Add pg_xlogdump contrib program

This program relies on rm_desc backend routines and the xlogreader
infrastructure to emit human-readable rendering of WAL records.

Author: Andres Freund, with many reworks by Álvaro
Reviewed (in a much earlier version) by Peter Eisentraut

contrib/pg_xlogdump/Makefile

+# contrib/pg_xlogdump/Makefile
+
+PGFILEDESC = "pg_xlogdump"
+PGAPPICON=win32
+
+PROGRAM = pg_xlogdump
+OBJS = pg_xlogdump.o compat.o xlogreader.o rmgrdesc.o \
+	$(RMGRDESCOBJS) $(WIN32RES)
+
+RMGRDESCSOURCES = $(notdir $(wildcard $(top_srcdir)/src/backend/access/rmgrdesc/*desc.c))
+RMGRDESCOBJS = $(patsubst %.c,%.o,$(RMGRDESCSOURCES))
+
+EXTRA_CLEAN = $(RMGRDESCSOURCES) xlogreader.c rmgrdesc.c
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/pg_xlogdump
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
+
+override CPPFLAGS := -DFRONTEND $(CPPFLAGS)
+
+rmgrdesc.c xlogreader.c: % : $(top_srcdir)/src/backend/access/transam/%
+	rm -f $@ && $(LN_S) $< .
+
+$(RMGRDESCSOURCES): % : $(top_srcdir)/src/backend/access/rmgrdesc/%
+	rm -f $@ && $(LN_S) $< .

contrib/pg_xlogdump/compat.c

+/*-------------------------------------------------------------------------
+ *
+ * compat.c
+ *		Reimplementations of various backend functions.
+ *
+ * Portions Copyright (c) 2012, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		contrib/pg_xlogdump/compat.c
+ *
+ * This file contains client-side implementations for various backend
+ * functions that the rm_desc functions in *desc.c files rely on.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/* ugly hack, same as in e.g pg_controldata */
+#define FRONTEND 1
+#include "postgres.h"
+
+#include <time.h>
+
+#include "utils/datetime.h"
+#include "lib/stringinfo.h"
+
+/* copied from timestamp.c */
+pg_time_t
+timestamptz_to_time_t(TimestampTz t)
+{
+	pg_time_t	result;
+
+#ifdef HAVE_INT64_TIMESTAMP
+	result = (pg_time_t) (t / USECS_PER_SEC +
+				 ((POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY));
+#else
+	result = (pg_time_t) (t +
+				 ((POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY));
+#endif
+	return result;
+}
+
+/*
+ * Stopgap implementation of timestamptz_to_str that doesn't depend on backend
+ * infrastructure.
+ *
+ * XXX: The backend timestamp infrastructure should instead be split out and
+ * moved into src/common.
+ */
+const char *
+timestamptz_to_str(TimestampTz dt)
+{
+	static char buf[MAXDATELEN + 1];
+	static char ts[MAXDATELEN + 1];
+	static char zone[MAXDATELEN + 1];
+	pg_time_t	result = timestamptz_to_time_t(dt);
+	struct tm  *ltime = localtime(&result);
+
+	strftime(ts, sizeof(zone), "%Y-%m-%d %H:%M:%S", ltime);
+	strftime(zone, sizeof(zone), "%Z", ltime);
+
+#ifdef HAVE_INT64_TIMESTAMP
+	sprintf(buf, "%s.%06d %s", ts, (int)(dt % USECS_PER_SEC), zone);
+#else
+	sprintf(buf, "%s.%.6f %s", ts, fabs(dt - floor(dt)), zone);
+#endif
+
+	return buf;
+}
+
+/*
+ * Provide a hacked up compat layer for StringInfos so xlog desc functions can
+ * be linked/called.
+ */
+void
+appendStringInfo(StringInfo str, const char *fmt, ...)
+{
+	va_list		args;
+
+	va_start(args, fmt);
+	vprintf(fmt, args);
+	va_end(args);
+}
+
+void
+appendStringInfoString(StringInfo str, const char *string)
+{
+	appendStringInfo(str, "%s", string);
+}
+
+void
+appendStringInfoChar(StringInfo str, char ch)
+{
+	appendStringInfo(str, "%c", ch);
+}

contrib/pg_xlogdump/rmgrdesc.c

+/*
+ * rmgrdesc.c
+ *
+ * pg_xlogdump resource managers definition
+ *
+ * contrib/pg_xlogdump/rmgrdesc.c
+ */
+#define FRONTEND 1
+#include "postgres.h"
+
+#include "access/clog.h"
+#include "access/gin.h"
+#include "access/gist_private.h"
+#include "access/hash.h"
+#include "access/heapam_xlog.h"
+#include "access/multixact.h"
+#include "access/nbtree.h"
+#include "access/rmgr.h"
+#include "access/spgist.h"
+#include "access/xact.h"
+#include "access/xlog_internal.h"
+#include "catalog/storage_xlog.h"
+#include "commands/dbcommands.h"
+#include "commands/sequence.h"
+#include "commands/tablespace.h"
+#include "rmgrdesc.h"
+#include "storage/standby.h"
+#include "utils/relmapper.h"
+
+#define PG_RMGR(symname,name,redo,desc,startup,cleanup,restartpoint) \
+	{ name, desc, },
+
+const RmgrDescData RmgrDescTable[RM_MAX_ID + 1] = {
+#include "access/rmgrlist.h"
+};
+

contrib/pg_xlogdump/rmgrdesc.h

+/*
+ * rmgrdesc.h
+ *
+ * pg_xlogdump resource managers declaration
+ *
+ * contrib/pg_xlogdump/rmgrdesc.h
+ */
+#ifndef RMGRDESC_H
+#define RMGRDESC_H
+
+#include "lib/stringinfo.h"
+
+typedef struct RmgrDescData
+{
+	const char *rm_name;
+	void	  (*rm_desc) (StringInfo buf, uint8 xl_info, char *rec);
+} RmgrDescData;
+
+extern const RmgrDescData RmgrDescTable[];
+
+#endif /* RMGRDESC_H */

doc/src/sgml/contrib.sgml

@@ -207,5 +207,6 @@ pages.
  &pgtestfsync;
  &pgtesttiming;
  &pgupgrade;
+ &pgxlogdump;
  </sect1>
 </appendix>

doc/src/sgml/filelist.sgml

@@ -134,6 +134,7 @@
 <!ENTITY pgtesttiming    SYSTEM "pgtesttiming.sgml">
 <!ENTITY pgtrgm          SYSTEM "pgtrgm.sgml">
 <!ENTITY pgupgrade       SYSTEM "pgupgrade.sgml">
+<!ENTITY pgxlogdump      SYSTEM "pg_xlogdump.sgml">
 <!ENTITY postgres-fdw    SYSTEM "postgres-fdw.sgml">
 <!ENTITY seg             SYSTEM "seg.sgml">
 <!ENTITY contrib-spi     SYSTEM "contrib-spi.sgml">

doc/src/sgml/pg_xlogdump.sgml

+<!--
+doc/src/sgml/ref/pg_xlogdump.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="pg_xlogdump">
+ <refmeta>
+  <refentrytitle><application>pg_xlogdump</application></refentrytitle>
+  <manvolnum>1</manvolnum>
+  <refmiscinfo>Application</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>pg_xlogdump</refname>
+  <refpurpose>Display a human-readable rendering of the write-ahead log of a <productname>PostgreSQL</productname> database cluster</refpurpose>
+ </refnamediv>
+
+ <indexterm zone="pg_xlogdump">
+  <primary>pg_xlogdump</primary>
+ </indexterm>
+
+ <refsynopsisdiv>
+  <cmdsynopsis>
+   <command>pg_xlogdump</command>
+   <arg rep="repeat" choice="opt"><option>option</option></arg>
+   <arg choice="opt"><option>startseg</option>
+    <arg choice="opt"><option>endseg</option></arg>
+   </arg>
+  </cmdsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1 id="R1-APP-PGXLOGDUMP-1">
+  <title>Description</title>
+  <para>
+   <command>pg_xlogdump</command> display the write-ahead log (WAL) and is mainly
+   useful for debugging or educational purposes.
+  </para>
+
+  <para>
+   This utility can only be run by the user who installed the server, because
+   it requires read-only access to the data directory.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Options</title>
+
+   <para>
+    The following command-line options control the location and format of the
+    output:
+
+    <variablelist>
+
+     <varlistentry>
+      <term><replaceable class="parameter">startseg</replaceable></term>
+      <listitem>
+       <para>
+        Start reading at the specified log segment file.  This implicitly determines
+        the path in which files will be searched for, and the timeline to use.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><replaceable class="parameter">endseg</replaceable></term>
+      <listitem>
+       <para>
+        Stop after reading the specified log segment file.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>-b</option></term>
+      <term><option>--bkp-details</option></term>
+      <listitem>
+       <para>
+        Output detailed information about backup blocks.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>-e <replaceable>end</replaceable></option></term>
+      <term><option>--end=<replaceable>end</replaceable></option></term>
+      <listitem>
+       <para>
+        Stop reading at the specified log position, instead of reading to the
+        end of the log stream.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>-n <replaceable>limit</replaceable></option></term>
+      <term><option>--limit=<replaceable>limit</replaceable></option></term>
+      <listitem>
+       <para>
+        Display the specified number of records, then stop.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>-p <replaceable>path</replaceable></option></term>
+      <term><option>--path=<replaceable>path</replaceable></option></term>
+      <listitem>
+       <para>
+        Directory in which to find log segment files.  The default is to search
+        for them in the <literal>pg_xlog</literal> subdirectory of the current
+        directory.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>-r <replaceable>rmgr</replaceable></option></term>
+      <term><option>--rmgr=<replaceable>rmgr</replaceable></option></term>
+      <listitem>
+       <para>
+        Only display records generated by the specified resource manager.
+        If <literal>list</> is passed as name, print a list of valid resource manager
+        names, and exit.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>-s <replaceable>start</replaceable></option></term>
+      <term><option>--start=<replaceable>start</replaceable></option></term>
+      <listitem>
+       <para>
+        Log position at which to start reading. The default is to start reading
+        the first valid log record found in the earliest file found.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>-t <replaceable>timeline</replaceable></option></term>
+      <term><option>--timelime=<replaceable>timeline</replaceable></option></term>
+      <listitem>
+       <para>
+        Timeline from which to read log records. The default is to use the
+        value in <literal>startseg</>, if that is specified; otherwise, the
+        default is 1.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+       <term><option>-V</></term>
+       <term><option>--version</></term>
+       <listitem>
+       <para>
+       Print the <application>pg_xlogdump</application> version and exit.
+       </para>
+       </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>-x <replaceable>xid</replaceable></option></term>
+      <term><option>--xid=<replaceable>xid</replaceable></option></term>
+      <listitem>
+       <para>
+        Only display records marked with the given TransactionId.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><option>-?</></term>
+      <term><option>--help</></term>
+       <listitem>
+        <para>
+         Show help about <application>pg_xlogdump</application> command line
+         arguments, and exit.
+        </para>
+       </listitem>
+      </varlistentry>
+    </variablelist>
+   </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Notes</title>
+  <para>
+    Can give wrong results when the server is running.
+  </para>
+
+  <para>
+    Only the specified timeline is displayed (or the default, if none is
+    specified). Records in other timelines are ignored.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="wal"></member>
+  </simplelist>
+ </rfsect1>
+
+</refentry>

doc/src/sgml/ref/pg_isready.sgml

@@ -12,7 +12,7 @@ PostgreSQL documentation
 
  <refnamediv>
   <refname>pg_isready</refname>
-  <refpurpose>checks the connection status of a <productname>PostgreSQL</productname> server</refpurpose>
+  <refpurpose>check the connection status of a <productname>PostgreSQL</productname> server</refpurpose>
  </refnamediv>
 
  <indexterm zone="app-pg-isready">

src/include/utils/palloc.h

@@ -28,8 +28,6 @@
 #ifndef PALLOC_H
 #define PALLOC_H
 
-#ifndef FRONTEND
-
 /*
  * Type MemoryContextData is declared in nodes/memnodes.h.	Most users
  * of memory allocation should just treat it as an abstract type, so we
@@ -37,6 +35,8 @@
  */
 typedef struct MemoryContextData *MemoryContext;
 
+#ifndef FRONTEND
+
 /*
  * CurrentMemoryContext is the default allocation context for palloc().
  * We declare it here so that palloc() can be a macro.	Avoid accessing it