Implement pipeline mode in libpq

Pipeline mode in libpq lets an application avoid the Sync messages in
the FE/BE protocol that are implicit in the old libpq API after each
query.  The application can then insert Sync at its leisure with a new
libpq function PQpipelineSync.  This can lead to substantial reductions
in query latency.

Co-authored-by: Craig Ringer <craig.ringer@enterprisedb.com>
Co-authored-by: Matthieu Garrigues <matthieu.garrigues@gmail.com>
Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Aya Iwata <iwata.aya@jp.fujitsu.com>
Reviewed-by: Daniel Vérité <daniel@manitou-mail.org>
Reviewed-by: David G. Johnston <david.g.johnston@gmail.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Kirk Jamison <k.jamison@fujitsu.com>
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
Reviewed-by: Nikhil Sontakke <nikhils@2ndquadrant.com>
Reviewed-by: Vaishnavi Prabakaran <VaishnaviP@fast.au.fujitsu.com>
Reviewed-by: Zhihong Yu <zyu@yugabyte.com>

Discussion: https://postgr.es/m/CAMsr+YFUjJytRyV4J-16bEoiZyH=4nj+sQ7JP9ajwz=B4dMMZw@mail.gmail.com
Discussion: https://postgr.es/m/CAJkzx4T5E-2cQe3dtv2R78dYFvz+in8PY7A8MArvLhs_pg75gg@mail.gmail.com

6 files changed, 1358 insertions, 0 deletions

diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 5391f461a2..93e7829c67 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -10,6 +10,7 @@ SUBDIRS = \
 		  delay_execution \
 		  dummy_index_am \
 		  dummy_seclabel \
+		  libpq_pipeline \
 		  plsample \
 		  snapshot_too_old \
 		  test_bloomfilter \
diff --git a/src/test/modules/libpq_pipeline/.gitignore b/src/test/modules/libpq_pipeline/.gitignore
new file mode 100644
index 0000000000..3a11e786b8
--- /dev/null
+++ b/src/test/modules/libpq_pipeline/.gitignore
@@ -0,0 +1,5 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
+/libpq_pipeline
diff --git a/src/test/modules/libpq_pipeline/Makefile b/src/test/modules/libpq_pipeline/Makefile
new file mode 100644
index 0000000000..b798f5fbbc
--- /dev/null
+++ b/src/test/modules/libpq_pipeline/Makefile
@@ -0,0 +1,20 @@
+# src/test/modules/libpq_pipeline/Makefile
+
+PROGRAM = libpq_pipeline
+OBJS = libpq_pipeline.o
+
+PG_CPPFLAGS = -I$(libpq_srcdir)
+PG_LIBS_INTERNAL += $(libpq_pgport)
+
+TAP_TESTS = 1
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/libpq_pipeline
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/libpq_pipeline/README b/src/test/modules/libpq_pipeline/README
new file mode 100644
index 0000000000..d8174dd579
--- /dev/null
+++ b/src/test/modules/libpq_pipeline/README
@@ -0,0 +1 @@
+Test programs and libraries for libpq
diff --git a/src/test/modules/libpq_pipeline/libpq_pipeline.c b/src/test/modules/libpq_pipeline/libpq_pipeline.c
new file mode 100644
index 0000000000..03eb3df504
--- /dev/null
+++ b/src/test/modules/libpq_pipeline/libpq_pipeline.c
@@ -0,0 +1,1303 @@
+/*-------------------------------------------------------------------------
+ *
+ * libpq_pipeline.c
+ *		Verify libpq pipeline execution functionality
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *		src/test/modules/libpq_pipeline/libpq_pipeline.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres_fe.h"
+
+#include <sys/time.h>
+#ifdef HAVE_SYS_SELECT_H
+#include <sys/select.h>
+#endif
+
+#include "catalog/pg_type_d.h"
+#include "common/fe_memutils.h"
+#include "libpq-fe.h"
+#include "portability/instr_time.h"
+
+
+static void exit_nicely(PGconn *conn);
+
+const char *const progname = "libpq_pipeline";
+
+
+#define DEBUG
+#ifdef DEBUG
+#define	pg_debug(...)  do { fprintf(stderr, __VA_ARGS__); } while (0)
+#else
+#define pg_debug(...)
+#endif
+
+static const char *const drop_table_sql =
+"DROP TABLE IF EXISTS pq_pipeline_demo";
+static const char *const create_table_sql =
+"CREATE UNLOGGED TABLE pq_pipeline_demo(id serial primary key, itemno integer);";
+static const char *const insert_sql =
+"INSERT INTO pq_pipeline_demo(itemno) VALUES ($1);";
+
+/* max char length of an int32, plus sign and null terminator */
+#define MAXINTLEN 12
+
+static void
+exit_nicely(PGconn *conn)
+{
+	PQfinish(conn);
+	exit(1);
+}
+
+/*
+ * Print an error to stderr and terminate the program.
+ */
+#define pg_fatal(...) pg_fatal_impl(__LINE__, __VA_ARGS__)
+static void
+pg_fatal_impl(int line, const char *fmt,...)
+{
+	va_list		args;
+
+
+	fflush(stdout);
+
+	fprintf(stderr, "\n%s:%d: ", progname, line);
+	va_start(args, fmt);
+	vfprintf(stderr, fmt, args);
+	va_end(args);
+	Assert(fmt[strlen(fmt) - 1] != '\n');
+	fprintf(stderr, "\n");
+	exit(1);
+}
+
+static void
+test_disallowed_in_pipeline(PGconn *conn)
+{
+	PGresult   *res = NULL;
+
+	fprintf(stderr, "test error cases... ");
+
+	if (PQisnonblocking(conn))
+		pg_fatal("Expected blocking connection mode");
+
+	if (PQenterPipelineMode(conn) != 1)
+		pg_fatal("Unable to enter pipeline mode");
+
+	if (PQpipelineStatus(conn) == PQ_PIPELINE_OFF)
+		pg_fatal("Pipeline mode not activated properly");
+
+	/* PQexec should fail in pipeline mode */
+	res = PQexec(conn, "SELECT 1");
+	if (PQresultStatus(res) != PGRES_FATAL_ERROR)
+		pg_fatal("PQexec should fail in pipeline mode but succeeded");
+
+	/* Entering pipeline mode when already in pipeline mode is OK */
+	if (PQenterPipelineMode(conn) != 1)
+		pg_fatal("re-entering pipeline mode should be a no-op but failed");
+
+	if (PQisBusy(conn) != 0)
+		pg_fatal("PQisBusy should return 0 when idle in pipeline mode, returned 1");
+
+	/* ok, back to normal command mode */
+	if (PQexitPipelineMode(conn) != 1)
+		pg_fatal("couldn't exit idle empty pipeline mode");
+
+	if (PQpipelineStatus(conn) != PQ_PIPELINE_OFF)
+		pg_fatal("Pipeline mode not terminated properly");
+
+	/* exiting pipeline mode when not in pipeline mode should be a no-op */
+	if (PQexitPipelineMode(conn) != 1)
+		pg_fatal("pipeline mode exit when not in pipeline mode should succeed but failed");
+
+	/* can now PQexec again */
+	res = PQexec(conn, "SELECT 1");
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+		pg_fatal("PQexec should succeed after exiting pipeline mode but failed with: %s",
+				 PQerrorMessage(conn));
+
+	fprintf(stderr, "ok\n");
+}
+
+static void
+test_multi_pipelines(PGconn *conn)
+{
+	PGresult   *res = NULL;
+	const char *dummy_params[1] = {"1"};
+	Oid			dummy_param_oids[1] = {INT4OID};
+
+	fprintf(stderr, "multi pipeline... ");
+
+	/*
+	 * Queue up a couple of small pipelines and process each without returning
+	 * to command mode first.
+	 */
+	if (PQenterPipelineMode(conn) != 1)
+		pg_fatal("failed to enter pipeline mode: %s", PQerrorMessage(conn));
+
+	if (PQsendQueryParams(conn, "SELECT $1", 1, dummy_param_oids,
+						  dummy_params, NULL, NULL, 0) != 1)
+		pg_fatal("dispatching first SELECT failed: %s", PQerrorMessage(conn));
+
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("Pipeline sync failed: %s", PQerrorMessage(conn));
+
+	if (PQsendQueryParams(conn, "SELECT $1", 1, dummy_param_oids,
+						  dummy_params, NULL, NULL, 0) != 1)
+		pg_fatal("dispatching second SELECT failed: %s", PQerrorMessage(conn));
+
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+
+	/* OK, start processing the results */
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("PQgetResult returned null when there's a pipeline item: %s",
+				 PQerrorMessage(conn));
+
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+		pg_fatal("Unexpected result code %s from first pipeline item",
+				 PQresStatus(PQresultStatus(res)));
+	PQclear(res);
+	res = NULL;
+
+	if (PQgetResult(conn) != NULL)
+		pg_fatal("PQgetResult returned something extra after first result");
+
+	if (PQexitPipelineMode(conn) != 0)
+		pg_fatal("exiting pipeline mode after query but before sync succeeded incorrectly");
+
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("PQgetResult returned null when sync result expected: %s",
+				 PQerrorMessage(conn));
+
+	if (PQresultStatus(res) != PGRES_PIPELINE_SYNC)
+		pg_fatal("Unexpected result code %s instead of sync result, error: %s",
+				 PQresStatus(PQresultStatus(res)), PQerrorMessage(conn));
+	PQclear(res);
+
+	/* second pipeline */
+
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("PQgetResult returned null when there's a pipeline item: %s",
+				 PQerrorMessage(conn));
+
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+		pg_fatal("Unexpected result code %s from second pipeline item",
+				 PQresStatus(PQresultStatus(res)));
+
+	res = PQgetResult(conn);
+	if (res != NULL)
+		pg_fatal("Expected null result, got %s",
+				 PQresStatus(PQresultStatus(res)));
+
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("PQgetResult returned null when there's a pipeline item: %s",
+				 PQerrorMessage(conn));
+
+	if (PQresultStatus(res) != PGRES_PIPELINE_SYNC)
+		pg_fatal("Unexpected result code %s from second pipeline sync",
+				 PQresStatus(PQresultStatus(res)));
+
+	/* We're still in pipeline mode ... */
+	if (PQpipelineStatus(conn) == PQ_PIPELINE_OFF)
+		pg_fatal("Fell out of pipeline mode somehow");
+
+	/* until we end it, which we can safely do now */
+	if (PQexitPipelineMode(conn) != 1)
+		pg_fatal("attempt to exit pipeline mode failed when it should've succeeded: %s",
+				 PQerrorMessage(conn));
+
+	if (PQpipelineStatus(conn) != PQ_PIPELINE_OFF)
+		pg_fatal("exiting pipeline mode didn't seem to work");
+
+	fprintf(stderr, "ok\n");
+}
+
+/*
+ * When an operation in a pipeline fails the rest of the pipeline is flushed. We
+ * still have to get results for each pipeline item, but the item will just be
+ * a PGRES_PIPELINE_ABORTED code.
+ *
+ * This intentionally doesn't use a transaction to wrap the pipeline. You should
+ * usually use an xact, but in this case we want to observe the effects of each
+ * statement.
+ */
+static void
+test_pipeline_abort(PGconn *conn)
+{
+	PGresult   *res = NULL;
+	const char *dummy_params[1] = {"1"};
+	Oid			dummy_param_oids[1] = {INT4OID};
+	int			i;
+	bool		goterror;
+
+	fprintf(stderr, "aborted pipeline... ");
+
+	res = PQexec(conn, drop_table_sql);
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		pg_fatal("dispatching DROP TABLE failed: %s", PQerrorMessage(conn));
+
+	res = PQexec(conn, create_table_sql);
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		pg_fatal("dispatching CREATE TABLE failed: %s", PQerrorMessage(conn));
+
+	/*
+	 * Queue up a couple of small pipelines and process each without returning
+	 * to command mode first. Make sure the second operation in the first
+	 * pipeline ERRORs.
+	 */
+	if (PQenterPipelineMode(conn) != 1)
+		pg_fatal("failed to enter pipeline mode: %s", PQerrorMessage(conn));
+
+	dummy_params[0] = "1";
+	if (PQsendQueryParams(conn, insert_sql, 1, dummy_param_oids,
+						  dummy_params, NULL, NULL, 0) != 1)
+		pg_fatal("dispatching first insert failed: %s", PQerrorMessage(conn));
+
+	if (PQsendQueryParams(conn, "SELECT no_such_function($1)",
+						  1, dummy_param_oids, dummy_params,
+						  NULL, NULL, 0) != 1)
+		pg_fatal("dispatching error select failed: %s", PQerrorMessage(conn));
+
+	dummy_params[0] = "2";
+	if (PQsendQueryParams(conn, insert_sql, 1, dummy_param_oids,
+						  dummy_params, NULL, NULL, 0) != 1)
+		pg_fatal("dispatching second insert failed: %s", PQerrorMessage(conn));
+
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+
+	dummy_params[0] = "3";
+	if (PQsendQueryParams(conn, insert_sql, 1, dummy_param_oids,
+						  dummy_params, NULL, NULL, 0) != 1)
+		pg_fatal("dispatching second-pipeline insert failed: %s",
+				 PQerrorMessage(conn));
+
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+
+	/*
+	 * OK, start processing the pipeline results.
+	 *
+	 * We should get a command-ok for the first query, then a fatal error and
+	 * a pipeline aborted message for the second insert, a pipeline-end, then
+	 * a command-ok and a pipeline-ok for the second pipeline operation.
+	 */
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("Unexpected NULL result: %s", PQerrorMessage(conn));
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		pg_fatal("Unexpected result status %s: %s",
+				 PQresStatus(PQresultStatus(res)),
+				 PQresultErrorMessage(res));
+	PQclear(res);
+
+	/* NULL result to signal end-of-results for this command */
+	if ((res = PQgetResult(conn)) != NULL)
+		pg_fatal("Expected null result, got %s",
+				 PQresStatus(PQresultStatus(res)));
+
+	/* Second query caused error, so we expect an error next */
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("Unexpected NULL result: %s", PQerrorMessage(conn));
+	if (PQresultStatus(res) != PGRES_FATAL_ERROR)
+		pg_fatal("Unexpected result code -- expected PGRES_FATAL_ERROR, got %s",
+				 PQresStatus(PQresultStatus(res)));
+	PQclear(res);
+
+	/* NULL result to signal end-of-results for this command */
+	if ((res = PQgetResult(conn)) != NULL)
+		pg_fatal("Expected null result, got %s",
+				 PQresStatus(PQresultStatus(res)));
+
+	/*
+	 * pipeline should now be aborted.
+	 *
+	 * Note that we could still queue more queries at this point if we wanted;
+	 * they'd get added to a new third pipeline since we've already sent a
+	 * second. The aborted flag relates only to the pipeline being received.
+	 */
+	if (PQpipelineStatus(conn) != PQ_PIPELINE_ABORTED)
+		pg_fatal("pipeline should be flagged as aborted but isn't");
+
+	/* third query in pipeline, the second insert */
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("Unexpected NULL result: %s", PQerrorMessage(conn));
+	if (PQresultStatus(res) != PGRES_PIPELINE_ABORTED)
+		pg_fatal("Unexpected result code -- expected PGRES_PIPELINE_ABORTED, got %s",
+				 PQresStatus(PQresultStatus(res)));
+	PQclear(res);
+
+	/* NULL result to signal end-of-results for this command */
+	if ((res = PQgetResult(conn)) != NULL)
+		pg_fatal("Expected null result, got %s", PQresStatus(PQresultStatus(res)));
+
+	if (PQpipelineStatus(conn) != PQ_PIPELINE_ABORTED)
+		pg_fatal("pipeline should be flagged as aborted but isn't");
+
+	/* Ensure we're still in pipeline */
+	if (PQpipelineStatus(conn) == PQ_PIPELINE_OFF)
+		pg_fatal("Fell out of pipeline mode somehow");
+
+	/*
+	 * The end of a failed pipeline is a PGRES_PIPELINE_SYNC.
+	 *
+	 * (This is so clients know to start processing results normally again and
+	 * can tell the difference between skipped commands and the sync.)
+	 */
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("Unexpected NULL result: %s", PQerrorMessage(conn));
+	if (PQresultStatus(res) != PGRES_PIPELINE_SYNC)
+		pg_fatal("Unexpected result code from first pipeline sync\n"
+				 "Expected PGRES_PIPELINE_SYNC, got %s",
+				 PQresStatus(PQresultStatus(res)));
+	PQclear(res);
+
+	if (PQpipelineStatus(conn) == PQ_PIPELINE_ABORTED)
+		pg_fatal("sync should've cleared the aborted flag but didn't");
+
+	/* We're still in pipeline mode... */
+	if (PQpipelineStatus(conn) == PQ_PIPELINE_OFF)
+		pg_fatal("Fell out of pipeline mode somehow");
+
+	/* the insert from the second pipeline */
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("Unexpected NULL result: %s", PQerrorMessage(conn));
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		pg_fatal("Unexpected result code %s from first item in second pipeline",
+				 PQresStatus(PQresultStatus(res)));
+	PQclear(res);
+
+	/* Read the NULL result at the end of the command */
+	if ((res = PQgetResult(conn)) != NULL)
+		pg_fatal("Expected null result, got %s", PQresStatus(PQresultStatus(res)));
+
+	/* the second pipeline sync */
+	if ((res = PQgetResult(conn)) == NULL)
+		pg_fatal("Unexpected NULL result: %s", PQerrorMessage(conn));
+	if (PQresultStatus(res) != PGRES_PIPELINE_SYNC)
+		pg_fatal("Unexpected result code %s from second pipeline sync",
+				 PQresStatus(PQresultStatus(res)));
+	PQclear(res);
+
+	if ((res = PQgetResult(conn)) != NULL)
+		pg_fatal("Expected null result, got %s: %s",
+				 PQresStatus(PQresultStatus(res)),
+				 PQerrorMessage(conn));
+
+	/* Try to send two queries in one command */
+	if (PQsendQuery(conn, "SELECT 1; SELECT 2") != 1)
+		pg_fatal("failed to send query: %s", PQerrorMessage(conn));
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+	goterror = false;
+	while ((res = PQgetResult(conn)) != NULL)
+	{
+		switch (PQresultStatus(res))
+		{
+			case PGRES_FATAL_ERROR:
+				if (strcmp(PQresultErrorField(res, PG_DIAG_SQLSTATE), "42601") != 0)
+					pg_fatal("expected error about multiple commands, got %s",
+							 PQerrorMessage(conn));
+				printf("got expected %s", PQerrorMessage(conn));
+				goterror = true;
+				break;
+			default:
+				pg_fatal("got unexpected status %s", PQresStatus(PQresultStatus(res)));
+				break;
+		}
+	}
+	if (!goterror)
+		pg_fatal("did not get cannot-insert-multiple-commands error");
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("got NULL result");
+	if (PQresultStatus(res) != PGRES_PIPELINE_SYNC)
+		pg_fatal("Unexpected result code %s from pipeline sync",
+				 PQresStatus(PQresultStatus(res)));
+
+	/* Test single-row mode with an error partways */
+	if (PQsendQuery(conn, "SELECT 1.0/g FROM generate_series(3, -1, -1) g") != 1)
+		pg_fatal("failed to send query: %s", PQerrorMessage(conn));
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+	PQsetSingleRowMode(conn);
+	goterror = false;
+	while ((res = PQgetResult(conn)) != NULL)
+	{
+		switch (PQresultStatus(res))
+		{
+			case PGRES_SINGLE_TUPLE:
+				printf("got row: %s\n", PQgetvalue(res, 0, 0));
+				break;
+			case PGRES_FATAL_ERROR:
+				if (strcmp(PQresultErrorField(res, PG_DIAG_SQLSTATE), "22012") != 0)
+					pg_fatal("expected division-by-zero, got: %s (%s)",
+							 PQerrorMessage(conn),
+							 PQresultErrorField(res, PG_DIAG_SQLSTATE));
+				printf("got expected division-by-zero\n");
+				goterror = true;
+				break;
+			default:
+				pg_fatal("got unexpected result %s", PQresStatus(PQresultStatus(res)));
+		}
+		PQclear(res);
+	}
+	if (!goterror)
+		pg_fatal("did not get division-by-zero error");
+	/* the third pipeline sync */
+	if ((res = PQgetResult(conn)) == NULL)
+		pg_fatal("Unexpected NULL result: %s", PQerrorMessage(conn));
+	if (PQresultStatus(res) != PGRES_PIPELINE_SYNC)
+		pg_fatal("Unexpected result code %s from third pipeline sync",
+				 PQresStatus(PQresultStatus(res)));
+	PQclear(res);
+
+	/* We're still in pipeline mode... */
+	if (PQpipelineStatus(conn) == PQ_PIPELINE_OFF)
+		pg_fatal("Fell out of pipeline mode somehow");
+
+	/* until we end it, which we can safely do now */
+	if (PQexitPipelineMode(conn) != 1)
+		pg_fatal("attempt to exit pipeline mode failed when it should've succeeded: %s",
+				 PQerrorMessage(conn));
+
+	if (PQpipelineStatus(conn) != PQ_PIPELINE_OFF)
+		pg_fatal("exiting pipeline mode didn't seem to work");
+
+	fprintf(stderr, "ok\n");
+
+	/*-
+	 * Since we fired the pipelines off without a surrounding xact, the results
+	 * should be:
+	 *
+	 * - Implicit xact started by server around 1st pipeline
+	 * - First insert applied
+	 * - Second statement aborted xact
+	 * - Third insert skipped
+	 * - Sync rolled back first implicit xact
+	 * - Implicit xact created by server around 2nd pipeline
+	 * - insert applied from 2nd pipeline
+	 * - Sync commits 2nd xact
+	 *
+	 * So we should only have the value 3 that we inserted.
+	 */
+	res = PQexec(conn, "SELECT itemno FROM pq_pipeline_demo");
+
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+		pg_fatal("Expected tuples, got %s: %s",
+				 PQresStatus(PQresultStatus(res)), PQerrorMessage(conn));
+	if (PQntuples(res) != 1)
+		pg_fatal("expected 1 result, got %d", PQntuples(res));
+	for (i = 0; i < PQntuples(res); i++)
+	{
+		const char *val = PQgetvalue(res, i, 0);
+
+		if (strcmp(val, "3") != 0)
+			pg_fatal("expected only insert with value 3, got %s", val);
+	}
+
+	PQclear(res);
+}
+
+/* State machine enum for test_pipelined_insert */
+enum PipelineInsertStep
+{
+	BI_BEGIN_TX,
+	BI_DROP_TABLE,
+	BI_CREATE_TABLE,
+	BI_PREPARE,
+	BI_INSERT_ROWS,
+	BI_COMMIT_TX,
+	BI_SYNC,
+	BI_DONE
+};
+
+static void
+test_pipelined_insert(PGconn *conn, int n_rows)
+{
+	const char *insert_params[1];
+	Oid			insert_param_oids[1] = {INT4OID};
+	char		insert_param_0[MAXINTLEN];
+	enum PipelineInsertStep send_step = BI_BEGIN_TX,
+				recv_step = BI_BEGIN_TX;
+	int			rows_to_send,
+				rows_to_receive;
+
+	insert_params[0] = &insert_param_0[0];
+
+	rows_to_send = rows_to_receive = n_rows;
+
+	/*
+	 * Do a pipelined insert into a table created at the start of the pipeline
+	 */
+	if (PQenterPipelineMode(conn) != 1)
+		pg_fatal("failed to enter pipeline mode: %s", PQerrorMessage(conn));
+
+	while (send_step != BI_PREPARE)
+	{
+		const char *sql;
+
+		switch (send_step)
+		{
+			case BI_BEGIN_TX:
+				sql = "BEGIN TRANSACTION";
+				send_step = BI_DROP_TABLE;
+				break;
+
+			case BI_DROP_TABLE:
+				sql = drop_table_sql;
+				send_step = BI_CREATE_TABLE;
+				break;
+
+			case BI_CREATE_TABLE:
+				sql = create_table_sql;
+				send_step = BI_PREPARE;
+				break;
+
+			default:
+				pg_fatal("invalid state");
+		}
+
+		pg_debug("sending: %s\n", sql);
+		if (PQsendQueryParams(conn, sql,
+							  0, NULL, NULL, NULL, NULL, 0) != 1)
+			pg_fatal("dispatching %s failed: %s", sql, PQerrorMessage(conn));
+	}
+
+	Assert(send_step == BI_PREPARE);
+	pg_debug("sending: %s\n", insert_sql);
+	if (PQsendPrepare(conn, "my_insert", insert_sql, 1, insert_param_oids) != 1)
+		pg_fatal("dispatching PREPARE failed: %s", PQerrorMessage(conn));
+	send_step = BI_INSERT_ROWS;
+
+	/*
+	 * Now we start inserting. We'll be sending enough data that we could fill
+	 * our output buffer, so to avoid deadlocking we need to enter nonblocking
+	 * mode and consume input while we send more output. As results of each
+	 * query are processed we should pop them to allow processing of the next
+	 * query. There's no need to finish the pipeline before processing
+	 * results.
+	 */
+	if (PQsetnonblocking(conn, 1) != 0)
+		pg_fatal("failed to set nonblocking mode: %s", PQerrorMessage(conn));
+
+	while (recv_step != BI_DONE)
+	{
+		int			sock;
+		fd_set		input_mask;
+		fd_set		output_mask;
+
+		sock = PQsocket(conn);
+
+		if (sock < 0)
+			break;				/* shouldn't happen */
+
+		FD_ZERO(&input_mask);
+		FD_SET(sock, &input_mask);
+		FD_ZERO(&output_mask);
+		FD_SET(sock, &output_mask);
+
+		if (select(sock + 1, &input_mask, &output_mask, NULL, NULL) < 0)
+		{
+			fprintf(stderr, "select() failed: %s\n", strerror(errno));
+			exit_nicely(conn);
+		}
+
+		/*
+		 * Process any results, so we keep the server's output buffer free
+		 * flowing and it can continue to process input
+		 */
+		if (FD_ISSET(sock, &input_mask))
+		{
+			PQconsumeInput(conn);
+
+			/* Read until we'd block if we tried to read */
+			while (!PQisBusy(conn) && recv_step < BI_DONE)
+			{
+				PGresult   *res;
+				const char *cmdtag;
+				const char *description = "";
+				int			status;
+
+				/*
+				 * Read next result.  If no more results from this query,
+				 * advance to the next query
+				 */
+				res = PQgetResult(conn);
+				if (res == NULL)
+					continue;
+
+				status = PGRES_COMMAND_OK;
+				switch (recv_step)
+				{
+					case BI_BEGIN_TX:
+						cmdtag = "BEGIN";
+						recv_step++;
+						break;
+					case BI_DROP_TABLE:
+						cmdtag = "DROP TABLE";
+						recv_step++;
+						break;
+					case BI_CREATE_TABLE:
+						cmdtag = "CREATE TABLE";
+						recv_step++;
+						break;
+					case BI_PREPARE:
+						cmdtag = "";
+						description = "PREPARE";
+						recv_step++;
+						break;
+					case BI_INSERT_ROWS:
+						cmdtag = "INSERT";
+						rows_to_receive--;
+						if (rows_to_receive == 0)
+							recv_step++;
+						break;
+					case BI_COMMIT_TX:
+						cmdtag = "COMMIT";
+						recv_step++;
+						break;
+					case BI_SYNC:
+						cmdtag = "";
+						description = "SYNC";
+						status = PGRES_PIPELINE_SYNC;
+						recv_step++;
+						break;
+					case BI_DONE:
+						/* unreachable */
+						description = "";
+						abort();
+				}
+
+				if (PQresultStatus(res) != status)
+					pg_fatal("%s reported status %s, expected %s\n"
+							 "Error message: \"%s\"",
+							 description, PQresStatus(PQresultStatus(res)),
+							 PQresStatus(status), PQerrorMessage(conn));
+
+				if (strncmp(PQcmdStatus(res), cmdtag, strlen(cmdtag)) != 0)
+					pg_fatal("%s expected command tag '%s', got '%s'",
+							 description, cmdtag, PQcmdStatus(res));
+
+				pg_debug("Got %s OK\n", cmdtag[0] != '\0' ? cmdtag : description);
+
+				PQclear(res);
+			}
+		}
+
+		/* Write more rows and/or the end pipeline message, if needed */
+		if (FD_ISSET(sock, &output_mask))
+		{
+			PQflush(conn);
+
+			if (send_step == BI_INSERT_ROWS)
+			{
+				snprintf(&insert_param_0[0], MAXINTLEN, "%d", rows_to_send);
+
+				if (PQsendQueryPrepared(conn, "my_insert",
+										1, insert_params, NULL, NULL, 0) == 1)
+				{
+					pg_debug("sent row %d\n", rows_to_send);
+
+					rows_to_send--;
+					if (rows_to_send == 0)
+						send_step++;
+				}
+				else
+				{
+					/*
+					 * in nonblocking mode, so it's OK for an insert to fail
+					 * to send
+					 */
+					fprintf(stderr, "WARNING: failed to send insert #%d: %s\n",
+							rows_to_send, PQerrorMessage(conn));
+				}
+			}
+			else if (send_step == BI_COMMIT_TX)
+			{
+				if (PQsendQueryParams(conn, "COMMIT",
+									  0, NULL, NULL, NULL, NULL, 0) == 1)
+				{
+					pg_debug("sent COMMIT\n");
+					send_step++;
+				}
+				else
+				{
+					fprintf(stderr, "WARNING: failed to send commit: %s\n",
+							PQerrorMessage(conn));
+				}
+			}
+			else if (send_step == BI_SYNC)
+			{
+				if (PQpipelineSync(conn) == 1)
+				{
+					fprintf(stdout, "pipeline sync sent\n");
+					send_step++;
+				}
+				else
+				{
+					fprintf(stderr, "WARNING: pipeline sync failed: %s\n",
+							PQerrorMessage(conn));
+				}
+			}
+		}
+	}
+
+	/* We've got the sync message and the pipeline should be done */
+	if (PQexitPipelineMode(conn) != 1)
+		pg_fatal("attempt to exit pipeline mode failed when it should've succeeded: %s",
+				 PQerrorMessage(conn));
+
+	if (PQsetnonblocking(conn, 0) != 0)
+		pg_fatal("failed to clear nonblocking mode: %s", PQerrorMessage(conn));
+
+	fprintf(stderr, "ok\n");
+}
+
+static void
+test_prepared(PGconn *conn)
+{
+	PGresult   *res = NULL;
+	Oid			param_oids[1] = {INT4OID};
+	Oid			expected_oids[4];
+	Oid			typ;
+
+	fprintf(stderr, "prepared... ");
+
+	if (PQenterPipelineMode(conn) != 1)
+		pg_fatal("failed to enter pipeline mode: %s", PQerrorMessage(conn));
+	if (PQsendPrepare(conn, "select_one", "SELECT $1, '42', $1::numeric, "
+					  "interval '1 sec'",
+					  1, param_oids) != 1)
+		pg_fatal("preparing query failed: %s", PQerrorMessage(conn));
+	expected_oids[0] = INT4OID;
+	expected_oids[1] = TEXTOID;
+	expected_oids[2] = NUMERICOID;
+	expected_oids[3] = INTERVALOID;
+	if (PQsendDescribePrepared(conn, "select_one") != 1)
+		pg_fatal("failed to send describePrepared: %s", PQerrorMessage(conn));
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("PQgetResult returned null");
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		pg_fatal("expected COMMAND_OK, got %s", PQresStatus(PQresultStatus(res)));
+	PQclear(res);
+	res = PQgetResult(conn);
+	if (res != NULL)
+		pg_fatal("expected NULL result");
+
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("PQgetResult returned NULL");
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		pg_fatal("expected COMMAND_OK, got %s", PQresStatus(PQresultStatus(res)));
+	if (PQnfields(res) != lengthof(expected_oids))
+		pg_fatal("expected %d columns, got %d",
+				 lengthof(expected_oids), PQnfields(res));
+	for (int i = 0; i < PQnfields(res); i++)
+	{
+		typ = PQftype(res, i);
+		if (typ != expected_oids[i])
+			pg_fatal("field %d: expected type %u, got %u",
+					 i, expected_oids[i], typ);
+	}
+	PQclear(res);
+	res = PQgetResult(conn);
+	if (res != NULL)
+		pg_fatal("expected NULL result");
+
+	res = PQgetResult(conn);
+	if (PQresultStatus(res) != PGRES_PIPELINE_SYNC)
+		pg_fatal("expected PGRES_PIPELINE_SYNC, got %s", PQresStatus(PQresultStatus(res)));
+
+	if (PQexitPipelineMode(conn) != 1)
+		pg_fatal("could not exit pipeline mode: %s", PQerrorMessage(conn));
+
+	PQexec(conn, "BEGIN");
+	PQexec(conn, "DECLARE cursor_one CURSOR FOR SELECT 1");
+	PQenterPipelineMode(conn);
+	if (PQsendDescribePortal(conn, "cursor_one") != 1)
+		pg_fatal("PQsendDescribePortal failed: %s", PQerrorMessage(conn));
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("expected NULL result");
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		pg_fatal("expected COMMAND_OK, got %s", PQresStatus(PQresultStatus(res)));
+
+	typ = PQftype(res, 0);
+	if (typ != INT4OID)
+		pg_fatal("portal: expected type %u, got %u",
+				 INT4OID, typ);
+	PQclear(res);
+	res = PQgetResult(conn);
+	if (res != NULL)
+		pg_fatal("expected NULL result");
+	res = PQgetResult(conn);
+	if (PQresultStatus(res) != PGRES_PIPELINE_SYNC)
+		pg_fatal("expected PGRES_PIPELINE_SYNC, got %s", PQresStatus(PQresultStatus(res)));
+
+	if (PQexitPipelineMode(conn) != 1)
+		pg_fatal("could not exit pipeline mode: %s", PQerrorMessage(conn));
+
+	fprintf(stderr, "ok\n");
+}
+
+static void
+test_simple_pipeline(PGconn *conn)
+{
+	PGresult   *res = NULL;
+	const char *dummy_params[1] = {"1"};
+	Oid			dummy_param_oids[1] = {INT4OID};
+
+	fprintf(stderr, "simple pipeline... ");
+
+	/*
+	 * Enter pipeline mode and dispatch a set of operations, which we'll then
+	 * process the results of as they come in.
+	 *
+	 * For a simple case we should be able to do this without interim
+	 * processing of results since our output buffer will give us enough slush
+	 * to work with and we won't block on sending. So blocking mode is fine.
+	 */
+	if (PQisnonblocking(conn))
+		pg_fatal("Expected blocking connection mode");
+
+	if (PQenterPipelineMode(conn) != 1)
+		pg_fatal("failed to enter pipeline mode: %s", PQerrorMessage(conn));
+
+	if (PQsendQueryParams(conn, "SELECT $1",
+						  1, dummy_param_oids, dummy_params,
+						  NULL, NULL, 0) != 1)
+		pg_fatal("dispatching SELECT failed: %s", PQerrorMessage(conn));
+
+	if (PQexitPipelineMode(conn) != 0)
+		pg_fatal("exiting pipeline mode with work in progress should fail, but succeeded");
+
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("PQgetResult returned null when there's a pipeline item: %s",
+				 PQerrorMessage(conn));
+
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+		pg_fatal("Unexpected result code %s from first pipeline item",
+				 PQresStatus(PQresultStatus(res)));
+
+	PQclear(res);
+	res = NULL;
+
+	if (PQgetResult(conn) != NULL)
+		pg_fatal("PQgetResult returned something extra after first query result.");
+
+	/*
+	 * Even though we've processed the result there's still a sync to come and
+	 * we can't exit pipeline mode yet
+	 */
+	if (PQexitPipelineMode(conn) != 0)
+		pg_fatal("exiting pipeline mode after query but before sync succeeded incorrectly");
+
+	res = PQgetResult(conn);
+	if (res == NULL)
+		pg_fatal("PQgetResult returned null when sync result PGRES_PIPELINE_SYNC expected: %s",
+				 PQerrorMessage(conn));
+
+	if (PQresultStatus(res) != PGRES_PIPELINE_SYNC)
+		pg_fatal("Unexpected result code %s instead of PGRES_PIPELINE_SYNC, error: %s",
+				 PQresStatus(PQresultStatus(res)), PQerrorMessage(conn));
+
+	PQclear(res);
+	res = NULL;
+
+	if (PQgetResult(conn) != NULL)
+		pg_fatal("PQgetResult returned something extra after pipeline end: %s",
+				 PQresStatus(PQresultStatus(res)));
+
+	/* We're still in pipeline mode... */
+	if (PQpipelineStatus(conn) == PQ_PIPELINE_OFF)
+		pg_fatal("Fell out of pipeline mode somehow");
+
+	/* ... until we end it, which we can safely do now */
+	if (PQexitPipelineMode(conn) != 1)
+		pg_fatal("attempt to exit pipeline mode failed when it should've succeeded: %s",
+				 PQerrorMessage(conn));
+
+	if (PQpipelineStatus(conn) != PQ_PIPELINE_OFF)
+		pg_fatal("Exiting pipeline mode didn't seem to work");
+
+	fprintf(stderr, "ok\n");
+}
+
+static void
+test_singlerowmode(PGconn *conn)
+{
+	PGresult   *res;
+	int			i;
+	bool		pipeline_ended = false;
+
+	/* 1 pipeline, 3 queries in it */
+	if (PQenterPipelineMode(conn) != 1)
+		pg_fatal("failed to enter pipeline mode: %s",
+				 PQerrorMessage(conn));
+
+	for (i = 0; i < 3; i++)
+	{
+		char	   *param[1];
+
+		param[0] = psprintf("%d", 44 + i);
+
+		if (PQsendQueryParams(conn,
+							  "SELECT generate_series(42, $1)",
+							  1,
+							  NULL,
+							  (const char **) param,
+							  NULL,
+							  NULL,
+							  0) != 1)
+			pg_fatal("failed to send query: %s",
+					 PQerrorMessage(conn));
+		pfree(param[0]);
+	}
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+
+	for (i = 0; !pipeline_ended; i++)
+	{
+		bool		first = true;
+		bool		saw_ending_tuplesok;
+		bool		isSingleTuple = false;
+
+		/* Set single row mode for only first 2 SELECT queries */
+		if (i < 2)
+		{
+			if (PQsetSingleRowMode(conn) != 1)
+				pg_fatal("PQsetSingleRowMode() failed for i=%d", i);
+		}
+
+		/* Consume rows for this query */
+		saw_ending_tuplesok = false;
+		while ((res = PQgetResult(conn)) != NULL)
+		{
+			ExecStatusType est = PQresultStatus(res);
+
+			if (est == PGRES_PIPELINE_SYNC)
+			{
+				fprintf(stderr, "end of pipeline reached\n");
+				pipeline_ended = true;
+				PQclear(res);
+				if (i != 3)
+					pg_fatal("Expected three results, got %d", i);
+				break;
+			}
+
+			/* Expect SINGLE_TUPLE for queries 0 and 1, TUPLES_OK for 2 */
+			if (first)
+			{
+				if (i <= 1 && est != PGRES_SINGLE_TUPLE)
+					pg_fatal("Expected PGRES_SINGLE_TUPLE for query %d, got %s",
+							 i, PQresStatus(est));
+				if (i >= 2 && est != PGRES_TUPLES_OK)
+					pg_fatal("Expected PGRES_TUPLES_OK for query %d, got %s",
+							 i, PQresStatus(est));
+				first = false;
+			}
+
+			fprintf(stderr, "Result status %s for query %d", PQresStatus(est), i);
+			switch (est)
+			{
+				case PGRES_TUPLES_OK:
+					fprintf(stderr, ", tuples: %d\n", PQntuples(res));
+					saw_ending_tuplesok = true;
+					if (isSingleTuple)
+					{
+						if (PQntuples(res) == 0)
+							fprintf(stderr, "all tuples received in query %d\n", i);
+						else
+							pg_fatal("Expected to follow PGRES_SINGLE_TUPLE, but received PGRES_TUPLES_OK directly instead");
+					}
+					break;
+
+				case PGRES_SINGLE_TUPLE:
+					isSingleTuple = true;
+					fprintf(stderr, ", %d tuple: %s\n", PQntuples(res), PQgetvalue(res, 0, 0));
+					break;
+
+				default:
+					pg_fatal("unexpected");
+			}
+			PQclear(res);
+		}
+		if (!pipeline_ended && !saw_ending_tuplesok)
+			pg_fatal("didn't get expected terminating TUPLES_OK");
+	}
+
+	if (PQexitPipelineMode(conn) != 1)
+		pg_fatal("failed to end pipeline mode: %s", PQerrorMessage(conn));
+}
+
+/*
+ * Simple test to verify that a pipeline is discarded as a whole when there's
+ * an error, ignoring transaction commands.
+ */
+static void
+test_transaction(PGconn *conn)
+{
+	PGresult   *res;
+	bool		expect_null;
+	int			num_syncs = 0;
+
+	res = PQexec(conn, "DROP TABLE IF EXISTS pq_pipeline_tst;"
+				 "CREATE TABLE pq_pipeline_tst (id int)");
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		pg_fatal("failed to create test table: %s",
+				 PQerrorMessage(conn));
+	PQclear(res);
+
+	if (PQenterPipelineMode(conn) != 1)
+		pg_fatal("failed to enter pipeline mode: %s",
+				 PQerrorMessage(conn));
+	if (PQsendPrepare(conn, "rollback", "ROLLBACK", 0, NULL) != 1)
+		pg_fatal("could not send prepare on pipeline: %s",
+				 PQerrorMessage(conn));
+
+	if (PQsendQueryParams(conn,
+						  "BEGIN",
+						  0, NULL, NULL, NULL, NULL, 0) != 1)
+		pg_fatal("failed to send query: %s",
+				 PQerrorMessage(conn));
+	if (PQsendQueryParams(conn,
+						  "SELECT 0/0",
+						  0, NULL, NULL, NULL, NULL, 0) != 1)
+		pg_fatal("failed to send query: %s",
+				 PQerrorMessage(conn));
+
+	/*
+	 * send a ROLLBACK using a prepared stmt. Doesn't work because we need to
+	 * get out of the pipeline-aborted state first.
+	 */
+	if (PQsendQueryPrepared(conn, "rollback", 0, NULL, NULL, NULL, 1) != 1)
+		pg_fatal("failed to execute prepared: %s",
+				 PQerrorMessage(conn));
+
+	/* This insert fails because we're in pipeline-aborted state */
+	if (PQsendQueryParams(conn,
+						  "INSERT INTO pq_pipeline_tst VALUES (1)",
+						  0, NULL, NULL, NULL, NULL, 0) != 1)
+		pg_fatal("failed to send query: %s",
+				 PQerrorMessage(conn));
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+	num_syncs++;
+
+	/*
+	 * This insert fails even though the pipeline got a SYNC, because we're in
+	 * an aborted transaction
+	 */
+	if (PQsendQueryParams(conn,
+						  "INSERT INTO pq_pipeline_tst VALUES (2)",
+						  0, NULL, NULL, NULL, NULL, 0) != 1)
+		pg_fatal("failed to send query: %s",
+				 PQerrorMessage(conn));
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+	num_syncs++;
+
+	/*
+	 * Send ROLLBACK using prepared stmt. This one works because we just did
+	 * PQpipelineSync above.
+	 */
+	if (PQsendQueryPrepared(conn, "rollback", 0, NULL, NULL, NULL, 1) != 1)
+		pg_fatal("failed to execute prepared: %s",
+				 PQerrorMessage(conn));
+
+	/*
+	 * Now that we're out of a transaction and in pipeline-good mode, this
+	 * insert works
+	 */
+	if (PQsendQueryParams(conn,
+						  "INSERT INTO pq_pipeline_tst VALUES (3)",
+						  0, NULL, NULL, NULL, NULL, 0) != 1)
+		pg_fatal("failed to send query: %s",
+				 PQerrorMessage(conn));
+	/* Send two syncs now -- match up to SYNC messages below */
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+	num_syncs++;
+	if (PQpipelineSync(conn) != 1)
+		pg_fatal("pipeline sync failed: %s", PQerrorMessage(conn));
+	num_syncs++;
+
+	expect_null = false;
+	for (int i = 0;; i++)
+	{
+		ExecStatusType restype;
+
+		res = PQgetResult(conn);
+		if (res == NULL)
+		{
+			printf("%d: got NULL result\n", i);
+			if (!expect_null)
+				pg_fatal("did not expect NULL here");
+			expect_null = false;
+			continue;
+		}
+		restype = PQresultStatus(res);
+		printf("%d: got status %s", i, PQresStatus(restype));
+		if (expect_null)
+			pg_fatal("expected NULL");
+		if (restype == PGRES_FATAL_ERROR)
+			printf("; error: %s", PQerrorMessage(conn));
+		else if (restype == PGRES_PIPELINE_ABORTED)
+		{
+			printf(": command didn't run because pipeline aborted\n");
+		}
+		else
+			printf("\n");
+		PQclear(res);
+
+		if (restype == PGRES_PIPELINE_SYNC)
+			num_syncs--;
+		else
+			expect_null = true;
+		if (num_syncs <= 0)
+			break;
+	}
+	if (PQgetResult(conn) != NULL)
+		pg_fatal("returned something extra after all the syncs: %s",
+				 PQresStatus(PQresultStatus(res)));
+
+	if (PQexitPipelineMode(conn) != 1)
+		pg_fatal("failed to end pipeline mode: %s", PQerrorMessage(conn));
+
+	/* We expect to find one tuple containing the value "3" */
+	res = PQexec(conn, "SELECT * FROM pq_pipeline_tst");
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+		pg_fatal("failed to obtain result: %s", PQerrorMessage(conn));
+	if (PQntuples(res) != 1)
+		pg_fatal("did not get 1 tuple");
+	if (strcmp(PQgetvalue(res, 0, 0), "3") != 0)
+		pg_fatal("did not get expected tuple");
+	PQclear(res);
+
+	fprintf(stderr, "ok\n");
+}
+
+static void
+usage(const char *progname)
+{
+	fprintf(stderr, "%s tests libpq's pipeline mode.\n\n", progname);
+	fprintf(stderr, "Usage:\n");
+	fprintf(stderr, "  %s tests", progname);
+	fprintf(stderr, "  %s testname [conninfo [number_of_rows]]\n", progname);
+}
+
+static void
+print_test_list(void)
+{
+	printf("disallowed_in_pipeline\n");
+	printf("multi_pipelines\n");
+	printf("pipeline_abort\n");
+	printf("pipelined_insert\n");
+	printf("prepared\n");
+	printf("simple_pipeline\n");
+	printf("singlerow\n");
+	printf("transaction\n");
+}
+
+int
+main(int argc, char **argv)
+{
+	const char *conninfo = "";
+	PGconn	   *conn;
+	int			numrows = 10000;
+	PGresult   *res;
+
+	if (strcmp(argv[1], "tests") == 0)
+	{
+		print_test_list();
+		exit(0);
+	}
+
+	/*
+	 * The testname parameter is mandatory; it can be followed by a conninfo
+	 * string and number of rows.
+	 */
+	if (argc < 2 || argc > 4)
+	{
+		usage(argv[0]);
+		exit(1);
+	}
+
+	if (argc >= 3)
+		conninfo = pg_strdup(argv[2]);
+
+	if (argc >= 4)
+	{
+		errno = 0;
+		numrows = strtol(argv[3], NULL, 10);
+		if (errno != 0 || numrows <= 0)
+		{
+			fprintf(stderr, "couldn't parse \"%s\" as a positive integer\n", argv[3]);
+			exit(1);
+		}
+	}
+
+	/* Make a connection to the database */
+	conn = PQconnectdb(conninfo);
+	if (PQstatus(conn) != CONNECTION_OK)
+	{
+		fprintf(stderr, "Connection to database failed: %s\n",
+				PQerrorMessage(conn));
+		exit_nicely(conn);
+	}
+	res = PQexec(conn, "SET lc_messages TO \"C\"");
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+		pg_fatal("failed to set lc_messages: %s", PQerrorMessage(conn));
+
+	if (strcmp(argv[1], "disallowed_in_pipeline") == 0)
+		test_disallowed_in_pipeline(conn);
+	else if (strcmp(argv[1], "multi_pipelines") == 0)
+		test_multi_pipelines(conn);
+	else if (strcmp(argv[1], "pipeline_abort") == 0)
+		test_pipeline_abort(conn);
+	else if (strcmp(argv[1], "pipelined_insert") == 0)
+		test_pipelined_insert(conn, numrows);
+	else if (strcmp(argv[1], "prepared") == 0)
+		test_prepared(conn);
+	else if (strcmp(argv[1], "simple_pipeline") == 0)
+		test_simple_pipeline(conn);
+	else if (strcmp(argv[1], "singlerow") == 0)
+		test_singlerowmode(conn);
+	else if (strcmp(argv[1], "transaction") == 0)
+		test_transaction(conn);
+	else
+	{
+		fprintf(stderr, "\"%s\" is not a recognized test name\n", argv[1]);
+		usage(argv[0]);
+		exit(1);
+	}
+
+	/* close the connection to the database and cleanup */
+	PQfinish(conn);
+	return 0;
+}
diff --git a/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl b/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
new file mode 100644
index 0000000000..ba15b64ca7
--- /dev/null
+++ b/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
@@ -0,0 +1,28 @@
+use strict;
+use warnings;
+
+use Config;
+use PostgresNode;
+use TestLib;
+use Test::More tests => 8;
+use Cwd;
+
+my $node = get_new_node('main');
+$node->init;
+$node->start;
+
+my $numrows = 10000;
+$ENV{PATH} = "$ENV{PATH}:" . getcwd();
+
+my ($out, $err) = run_command(['libpq_pipeline', 'tests']);
+die "oops: $err" unless $err eq '';
+my @tests = split(/\s/, $out);
+
+for my $testname (@tests)
+{
+	$node->command_ok(
+		[ 'libpq_pipeline', $testname, $node->connstr('postgres'), $numrows ],
+		"libpq_pipeline $testname");
+}
+
+$node->stop('fast');