Expand pg_control information so that we can verify that the database

was created on a machine with alignment rules and floating-point format
similar to the current machine.  Per recent discussion, this seems like
a good idea with the increasing prevalence of 32/64 bit environments.

src/backend/access/transam/xlog.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.218 2005/08/22 23:59:04 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.219 2005/10/03 00:28:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3417,6 +3417,10 @@ WriteControlFile(void)
 	 */
 	ControlFile->pg_control_version = PG_CONTROL_VERSION;
 	ControlFile->catalog_version_no = CATALOG_VERSION_NO;
+
+	ControlFile->maxAlign = MAXIMUM_ALIGNOF;
+	ControlFile->floatFormat = FLOATFORMAT_VALUE;
+
 	ControlFile->blcksz = BLCKSZ;
 	ControlFile->relseg_size = RELSEG_SIZE;
 	ControlFile->xlog_seg_size = XLOG_SEG_SIZE;
@@ -3562,6 +3566,18 @@ ReadControlFile(void)
 			  " but the server was compiled with CATALOG_VERSION_NO %d.",
 					ControlFile->catalog_version_no, CATALOG_VERSION_NO),
 				 errhint("It looks like you need to initdb.")));
+	if (ControlFile->maxAlign != MAXIMUM_ALIGNOF)
+		ereport(FATAL,
+				(errmsg("database files are incompatible with server"),
+		 errdetail("The database cluster was initialized with MAXALIGN %d,"
+				   " but the server was compiled with MAXALIGN %d.",
+				   ControlFile->maxAlign, MAXIMUM_ALIGNOF),
+				   errhint("It looks like you need to initdb.")));
+	if (ControlFile->floatFormat != FLOATFORMAT_VALUE)
+		ereport(FATAL,
+				(errmsg("database files are incompatible with server"),
+				 errdetail("The database cluster appears to use a different floating-point format than the server executable."),
+				 errhint("It looks like you need to initdb.")));
 	if (ControlFile->blcksz != BLCKSZ)
 		ereport(FATAL,
 				(errmsg("database files are incompatible with server"),

src/bin/pg_controldata/pg_controldata.c

@@ -6,7 +6,7 @@
  * copyright (c) Oliver Elphick <olly@lfix.co.uk>, 2001;
  * licence: BSD
  *
- * $PostgreSQL: pgsql/src/bin/pg_controldata/pg_controldata.c,v 1.25 2005/06/08 15:50:27 tgl Exp $
+ * $PostgreSQL: pgsql/src/bin/pg_controldata/pg_controldata.c,v 1.26 2005/10/03 00:28:41 tgl Exp $
  */
 #include "postgres.h"
 
@@ -168,6 +168,8 @@ main(int argc, char *argv[])
 	printf(_("Latest checkpoint's NextMultiXactId:  %u\n"), ControlFile.checkPointCopy.nextMulti);
 	printf(_("Latest checkpoint's NextMultiOffset:  %u\n"), ControlFile.checkPointCopy.nextMultiOffset);
 	printf(_("Time of latest checkpoint:            %s\n"), ckpttime_str);
+	printf(_("Maximum data alignment:               %u\n"), ControlFile.maxAlign);
+	/* we don't print floatFormat since can't say much useful about it */
 	printf(_("Database block size:                  %u\n"), ControlFile.blcksz);
 	printf(_("Blocks per segment of large relation: %u\n"), ControlFile.relseg_size);
 	printf(_("Bytes per WAL segment:                %u\n"), ControlFile.xlog_seg_size);

src/bin/pg_resetxlog/pg_resetxlog.c

@@ -23,7 +23,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/bin/pg_resetxlog/pg_resetxlog.c,v 1.36 2005/09/29 08:34:50 petere Exp $
+ * $PostgreSQL: pgsql/src/bin/pg_resetxlog/pg_resetxlog.c,v 1.37 2005/10/03 00:28:42 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -456,6 +456,8 @@ GuessControlValues(void)
 	ControlFile.logSeg = 1;
 	ControlFile.checkPoint = ControlFile.checkPointCopy.redo;
 
+	ControlFile.maxAlign = MAXIMUM_ALIGNOF;
+	ControlFile.floatFormat = FLOATFORMAT_VALUE;
 	ControlFile.blcksz = BLCKSZ;
 	ControlFile.relseg_size = RELSEG_SIZE;
 	ControlFile.xlog_seg_size = XLOG_SEG_SIZE;
@@ -523,6 +525,8 @@ PrintControlValues(bool guessed)
 	printf(_("Latest checkpoint's NextOID:          %u\n"), ControlFile.checkPointCopy.nextOid);
 	printf(_("Latest checkpoint's NextMultiXactId:  %u\n"), ControlFile.checkPointCopy.nextMulti);
 	printf(_("Latest checkpoint's NextMultiOffset:  %u\n"), ControlFile.checkPointCopy.nextMultiOffset);
+	printf(_("Maximum data alignment:               %u\n"), ControlFile.maxAlign);
+	/* we don't print floatFormat since can't say much useful about it */
 	printf(_("Database block size:                  %u\n"), ControlFile.blcksz);
 	printf(_("Blocks per segment of large relation: %u\n"), ControlFile.relseg_size);
 	printf(_("Maximum length of identifiers:        %u\n"), ControlFile.nameDataLen);

src/include/catalog/pg_control.h

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_control.h,v 1.23 2005/06/08 15:50:28 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_control.h,v 1.24 2005/10/03 00:28:43 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -22,7 +22,7 @@
 
 
 /* Version identifier for this pg_control format */
-#define PG_CONTROL_VERSION	811
+#define PG_CONTROL_VERSION	812
 
 /*
  * Body of CheckPoint XLOG records.  This is declared here because we keep
@@ -107,6 +107,22 @@ typedef struct ControlFileData
 
 	CheckPoint	checkPointCopy; /* copy of last check point record */
 
+	/*
+	 * This data is used to check for hardware-architecture compatibility
+	 * of the database and the backend executable.  We need not check
+	 * endianness explicitly, since the pg_control version will surely
+	 * look wrong to a machine of different endianness, but we do need
+	 * to worry about MAXALIGN and floating-point format.  (Note: storage
+	 * layout nominally also depends on SHORTALIGN and INTALIGN, but in
+	 * practice these are the same on all architectures of interest.)
+	 *
+	 * Testing just one double value is not a very bulletproof test for
+	 * floating-point compatibility, but it will catch most cases.
+	 */
+	uint32		maxAlign;		/* alignment requirement for tuples */
+	double		floatFormat;	/* constant 1234567.0 */
+#define FLOATFORMAT_VALUE	1234567.0
+
 	/*
 	 * This data is used to make sure that configuration of this database
 	 * is compatible with the backend executable.