Add timeline ID to file names generated with pg_waldump --save-fullpage

Not including the timeline IDs to the file names generated by pg_waldump
for the individual blocks saved could cause some of these files to be
overwritten when scanning segments across multiple timelines.  Having
this information is also as much useful as the LSNs, to be able to know
from exactly which WAL segment a block is comes from.

While on it, this fixes a few comments in the tests, where the format of
the file was not described as matching with the reality.

Reported-by: Fujii Masao
Reviewed-by: Kyotaro Horiguchi, David Christensen
Discussion: https://postgr.es/m/ZJp921+nITFnvBVS@paquier.xyz

Author: michaelpq

doc/src/sgml/ref/pg_waldump.sgml

@@ -283,7 +283,7 @@ PostgreSQL documentation
        </para>
        <para>
         The full page images are saved with the following file name format:
-        <literal><replaceable>LSN</replaceable>.<replaceable>RELTABLESPACE</replaceable>.<replaceable>DATOID</replaceable>.<replaceable>RELNODE</replaceable>.<replaceable>BLKNO</replaceable><replaceable>FORK</replaceable></literal>
+        <literal><replaceable>TIMELINE</replaceable>-<replaceable>LSN</replaceable>.<replaceable>RELTABLESPACE</replaceable>.<replaceable>DATOID</replaceable>.<replaceable>RELNODE</replaceable>.<replaceable>BLKNO</replaceable><replaceable>FORK</replaceable></literal>
 
         The file names are composed of the following parts:
         <informaltable>
@@ -296,6 +296,13 @@ PostgreSQL documentation
           </thead>
 
           <tbody>
+           <row>
+            <entry>TIMELINE</entry>
+            <entry>The timeline of the WAL segment file where the record
+             is located formatted as one 8-character hexadecimal number
+             <literal>%08X</literal></entry>
+           </row>
+
            <row>
             <entry>LSN</entry>
             <entry>The <acronym>LSN</acronym> of the record with this image,

src/bin/pg_waldump/pg_waldump.c

@@ -518,7 +518,8 @@ XLogRecordSaveFPWs(XLogReaderState *record, const char *savepath)
 		else
 			pg_fatal("invalid fork number: %u", fork);
 
-		snprintf(filename, MAXPGPATH, "%s/%08X-%08X.%u.%u.%u.%u%s", savepath,
+		snprintf(filename, MAXPGPATH, "%s/%08X-%08X-%08X.%u.%u.%u.%u%s", savepath,
+				 record->seg.ws_tli,
 				 LSN_FORMAT_ARGS(record->ReadRecPtr),
 				 rnode.spcOid, rnode.dbOid, rnode.relNumber, blk, forkname);
 

src/bin/pg_waldump/t/002_save_fullpage.pl

@@ -79,15 +79,16 @@ sub get_block_lsn
 	'pg_waldump with --save-fullpage runs');
 
 # This regexp will match filenames formatted as:
-# XXXXXXXX-XXXXXXXX.DBOID.TLOID.NODEOID.dd_fork with the components being:
-# - WAL LSN in hex format,
-# - Tablespace OID (0 for global)
+# TLI-LSNh-LSNl.TBLSPCOID.DBOID.NODEOID.dd_fork with the components being:
+# - Timeline ID in hex format.
+# - WAL LSN in hex format, as two 8-character numbers.
+# - Tablespace OID (0 for global).
 # - Database OID.
 # - Relfilenode.
 # - Block number.
 # - Fork this block came from (vm, init, fsm, or main).
 my $file_re =
-  qr/^([0-9A-F]{8})-([0-9A-F]{8})[.][0-9]+[.][0-9]+[.][0-9]+[.][0-9]+(?:_vm|_init|_fsm|_main)?$/;
+  qr/^[0-9A-F]{8}-([0-9A-F]{8})-([0-9A-F]{8})[.][0-9]+[.][0-9]+[.][0-9]+[.][0-9]+(?:_vm|_init|_fsm|_main)?$/;
 
 my $file_count = 0;