Move some code from src/bin/scripts to src/fe_utils to permit reuse.

The parallel slots infrastructure (which implements client-side
multiplexing of server connections doing similar things, not
threading or multiple processes or anything like that) are moved from
src/bin/scripts/scripts_parallel.c to src/fe_utils/parallel_slot.c.

The functions consumeQueryResult() and processQueryResult() which were
previously part of src/bin/scripts/common.c are now moved into that
file as well, becoming static helper functions. This might need to be
changed in the future, but currently they're not used for anything
else.

Some other functions from src/bin/scripts/common.c are moved to to
src/fe_utils and are split up among several files.  connectDatabase(),
connectMaintenanceDatabase(), and disconnectDatabase() are moved to
connect_utils.c.  executeQuery(), executeCommand(), and
executeMaintenanceCommand() are move to query_utils.c.
handle_help_version_opts() is moved to option_utils.c.

Mark Dilger, reviewed by me. The larger patch series of which this is
a part has also had review from Peter Geoghegan, Andres Freund, Álvaro
Herrera, Michael Paquier, and Amul Sul, but I don't know whether any
of them have reviewed this bit specifically.

Discussion: http://postgr.es/m/12ED3DA8-25F0-4B68-937D-D907CFBF08E7@enterprisedb.com
Discussion: http://postgr.es/m/5F743835-3399-419C-8324-2D424237E999@enterprisedb.com
Discussion: http://postgr.es/m/70655DF3-33CE-4527-9A4D-DDEB582B6BA0@enterprisedb.com

22 files changed, 498 insertions, 385 deletions

diff --git a/src/bin/scripts/Makefile b/src/bin/scripts/Makefile
index a02e4e430c..b8d7cf2f2d 100644
--- a/src/bin/scripts/Makefile
+++ b/src/bin/scripts/Makefile
@@ -28,8 +28,8 @@ createuser: createuser.o common.o $(WIN32RES) | submake-libpq submake-libpgport
 dropdb: dropdb.o common.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
 dropuser: dropuser.o common.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
 clusterdb: clusterdb.o common.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
-vacuumdb: vacuumdb.o common.o scripts_parallel.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
-reindexdb: reindexdb.o common.o scripts_parallel.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
+vacuumdb: vacuumdb.o common.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
+reindexdb: reindexdb.o common.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
 pg_isready: pg_isready.o common.o $(WIN32RES) | submake-libpq submake-libpgport submake-libpgfeutils
 
 install: all installdirs
@@ -50,7 +50,7 @@ uninstall:
 
 clean distclean maintainer-clean:
 	rm -f $(addsuffix $(X), $(PROGRAMS)) $(addsuffix .o, $(PROGRAMS))
-	rm -f common.o scripts_parallel.o $(WIN32RES)
+	rm -f common.o $(WIN32RES)
 	rm -rf tmp_check
 
 check:
diff --git a/src/bin/scripts/clusterdb.c b/src/bin/scripts/clusterdb.c
index 7d25bb31d4..fc771eed77 100644
--- a/src/bin/scripts/clusterdb.c
+++ b/src/bin/scripts/clusterdb.c
@@ -13,6 +13,8 @@
 #include "common.h"
 #include "common/logging.h"
 #include "fe_utils/cancel.h"
+#include "fe_utils/option_utils.h"
+#include "fe_utils/query_utils.h"
 #include "fe_utils/simple_list.h"
 #include "fe_utils/string_utils.h"
 
diff --git a/src/bin/scripts/common.c b/src/bin/scripts/common.c
index 21ef297e6e..c86c19eae2 100644
--- a/src/bin/scripts/common.c
+++ b/src/bin/scripts/common.c
@@ -22,325 +22,9 @@
 #include "common/logging.h"
 #include "common/string.h"
 #include "fe_utils/cancel.h"
+#include "fe_utils/query_utils.h"
 #include "fe_utils/string_utils.h"
 
-#define ERRCODE_UNDEFINED_TABLE  "42P01"
-
-/*
- * Provide strictly harmonized handling of --help and --version
- * options.
- */
-void
-handle_help_version_opts(int argc, char *argv[],
-						 const char *fixed_progname, help_handler hlp)
-{
-	if (argc > 1)
-	{
-		if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-?") == 0)
-		{
-			hlp(get_progname(argv[0]));
-			exit(0);
-		}
-		if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
-		{
-			printf("%s (PostgreSQL) " PG_VERSION "\n", fixed_progname);
-			exit(0);
-		}
-	}
-}
-
-
-/*
- * Make a database connection with the given parameters.
- *
- * An interactive password prompt is automatically issued if needed and
- * allowed by cparams->prompt_password.
- *
- * If allow_password_reuse is true, we will try to re-use any password
- * given during previous calls to this routine.  (Callers should not pass
- * allow_password_reuse=true unless reconnecting to the same database+user
- * as before, else we might create password exposure hazards.)
- */
-PGconn *
-connectDatabase(const ConnParams *cparams, const char *progname,
-				bool echo, bool fail_ok, bool allow_password_reuse)
-{
-	PGconn	   *conn;
-	bool		new_pass;
-	static char *password = NULL;
-
-	/* Callers must supply at least dbname; other params can be NULL */
-	Assert(cparams->dbname);
-
-	if (!allow_password_reuse && password)
-	{
-		free(password);
-		password = NULL;
-	}
-
-	if (cparams->prompt_password == TRI_YES && password == NULL)
-		password = simple_prompt("Password: ", false);
-
-	/*
-	 * Start the connection.  Loop until we have a password if requested by
-	 * backend.
-	 */
-	do
-	{
-		const char *keywords[8];
-		const char *values[8];
-		int			i = 0;
-
-		/*
-		 * If dbname is a connstring, its entries can override the other
-		 * values obtained from cparams; but in turn, override_dbname can
-		 * override the dbname component of it.
-		 */
-		keywords[i] = "host";
-		values[i++] = cparams->pghost;
-		keywords[i] = "port";
-		values[i++] = cparams->pgport;
-		keywords[i] = "user";
-		values[i++] = cparams->pguser;
-		keywords[i] = "password";
-		values[i++] = password;
-		keywords[i] = "dbname";
-		values[i++] = cparams->dbname;
-		if (cparams->override_dbname)
-		{
-			keywords[i] = "dbname";
-			values[i++] = cparams->override_dbname;
-		}
-		keywords[i] = "fallback_application_name";
-		values[i++] = progname;
-		keywords[i] = NULL;
-		values[i++] = NULL;
-		Assert(i <= lengthof(keywords));
-
-		new_pass = false;
-		conn = PQconnectdbParams(keywords, values, true);
-
-		if (!conn)
-		{
-			pg_log_error("could not connect to database %s: out of memory",
-						 cparams->dbname);
-			exit(1);
-		}
-
-		/*
-		 * No luck?  Trying asking (again) for a password.
-		 */
-		if (PQstatus(conn) == CONNECTION_BAD &&
-			PQconnectionNeedsPassword(conn) &&
-			cparams->prompt_password != TRI_NO)
-		{
-			PQfinish(conn);
-			if (password)
-				free(password);
-			password = simple_prompt("Password: ", false);
-			new_pass = true;
-		}
-	} while (new_pass);
-
-	/* check to see that the backend connection was successfully made */
-	if (PQstatus(conn) == CONNECTION_BAD)
-	{
-		if (fail_ok)
-		{
-			PQfinish(conn);
-			return NULL;
-		}
-		pg_log_error("%s", PQerrorMessage(conn));
-		exit(1);
-	}
-
-	/* Start strict; callers may override this. */
-	PQclear(executeQuery(conn, ALWAYS_SECURE_SEARCH_PATH_SQL, echo));
-
-	return conn;
-}
-
-/*
- * Try to connect to the appropriate maintenance database.
- *
- * This differs from connectDatabase only in that it has a rule for
- * inserting a default "dbname" if none was given (which is why cparams
- * is not const).  Note that cparams->dbname should typically come from
- * a --maintenance-db command line parameter.
- */
-PGconn *
-connectMaintenanceDatabase(ConnParams *cparams,
-						   const char *progname, bool echo)
-{
-	PGconn	   *conn;
-
-	/* If a maintenance database name was specified, just connect to it. */
-	if (cparams->dbname)
-		return connectDatabase(cparams, progname, echo, false, false);
-
-	/* Otherwise, try postgres first and then template1. */
-	cparams->dbname = "postgres";
-	conn = connectDatabase(cparams, progname, echo, true, false);
-	if (!conn)
-	{
-		cparams->dbname = "template1";
-		conn = connectDatabase(cparams, progname, echo, false, false);
-	}
-	return conn;
-}
-
-/*
- * Disconnect the given connection, canceling any statement if one is active.
- */
-void
-disconnectDatabase(PGconn *conn)
-{
-	char		errbuf[256];
-
-	Assert(conn != NULL);
-
-	if (PQtransactionStatus(conn) == PQTRANS_ACTIVE)
-	{
-		PGcancel   *cancel;
-
-		if ((cancel = PQgetCancel(conn)))
-		{
-			(void) PQcancel(cancel, errbuf, sizeof(errbuf));
-			PQfreeCancel(cancel);
-		}
-	}
-
-	PQfinish(conn);
-}
-
-/*
- * Run a query, return the results, exit program on failure.
- */
-PGresult *
-executeQuery(PGconn *conn, const char *query, bool echo)
-{
-	PGresult   *res;
-
-	if (echo)
-		printf("%s\n", query);
-
-	res = PQexec(conn, query);
-	if (!res ||
-		PQresultStatus(res) != PGRES_TUPLES_OK)
-	{
-		pg_log_error("query failed: %s", PQerrorMessage(conn));
-		pg_log_info("query was: %s", query);
-		PQfinish(conn);
-		exit(1);
-	}
-
-	return res;
-}
-
-
-/*
- * As above for a SQL command (which returns nothing).
- */
-void
-executeCommand(PGconn *conn, const char *query, bool echo)
-{
-	PGresult   *res;
-
-	if (echo)
-		printf("%s\n", query);
-
-	res = PQexec(conn, query);
-	if (!res ||
-		PQresultStatus(res) != PGRES_COMMAND_OK)
-	{
-		pg_log_error("query failed: %s", PQerrorMessage(conn));
-		pg_log_info("query was: %s", query);
-		PQfinish(conn);
-		exit(1);
-	}
-
-	PQclear(res);
-}
-
-
-/*
- * As above for a SQL maintenance command (returns command success).
- * Command is executed with a cancel handler set, so Ctrl-C can
- * interrupt it.
- */
-bool
-executeMaintenanceCommand(PGconn *conn, const char *query, bool echo)
-{
-	PGresult   *res;
-	bool		r;
-
-	if (echo)
-		printf("%s\n", query);
-
-	SetCancelConn(conn);
-	res = PQexec(conn, query);
-	ResetCancelConn();
-
-	r = (res && PQresultStatus(res) == PGRES_COMMAND_OK);
-
-	if (res)
-		PQclear(res);
-
-	return r;
-}
-
-/*
- * Consume all the results generated for the given connection until
- * nothing remains.  If at least one error is encountered, return false.
- * Note that this will block if the connection is busy.
- */
-bool
-consumeQueryResult(PGconn *conn)
-{
-	bool		ok = true;
-	PGresult   *result;
-
-	SetCancelConn(conn);
-	while ((result = PQgetResult(conn)) != NULL)
-	{
-		if (!processQueryResult(conn, result))
-			ok = false;
-	}
-	ResetCancelConn();
-	return ok;
-}
-
-/*
- * Process (and delete) a query result.  Returns true if there's no error,
- * false otherwise -- but errors about trying to work on a missing relation
- * are reported and subsequently ignored.
- */
-bool
-processQueryResult(PGconn *conn, PGresult *result)
-{
-	/*
-	 * If it's an error, report it.  Errors about a missing table are harmless
-	 * so we continue processing; but die for other errors.
-	 */
-	if (PQresultStatus(result) != PGRES_COMMAND_OK)
-	{
-		char	   *sqlState = PQresultErrorField(result, PG_DIAG_SQLSTATE);
-
-		pg_log_error("processing of database \"%s\" failed: %s",
-					 PQdb(conn), PQerrorMessage(conn));
-
-		if (sqlState && strcmp(sqlState, ERRCODE_UNDEFINED_TABLE) != 0)
-		{
-			PQclear(result);
-			return false;
-		}
-	}
-
-	PQclear(result);
-	return true;
-}
-
-
 /*
  * Split TABLE[(COLUMNS)] into TABLE and [(COLUMNS)] portions.  When you
  * finish using them, pg_free(*table).  *columns is a pointer into "spec",
diff --git a/src/bin/scripts/common.h b/src/bin/scripts/common.h
index 5630975712..ddd8f35274 100644
--- a/src/bin/scripts/common.h
+++ b/src/bin/scripts/common.h
@@ -10,58 +10,11 @@
 #define COMMON_H
 
 #include "common/username.h"
+#include "fe_utils/connect_utils.h"
 #include "getopt_long.h"		/* pgrminclude ignore */
 #include "libpq-fe.h"
 #include "pqexpbuffer.h"		/* pgrminclude ignore */
 
-enum trivalue
-{
-	TRI_DEFAULT,
-	TRI_NO,
-	TRI_YES
-};
-
-/* Parameters needed by connectDatabase/connectMaintenanceDatabase */
-typedef struct _connParams
-{
-	/* These fields record the actual command line parameters */
-	const char *dbname;			/* this may be a connstring! */
-	const char *pghost;
-	const char *pgport;
-	const char *pguser;
-	enum trivalue prompt_password;
-	/* If not NULL, this overrides the dbname obtained from command line */
-	/* (but *only* the DB name, not anything else in the connstring) */
-	const char *override_dbname;
-} ConnParams;
-
-typedef void (*help_handler) (const char *progname);
-
-extern void handle_help_version_opts(int argc, char *argv[],
-									 const char *fixed_progname,
-									 help_handler hlp);
-
-extern PGconn *connectDatabase(const ConnParams *cparams,
-							   const char *progname,
-							   bool echo, bool fail_ok,
-							   bool allow_password_reuse);
-
-extern PGconn *connectMaintenanceDatabase(ConnParams *cparams,
-										  const char *progname, bool echo);
-
-extern void disconnectDatabase(PGconn *conn);
-
-extern PGresult *executeQuery(PGconn *conn, const char *query, bool echo);
-
-extern void executeCommand(PGconn *conn, const char *query, bool echo);
-
-extern bool executeMaintenanceCommand(PGconn *conn, const char *query,
-									  bool echo);
-
-extern bool consumeQueryResult(PGconn *conn);
-
-extern bool processQueryResult(PGconn *conn, PGresult *result);
-
 extern void splitTableColumnsSpec(const char *spec, int encoding,
 								  char **table, const char **columns);
 
diff --git a/src/bin/scripts/createdb.c b/src/bin/scripts/createdb.c
index abf21d4942..041454f075 100644
--- a/src/bin/scripts/createdb.c
+++ b/src/bin/scripts/createdb.c
@@ -13,6 +13,7 @@
 
 #include "common.h"
 #include "common/logging.h"
+#include "fe_utils/option_utils.h"
 #include "fe_utils/string_utils.h"
 
 
diff --git a/src/bin/scripts/createuser.c b/src/bin/scripts/createuser.c
index 47b0e28bc6..ef7e0e549f 100644
--- a/src/bin/scripts/createuser.c
+++ b/src/bin/scripts/createuser.c
@@ -14,6 +14,7 @@
 #include "common.h"
 #include "common/logging.h"
 #include "common/string.h"
+#include "fe_utils/option_utils.h"
 #include "fe_utils/simple_list.h"
 #include "fe_utils/string_utils.h"
 
diff --git a/src/bin/scripts/dropdb.c b/src/bin/scripts/dropdb.c
index ba0dcdecb9..b154ed1bb6 100644
--- a/src/bin/scripts/dropdb.c
+++ b/src/bin/scripts/dropdb.c
@@ -13,6 +13,7 @@
 #include "postgres_fe.h"
 #include "common.h"
 #include "common/logging.h"
+#include "fe_utils/option_utils.h"
 #include "fe_utils/string_utils.h"
 
 
diff --git a/src/bin/scripts/dropuser.c b/src/bin/scripts/dropuser.c
index ff5b455ae5..61b8557bc7 100644
--- a/src/bin/scripts/dropuser.c
+++ b/src/bin/scripts/dropuser.c
@@ -14,6 +14,7 @@
 #include "common.h"
 #include "common/logging.h"
 #include "common/string.h"
+#include "fe_utils/option_utils.h"
 #include "fe_utils/string_utils.h"
 
 
diff --git a/src/bin/scripts/nls.mk b/src/bin/scripts/nls.mk
index 5d5dd11b7b..7fc716092e 100644
--- a/src/bin/scripts/nls.mk
+++ b/src/bin/scripts/nls.mk
@@ -7,7 +7,7 @@ GETTEXT_FILES    = $(FRONTEND_COMMON_GETTEXT_FILES) \
                    clusterdb.c vacuumdb.c reindexdb.c \
                    pg_isready.c \
                    common.c \
-                   scripts_parallel.c \
+                   ../../fe_utils/parallel_slot.c \
                    ../../fe_utils/cancel.c ../../fe_utils/print.c \
                    ../../common/fe_memutils.c ../../common/username.c
 GETTEXT_TRIGGERS = $(FRONTEND_COMMON_GETTEXT_TRIGGERS) simple_prompt yesno_prompt
diff --git a/src/bin/scripts/pg_isready.c b/src/bin/scripts/pg_isready.c
index ceb8a09b4c..fc6f7b0a93 100644
--- a/src/bin/scripts/pg_isready.c
+++ b/src/bin/scripts/pg_isready.c
@@ -12,6 +12,7 @@
 #include "postgres_fe.h"
 #include "common.h"
 #include "common/logging.h"
+#include "fe_utils/option_utils.h"
 
 #define DEFAULT_CONNECT_TIMEOUT "3"
 
diff --git a/src/bin/scripts/reindexdb.c b/src/bin/scripts/reindexdb.c
index dece8200fa..7781fb1151 100644
--- a/src/bin/scripts/reindexdb.c
+++ b/src/bin/scripts/reindexdb.c
@@ -16,9 +16,11 @@
 #include "common/connect.h"
 #include "common/logging.h"
 #include "fe_utils/cancel.h"
+#include "fe_utils/option_utils.h"
+#include "fe_utils/parallel_slot.h"
+#include "fe_utils/query_utils.h"
 #include "fe_utils/simple_list.h"
 #include "fe_utils/string_utils.h"
-#include "scripts_parallel.h"
 
 typedef enum ReindexType
 {
diff --git a/src/bin/scripts/vacuumdb.c b/src/bin/scripts/vacuumdb.c
index 8246327770..ed320817bc 100644
--- a/src/bin/scripts/vacuumdb.c
+++ b/src/bin/scripts/vacuumdb.c
@@ -18,9 +18,11 @@
 #include "common/connect.h"
 #include "common/logging.h"
 #include "fe_utils/cancel.h"
+#include "fe_utils/option_utils.h"
+#include "fe_utils/parallel_slot.h"
+#include "fe_utils/query_utils.h"
 #include "fe_utils/simple_list.h"
 #include "fe_utils/string_utils.h"
-#include "scripts_parallel.h"
 
 
 /* vacuum options controlled by user flags */
diff --git a/src/fe_utils/Makefile b/src/fe_utils/Makefile
index 10d6838cf9..456c441a33 100644
--- a/src/fe_utils/Makefile
+++ b/src/fe_utils/Makefile
@@ -23,9 +23,13 @@ OBJS = \
 	archive.o \
 	cancel.o \
 	conditional.o \
+	connect_utils.o \
 	mbprint.o \
+	option_utils.o \
+	parallel_slot.o \
 	print.o \
 	psqlscan.o \
+	query_utils.o \
 	recovery_gen.o \
 	simple_list.o \
 	string_utils.o
diff --git a/src/fe_utils/connect_utils.c b/src/fe_utils/connect_utils.c
new file mode 100644
index 0000000000..96bb798316
--- /dev/null
+++ b/src/fe_utils/connect_utils.c
@@ -0,0 +1,181 @@
+/*-------------------------------------------------------------------------
+ *
+ * Facilities for frontend code to connect to and disconnect from databases.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/fe_utils/connect_utils.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres_fe.h"
+
+#include "common/connect.h"
+#include "common/logging.h"
+#include "common/string.h"
+#include "fe_utils/connect_utils.h"
+#include "fe_utils/query_utils.h"
+
+/*
+ * Make a database connection with the given parameters.
+ *
+ * An interactive password prompt is automatically issued if needed and
+ * allowed by cparams->prompt_password.
+ *
+ * If allow_password_reuse is true, we will try to re-use any password
+ * given during previous calls to this routine.  (Callers should not pass
+ * allow_password_reuse=true unless reconnecting to the same database+user
+ * as before, else we might create password exposure hazards.)
+ */
+PGconn *
+connectDatabase(const ConnParams *cparams, const char *progname,
+				bool echo, bool fail_ok, bool allow_password_reuse)
+{
+	PGconn	   *conn;
+	bool		new_pass;
+	static char *password = NULL;
+
+	/* Callers must supply at least dbname; other params can be NULL */
+	Assert(cparams->dbname);
+
+	if (!allow_password_reuse && password)
+	{
+		free(password);
+		password = NULL;
+	}
+
+	if (cparams->prompt_password == TRI_YES && password == NULL)
+		password = simple_prompt("Password: ", false);
+
+	/*
+	 * Start the connection.  Loop until we have a password if requested by
+	 * backend.
+	 */
+	do
+	{
+		const char *keywords[8];
+		const char *values[8];
+		int			i = 0;
+
+		/*
+		 * If dbname is a connstring, its entries can override the other
+		 * values obtained from cparams; but in turn, override_dbname can
+		 * override the dbname component of it.
+		 */
+		keywords[i] = "host";
+		values[i++] = cparams->pghost;
+		keywords[i] = "port";
+		values[i++] = cparams->pgport;
+		keywords[i] = "user";
+		values[i++] = cparams->pguser;
+		keywords[i] = "password";
+		values[i++] = password;
+		keywords[i] = "dbname";
+		values[i++] = cparams->dbname;
+		if (cparams->override_dbname)
+		{
+			keywords[i] = "dbname";
+			values[i++] = cparams->override_dbname;
+		}
+		keywords[i] = "fallback_application_name";
+		values[i++] = progname;
+		keywords[i] = NULL;
+		values[i++] = NULL;
+		Assert(i <= lengthof(keywords));
+
+		new_pass = false;
+		conn = PQconnectdbParams(keywords, values, true);
+
+		if (!conn)
+		{
+			pg_log_error("could not connect to database %s: out of memory",
+						 cparams->dbname);
+			exit(1);
+		}
+
+		/*
+		 * No luck?  Trying asking (again) for a password.
+		 */
+		if (PQstatus(conn) == CONNECTION_BAD &&
+			PQconnectionNeedsPassword(conn) &&
+			cparams->prompt_password != TRI_NO)
+		{
+			PQfinish(conn);
+			if (password)
+				free(password);
+			password = simple_prompt("Password: ", false);
+			new_pass = true;
+		}
+	} while (new_pass);
+
+	/* check to see that the backend connection was successfully made */
+	if (PQstatus(conn) == CONNECTION_BAD)
+	{
+		if (fail_ok)
+		{
+			PQfinish(conn);
+			return NULL;
+		}
+		pg_log_error("%s", PQerrorMessage(conn));
+		exit(1);
+	}
+
+	/* Start strict; callers may override this. */
+	PQclear(executeQuery(conn, ALWAYS_SECURE_SEARCH_PATH_SQL, echo));
+
+	return conn;
+}
+
+/*
+ * Try to connect to the appropriate maintenance database.
+ *
+ * This differs from connectDatabase only in that it has a rule for
+ * inserting a default "dbname" if none was given (which is why cparams
+ * is not const).  Note that cparams->dbname should typically come from
+ * a --maintenance-db command line parameter.
+ */
+PGconn *
+connectMaintenanceDatabase(ConnParams *cparams,
+						   const char *progname, bool echo)
+{
+	PGconn	   *conn;
+
+	/* If a maintenance database name was specified, just connect to it. */
+	if (cparams->dbname)
+		return connectDatabase(cparams, progname, echo, false, false);
+
+	/* Otherwise, try postgres first and then template1. */
+	cparams->dbname = "postgres";
+	conn = connectDatabase(cparams, progname, echo, true, false);
+	if (!conn)
+	{
+		cparams->dbname = "template1";
+		conn = connectDatabase(cparams, progname, echo, false, false);
+	}
+	return conn;
+}
+
+/*
+ * Disconnect the given connection, canceling any statement if one is active.
+ */
+void
+disconnectDatabase(PGconn *conn)
+{
+	char		errbuf[256];
+
+	Assert(conn != NULL);
+
+	if (PQtransactionStatus(conn) == PQTRANS_ACTIVE)
+	{
+		PGcancel   *cancel;
+
+		if ((cancel = PQgetCancel(conn)))
+		{
+			(void) PQcancel(cancel, errbuf, sizeof(errbuf));
+			PQfreeCancel(cancel);
+		}
+	}
+
+	PQfinish(conn);
+}
diff --git a/src/fe_utils/option_utils.c b/src/fe_utils/option_utils.c
new file mode 100644
index 0000000000..e19a495dba
--- /dev/null
+++ b/src/fe_utils/option_utils.c
@@ -0,0 +1,38 @@
+/*-------------------------------------------------------------------------
+ *
+ * Command line option processing facilities for frontend code
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/fe_utils/option_utils.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres_fe.h"
+
+#include "fe_utils/option_utils.h"
+
+/*
+ * Provide strictly harmonized handling of --help and --version
+ * options.
+ */
+void
+handle_help_version_opts(int argc, char *argv[],
+						 const char *fixed_progname, help_handler hlp)
+{
+	if (argc > 1)
+	{
+		if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-?") == 0)
+		{
+			hlp(get_progname(argv[0]));
+			exit(0);
+		}
+		if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0)
+		{
+			printf("%s (PostgreSQL) " PG_VERSION "\n", fixed_progname);
+			exit(0);
+		}
+	}
+}
diff --git a/src/bin/scripts/scripts_parallel.c b/src/fe_utils/parallel_slot.c
index 1f863a1bb4..3987a4702b 100644
--- a/src/bin/scripts/scripts_parallel.c
+++ b/src/fe_utils/parallel_slot.c
@@ -1,13 +1,13 @@
 /*-------------------------------------------------------------------------
  *
- *	scripts_parallel.c
- *		Parallel support for bin/scripts/
+ *	parallel_slot.c
+ *		Parallel support for front-end parallel database connections
  *
  *
  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * src/bin/scripts/scripts_parallel.c
+ * src/fe_utils/parallel_slot.c
  *
  *-------------------------------------------------------------------------
  */
@@ -22,13 +22,15 @@
 #include <sys/select.h>
 #endif
 
-#include "common.h"
 #include "common/logging.h"
 #include "fe_utils/cancel.h"
-#include "scripts_parallel.h"
+#include "fe_utils/parallel_slot.h"
+
+#define ERRCODE_UNDEFINED_TABLE  "42P01"
 
 static void init_slot(ParallelSlot *slot, PGconn *conn);
 static int	select_loop(int maxFd, fd_set *workerset);
+static bool processQueryResult(PGconn *conn, PGresult *result);
 
 static void
 init_slot(ParallelSlot *slot, PGconn *conn)
@@ -39,6 +41,57 @@ init_slot(ParallelSlot *slot, PGconn *conn)
 }
 
 /*
+ * Process (and delete) a query result.  Returns true if there's no error,
+ * false otherwise -- but errors about trying to work on a missing relation
+ * are reported and subsequently ignored.
+ */
+static bool
+processQueryResult(PGconn *conn, PGresult *result)
+{
+	/*
+	 * If it's an error, report it.  Errors about a missing table are harmless
+	 * so we continue processing; but die for other errors.
+	 */
+	if (PQresultStatus(result) != PGRES_COMMAND_OK)
+	{
+		char	   *sqlState = PQresultErrorField(result, PG_DIAG_SQLSTATE);
+
+		pg_log_error("processing of database \"%s\" failed: %s",
+					 PQdb(conn), PQerrorMessage(conn));
+
+		if (sqlState && strcmp(sqlState, ERRCODE_UNDEFINED_TABLE) != 0)
+		{
+			PQclear(result);
+			return false;
+		}
+	}
+
+	PQclear(result);
+	return true;
+}
+
+/*
+ * Consume all the results generated for the given connection until
+ * nothing remains.  If at least one error is encountered, return false.
+ * Note that this will block if the connection is busy.
+ */
+static bool
+consumeQueryResult(PGconn *conn)
+{
+	bool		ok = true;
+	PGresult   *result;
+
+	SetCancelConn(conn);
+	while ((result = PQgetResult(conn)) != NULL)
+	{
+		if (!processQueryResult(conn, result))
+			ok = false;
+	}
+	ResetCancelConn();
+	return ok;
+}
+
+/*
  * Wait until a file descriptor from the given set becomes readable.
  *
  * Returns the number of ready descriptors, or -1 on failure (including
diff --git a/src/fe_utils/query_utils.c b/src/fe_utils/query_utils.c
new file mode 100644
index 0000000000..d5ffe56fd6
--- /dev/null
+++ b/src/fe_utils/query_utils.c
@@ -0,0 +1,92 @@
+/*-------------------------------------------------------------------------
+ *
+ * Facilities for frontend code to query a databases.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/fe_utils/query_utils.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres_fe.h"
+
+#include "common/logging.h"
+#include "fe_utils/cancel.h"
+#include "fe_utils/query_utils.h"
+
+/*
+ * Run a query, return the results, exit program on failure.
+ */
+PGresult *
+executeQuery(PGconn *conn, const char *query, bool echo)
+{
+	PGresult   *res;
+
+	if (echo)
+		printf("%s\n", query);
+
+	res = PQexec(conn, query);
+	if (!res ||
+		PQresultStatus(res) != PGRES_TUPLES_OK)
+	{
+		pg_log_error("query failed: %s", PQerrorMessage(conn));
+		pg_log_info("query was: %s", query);
+		PQfinish(conn);
+		exit(1);
+	}
+
+	return res;
+}
+
+
+/*
+ * As above for a SQL command (which returns nothing).
+ */
+void
+executeCommand(PGconn *conn, const char *query, bool echo)
+{
+	PGresult   *res;
+
+	if (echo)
+		printf("%s\n", query);
+
+	res = PQexec(conn, query);
+	if (!res ||
+		PQresultStatus(res) != PGRES_COMMAND_OK)
+	{
+		pg_log_error("query failed: %s", PQerrorMessage(conn));
+		pg_log_info("query was: %s", query);
+		PQfinish(conn);
+		exit(1);
+	}
+
+	PQclear(res);
+}
+
+
+/*
+ * As above for a SQL maintenance command (returns command success).
+ * Command is executed with a cancel handler set, so Ctrl-C can
+ * interrupt it.
+ */
+bool
+executeMaintenanceCommand(PGconn *conn, const char *query, bool echo)
+{
+	PGresult   *res;
+	bool		r;
+
+	if (echo)
+		printf("%s\n", query);
+
+	SetCancelConn(conn);
+	res = PQexec(conn, query);
+	ResetCancelConn();
+
+	r = (res && PQresultStatus(res) == PGRES_COMMAND_OK);
+
+	if (res)
+		PQclear(res);
+
+	return r;
+}
diff --git a/src/include/fe_utils/connect_utils.h b/src/include/fe_utils/connect_utils.h
new file mode 100644
index 0000000000..5048940509
--- /dev/null
+++ b/src/include/fe_utils/connect_utils.h
@@ -0,0 +1,48 @@
+/*-------------------------------------------------------------------------
+ *
+ * Facilities for frontend code to connect to and disconnect from databases.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/fe_utils/connect_utils.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef CONNECT_UTILS_H
+#define CONNECT_UTILS_H
+
+#include "libpq-fe.h"
+
+enum trivalue
+{
+	TRI_DEFAULT,
+	TRI_NO,
+	TRI_YES
+};
+
+/* Parameters needed by connectDatabase/connectMaintenanceDatabase */
+typedef struct _connParams
+{
+	/* These fields record the actual command line parameters */
+	const char *dbname;			/* this may be a connstring! */
+	const char *pghost;
+	const char *pgport;
+	const char *pguser;
+	enum trivalue prompt_password;
+	/* If not NULL, this overrides the dbname obtained from command line */
+	/* (but *only* the DB name, not anything else in the connstring) */
+	const char *override_dbname;
+} ConnParams;
+
+extern PGconn *connectDatabase(const ConnParams *cparams,
+							   const char *progname,
+							   bool echo, bool fail_ok,
+							   bool allow_password_reuse);
+
+extern PGconn *connectMaintenanceDatabase(ConnParams *cparams,
+										  const char *progname, bool echo);
+
+extern void disconnectDatabase(PGconn *conn);
+
+#endif							/* CONNECT_UTILS_H */
diff --git a/src/include/fe_utils/option_utils.h b/src/include/fe_utils/option_utils.h
new file mode 100644
index 0000000000..d653cb94e3
--- /dev/null
+++ b/src/include/fe_utils/option_utils.h
@@ -0,0 +1,23 @@
+/*-------------------------------------------------------------------------
+ *
+ * Command line option processing facilities for frontend code
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/fe_utils/option_utils.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef OPTION_UTILS_H
+#define OPTION_UTILS_H
+
+#include "postgres_fe.h"
+
+typedef void (*help_handler) (const char *progname);
+
+extern void handle_help_version_opts(int argc, char *argv[],
+									 const char *fixed_progname,
+									 help_handler hlp);
+
+#endif							/* OPTION_UTILS_H */
diff --git a/src/bin/scripts/scripts_parallel.h b/src/include/fe_utils/parallel_slot.h
index f62692510a..99eeb3328d 100644
--- a/src/bin/scripts/scripts_parallel.h
+++ b/src/include/fe_utils/parallel_slot.h
@@ -1,21 +1,20 @@
 /*-------------------------------------------------------------------------
  *
- *	scripts_parallel.h
+ *	parallel_slot.h
  *		Parallel support for bin/scripts/
  *
  *	Copyright (c) 2003-2021, PostgreSQL Global Development Group
  *
- *	src/bin/scripts/scripts_parallel.h
+ *	src/include/fe_utils/parallel_slot.h
  *
  *-------------------------------------------------------------------------
  */
-#ifndef SCRIPTS_PARALLEL_H
-#define SCRIPTS_PARALLEL_H
+#ifndef PARALLEL_SLOT_H
+#define PARALLEL_SLOT_H
 
-#include "common.h"
+#include "fe_utils/connect_utils.h"
 #include "libpq-fe.h"
 
-
 typedef struct ParallelSlot
 {
 	PGconn	   *connection;		/* One connection */
@@ -33,4 +32,4 @@ extern void ParallelSlotsTerminate(ParallelSlot *slots, int numslots);
 extern bool ParallelSlotsWaitCompletion(ParallelSlot *slots, int numslots);
 
 
-#endif							/* SCRIPTS_PARALLEL_H */
+#endif							/* PARALLEL_SLOT_H */
diff --git a/src/include/fe_utils/query_utils.h b/src/include/fe_utils/query_utils.h
new file mode 100644
index 0000000000..1099260193
--- /dev/null
+++ b/src/include/fe_utils/query_utils.h
@@ -0,0 +1,26 @@
+/*-------------------------------------------------------------------------
+ *
+ * Facilities for frontend code to query a databases.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/fe_utils/query_utils.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef QUERY_UTILS_H
+#define QUERY_UTILS_H
+
+#include "postgres_fe.h"
+
+#include "libpq-fe.h"
+
+extern PGresult *executeQuery(PGconn *conn, const char *query, bool echo);
+
+extern void executeCommand(PGconn *conn, const char *query, bool echo);
+
+extern bool executeMaintenanceCommand(PGconn *conn, const char *query,
+									  bool echo);
+
+#endif							/* QUERY_UTILS_H */
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
index 90328db04e..49614106dc 100644
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@@ -147,8 +147,9 @@ sub mkvcbuild
 	our @pgcommonbkndfiles = @pgcommonallfiles;
 
 	our @pgfeutilsfiles = qw(
-	  archive.c cancel.c conditional.c mbprint.c print.c psqlscan.l
-	  psqlscan.c simple_list.c string_utils.c recovery_gen.c);
+	  archive.c cancel.c conditional.c connect_utils.c mbprint.c option_utils.c
+	  parallel_slot.c print.c psqlscan.l psqlscan.c query_utils.c simple_list.c
+	  string_utils.c recovery_gen.c);
 
 	$libpgport = $solution->AddProject('libpgport', 'lib', 'misc');
 	$libpgport->AddDefine('FRONTEND');