Improve vacuum code to track minimum Xids per table instead of per database.

To this end, add a couple of columns to pg_class, relminxid and relvacuumxid,
based on which we calculate the pg_database columns after each vacuum.

We now force all databases to be vacuumed, even template ones.  A backend
noticing too old a database (meaning pg_database.datminxid is in danger of
falling behind Xid wraparound) will signal the postmaster, which in turn will
start an autovacuum iteration to process the offending database.  In principle
this is only there to cope with frozen (non-connectable) databases without
forcing users to set them to connectable, but it could force regular user
database to go through a database-wide vacuum at any time.  Maybe we should
warn users about this somehow.  Of course the real solution will be to use
autovacuum all the time ;-)

There are some additional improvements we could have in this area: for example
the vacuum code could be smarter about not updating pg_database for each table
when called by autovacuum, and do it only once the whole autovacuum iteration
is done.

I updated the system catalogs documentation, but I didn't modify the
maintenance section.  Also having some regression tests for this would be nice
but it's not really a very straightforward thing to do.

Catalog version bumped due to system catalog changes.

8 files changed, 40 insertions, 26 deletions

diff --git a/src/include/access/transam.h b/src/include/access/transam.h
index 97a180005d9..f1b91145f67 100644
--- a/src/include/access/transam.h
+++ b/src/include/access/transam.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/transam.h,v 1.57 2006/03/05 15:58:53 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/transam.h,v 1.58 2006/07/10 16:20:51 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -23,6 +23,7 @@
  * always be considered valid.
  *
  * FirstNormalTransactionId is the first "normal" transaction id.
+ * Note: if you need to change it, you must change it in pg_class.h as well.
  * ----------------
  */
 #define InvalidTransactionId		((TransactionId) 0)
@@ -123,7 +124,7 @@ extern bool TransactionIdFollowsOrEquals(TransactionId id1, TransactionId id2);
 /* in transam/varsup.c */
 extern TransactionId GetNewTransactionId(bool isSubXact);
 extern TransactionId ReadNewTransactionId(void);
-extern void SetTransactionIdLimit(TransactionId oldest_datfrozenxid,
+extern void SetTransactionIdLimit(TransactionId oldest_datminxid,
 					  Name oldest_datname);
 extern Oid	GetNewObjectId(void);
 
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 59dea36fe42..0d62211f28a 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.336 2006/07/03 22:45:40 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.337 2006/07/10 16:20:51 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200607021
+#define CATALOG_VERSION_NO	200607101
 
 #endif
diff --git a/src/include/catalog/pg_attribute.h b/src/include/catalog/pg_attribute.h
index fe4a7189bae..e098079b93e 100644
--- a/src/include/catalog/pg_attribute.h
+++ b/src/include/catalog/pg_attribute.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_attribute.h,v 1.122 2006/07/03 22:45:40 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_attribute.h,v 1.123 2006/07/10 16:20:51 alvherre Exp $
  *
  * NOTES
  *	  the genbki.sh script reads this file and generates .bki
@@ -404,8 +404,10 @@ DATA(insert ( 1249 tableoid			26 0  4  -7 0 -1 -1 t p i t f f t 0));
 { 1259, {"relhaspkey"},    16, -1,	1, 22, 0, -1, -1, true, 'p', 'c', true, false, false, true, 0 }, \
 { 1259, {"relhasrules"},   16, -1,	1, 23, 0, -1, -1, true, 'p', 'c', true, false, false, true, 0 }, \
 { 1259, {"relhassubclass"},16, -1,	1, 24, 0, -1, -1, true, 'p', 'c', true, false, false, true, 0 }, \
-{ 1259, {"relacl"},		 1034, -1, -1, 25, 1, -1, -1, false, 'x', 'i', false, false, false, true, 0 }, \
-{ 1259, {"reloptions"},  1009, -1, -1, 26, 1, -1, -1, false, 'x', 'i', false, false, false, true, 0 }
+{ 1259, {"relminxid"},     28, -1,	4, 25, 0, -1, -1, true, 'p', 'i', true, false, false, true, 0 }, \
+{ 1259, {"relvacuumxid"},  28, -1,	4, 26, 0, -1, -1, true, 'p', 'i', true, false, false, true, 0 }, \
+{ 1259, {"relacl"},		 1034, -1, -1, 27, 1, -1, -1, false, 'x', 'i', false, false, false, true, 0 }, \
+{ 1259, {"reloptions"},  1009, -1, -1, 28, 1, -1, -1, false, 'x', 'i', false, false, false, true, 0 }
 
 DATA(insert ( 1259 relname			19 -1 NAMEDATALEN	1 0 -1 -1 f p i t f f t 0));
 DATA(insert ( 1259 relnamespace		26 -1 4   2 0 -1 -1 t p i t f f t 0));
@@ -431,8 +433,10 @@ DATA(insert ( 1259 relhasoids		16 -1 1  21 0 -1 -1 t p c t f f t 0));
 DATA(insert ( 1259 relhaspkey		16 -1 1  22 0 -1 -1 t p c t f f t 0));
 DATA(insert ( 1259 relhasrules		16 -1 1  23 0 -1 -1 t p c t f f t 0));
 DATA(insert ( 1259 relhassubclass	16 -1 1  24 0 -1 -1 t p c t f f t 0));
-DATA(insert ( 1259 relacl		  1034 -1 -1 25 1 -1 -1 f x i f f f t 0));
-DATA(insert ( 1259 reloptions	  1009 -1 -1 26 1 -1 -1 f x i f f f t 0));
+DATA(insert ( 1259 relminxid		28 -1 4  25 0 -1 -1 t p i t f f t 0));
+DATA(insert ( 1259 relvacuumxid		28 -1 4  26 0 -1 -1 t p i t f f t 0));
+DATA(insert ( 1259 relacl		  1034 -1 -1 27 1 -1 -1 f x i f f f t 0));
+DATA(insert ( 1259 reloptions	  1009 -1 -1 28 1 -1 -1 f x i f f f t 0));
 DATA(insert ( 1259 ctid				27 0  6  -1 0 -1 -1 f p s t f f t 0));
 DATA(insert ( 1259 oid				26 0  4  -2 0 -1 -1 t p i t f f t 0));
 DATA(insert ( 1259 xmin				28 0  4  -3 0 -1 -1 t p i t f f t 0));
diff --git a/src/include/catalog/pg_class.h b/src/include/catalog/pg_class.h
index 6d303b1cd66..931875a4c50 100644
--- a/src/include/catalog/pg_class.h
+++ b/src/include/catalog/pg_class.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_class.h,v 1.94 2006/07/03 22:45:40 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_class.h,v 1.95 2006/07/10 16:20:51 alvherre Exp $
  *
  * NOTES
  *	  the genbki.sh script reads this file and generates .bki
@@ -65,6 +65,8 @@ CATALOG(pg_class,1259) BKI_BOOTSTRAP
 	bool		relhaspkey;		/* has PRIMARY KEY index */
 	bool		relhasrules;	/* has associated rules */
 	bool		relhassubclass; /* has derived classes */
+	TransactionId relminxid;	/* minimum Xid present in table */
+	TransactionId relvacuumxid;	/* Xid used as last vacuum OldestXmin */
 
 	/*
 	 * VARIABLE LENGTH FIELDS start here.  These fields may be NULL, too.
@@ -78,7 +80,7 @@ CATALOG(pg_class,1259) BKI_BOOTSTRAP
 
 /* Size of fixed part of pg_class tuples, not counting var-length fields */
 #define CLASS_TUPLE_SIZE \
-	 (offsetof(FormData_pg_class,relhassubclass) + sizeof(bool))
+	 (offsetof(FormData_pg_class,relvacuumxid) + sizeof(TransactionId))
 
 /* ----------------
  *		Form_pg_class corresponds to a pointer to a tuple with
@@ -92,7 +94,7 @@ typedef FormData_pg_class *Form_pg_class;
  * ----------------
  */
 
-#define Natts_pg_class					26
+#define Natts_pg_class					28
 #define Anum_pg_class_relname			1
 #define Anum_pg_class_relnamespace		2
 #define Anum_pg_class_reltype			3
@@ -117,8 +119,10 @@ typedef FormData_pg_class *Form_pg_class;
 #define Anum_pg_class_relhaspkey		22
 #define Anum_pg_class_relhasrules		23
 #define Anum_pg_class_relhassubclass	24
-#define Anum_pg_class_relacl			25
-#define Anum_pg_class_reloptions		26
+#define Anum_pg_class_relminxid			25
+#define Anum_pg_class_relvacuumxid		26
+#define Anum_pg_class_relacl			27
+#define Anum_pg_class_reloptions		28
 
 /* ----------------
  *		initial contents of pg_class
@@ -128,13 +132,14 @@ typedef FormData_pg_class *Form_pg_class;
  * ----------------
  */
 
-DATA(insert OID = 1247 (  pg_type		PGNSP 71 PGUID 0 1247 0 0 0 0 0 f f r 23 0 0 0 0 0 t f f f _null_ _null_ ));
+/* Note: the "3" here stands for FirstNormalTransactionId */
+DATA(insert OID = 1247 (  pg_type		PGNSP 71 PGUID 0 1247 0 0 0 0 0 f f r 23 0 0 0 0 0 t f f f 3 3 _null_ _null_ ));
 DESCR("");
-DATA(insert OID = 1249 (  pg_attribute	PGNSP 75 PGUID 0 1249 0 0 0 0 0 f f r 17 0 0 0 0 0 f f f f _null_ _null_ ));
+DATA(insert OID = 1249 (  pg_attribute	PGNSP 75 PGUID 0 1249 0 0 0 0 0 f f r 17 0 0 0 0 0 f f f f 3 3 _null_ _null_ ));
 DESCR("");
-DATA(insert OID = 1255 (  pg_proc		PGNSP 81 PGUID 0 1255 0 0 0 0 0 f f r 18 0 0 0 0 0 t f f f _null_ _null_ ));
+DATA(insert OID = 1255 (  pg_proc		PGNSP 81 PGUID 0 1255 0 0 0 0 0 f f r 18 0 0 0 0 0 t f f f 3 3 _null_ _null_ ));
 DESCR("");
-DATA(insert OID = 1259 (  pg_class		PGNSP 83 PGUID 0 1259 0 0 0 0 0 f f r 26 0 0 0 0 0 t f f f _null_ _null_ ));
+DATA(insert OID = 1259 (  pg_class		PGNSP 83 PGUID 0 1259 0 0 0 0 0 f f r 28 0 0 0 0 0 t f f f 3 3 _null_ _null_ ));
 DESCR("");
 
 #define		  RELKIND_INDEX			  'i'		/* secondary index */
diff --git a/src/include/catalog/pg_database.h b/src/include/catalog/pg_database.h
index 09a2d8a4fc4..d62a4b94928 100644
--- a/src/include/catalog/pg_database.h
+++ b/src/include/catalog/pg_database.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_database.h,v 1.40 2006/03/05 15:58:54 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_database.h,v 1.41 2006/07/10 16:20:51 alvherre Exp $
  *
  * NOTES
  *	  the genbki.sh script reads this file and generates .bki
@@ -43,7 +43,7 @@ CATALOG(pg_database,1262) BKI_SHARED_RELATION
 	int4		datconnlimit;	/* max connections allowed (-1=no limit) */
 	Oid			datlastsysoid;	/* highest OID to consider a system OID */
 	TransactionId datvacuumxid; /* all XIDs before this are vacuumed */
-	TransactionId datfrozenxid; /* all XIDs before this are frozen */
+	TransactionId datminxid;	/* minimum XID present anywhere in the DB */
 	Oid			dattablespace;	/* default table space for this DB */
 	text		datconfig[1];	/* database-specific GUC (VAR LENGTH) */
 	aclitem		datacl[1];		/* access permissions (VAR LENGTH) */
@@ -69,7 +69,7 @@ typedef FormData_pg_database *Form_pg_database;
 #define Anum_pg_database_datconnlimit	6
 #define Anum_pg_database_datlastsysoid	7
 #define Anum_pg_database_datvacuumxid	8
-#define Anum_pg_database_datfrozenxid	9
+#define Anum_pg_database_datminxid		9
 #define Anum_pg_database_dattablespace	10
 #define Anum_pg_database_datconfig		11
 #define Anum_pg_database_datacl			12
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index f22246ee6e5..a78ab7a7b96 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.63 2006/03/05 15:58:55 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.64 2006/07/10 16:20:51 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -117,12 +117,15 @@ extern void vac_close_indexes(int nindexes, Relation *Irel, LOCKMODE lockmode);
 extern void vac_update_relstats(Oid relid,
 					BlockNumber num_pages,
 					double num_tuples,
-					bool hasindex);
+					bool hasindex,
+					TransactionId minxid,
+					TransactionId vacuumxid);
 extern void vacuum_set_xid_limits(VacuumStmt *vacstmt, bool sharedRel,
 					  TransactionId *oldestXmin,
 					  TransactionId *freezeLimit);
 extern bool vac_is_partial_index(Relation indrel);
 extern void vacuum_delay_point(void);
+extern TransactionId vactuple_get_minxid(HeapTuple tuple);
 
 /* in commands/vacuumlazy.c */
 extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index eaa3cf529ce..a50b3ca0a9b 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -4,7 +4,7 @@
  *	  Interface to hba.c
  *
  *
- * $PostgreSQL: pgsql/src/include/libpq/hba.h,v 1.42 2006/03/06 17:41:44 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/libpq/hba.h,v 1.43 2006/07/10 16:20:52 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -40,7 +40,7 @@ extern void load_role(void);
 extern int	hba_getauthmethod(hbaPort *port);
 extern int	authident(hbaPort *port);
 extern bool read_pg_database_line(FILE *fp, char *dbname, Oid *dboid,
-					  Oid *dbtablespace, TransactionId *dbfrozenxid,
+					  Oid *dbtablespace, TransactionId *dbminxid,
 					  TransactionId *dbvacuumxid);
 
 #endif   /* HBA_H */
diff --git a/src/include/storage/pmsignal.h b/src/include/storage/pmsignal.h
index acdbe01d6e8..afa819e7cd1 100644
--- a/src/include/storage/pmsignal.h
+++ b/src/include/storage/pmsignal.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/pmsignal.h,v 1.14 2006/03/05 15:58:59 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/storage/pmsignal.h,v 1.15 2006/07/10 16:20:52 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -26,6 +26,7 @@ typedef enum
 	PMSIGNAL_WAKEN_CHILDREN,	/* send a SIGUSR1 signal to all backends */
 	PMSIGNAL_WAKEN_ARCHIVER,	/* send a NOTIFY signal to xlog archiver */
 	PMSIGNAL_ROTATE_LOGFILE,	/* send SIGUSR1 to syslogger to rotate logfile */
+	PMSIGNAL_START_AUTOVAC,		/* start an autovacuum iteration */
 
 	NUM_PMSIGNALS				/* Must be last value of enum! */
 } PMSignalReason;