initdb: Add new option "--no-data-checksums"

Right now this does nothing except override any earlier
--data-checksums option.  But the idea is that --data-checksums could
become the default, and then this option would allow forcing it off
instead.

Author: Greg Sabino Mullane <greg@turnstep.com>
Discussion: https://www.postgresql.org/message-id/flat/CAKAnmmKwiMHik5AHmBEdf5vqzbOBbcwEPHo4-PioWeAbzwcTOQ@mail.gmail.com

doc/src/sgml/ref/initdb.sgml

@@ -343,6 +343,16 @@ PostgreSQL documentation
       </listitem>
      </varlistentry>
 
+     <varlistentry id="app-initdb-no-data-checksums" xreflabel="no data checksums">
+      <term><option>--no-data-checksums</option></term>
+      <listitem>
+       <para>
+        Do not enable data checksums.  This can be used to override a
+        <option>--data-checksums</option> option.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="app-initdb-option-pwfile">
       <term><option>--pwfile=<replaceable>filename</replaceable></option></term>
       <listitem>

src/bin/initdb/initdb.c

@@ -2466,6 +2466,7 @@ usage(const char *progname)
 			 "                            set builtin locale name for new databases\n"));
 	printf(_("      --locale-provider={builtin|libc|icu}\n"
 			 "                            set default locale provider for new databases\n"));
+	printf(_("      --no-data-checksums   do not use data page checksums\n"));
 	printf(_("      --pwfile=FILE         read password for the new superuser from file\n"));
 	printf(_("  -T, --text-search-config=CFG\n"
 			 "                            default text search configuration\n"));
@@ -3128,6 +3129,7 @@ main(int argc, char *argv[])
 		{"icu-locale", required_argument, NULL, 17},
 		{"icu-rules", required_argument, NULL, 18},
 		{"sync-method", required_argument, NULL, 19},
+		{"no-data-checksums", no_argument, NULL, 20},
 		{NULL, 0, NULL, 0}
 	};
 
@@ -3319,6 +3321,9 @@ main(int argc, char *argv[])
 				if (!parse_sync_method(optarg, &sync_method))
 					exit(1);
 				break;
+			case 20:
+				data_checksums = false;
+				break;
 			default:
 				/* getopt_long already emitted a complaint */
 				pg_log_error_hint("Try \"%s --help\" for more information.", progname);

src/bin/initdb/t/001_initdb.pl

@@ -268,4 +268,16 @@ ok($conf !~ qr/^WORK_MEM = /m, "WORK_MEM should not be configured");
 ok($conf !~ qr/^Work_Mem = /m, "Work_Mem should not be configured");
 ok($conf =~ qr/^work_mem = 512/m, "work_mem should be in config");
 
+# Test the no-data-checksums flag
+my $datadir_nochecksums = "$tempdir/data_no_checksums";
+
+command_ok([ 'initdb', '--no-data-checksums', $datadir_nochecksums ],
+	'successful creation without data checksums');
+
+# Control file should tell that data checksums are disabled.
+command_like(
+	[ 'pg_controldata', $datadir_nochecksums ],
+	qr/Data page checksum version:.*0/,
+	'checksums are disabled in control file');
+
 done_testing();