pg_resetwal: Allow users to change the WAL segment size
This adds a new option --wal-segsize (analogous to initdb) that changes the WAL segment size in pg_control. Author: Nathan Bossart <bossartn@amazon.com>
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@ -275,6 +275,28 @@ PostgreSQL documentation
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>--wal-segsize=<replaceable class="parameter">wal_segment_size</replaceable></option></term>
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<listitem>
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<para>
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Set the new WAL segment size, in megabytes. The value must be set to a
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power of 2 between 1 and 1024 (megabytes). See the same option of <xref
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linkend="app-initdb"/> for more information.
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</para>
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<note>
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<para>
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While <command>pg_resetwal</command> will set the WAL starting address
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beyond the latest existing WAL segment file, some segment size changes
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can cause previous WAL file names to be reused. It is recommended to
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use <option>-l</option> together with this option to manually set the
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WAL starting address if WAL file name overlap will cause problems with
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your archiving strategy.
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</para>
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</note>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><option>-x <replaceable class="parameter">xid</replaceable></option></term>
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<term><option>--next-transaction-id=<replaceable class="parameter">xid</replaceable></option></term>
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@ -72,6 +72,7 @@ static MultiXactOffset set_mxoff = (MultiXactOffset) -1;
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static uint32 minXlogTli = 0;
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static XLogSegNo minXlogSegNo = 0;
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static int WalSegSz;
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static int set_wal_segsize;
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static void CheckDataVersion(void);
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static bool ReadControlFile(void);
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@ -100,6 +101,7 @@ main(int argc, char *argv[])
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{"next-oid", required_argument, NULL, 'o'},
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{"multixact-offset", required_argument, NULL, 'O'},
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{"next-transaction-id", required_argument, NULL, 'x'},
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{"wal-segsize", required_argument, NULL, 1},
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{NULL, 0, NULL, 0}
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};
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@ -290,6 +292,24 @@ main(int argc, char *argv[])
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log_fname = pg_strdup(optarg);
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break;
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case 1:
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set_wal_segsize = strtol(optarg, &endptr, 10) * 1024 * 1024;
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if (endptr == optarg || *endptr != '\0')
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{
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fprintf(stderr,
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_("%s: argument of --wal-segsize must be a number\n"),
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progname);
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exit(1);
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}
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if (!IsValidWalSegSize(set_wal_segsize))
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{
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fprintf(stderr,
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_("%s: argument of --wal-segsize must be a power of 2 between 1 and 1024\n"),
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progname);
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exit(1);
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}
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break;
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default:
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fprintf(stderr, _("Try \"%s --help\" for more information.\n"), progname);
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exit(1);
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@ -372,6 +392,14 @@ main(int argc, char *argv[])
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if (!ReadControlFile())
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GuessControlValues();
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/*
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* If no new WAL segment size was specified, use the control file value.
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*/
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if (set_wal_segsize != 0)
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WalSegSz = set_wal_segsize;
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else
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WalSegSz = ControlFile.xlog_seg_size;
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if (log_fname != NULL)
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XLogFromFileName(log_fname, &minXlogTli, &minXlogSegNo, WalSegSz);
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@ -438,6 +466,9 @@ main(int argc, char *argv[])
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ControlFile.checkPointCopy.PrevTimeLineID = minXlogTli;
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}
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if (set_wal_segsize != 0)
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ControlFile.xlog_seg_size = WalSegSz;
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if (minXlogSegNo > newXlogSegNo)
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newXlogSegNo = minXlogSegNo;
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@ -608,14 +639,13 @@ ReadControlFile(void)
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}
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memcpy(&ControlFile, buffer, sizeof(ControlFile));
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WalSegSz = ControlFile.xlog_seg_size;
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/* return false if WalSegSz is not valid */
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if (!IsValidWalSegSize(WalSegSz))
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/* return false if WAL segment size is not valid */
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if (!IsValidWalSegSize(ControlFile.xlog_seg_size))
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{
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fprintf(stderr,
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_("%s: pg_control specifies invalid WAL segment size (%d bytes); proceed with caution \n"),
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progname, WalSegSz);
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progname, ControlFile.xlog_seg_size);
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return false;
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}
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@ -694,7 +724,7 @@ GuessControlValues(void)
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ControlFile.blcksz = BLCKSZ;
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ControlFile.relseg_size = RELSEG_SIZE;
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ControlFile.xlog_blcksz = XLOG_BLCKSZ;
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WalSegSz = ControlFile.xlog_seg_size = DEFAULT_XLOG_SEG_SIZE;
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ControlFile.xlog_seg_size = DEFAULT_XLOG_SEG_SIZE;
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ControlFile.nameDataLen = NAMEDATALEN;
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ControlFile.indexMaxKeys = INDEX_MAX_KEYS;
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ControlFile.toast_max_chunk_size = TOAST_MAX_CHUNK_SIZE;
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@ -859,6 +889,12 @@ PrintNewControlValues(void)
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printf(_("newestCommitTsXid: %u\n"),
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ControlFile.checkPointCopy.newestCommitTsXid);
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}
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if (set_wal_segsize != 0)
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{
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printf(_("Bytes per WAL segment: %u\n"),
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ControlFile.xlog_seg_size);
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}
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}
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@ -910,9 +946,6 @@ RewriteControlFile(void)
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ControlFile.max_prepared_xacts = 0;
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ControlFile.max_locks_per_xact = 64;
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/* Now we can force the recorded xlog seg size to the right thing. */
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ControlFile.xlog_seg_size = WalSegSz;
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/* Contents are protected with a CRC */
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INIT_CRC32C(ControlFile.crc);
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COMP_CRC32C(ControlFile.crc,
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@ -1048,7 +1081,7 @@ FindEndOfXLOG(void)
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* are in virgin territory.
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*/
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xlogbytepos = newXlogSegNo * ControlFile.xlog_seg_size;
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newXlogSegNo = (xlogbytepos + WalSegSz - 1) / WalSegSz;
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newXlogSegNo = (xlogbytepos + ControlFile.xlog_seg_size - 1) / WalSegSz;
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newXlogSegNo++;
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}
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@ -1279,6 +1312,7 @@ usage(void)
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printf(_(" -O, --multixact-offset=OFFSET set next multitransaction offset\n"));
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printf(_(" -V, --version output version information, then exit\n"));
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printf(_(" -x, --next-transaction-id=XID set next transaction ID\n"));
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printf(_(" --wal-segsize=SIZE size of WAL segments, in megabytes\n"));
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printf(_(" -?, --help show this help, then exit\n"));
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printf(_("\nReport bugs to <pgsql-bugs@postgresql.org>.\n"));
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}
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