Support for COPY FROM, based on pg_shard PR by Postres Pro

src/backend/distributed/executor/multi_utility.c

@@ -17,6 +17,7 @@
 #include "commands/tablecmds.h"
 #include "distributed/master_protocol.h"
 #include "distributed/metadata_cache.h"
+#include "distributed/multi_copy.h"
 #include "distributed/multi_utility.h"
 #include "distributed/multi_join_order.h"
 #include "distributed/transmit.h"
@@ -50,7 +51,7 @@ static bool IsTransmitStmt(Node *parsetree);
 static void VerifyTransmitStmt(CopyStmt *copyStatement);
 
 /* Local functions forward declarations for processing distributed table commands */
-static Node * ProcessCopyStmt(CopyStmt *copyStatement);
+static Node * ProcessCopyStmt(CopyStmt *copyStatement, char *completionTag);
 static Node * ProcessIndexStmt(IndexStmt *createIndexStatement,
 							   const char *createIndexCommand);
 static Node * ProcessDropIndexStmt(DropStmt *dropIndexStatement,
@@ -122,7 +123,12 @@ multi_ProcessUtility(Node *parsetree,
 
 	if (IsA(parsetree, CopyStmt))
 	{
-		parsetree = ProcessCopyStmt((CopyStmt *) parsetree);
+		parsetree = ProcessCopyStmt((CopyStmt *) parsetree, completionTag);
+
+		if (parsetree == NULL)
+		{
+			return;
+		}
 	}
 
 	if (IsA(parsetree, IndexStmt))
@@ -300,7 +306,7 @@ VerifyTransmitStmt(CopyStmt *copyStatement)
  * COPYing from distributed tables and preventing unsupported actions.
  */
 static Node *
-ProcessCopyStmt(CopyStmt *copyStatement)
+ProcessCopyStmt(CopyStmt *copyStatement, char *completionTag)
 {
 	/*
 	 * We first check if we have a "COPY (query) TO filename". If we do, copy doesn't
@@ -344,9 +350,8 @@ ProcessCopyStmt(CopyStmt *copyStatement)
 		{
 			if (copyStatement->is_from)
 			{
-				ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				CitusCopyFrom(copyStatement, completionTag);
-								errmsg("cannot execute COPY FROM on a distributed table "
+				return NULL;
-									   "on master node")));
 			}
 			else if (!copyStatement->is_from)
 			{

src/backend/distributed/planner/multi_physical_planner.c

@@ -110,8 +110,6 @@ static MapMergeJob * BuildMapMergeJob(Query *jobQuery, List *dependedJobList,
 									  Oid baseRelationId,
 									  BoundaryNodeJobType boundaryNodeJobType);
 static uint32 HashPartitionCount(void);
-static int CompareShardIntervals(const void *leftElement, const void *rightElement,
-								 FmgrInfo *typeCompareFunction);
 static ArrayType * SplitPointObject(ShardInterval **shardIntervalArray,
 									uint32 shardIntervalCount);
 
@@ -169,7 +167,6 @@ static List * RoundRobinAssignTaskList(List *taskList);
 static List * RoundRobinReorder(Task *task, List *placementList);
 static List * ReorderAndAssignTaskList(List *taskList,
 									   List * (*reorderFunction)(Task *, List *));
-static int CompareTasksByShardId(const void *leftElement, const void *rightElement);
 static List * ActiveShardPlacementLists(List *taskList);
 static List * ActivePlacementList(List *placementList);
 static List * LeftRotateList(List *list, uint32 rotateCount);
@@ -1810,7 +1807,7 @@ SortedShardIntervalArray(List *shardIntervalList)
  * CompareShardIntervals acts as a helper function to compare two shard interval
  * pointers by their minimum values, using the value's type comparison function.
  */
-static int
+int
 CompareShardIntervals(const void *leftElement, const void *rightElement,
 					  FmgrInfo *typeCompareFunction)
 {
@@ -5073,7 +5070,7 @@ ReorderAndAssignTaskList(List *taskList, List * (*reorderFunction)(Task *, List
 
 
 /* Helper function to compare two tasks by their anchor shardId. */
-static int
+int
 CompareTasksByShardId(const void *leftElement, const void *rightElement)
 {
 	const Task *leftTask = *((const Task **) leftElement);

src/backend/distributed/shared_library_init.c

@@ -20,6 +20,7 @@
 #include "executor/executor.h"
 #include "distributed/master_protocol.h"
 #include "distributed/modify_planner.h"
+#include "distributed/multi_copy.h"
 #include "distributed/multi_executor.h"
 #include "distributed/multi_explain.h"
 #include "distributed/multi_join_order.h"
@@ -29,6 +30,7 @@
 #include "distributed/multi_server_executor.h"
 #include "distributed/multi_utility.h"
 #include "distributed/task_tracker.h"
+#include "distributed/transaction_manager.h"
 #include "distributed/worker_manager.h"
 #include "distributed/worker_protocol.h"
 #include "postmaster/postmaster.h"
@@ -67,6 +69,12 @@ static const struct config_enum_entry shard_placement_policy_options[] = {
 	{ NULL, 0, false }
 };
 
+static const struct config_enum_entry transaction_manager_options[] =  {
+	{ "1pc", TRANSACTION_MANAGER_1PC, false },
+	{ "2pc", TRANSACTION_MANAGER_2PC, false },
+	{ NULL, 0, false }
+};
+
 
 /* shared library initialization function */
 void
@@ -437,6 +445,21 @@ RegisterCitusConfigVariables(void)
 		0,
 		NULL, NULL, NULL);
 
+	DefineCustomEnumVariable(
+		"citus.copy_transaction_manager",
+		gettext_noop("Sets the transaction manager for COPY into distributed tables."),
+		gettext_noop("When a failure occurs during when copying into a distributed "
+					 "table, 2PC is required to ensure data is never lost. Change "
+					 "this setting to '2pc' from its default '1pc' to enable 2PC."
+					 "You must also set max_prepared_transactions on the worker "
+					 "nodes. Recovery from failed 2PCs is currently manual."),
+		&CopyTransactionManager,
+		TRANSACTION_MANAGER_1PC,
+		transaction_manager_options,
+		PGC_USERSET,
+		0,
+		NULL, NULL, NULL);
+
 	DefineCustomEnumVariable(
 		"citus.task_assignment_policy",
 		gettext_noop("Sets the policy to use when assigning tasks to worker nodes."),

src/backend/distributed/utils/connection_cache.c

@@ -39,8 +39,6 @@ static HTAB *NodeConnectionHash = NULL;
 
 /* local function forward declarations */
 static HTAB * CreateNodeConnectionHash(void);
-static PGconn * ConnectToNode(char *nodeName, char *nodePort);
-static char * ConnectionGetOptionValue(PGconn *connection, char *optionKeyword);
 
 
 /*
@@ -99,10 +97,7 @@ GetOrEstablishConnection(char *nodeName, int32 nodePort)
 
 	if (needNewConnection)
 	{
-		StringInfo nodePortString = makeStringInfo();
+		connection = ConnectToNode(nodeName, nodePort);
-		appendStringInfo(nodePortString, "%d", nodePort);
-
-		connection = ConnectToNode(nodeName, nodePortString->data);
 		if (connection != NULL)
 		{
 			nodeConnectionEntry = hash_search(NodeConnectionHash, &nodeConnectionKey,
@@ -264,8 +259,8 @@ CreateNodeConnectionHash(void)
  * We attempt to connect up to MAX_CONNECT_ATTEMPT times. After that we give up
  * and return NULL.
  */
-static PGconn *
+PGconn *
-ConnectToNode(char *nodeName, char *nodePort)
+ConnectToNode(char *nodeName, int32 nodePort)
 {
 	PGconn *connection = NULL;
 	const char *clientEncoding = GetDatabaseEncodingName();
@@ -276,11 +271,14 @@ ConnectToNode(char *nodeName, char *nodePort)
 		"host", "port", "fallback_application_name",
 		"client_encoding", "connect_timeout", "dbname", NULL
 	};
+	char nodePortString[12];
 	const char *valueArray[] = {
-		nodeName, nodePort, "citus", clientEncoding,
+		nodeName, nodePortString, "citus", clientEncoding,
 		CLIENT_CONNECT_TIMEOUT_SECONDS, dbname, NULL
 	};
 
+	sprintf(nodePortString, "%d", nodePort);
+
 	Assert(sizeof(keywordArray) == sizeof(valueArray));
 
 	for (attemptIndex = 0; attemptIndex < MAX_CONNECT_ATTEMPTS; attemptIndex++)
@@ -313,7 +311,7 @@ ConnectToNode(char *nodeName, char *nodePort)
  * The function returns NULL if the connection has no setting for an option with
  * the provided keyword.
  */
-static char *
+char *
 ConnectionGetOptionValue(PGconn *connection, char *optionKeyword)
 {
 	char *optionValue = NULL;

src/backend/distributed/utils/transaction_manager.c

@@ -0,0 +1,173 @@
+/*-------------------------------------------------------------------------
+ *
+ * transaction_manager.c
+ *     This file contains functions that comprise a pluggable API for
+ *     managing transactions across many worker nodes using 1PC or 2PC.
+ *
+ * Contributed by Konstantin Knizhnik, Postgres Professional
+ *
+ * Copyright (c) 2016, Citus Data, Inc.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+#include "libpq-fe.h"
+#include "miscadmin.h"
+
+#include "access/xact.h"
+#include "distributed/connection_cache.h"
+#include "distributed/transaction_manager.h"
+
+static bool BeginTransaction(PGconn *connection);
+static bool Prepare1PC(PGconn *connection, char *transactionId);
+static bool CommitPrepared1PC(PGconn *connection, char *transactionId);
+static bool RollbackPrepared1PC(PGconn *connection, char *transactionId);
+static bool RollbackTransaction(PGconn *connection);
+
+static bool Prepare2PC(PGconn *connection, char *transactionId);
+static bool CommitPrepared2PC(PGconn *connection, char *transactionId);
+static bool RollbackPrepared2PC(PGconn *connection, char *transactionId);
+
+static char * Build2PCCommand(char const *command, char *transactionId);
+
+CitusTransactionManager const CitusTransactionManagerImpl[] =
+{
+	{ BeginTransaction, Prepare1PC, CommitPrepared1PC,
+	  RollbackPrepared1PC, RollbackTransaction },
+	{ BeginTransaction, Prepare2PC, CommitPrepared2PC,
+	  RollbackPrepared2PC, RollbackTransaction }
+};
+
+
+/*
+ * BeginTransaction sends a BEGIN command to start a transaction.
+ */
+static bool
+BeginTransaction(PGconn *connection)
+{
+	return ExecuteCommand(connection, PGRES_COMMAND_OK, "BEGIN");
+}
+
+
+/*
+ * Prepare1PC does nothing since 1PC mode does not have a prepare phase.
+ * This function is provided for compatibility with the 2PC API.
+ */
+static bool
+Prepare1PC(PGconn *connection, char *transactionId)
+{
+	return true;
+}
+
+
+/*
+ * Commit1PC sends a COMMIT command to commit a transaction.
+ */
+static bool
+CommitPrepared1PC(PGconn *connection, char *transactionId)
+{
+	return ExecuteCommand(connection, PGRES_COMMAND_OK, "COMMIT");
+}
+
+
+/*
+ * RollbackPrepared1PC sends a ROLLBACK command to roll a transaction
+ * back. This function is provided for compatibility with the 2PC API.
+ */
+static bool
+RollbackPrepared1PC(PGconn *connection, char *transactionId)
+{
+	return ExecuteCommand(connection, PGRES_COMMAND_OK, "ROLLBACK");
+}
+
+
+/*
+ * Prepare2PC sends a PREPARE TRANSACTION command to prepare a 2PC.
+ */
+static bool
+Prepare2PC(PGconn *connection, char *transactionId)
+{
+	return ExecuteCommand(connection, PGRES_COMMAND_OK,
+						  Build2PCCommand("PREPARE TRANSACTION", transactionId));
+}
+
+
+/*
+ * CommitPrepared2PC sends a COMMIT TRANSACTION command to commit a 2PC.
+ */
+static bool
+CommitPrepared2PC(PGconn *connection, char *transactionId)
+{
+	return ExecuteCommand(connection, PGRES_COMMAND_OK,
+						  Build2PCCommand("COMMIT PREPARED", transactionId));
+}
+
+
+/*
+ * RollbackPrepared2PC sends a COMMIT TRANSACTION command to commit a 2PC.
+ */
+static bool
+RollbackPrepared2PC(PGconn *connection, char *transactionId)
+{
+	return ExecuteCommand(connection, PGRES_COMMAND_OK,
+						  Build2PCCommand("ROLLBACK PREPARED", transactionId));
+}
+
+
+/*
+ * RollbackTransaction sends a ROLLBACK command to roll a transaction back.
+ */
+static bool
+RollbackTransaction(PGconn *connection)
+{
+	return ExecuteCommand(connection, PGRES_COMMAND_OK, "ROLLBACK");
+}
+
+
+/*
+ * Build2PCCommand builds a command with a unique transaction ID for a two-phase commit.
+ */
+static char *
+Build2PCCommand(char const *command, char *transactionId)
+{
+	StringInfo commandString = makeStringInfo();
+
+	appendStringInfo(commandString, "%s '%s'", transactionId);
+
+	return commandString->data;
+}
+
+
+/*
+ * BuildTransactionId helps users construct a unique transaction id from an
+ * application-specific id.
+ */
+char *
+BuildTransactionId(int localId)
+{
+	StringInfo commandString = makeStringInfo();
+
+	appendStringInfo(commandString, "citus_%d_%u_%d", MyProcPid,
+									GetCurrentTransactionId(), localId);
+
+	return commandString->data;
+}
+
+
+/*
+ * ExecuteCommand executes a statement on a remote node and checks its result.
+ */
+bool
+ExecuteCommand(PGconn *connection, ExecStatusType expectedResult, char const *command)
+{
+	bool ret = true;
+	PGresult *result = PQexec(connection, command);
+	if (PQresultStatus(result) != expectedResult)
+	{
+		ReportRemoteError(connection, result);
+		ret = false;
+	}
+	PQclear(result);
+	return ret;
+}

src/include/distributed/connection_cache.h

@@ -54,6 +54,8 @@ typedef struct NodeConnectionEntry
 extern PGconn * GetOrEstablishConnection(char *nodeName, int32 nodePort);
 extern void PurgeConnection(PGconn *connection);
 extern void ReportRemoteError(PGconn *connection, PGresult *result);
+extern PGconn * ConnectToNode(char *nodeName, int nodePort);
+extern char * ConnectionGetOptionValue(PGconn *connection, char *optionKeyword);
 
 
 #endif /* CONNECTION_CACHE_H */

src/include/distributed/multi_copy.h

@@ -0,0 +1,29 @@
+/*-------------------------------------------------------------------------
+ *
+ * multi_copy.h
+ *
+ * Declarations for public functions and variables used in COPY for
+ * distributed tables.
+ *
+ * Copyright (c) 2016, Citus Data, Inc.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef MULTI_COPY_H
+#define MULTI_COPY_H
+
+
+#include "libpq-fe.h"
+#include "distributed/transaction_manager.h"
+
+
+/* config variable managed via guc.c */
+extern int CopyTransactionManager;
+
+
+/* function declarations for copying into a distributed table */
+extern void CitusCopyFrom(CopyStmt *copyStatement, char* completionTag);
+
+
+#endif /* MULTI_COPY_H */

src/include/distributed/multi_physical_planner.h

@@ -238,6 +238,8 @@ extern int CompareShardPlacements(const void *leftElement, const void *rightElem
 extern ShardInterval ** SortedShardIntervalArray(List *shardList);
 extern bool ShardIntervalsOverlap(ShardInterval *firstInterval,
 								  ShardInterval *secondInterval);
+extern int CompareShardIntervals(const void *leftElement, const void *rightElement,
+								 FmgrInfo *typeCompareFunction);
 
 /* function declarations for Task and Task list operations */
 extern bool TasksEqual(const Task *a, const Task *b);
@@ -247,6 +249,7 @@ extern bool TaskListMember(const List *taskList, const Task *task);
 extern List * TaskListDifference(const List *list1, const List *list2);
 extern List * TaskListUnion(const List *list1, const List *list2);
 extern List * FirstReplicaAssignTaskList(List *taskList);
+extern int CompareTasksByShardId(const void *leftElement, const void *rightElement);
 
 
 #endif   /* MULTI_PHYSICAL_PLANNER_H */

src/include/distributed/transaction_manager.h

@@ -0,0 +1,49 @@
+/*-------------------------------------------------------------------------
+ *
+ * transaction_manager.h
+ *
+ * Transaction manager API.
+ *
+ * Copyright (c) 2016, Citus Data, Inc.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef TRANSACTION_MANAGER_H
+#define TRANSACTION_MANAGER_H
+
+
+#include "libpq-fe.h"
+#include "utils/guc.h"
+
+
+/* pluggable transaction manager API */
+typedef struct CitusTransactionManager
+{
+	bool (*Begin)(PGconn *conn);
+	bool (*Prepare)(PGconn *conn, char *transactionId);
+	bool (*CommitPrepared)(PGconn *conn, char *transactionId);
+	bool (*RollbackPrepared)(PGconn *conn, char *transactionId);
+	bool (*Rollback)(PGconn *conn);
+} CitusTransactionManager;
+
+
+/* Enumeration that defines the transaction manager to use */
+typedef enum
+{
+	TRANSACTION_MANAGER_1PC = 0,
+	TRANSACTION_MANAGER_2PC = 1
+} TransactionManagerType;
+
+
+/* Implementations of the transaction manager API */
+extern CitusTransactionManager const CitusTransactionManagerImpl[];
+
+
+/* Function declarations for copying into a distributed table */
+extern bool ExecuteCommand(PGconn *connection, ExecStatusType expectedResult,
+						   char const *command);
+extern char * BuildTransactionId(int localId);
+
+
+#endif /* TRANSACTION_MANAGER_H */

src/test/regress/expected/multi_utilities.out

@@ -18,9 +18,6 @@ SELECT master_create_worker_shards('sharded_table', 2, 1);
 COPY sharded_table TO STDOUT;
 COPY (SELECT COUNT(*) FROM sharded_table) TO STDOUT;
 0
--- but COPY in is not
-COPY sharded_table FROM STDIN;
-ERROR:  cannot execute COPY FROM on a distributed table on master node
 -- cursors may not involve distributed tables
 DECLARE all_sharded_rows CURSOR FOR SELECT * FROM sharded_table;
 ERROR:  DECLARE CURSOR can only be used in transaction blocks

src/test/regress/expected/multi_utility_statements.out

@@ -188,9 +188,6 @@ VIETNAM
 RUSSIA                   
 UNITED KINGDOM           
 UNITED STATES            
--- Ensure that preventing COPY FROM against distributed tables works
-COPY customer FROM STDIN;
-ERROR:  cannot execute COPY FROM on a distributed table on master node
 -- Test that we can create on-commit drop tables, and also test creating with
 -- oids, along with changing column names
 BEGIN;

src/test/regress/sql/multi_utilities.sql

@@ -10,9 +10,6 @@ SELECT master_create_worker_shards('sharded_table', 2, 1);
 COPY sharded_table TO STDOUT;
 COPY (SELECT COUNT(*) FROM sharded_table) TO STDOUT;
 
--- but COPY in is not
-COPY sharded_table FROM STDIN;
-
 -- cursors may not involve distributed tables
 DECLARE all_sharded_rows CURSOR FOR SELECT * FROM sharded_table;
 

src/test/regress/sql/multi_utility_statements.sql

@@ -104,9 +104,6 @@ COPY nation TO STDOUT;
 -- ensure individual cols can be copied out, too
 COPY nation(n_name) TO STDOUT;
 
--- Ensure that preventing COPY FROM against distributed tables works
-COPY customer FROM STDIN;
-
 -- Test that we can create on-commit drop tables, and also test creating with
 -- oids, along with changing column names