From 59e3146f585e288d41738daa9a1d18687e2851d1 Mon Sep 17 00:00:00 2001
From: Masahiko Sawada <sawada.mshk@gmail.com>
Date: Wed, 15 May 2019 15:27:51 +0900
Subject: [PATCH v3 2/2] Add --truncate option to vacuumdb.

---
 doc/src/sgml/ref/vacuumdb.sgml    | 18 ++++++++++++++++++
 src/bin/scripts/t/100_vacuumdb.pl | 13 ++++++++++++-
 src/bin/scripts/vacuumdb.c        | 28 ++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/doc/src/sgml/ref/vacuumdb.sgml b/doc/src/sgml/ref/vacuumdb.sgml
index 5ec043e..6bb63c7 100644
--- a/doc/src/sgml/ref/vacuumdb.sgml
+++ b/doc/src/sgml/ref/vacuumdb.sgml
@@ -290,6 +290,24 @@ PostgreSQL documentation
      </varlistentry>
 
      <varlistentry>
+      <term><option>--truncate=<replaceable class="parameter">boolean</replaceable></option></term>
+      <listitem>
+       <para>
+         Specify that <command>VACUUM</command> should attempt to truncate off
+         any empty pages at the end of the table. If this option is not specified
+         the behavior depends on <literal>vacuum_truncate</literal> option
+         for the table to be vacuumed.
+       </para>
+       <note>
+        <para>
+         This option is only available for servers running
+         <productname>PostgreSQL</productname> 12 and later.
+        </para>
+       </note>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><option>-v</option></term>
       <term><option>--verbose</option></term>
       <listitem>
diff --git a/src/bin/scripts/t/100_vacuumdb.pl b/src/bin/scripts/t/100_vacuumdb.pl
index 984f2a8..555e9b6 100644
--- a/src/bin/scripts/t/100_vacuumdb.pl
+++ b/src/bin/scripts/t/100_vacuumdb.pl
@@ -3,7 +3,7 @@ use warnings;
 
 use PostgresNode;
 use TestLib;
-use Test::More tests => 50;
+use Test::More tests => 55;
 
 program_help_ok('vacuumdb');
 program_version_ok('vacuumdb');
@@ -53,6 +53,14 @@ $node->issues_sql_like(
 	[ 'vacuumdb', '--index-cleanup=true', 'postgres' ],
 	qr/statement: VACUUM \(INDEX_CLEANUP true\).*;/,
 	'vacuumdb --index-cleanup=true');
+$node->issues_sql_like(
+	[ 'vacuumdb', '--truncate=false', 'postgres' ],
+	qr/statement: VACUUM \(TRUNCATE false\).*;/,
+	'vacuumdb --truncate=false');
+$node->issues_sql_like(
+	[ 'vacuumdb', '--truncate=true', 'postgres' ],
+	qr/statement: VACUUM \(TRUNCATE true\).*;/,
+	'vacuumdb --truncate=true');
 $node->command_fails(
 	[ 'vacuumdb', '--analyze-only', '--disable-page-skipping', 'postgres' ],
 	'--analyze-only and --disable-page-skipping specified together');
@@ -60,6 +68,9 @@ $node->command_fails(
 	[ 'vacuumdb', '--analyze-only', '--index-cleanup=true', 'postgres' ],
 	'--analyze-only and --index-cleanup specified together');
 $node->command_fails(
+	[ 'vacuumdb', '--analyze-only', '--truncate=true', 'postgres' ],
+	'--analyze-only and --truncate specified together');
+$node->command_fails(
 	[ 'vacuumdb', '--index-cleanup=invalid', 'postgres' ],
 	'--index-cleanup with an invalid argument');
 $node->command_ok([qw(vacuumdb -Z --table=pg_am dbname=template1)],
diff --git a/src/bin/scripts/vacuumdb.c b/src/bin/scripts/vacuumdb.c
index 7f91d18..a7aaa82 100644
--- a/src/bin/scripts/vacuumdb.c
+++ b/src/bin/scripts/vacuumdb.c
@@ -47,6 +47,7 @@ typedef struct vacuumingOptions
 	int			min_xid_age;
 	int			min_mxid_age;
 	char		*index_cleanup;
+	char		*truncate;
 } vacuumingOptions;
 
 
@@ -121,6 +122,7 @@ main(int argc, char *argv[])
 		{"min-xid-age", required_argument, NULL, 6},
 		{"min-mxid-age", required_argument, NULL, 7},
 		{"index-cleanup", required_argument, NULL, 8},
+		{"truncate", required_argument, NULL, 9},
 		{NULL, 0, NULL, 0}
 	};
 
@@ -248,6 +250,9 @@ main(int argc, char *argv[])
 			case 8:
 				vacopts.index_cleanup = pg_strdup(optarg);
 				break;
+			case 9:
+				vacopts.truncate = pg_strdup(optarg);
+				break;
 			default:
 				fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
 				exit(1);
@@ -298,6 +303,12 @@ main(int argc, char *argv[])
 						 "index-cleanup");
 			exit(1);
 		}
+		if (vacopts.truncate != NULL)
+		{
+			pg_log_error("cannot use the \"%s\" option when performing only analyze",
+						 "truncate");
+			exit(1);
+		}
 		/* allow 'and_analyze' with 'analyze_only' */
 	}
 
@@ -434,6 +445,14 @@ vacuum_one_database(const char *dbname, vacuumingOptions *vacopts,
 		exit(1);
 	}
 
+	if (vacopts->truncate != NULL && PQserverVersion(conn) < 120000)
+	{
+		PQfinish(conn);
+		pg_log_error("cannot use the \"%s\" option on server versions older than PostgreSQL 12",
+					 "truncate");
+		exit(1);
+	}
+
 	if (vacopts->skip_locked && PQserverVersion(conn) < 120000)
 	{
 		PQfinish(conn);
@@ -902,6 +921,14 @@ prepare_vacuum_command(PQExpBuffer sql, int serverVersion,
 								  vacopts->index_cleanup);
 				sep = comma;
 			}
+			if (vacopts->truncate)
+			{
+				/* TRUNCATE is supported since 12 */
+				Assert(serverVersion >= 120000);
+				appendPQExpBuffer(sql, "%sTRUNCATE %s", sep,
+								  vacopts->truncate);
+				sep = comma;
+			}
 			if (vacopts->full)
 			{
 				appendPQExpBuffer(sql, "%sFULL", sep);
@@ -1257,6 +1284,7 @@ help(const char *progname)
 	printf(_("  -q, --quiet                     don't write any messages\n"));
 	printf(_("      --skip-locked               skip relations that cannot be immediately locked\n"));
 	printf(_("  -t, --table='TABLE[(COLUMNS)]'  vacuum specific table(s) only\n"));
+	printf(_("      --truncate=BOOLEAN          do or do not truncate off empty pages at the end of the table\n"));
 	printf(_("  -v, --verbose                   write a lot of output\n"));
 	printf(_("  -V, --version                   output version information, then exit\n"));
 	printf(_("  -z, --analyze                   update optimizer statistics\n"));
-- 
2.10.5