
+
+		processedRowCount = CopyToNewShards(tupleSource, relation, relationId);
 
 		/* commit metadata transactions */
 		queryResult = PQexec(masterConnection, "COMMIT");
@@ -341,6 +473,8 @@ CopyFromWorkerNode(CopyStmt *copyStatement, char *completionTag)
 		PG_RE_THROW();
 	}
 	PG_END_TRY();
+
+	return processedRowCount;
 }
 
 
@@ -349,10 +483,10 @@ CopyFromWorkerNode(CopyStmt *copyStatement, char *completionTag)
  * range-partitioned tables where there are already shards into which to copy
  * rows.
  */
-static void
+static uint64
-CopyToExistingShards(CopyStmt *copyStatement, char *completionTag)
+CopyToExistingShards(CopyTupleSource *tupleSource, RangeVar *relation)
 {
-	Oid tableId = RangeVarGetRelid(copyStatement->relation, NoLock, false);
+	Oid tableId = RangeVarGetRelid(relation, NoLock, false);
 	char *relationName = get_rel_name(tableId);
 	Relation distributedRelation = NULL;
 	TupleDesc tupleDescriptor = NULL;
@@ -363,8 +497,6 @@ CopyToExistingShards(CopyStmt *copyStatement, char *completionTag)
 	FmgrInfo *compareFunction = NULL;
 	bool hasUniformHashDistribution = false;
 	DistTableCacheEntry *cacheEntry = DistributedTableCacheEntry(tableId);
-	const char *delimiterCharacter = "\t";
-	const char *nullPrintCharacter = "\\N";
 
 	int shardCount = 0;
 	List *shardIntervalList = NULL;
@@ -375,11 +507,6 @@ CopyToExistingShards(CopyStmt *copyStatement, char *completionTag)
 	ShardConnections *shardConnections = NULL;
 	List *connectionList = NIL;
 
-	EState *executorState = NULL;
-	MemoryContext executorTupleContext = NULL;
-	ExprContext *executorExpressionContext = NULL;
-
-	CopyState copyState = NULL;
 	CopyOutState copyOutState = NULL;
 	FmgrInfo *columnOutputFunctions = NULL;
 	uint64 processedRowCount = 0;
@@ -446,25 +573,7 @@ CopyToExistingShards(CopyStmt *copyStatement, char *completionTag)
 		useBinarySearch = true;
 	}
 
-	/* initialize copy state to read from COPY data source */
+	copyOutState = CreateCopyOutState(tupleDescriptor, tupleSource->rowContext);
-	copyState = BeginCopyFrom(distributedRelation,
-							  copyStatement->filename,
-							  copyStatement->is_program,
-							  copyStatement->attlist,
-							  copyStatement->options);
-
-	executorState = CreateExecutorState();
-	executorTupleContext = GetPerTupleMemoryContext(executorState);
-	executorExpressionContext = GetPerTupleExprContext(executorState);
-
-	copyOutState = (CopyOutState) palloc0(sizeof(CopyOutStateData));
-	copyOutState->delim = (char *) delimiterCharacter;
-	copyOutState->null_print = (char *) nullPrintCharacter;
-	copyOutState->null_print_client = (char *) nullPrintCharacter;
-	copyOutState->binary = CanUseBinaryCopyFormat(tupleDescriptor, copyOutState);
-	copyOutState->fe_msgbuf = makeStringInfo();
-	copyOutState->rowcontext = executorTupleContext;
-
 	columnOutputFunctions = ColumnOutputFunctions(tupleDescriptor, copyOutState->binary);
 
 	/*
@@ -480,10 +589,10 @@ CopyToExistingShards(CopyStmt *copyStatement, char *completionTag)
 	{
 		ErrorContextCallback errorCallback;
 
+		/* open the tuple source */
+		tupleSource->Open(tupleSource->context, distributedRelation, &errorCallback);
+
 		/* set up callback to identify error line number */
-		errorCallback.callback = CopyFromErrorCallback;
-		errorCallback.arg = (void *) copyState;
-		errorCallback.previous = error_context_stack;
 		error_context_stack = &errorCallback;
 
 		/* ensure transactions have unique names on worker nodes */
@@ -498,14 +607,13 @@ CopyToExistingShards(CopyStmt *copyStatement, char *completionTag)
 			bool shardConnectionsFound = false;
 			MemoryContext oldContext = NULL;
 
-			ResetPerTupleExprContext(executorState);
+			MemoryContextReset(tupleSource->rowContext);
 
-			oldContext = MemoryContextSwitchTo(executorTupleContext);
+			oldContext = MemoryContextSwitchTo(tupleSource->rowContext);
 
 			/* parse a row from the input */
-			nextRowFound = NextCopyFrom(copyState, executorExpressionContext,
+			nextRowFound = tupleSource->NextTuple(tupleSource->context, columnValues,
-										columnValues, columnNulls, NULL);
+												  columnNulls);
-
 			if (!nextRowFound)
 			{
 				MemoryContextSwitchTo(oldContext);
@@ -547,7 +655,7 @@ CopyToExistingShards(CopyStmt *copyStatement, char *completionTag)
 			if (!shardConnectionsFound)
 			{
 				/* open connections and initiate COPY on shard placements */
-				OpenCopyTransactions(copyStatement, shardConnections, false,
+				OpenCopyTransactions(relation, shardConnections, false,
 									 copyOutState->binary);
 
 				/* send copy binary headers to shard placements */
@@ -586,7 +694,8 @@ CopyToExistingShards(CopyStmt *copyStatement, char *completionTag)
 			PrepareRemoteTransactions(connectionList);
 		}
 
-		EndCopyFrom(copyState);
+		tupleSource->Close(tupleSource->context);
+
 		heap_close(distributedRelation, NoLock);
 
 		/* check for cancellation one last time before committing */
@@ -614,11 +723,7 @@ CopyToExistingShards(CopyStmt *copyStatement, char *completionTag)
 	CommitRemoteTransactions(connectionList, false);
 	CloseConnections(connectionList);
 
-	if (completionTag != NULL)
+	return processedRowCount;
-	{
-		snprintf(completionTag, COMPLETION_TAG_BUFSIZE,
-				 "COPY " UINT64_FORMAT, processedRowCount);
-	}
 }
 
 
@@ -626,10 +731,10 @@ CopyToExistingShards(CopyStmt *copyStatement, char *completionTag)
  * CopyToNewShards implements the COPY table_name FROM ... for append-partitioned
  * tables where we create new shards into which to copy rows.
  */
-static void
+static uint64
-CopyToNewShards(CopyStmt *copyStatement, char *completionTag, Oid relationId)
+CopyToNewShards(CopyTupleSource *tupleSource, RangeVar *relation, Oid relationId)
 {
-	FmgrInfo *columnOutputFunctions = NULL;
+	uint64 processedRowCount = 0;
 
 	/* allocate column values and nulls arrays */
 	Relation distributedRelation = heap_open(relationId, RowExclusiveLock);
@@ -638,36 +743,18 @@ CopyToNewShards(CopyStmt *copyStatement, char *completionTag, Oid relationId)
 	Datum *columnValues = palloc0(columnCount * sizeof(Datum));
 	bool *columnNulls = palloc0(columnCount * sizeof(bool));
 
-	EState *executorState = CreateExecutorState();
+	ShardConnections *shardConnections = NULL;
-	MemoryContext executorTupleContext = GetPerTupleMemoryContext(executorState);
+	CopyOutState copyOutState = NULL;
-	ExprContext *executorExpressionContext = GetPerTupleExprContext(executorState);
+	FmgrInfo *columnOutputFunctions = NULL;
-
-	const char *delimiterCharacter = "\t";
-	const char *nullPrintCharacter = "\\N";
 
 	/*
 	 * Shard connections should be initialized before the PG_TRY, since it is
 	 * used in PG_CATCH. Otherwise, it may be undefined in the PG_CATCH
 	 * (see sigsetjmp documentation).
 	 */
-	ShardConnections *shardConnections =
+	shardConnections = palloc0(sizeof(ShardConnections));
-		(ShardConnections *) palloc0(sizeof(ShardConnections));
-
-	/* initialize copy state to read from COPY data source */
-	CopyState copyState = BeginCopyFrom(distributedRelation,
-										copyStatement->filename,
-										copyStatement->is_program,
-										copyStatement->attlist,
-										copyStatement->options);
-
-	CopyOutState copyOutState = (CopyOutState) palloc0(sizeof(CopyOutStateData));
-	copyOutState->delim = (char *) delimiterCharacter;
-	copyOutState->null_print = (char *) nullPrintCharacter;
-	copyOutState->null_print_client = (char *) nullPrintCharacter;
-	copyOutState->binary = CanUseBinaryCopyFormat(tupleDescriptor, copyOutState);
-	copyOutState->fe_msgbuf = makeStringInfo();
-	copyOutState->rowcontext = executorTupleContext;
 
+	copyOutState = CreateCopyOutState(tupleDescriptor, tupleSource->rowContext);
 	columnOutputFunctions = ColumnOutputFunctions(tupleDescriptor, copyOutState->binary);
 
 	/* we use a PG_TRY block to close connections on errors (e.g. in NextCopyFrom) */
@@ -675,14 +762,12 @@ CopyToNewShards(CopyStmt *copyStatement, char *completionTag, Oid relationId)
 	{
 		uint64 shardMaxSizeInBytes = (int64) ShardMaxSize * 1024L;
 		uint64 copiedDataSizeInBytes = 0;
-		uint64 processedRowCount = 0;
 
 		/* set up callback to identify error line number */
 		ErrorContextCallback errorCallback;
 
-		errorCallback.callback = CopyFromErrorCallback;
+		/* open the tuple source */
-		errorCallback.arg = (void *) copyState;
+		tupleSource->Open(tupleSource->context, distributedRelation, &errorCallback);
-		errorCallback.previous = error_context_stack;
 
 		while (true)
 		{
@@ -690,16 +775,18 @@ CopyToNewShards(CopyStmt *copyStatement, char *completionTag, Oid relationId)
 			MemoryContext oldContext = NULL;
 			uint64 messageBufferSize = 0;
 
-			ResetPerTupleExprContext(executorState);
+			/* clear the previous tuple's memory */
+			MemoryContextReset(tupleSource->rowContext);
 
-			/* switch to tuple memory context and start showing line number in errors */
+			/* start showing the line number in errors */
 			error_context_stack = &errorCallback;
-			oldContext = MemoryContextSwitchTo(executorTupleContext);
+
+			/* switch to tuple memory context */
+			oldContext = MemoryContextSwitchTo(tupleSource->rowContext);
 
 			/* parse a row from the input */
-			nextRowFound = NextCopyFrom(copyState, executorExpressionContext,
+			nextRowFound = tupleSource->NextTuple(tupleSource->context, columnValues,
-										columnValues, columnNulls, NULL);
+												  columnNulls);
-
 			if (!nextRowFound)
 			{
 				/* switch to regular memory context and stop showing line number in errors */
@@ -723,8 +810,7 @@ CopyToNewShards(CopyStmt *copyStatement, char *completionTag, Oid relationId)
 			if (copiedDataSizeInBytes == 0)
 			{
 				/* create shard and open connections to shard placements */
-				StartCopyToNewShard(shardConnections, copyStatement,
+				StartCopyToNewShard(relation, shardConnections, copyOutState->binary);
-									copyOutState->binary);
 
 				/* send copy binary headers to shard placements */
 				if (copyOutState->binary)
@@ -782,17 +868,12 @@ CopyToNewShards(CopyStmt *copyStatement, char *completionTag, Oid relationId)
 			MasterUpdateShardStatistics(shardConnections->shardId);
 		}
 
-		EndCopyFrom(copyState);
+		tupleSource->Close(tupleSource->context);
+
 		heap_close(distributedRelation, NoLock);
 
 		/* check for cancellation one last time before returning */
 		CHECK_FOR_INTERRUPTS();
-
-		if (completionTag != NULL)
-		{
-			snprintf(completionTag, COMPLETION_TAG_BUFSIZE,
-					 "COPY " UINT64_FORMAT, processedRowCount);
-		}
 	}
 	PG_CATCH();
 	{
@@ -804,6 +885,8 @@ CopyToNewShards(CopyStmt *copyStatement, char *completionTag, Oid relationId)
 		PG_RE_THROW();
 	}
 	PG_END_TRY();
+
+	return processedRowCount;
 }
 
 
@@ -920,7 +1003,7 @@ RemoveMasterOptions(CopyStmt *copyStatement)
  * shard placements.
  */
 static void
-OpenCopyTransactions(CopyStmt *copyStatement, ShardConnections *shardConnections,
+OpenCopyTransactions(RangeVar *relation, ShardConnections *shardConnections,
 					 bool stopOnFailure, bool useBinaryCopyFormat)
 {
 	List *finalizedPlacementList = NIL;
@@ -986,7 +1069,7 @@ OpenCopyTransactions(CopyStmt *copyStatement, ShardConnections *shardConnections
 		}
 
 		PQclear(result);
-		copyCommand = ConstructCopyStatement(copyStatement, shardConnections->shardId,
+		copyCommand = ConstructCopyStatement(relation, shardConnections->shardId,
 											 useBinaryCopyFormat);
 
 		result = PQexec(connection, copyCommand->data);
@@ -1040,6 +1123,28 @@ OpenCopyTransactions(CopyStmt *copyStatement, ShardConnections *shardConnections
 }
 
 
+/*
+ * CreateCopyOutState creates a copy output state to pass to the COPY
+ * functions.
+ */
+static CopyOutState
+CreateCopyOutState(TupleDesc tupleDescriptor, MemoryContext rowContext)
+{
+	static const char *delimiterCharacter = "\t";
+	static const char *nullPrintCharacter = "\\N";
+
+	CopyOutState copyOutState = (CopyOutState) palloc0(sizeof(CopyOutStateData));
+	copyOutState->delim = (char *) delimiterCharacter;
+	copyOutState->null_print = (char *) nullPrintCharacter;
+	copyOutState->null_print_client = (char *) nullPrintCharacter;
+	copyOutState->binary = CanUseBinaryCopyFormat(tupleDescriptor, copyOutState);
+	copyOutState->fe_msgbuf = makeStringInfo();
+	copyOutState->rowcontext = rowContext;
+
+	return copyOutState;
+}
+
+
 /*
  * CanUseBinaryCopyFormat iterates over columns of the relation given in rowOutputState
  * and looks for a column whose type is array of user-defined type or composite type.
@@ -1173,12 +1278,12 @@ SendCopyBinaryFooters(CopyOutState copyOutState, List *connectionList)
  * shard.
  */
 static StringInfo
-ConstructCopyStatement(CopyStmt *copyStatement, int64 shardId, bool useBinaryCopyFormat)
+ConstructCopyStatement(RangeVar *relation, int64 shardId, bool useBinaryCopyFormat)
 {
 	StringInfo command = makeStringInfo();
 
-	char *schemaName = copyStatement->relation->schemaname;
+	char *schemaName = relation->schemaname;
-	char *relationName = copyStatement->relation->relname;
+	char *relationName = relation->relname;
 
 	char *shardName = pstrdup(relationName);
 	char *shardQualifiedName = NULL;
@@ -1536,11 +1641,11 @@ AppendCopyBinaryFooters(CopyOutState footerOutputState)
  * opens connections to shard placements.
  */
 static void
-StartCopyToNewShard(ShardConnections *shardConnections, CopyStmt *copyStatement,
+StartCopyToNewShard(RangeVar *relation, ShardConnections *shardConnections,
 					bool useBinaryCopyFormat)
 {
-	char *relationName = copyStatement->relation->relname;
+	char *relationName = relation->relname;
-	char *schemaName = copyStatement->relation->schemaname;
+	char *schemaName = relation->schemaname;
 	char *qualifiedName = quote_qualified_identifier(schemaName, relationName);
 
 	int64 shardId = MasterCreateEmptyShard(qualifiedName);
@@ -1551,7 +1656,7 @@ StartCopyToNewShard(ShardConnections *shardConnections, CopyStmt *copyStatement,
 	shardConnections->connectionList = NIL;
 
 	/* connect to shards placements and start transactions */
-	OpenCopyTransactions(copyStatement, shardConnections, true, useBinaryCopyFormat);
+	OpenCopyTransactions(relation, shardConnections, true, useBinaryCopyFormat);
 }
 
 

src/include/distributed/multi_copy.h

@@ -43,8 +43,20 @@ typedef struct NodeAddress
 	int32 nodePort;
 } NodeAddress;
 
+/* struct type for a generic source of tuples to copy to shards */
+typedef struct CopyTupleSource
+{
+	void *context;
+	MemoryContext rowContext;
+
+	void (*Open)(void *context, Relation relation, ErrorContextCallback *errorCallback);
+	bool (*NextTuple)(void *context, Datum *columnValues, bool *columnNulls);
+	void (*Close)(void *context);
+} CopyTupleSource;
+
 
 /* function declarations for copying into a distributed table */
+extern uint64 CopyTupleSourceToShards(CopyTupleSource *tupleSource, RangeVar *relation);
 extern FmgrInfo * ColumnOutputFunctions(TupleDesc rowDescriptor, bool binaryFormat);
 extern void AppendCopyRowData(Datum *valueArray, bool *isNullArray,
 							  TupleDesc rowDescriptor,