Add recovery_target='immediate' option.

This allows ending recovery as a consistent state has been reached. Without
this, there was no easy way to e.g restore an online backup, without
replaying any extra WAL after the backup ended.

MauMau and me.

Author: hlinnaka

doc/src/sgml/backup.sgml

@@ -1124,7 +1124,7 @@ restore_command = 'cp /mnt/server/archivedir/%f %p'
    <para>
     If you want to recover to some previous point in time (say, right before
     the junior DBA dropped your main transaction table), just specify the
-    required stopping point in <filename>recovery.conf</>.  You can specify
+    required <link linkend="recovery-target-settings">stopping point</link> in <filename>recovery.conf</>.  You can specify
     the stop point, known as the <quote>recovery target</>, either by
     date/time, named restore point or by completion of a specific transaction
     ID.  As of this writing only the date/time and named restore point options

doc/src/sgml/recovery-config.sgml

@@ -199,8 +199,33 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
   <sect1 id="recovery-target-settings">
 
     <title>Recovery Target Settings</title>
+     <para>
+      By default, recovery will recover to the end of the WAL log. The
+      following parameters can be used to specify an earlier stopping point.
+      At most one of <varname>recovery_target</>,
+      <varname>recovery_target_name</>, <varname>recovery_target_time</>, or
+      <varname>recovery_target_xid</> can be specified. 
+     </para>
      <variablelist>
 
+     <varlistentry id="recovery-target" xreflabel="recovery_target_name">
+      <term><varname>recovery_target</varname><literal> = 'immediate'</literal></term>
+      <indexterm>
+        <primary><varname>recovery_target</> recovery parameter</primary>
+      </indexterm>
+      <listitem>
+       <para>
+        This parameter specifies that recovery should end as soon as a
+        consistency is reached, ie. as early as possible. When restoring from an
+        online backup, this means the point where taking the backup ended.
+       </para>
+       <para>
+        Technically, this is a string parameter, but <literal>'immediate'</>
+        is currently the only allowed value.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="recovery-target-name" xreflabel="recovery_target_name">
       <term><varname>recovery_target_name</varname>
            (<type>string</type>)
@@ -212,10 +237,6 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
        <para>
         This parameter specifies the named restore point, created with
         <function>pg_create_restore_point()</> to which recovery will proceed.
-        At most one of <varname>recovery_target_name</>,
-        <xref linkend="recovery-target-time"> or
-        <xref linkend="recovery-target-xid"> can be specified.  The default is to
-        recover to the end of the WAL log.
        </para>
       </listitem>
      </varlistentry>
@@ -231,10 +252,6 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
        <para>
         This parameter specifies the time stamp up to which recovery
         will proceed.
-        At most one of <varname>recovery_target_time</>,
-        <xref linkend="recovery-target-name"> or
-        <xref linkend="recovery-target-xid"> can be specified.
-        The default is to recover to the end of the WAL log.
         The precise stopping point is also influenced by
         <xref linkend="recovery-target-inclusive">.
        </para>
@@ -254,15 +271,18 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
         start, transactions can complete in a different numeric order.
         The transactions that will be recovered are those that committed
         before (and optionally including) the specified one.
-        At most one of <varname>recovery_target_xid</>,
-        <xref linkend="recovery-target-name"> or
-        <xref linkend="recovery-target-time"> can be specified.
-        The default is to recover to the end of the WAL log.
         The precise stopping point is also influenced by
         <xref linkend="recovery-target-inclusive">.
        </para>
       </listitem>
      </varlistentry>
+     </variablelist>
+     <para>
+       The following options further specify the recovery target, and affect
+       what happens when the target is reached:
+     </para>
+
+     <variablelist>
 
      <varlistentry id="recovery-target-inclusive"
                    xreflabel="recovery_target_inclusive">

src/backend/access/transam/recovery.conf.sample

@@ -81,6 +81,12 @@
 #recovery_target_inclusive = true
 #
 #
+# Alternatively, you can request stopping as soon as a consistent state
+# is reached, by uncommenting this option.
+#
+#recovery_target = 'immediate'
+#
+#
 # If you want to recover into a timeline other than the "main line" shown in
 # pg_control, specify the timeline number here, or write 'latest' to get
 # the latest branch for which there's a history file.

src/backend/access/transam/xlog.c

@@ -5434,6 +5434,19 @@ readRecoveryCommandFile(void)
 					(errmsg_internal("recovery_target_name = '%s'",
 									 recoveryTargetName)));
 		}
+		else if (strcmp(item->name, "recovery_target") == 0)
+		{
+			if (strcmp(item->value, "immediate") == 0)
+				recoveryTarget = RECOVERY_TARGET_IMMEDIATE;
+			else
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("invalid recovery_target parameter"),
+						 errhint("The only allowed value is 'immediate'")));
+			ereport(DEBUG2,
+					(errmsg_internal("recovery_target = '%s'",
+									 item->value)));
+		}
 		else if (strcmp(item->name, "recovery_target_inclusive") == 0)
 		{
 			/*
@@ -5676,7 +5689,20 @@ recoveryStopsBefore(XLogRecord *record)
 	bool		isCommit;
 	TimestampTz recordXtime = 0;
 
-	/* We only consider stopping before COMMIT or ABORT records. */
+	/* Check if we should stop as soon as reaching consistency */
+	if (recoveryTarget == RECOVERY_TARGET_IMMEDIATE && reachedConsistency)
+	{
+		ereport(LOG,
+				(errmsg("recovery stopping after reaching consistency")));
+
+		recoveryStopAfter = false;
+		recoveryStopXid = InvalidTransactionId;
+		recoveryStopTime = 0;
+		recoveryStopName[0] = '\0';
+		return true;
+	}
+
+	/* Otherwise we only consider stopping before COMMIT or ABORT records. */
 	if (record->xl_rmid != RM_XACT_ID)
 		return false;
 	record_info = record->xl_info & ~XLR_INFO_MASK;
@@ -5825,6 +5851,19 @@ recoveryStopsAfter(XLogRecord *record)
 		}
 	}
 
+	/* Check if we should stop as soon as reaching consistency */
+	if (recoveryTarget == RECOVERY_TARGET_IMMEDIATE && reachedConsistency)
+	{
+		ereport(LOG,
+				(errmsg("recovery stopping after reaching consistency")));
+
+		recoveryStopAfter = true;
+		recoveryStopXid = InvalidTransactionId;
+		recoveryStopTime = 0;
+		recoveryStopName[0] = '\0';
+		return true;
+	}
+
 	return false;
 }
 
@@ -6246,6 +6285,9 @@ StartupXLOG(void)
 			ereport(LOG,
 					(errmsg("starting point-in-time recovery to \"%s\"",
 							recoveryTargetName)));
+		else if (recoveryTarget == RECOVERY_TARGET_IMMEDIATE)
+			ereport(LOG,
+					(errmsg("starting point-in-time recovery to earliest consistent point")));
 		else
 			ereport(LOG,
 					(errmsg("starting archive recovery")));
@@ -7125,6 +7167,8 @@ StartupXLOG(void)
 			snprintf(reason, sizeof(reason),
 					 "at restore point \"%s\"",
 					 recoveryStopName);
+		else if (recoveryTarget == RECOVERY_TARGET_IMMEDIATE)
+			snprintf(reason, sizeof(reason), "reached consistency");
 		else
 			snprintf(reason, sizeof(reason), "no recovery target specified");
 

src/include/access/xlog.h

@@ -173,7 +173,8 @@ typedef enum
 	RECOVERY_TARGET_UNSET,
 	RECOVERY_TARGET_XID,
 	RECOVERY_TARGET_TIME,
-	RECOVERY_TARGET_NAME
+	RECOVERY_TARGET_NAME,
+	RECOVERY_TARGET_IMMEDIATE
 } RecoveryTargetType;
 
 extern XLogRecPtr XactLastRecEnd;