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Refactor code in charge of running shell-based recovery commands
The code specific to the execution of archive_cleanup_command, recovery_end_command and restore_command is moved to a new file named shell_restore.c. The code is split into three functions: - shell_restore(), that attempts the execution of a shell-based restore_command. - shell_archive_cleanup(), for archive_cleanup_command. - shell_recovery_end(), for recovery_end_command. This introduces no functional changes, with failure patterns and logs generated in consequence being the same as before (one case actually generates one less DEBUG2 message "could not restore" when a restore command succeeds but the follow-up stat() to check the size fails, but that only matters with a elevel high enough). This is preparatory work for allowing recovery modules, a facility similar to archive modules, with callbacks shaped similarly to the functions introduced here. Author: Nathan Bossart Reviewed-by: Andres Freund, Michael Paquier Discussion: https://postgr.es/m/20221227192449.GA3672473@nathanxps13
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6 files changed

+214
-127
lines changed

6 files changed

+214
-127
lines changed

‎src/backend/access/transam/Makefile

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Original file line numberDiff line numberDiff line change
@@ -19,6 +19,7 @@ OBJS = \
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multixact.o \
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parallel.o \
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rmgr.o \
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shell_restore.o \
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slru.o \
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subtrans.o \
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timeline.o \

‎src/backend/access/transam/meson.build

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@@ -7,6 +7,7 @@ backend_sources += files(
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'multixact.c',
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'parallel.c',
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'rmgr.c',
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'shell_restore.c',
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'slru.c',
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'subtrans.c',
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'timeline.c',

‎src/backend/access/transam/shell_restore.c

Lines changed: 175 additions & 0 deletions
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@@ -0,0 +1,175 @@
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/*-------------------------------------------------------------------------
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*
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* shell_restore.c
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* Recovery functions for a user-specified shell command.
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*
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* These recovery functions use a user-specified shell command (e.g. based
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* on the GUC restore_command).
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*
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* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/backend/access/transam/shell_restore.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <signal.h>
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#include "access/xlogarchive.h"
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#include "access/xlogrecovery.h"
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#include "common/archive.h"
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#include "common/percentrepl.h"
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#include "storage/ipc.h"
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#include "utils/wait_event.h"
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static void ExecuteRecoveryCommand(const char *command,
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const char *commandName,
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bool failOnSignal,
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uint32 wait_event_info,
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const char *lastRestartPointFileName);
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/*
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* Attempt to execute a shell-based restore command.
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*
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* Returns true if the command has succeeded, false otherwise.
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*/
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bool
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shell_restore(const char *file, const char *path,
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const char *lastRestartPointFileName)
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{
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char *cmd;
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int rc;
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/* Build the restore command to execute */
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cmd = BuildRestoreCommand(recoveryRestoreCommand, path, file,
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lastRestartPointFileName);
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ereport(DEBUG3,
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(errmsg_internal("executing restore command \"%s\"", cmd)));
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/*
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* Copy xlog from archival storage to XLOGDIR
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*/
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fflush(NULL);
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pgstat_report_wait_start(WAIT_EVENT_RESTORE_COMMAND);
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rc = system(cmd);
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pgstat_report_wait_end();
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pfree(cmd);
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/*
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* Remember, we rollforward UNTIL the restore fails so failure here is
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* just part of the process... that makes it difficult to determine
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* whether the restore failed because there isn't an archive to restore,
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* or because the administrator has specified the restore program
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* incorrectly. We have to assume the former.
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*
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* However, if the failure was due to any sort of signal, it's best to
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* punt and abort recovery. (If we "return false" here, upper levels will
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* assume that recovery is complete and start up the database!) It's
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* essential to abort on child SIGINT and SIGQUIT, because per spec
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* system() ignores SIGINT and SIGQUIT while waiting; if we see one of
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* those it's a good bet we should have gotten it too.
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*
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* On SIGTERM, assume we have received a fast shutdown request, and exit
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* cleanly. It's pure chance whether we receive the SIGTERM first, or the
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* child process. If we receive it first, the signal handler will call
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* proc_exit, otherwise we do it here. If we or the child process received
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* SIGTERM for any other reason than a fast shutdown request, postmaster
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* will perform an immediate shutdown when it sees us exiting
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* unexpectedly.
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*
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* We treat hard shell errors such as "command not found" as fatal, too.
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*/
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if (rc != 0)
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{
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if (wait_result_is_signal(rc, SIGTERM))
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proc_exit(1);
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ereport(wait_result_is_any_signal(rc, true) ? FATAL : DEBUG2,
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(errmsg("could not restore file \"%s\" from archive: %s",
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file, wait_result_to_str(rc))));
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}
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return (rc == 0);
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}
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/*
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* Attempt to execute a shell-based archive cleanup command.
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*/
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void
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shell_archive_cleanup(const char *lastRestartPointFileName)
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{
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ExecuteRecoveryCommand(archiveCleanupCommand, "archive_cleanup_command",
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false, WAIT_EVENT_ARCHIVE_CLEANUP_COMMAND,
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lastRestartPointFileName);
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}
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/*
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* Attempt to execute a shell-based end-of-recovery command.
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*/
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void
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shell_recovery_end(const char *lastRestartPointFileName)
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{
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ExecuteRecoveryCommand(recoveryEndCommand, "recovery_end_command", true,
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WAIT_EVENT_RECOVERY_END_COMMAND,
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lastRestartPointFileName);
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}
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/*
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* Attempt to execute an external shell command during recovery.
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*
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* 'command' is the shell command to be executed, 'commandName' is a
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* human-readable name describing the command emitted in the logs. If
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* 'failOnSignal' is true and the command is killed by a signal, a FATAL
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* error is thrown. Otherwise a WARNING is emitted.
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*
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* This is currently used for recovery_end_command and archive_cleanup_command.
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*/
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static void
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ExecuteRecoveryCommand(const char *command, const char *commandName,
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bool failOnSignal, uint32 wait_event_info,
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const char *lastRestartPointFileName)
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{
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char *xlogRecoveryCmd;
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int rc;
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Assert(command && commandName);
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/*
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* construct the command to be executed
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*/
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xlogRecoveryCmd = replace_percent_placeholders(command, commandName, "r",
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lastRestartPointFileName);
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ereport(DEBUG3,
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(errmsg_internal("executing %s \"%s\"", commandName, command)));
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/*
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* execute the constructed command
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*/
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fflush(NULL);
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pgstat_report_wait_start(wait_event_info);
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rc = system(xlogRecoveryCmd);
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pgstat_report_wait_end();
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pfree(xlogRecoveryCmd);
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if (rc != 0)
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{
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/*
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* If the failure was due to any sort of signal, it's best to punt and
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* abort recovery. See comments in shell_restore().
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*/
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ereport((failOnSignal && wait_result_is_any_signal(rc, true)) ? FATAL : WARNING,
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/*------
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translator: First %s represents a postgresql.conf parameter name like
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"recovery_end_command", the 2nd is the value of that parameter, the
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third an already translated error message. */
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(errmsg("%s \"%s\": %s", commandName,
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command, wait_result_to_str(rc))));
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}
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}

‎src/backend/access/transam/xlog.c

Lines changed: 29 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -692,6 +692,7 @@ static char *GetXLogBuffer(XLogRecPtr ptr, TimeLineID tli);
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static XLogRecPtr XLogBytePosToRecPtr(uint64 bytepos);
693693
static XLogRecPtr XLogBytePosToEndRecPtr(uint64 bytepos);
694694
static uint64 XLogRecPtrToBytePos(XLogRecPtr ptr);
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static void GetOldestRestartPointFileName(char *fname);
695696

696697
static void WALInsertLockAcquire(void);
697698
static void WALInsertLockAcquireExclusive(void);
@@ -4887,10 +4888,12 @@ CleanupAfterArchiveRecovery(TimeLineID EndOfLogTLI, XLogRecPtr EndOfLog,
48874888
* Execute the recovery_end_command, if any.
48884889
*/
48894890
if (recoveryEndCommand && strcmp(recoveryEndCommand, "") != 0)
4890-
ExecuteRecoveryCommand(recoveryEndCommand,
4891-
"recovery_end_command",
4892-
true,
4893-
WAIT_EVENT_RECOVERY_END_COMMAND);
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{
4892+
char lastRestartPointFname[MAXFNAMELEN];
4893+
4894+
GetOldestRestartPointFileName(lastRestartPointFname);
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shell_recovery_end(lastRestartPointFname);
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}
48944897

48954898
/*
48964899
* We switched to a new timeline. Clean up segments on the old timeline.
@@ -7307,10 +7310,12 @@ CreateRestartPoint(int flags)
73077310
* Finally, execute archive_cleanup_command, if any.
73087311
*/
73097312
if (archiveCleanupCommand && strcmp(archiveCleanupCommand, "") != 0)
7310-
ExecuteRecoveryCommand(archiveCleanupCommand,
7311-
"archive_cleanup_command",
7312-
false,
7313-
WAIT_EVENT_ARCHIVE_CLEANUP_COMMAND);
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{
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char lastRestartPointFname[MAXFNAMELEN];
7315+
7316+
GetOldestRestartPointFileName(lastRestartPointFname);
7317+
shell_archive_cleanup(lastRestartPointFname);
7318+
}
73147319

73157320
return true;
73167321
}
@@ -8884,6 +8889,22 @@ GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli)
88848889
LWLockRelease(ControlFileLock);
88858890
}
88868891

8892+
/*
8893+
* Returns the WAL file name for the last checkpoint or restartpoint. This is
8894+
* the oldest WAL file that we still need if we have to restart recovery.
8895+
*/
8896+
static void
8897+
GetOldestRestartPointFileName(char *fname)
8898+
{
8899+
XLogRecPtr restartRedoPtr;
8900+
TimeLineID restartTli;
8901+
XLogSegNo restartSegNo;
8902+
8903+
GetOldestRestartPoint(&restartRedoPtr, &restartTli);
8904+
XLByteToSeg(restartRedoPtr, restartSegNo, wal_segment_size);
8905+
XLogFileName(fname, restartTli, restartSegNo, wal_segment_size);
8906+
}
8907+
88878908
/* Thin wrapper around ShutdownWalRcv(). */
88888909
void
88898910
XLogShutdownWalRcv(void)

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