I have updated my pg_autovacuum program (formerly pg_avd, the name

changed as per discussion on the patches list).

This version should be a good bit better.  It addresses all the issues
pointed out by Neil Conway. Vacuum and Analyze are now handled
separately.  It now monitors for xid wraparound.  The number of database
connections and queries has been significantly reduced compared the
previous version.  I have moved it from bin to contrib.  More detail on
the changes are in the TODO file.

I have not tested the xid wraparound code as I have to let my AthlonXP
1600 run select 1 in a tight loop for approx. two days in order to
perform the required 500,000,000 xacts.

Matthew T. O'Connor

contrib/Makefile

-# $Header: /cvsroot/pgsql/contrib/Makefile,v 1.40 2002/10/21 00:12:46 momjian Exp $
+# $Header: /cvsroot/pgsql/contrib/Makefile,v 1.41 2003/03/20 18:14:46 momjian Exp $
 
 subdir = contrib
 top_builddir = ..
@@ -25,6 +25,7 @@ WANTED_DIRS = \
 		miscutil	\
 		noupdate	\
 		oid2name	\
+		pg_autovacuum	\
 		pg_dumplo	\
 		pg_logger	\
 		pgbench		\

contrib/README

@@ -132,6 +132,10 @@ oracle -
 	Converts Oracle database schema to PostgreSQL
 	by Gilles Darold <gilles@darold.net>
 
+pg_autovacuum -
+	Automatically performs vacuum
+	by Matthew T. O'Connor <matthew@zeut.net>
+
 pg_dumplo -
 	Dump large objects
 	by Karel Zak <zakkr@zf.jcu.cz>

contrib/pg_autovacuum/Makefile

+
+subdir = contrib/pg_autovacuum
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+
+PROGRAM = pg_autovacuum
+OBJS	= pg_autovacuum.o
+
+PG_CPPFLAGS = -I$(libpq_srcdir)
+PG_LIBS = $(libpq)
+
+DOCS = README.pg_autovacuum
+
+include $(top_srcdir)/contrib/contrib-global.mk

contrib/pg_autovacuum/README

+pg_autovacuum README
+
+pg_autovacuum is a libpq client program that monitors all the databases of a
+postgresql server.  It uses the stats collector to monitor insert, update and
+delete activity.  When an individual table exceeds it's insert or delete
+threshold (more detail on thresholds below) then that table is vacuumed or
+analyzed.  This allows postgresql to keep the fsm and table statistics up to
+date without having to schedule periodic vacuums with cron regardless of need.
+
+The primary benefit of pg_autovacuum is that the FSM and table statistic information
+are updated as needed.  When a table is actively changed pg_autovacuum performs the
+necessary vacuums and analyzes, when a table is inactive, no cycles are wasted
+performing vacuums and analyzes that are not needed.
+
+A secondary benefit of pg_autovacuum is that it guarantees that a database wide
+vacuum is performed prior to xid wraparound.  This is important as failing to do
+so can result in major data loss.
+
+INSTALL:
+To use pg_autovacuum, uncompress the tar.gz into the contrib directory and modify the
+contrib/Makefile to include the pg_autovacuum directory.  pg_autovacuum will then be made as
+part of the standard postgresql install.
+
+make sure that the folowing are set in postgresql.conf
+stats_start_collector = true
+stats_row_level = true
+
+start up the postmaster
+then, just execute the pg_autovacuum executable.
+
+
+Command line arguments:
+pg_autovacuum has the following optional arguments:
+-d debug: 0 silent, 1 basic info, 2 more debug info,  etc...
+-s sleep base value: see "Sleeping" below.
+-S sleep scaling factor: see "Sleeping" below.
+-t tuple base threshold: see Vacuuming.
+-T tuple scaling factor: see Vacuuming.
+-U username: Username pg_autovacuum will use to connect with, if not specified the
+   current username is used
+-P password: Password pg_autovacuum will use to connect with.
+-H host: host name or IP to connect too.
+-p port: port used for connection.
+-h help: list of command line options.
+
+All arguments have default values defined in pg_autovacuum.h.  At the time of this
+writing they are:
+#define AUTOVACUUM_DEBUG    1
+#define BASETHRESHOLD       100
+#define SCALINGFACTOR       2
+#define SLEEPVALUE          3
+#define SLEEPSCALINGFACTOR  2
+#define UPDATE_INTERVAL     2
+
+
+Vacuum and Analyze:
+pg_autovacuum performes either a vacuums analyze or just analyze depending on the table activity.
+If the number of (inserts + updates) > insertThreshold, then an only an analyze is performed.
+If the number of (deletes + updates ) > deleteThreshold, then a vacuum analyze is performed.
+deleteThreshold is equal to: tuple_base_value + (tuple_scaling_factor * "number of tuples in the table")
+insertThreshold is equal to: 0.5 * tuple_base_value + (tuple_scaling_factor * "number of tuples in the table")
+The insertThreshold is half the deleteThreshold because it's a much lighter operation (approx 5%-10% of vacuum),
+so running it more often costs us little in performance degredation.
+
+Sleeping:
+pg_autovacuum sleeps after it is done checking all the databases.  It does this so as
+to limit the amount of system resources it consumes.  This also allows the system
+administrator to configure pg_autovacuum to be more or less aggressive.  Reducing the
+sleep time will cause pg_autovacuum to respond more quickly to changes, be they database
+addition / removal, table addition / removal, or just normal table activity.  However,
+setting these values to high can have a negative net effect on the server.  If a table
+gets vacuumed 5 times during the course of a large update, it might take much longer
+than if it was vacuumed only once.
+The total time it sleeps is equal to:
+base_sleep_value + sleep_scaling_factor * "duration of the previous loop"
+
+What it monitors:
+pg_autovacuum dynamically generates a list of databases and tables to monitor, in
+addition it will dynamically add and remove databases and tables that are
+removed from the database server while pg_autovacuum is running.

contrib/pg_autovacuum/TODO

+Todo Items for pg_autovacuum client
+
+_Allow it to detach from the tty
+
+_create a FSM export function and see if I can use it for pg_autovacuum
+
+_look into possible benifits of pgstattuple contrib work
+
+_Continue trying to reduce server load created by polling.
+
+Done:
+_Check if required pg_stats are enables, if not exit with error
+
+_Reduce the number connections and queries to the server
+	_Make database adding and removal part of the normal loop
+	_make table adding and removal part of the normal loop
+
+_Separate logic for vacuum and analyze
+
+_all pg_autovacuum specific functions are now static
+
+_correct usage of snprintf
+
+_reworked database and table update functions, now they
+	use the existing database connection and only one query
+
+_fixed -h option output
+
+_cleanup of 'constant == variable' used much more consistently now.
+
+_Guarantee database wide vacuum prior to Xid wraparound
+
+_change name to pg_autovacuum
+
+_Add proper table and database removal functions so that we can properly
+	clear up before we exit, and make sure we don't leak memory when removing tables and such.

contrib/pg_autovacuum/pg_autovacuum.c

+/* pg_autovacuum.c
+ * All the code for the pg_autovacuum program
+ * (c) 2003 Matthew T. O'Connor
+ */
+
+#include "pg_autovacuum.h"
+
+/* Create and return tbl_info struct with initalized to values from row or res */
+tbl_info *init_table_info(PGresult *res, int row)
+{
+  tbl_info *new_tbl=(tbl_info *)malloc(sizeof(tbl_info));
+
+  if(!new_tbl)
+  {
+    fprintf(stderr,"init_table_info: Cannot get memory\n");
+    return NULL;
+  }
+
+  if(NULL == res)
+    return NULL;
+
+  new_tbl->schema_name=(char *)malloc(strlen(PQgetvalue(res,row,PQfnumber(res,"schemaname")))+1);
+  if(!new_tbl->schema_name)
+  {
+    fprintf(stderr,"init_table_info: malloc failed on new_tbl->schema_name\n");
+    return NULL;
+  }
+  strcpy(new_tbl->schema_name,PQgetvalue(res,row,PQfnumber(res,"schemaname")));
+
+  new_tbl->table_name=(char *)malloc(strlen(PQgetvalue(res,row,PQfnumber(res,"relname"))) + strlen(new_tbl->schema_name)+2);
+  if(!new_tbl->table_name)
+  {
+    fprintf(stderr,"init_table_info: malloc failed on new_tbl->table_name\n");
+    return NULL;
+  }
+  strcpy(new_tbl->table_name,new_tbl->schema_name);
+  strcat(new_tbl->table_name,".");
+  strcat(new_tbl->table_name,PQgetvalue(res,row,PQfnumber(res,"relname")));
+
+  new_tbl->InsertsAtLastAnalyze=(atol(PQgetvalue(res,row,PQfnumber(res,"n_tup_ins"))) + atol(PQgetvalue(res,row,PQfnumber(res,"n_tup_upd"))));
+  new_tbl->DeletesAtLastVacuum =(atol(PQgetvalue(res,row,PQfnumber(res,"n_tup_del"))) + atol(PQgetvalue(res,row,PQfnumber(res,"n_tup_upd"))));
+
+  new_tbl->relfilenode=atoi(PQgetvalue(res,row,PQfnumber(res,"relfilenode")));
+  new_tbl->reltuples=atoi(PQgetvalue(res,row,PQfnumber(res,"reltuples")));
+  new_tbl->relpages=atoi(PQgetvalue(res,row,PQfnumber(res,"relpages")));
+
+  new_tbl->insertThreshold=args->tuple_base_threshold + args->tuple_scaling_factor*new_tbl->reltuples;
+  new_tbl->deleteThreshold=args->tuple_base_threshold + args->tuple_scaling_factor*new_tbl->reltuples;
+
+  if(args->debug >= 2) {print_table_info(new_tbl);}
+  
+  return new_tbl;
+}
+
+/* Set thresholds = base_value + scaling_factor * reltuples
+   Should be called after a vacuum since vacuum updates valuesin pg_class */
+void update_table_thresholds(db_info *dbi,tbl_info *tbl)
+{
+  PGresult *res=NULL;
+  int disconnect=0;
+	char query[128];
+
+  if(NULL==dbi->conn)
+  { dbi->conn=db_connect(dbi); disconnect=1;}
+
+  if(NULL != dbi->conn)
+  {
+    snprintf(query,sizeof(query),"select relfilenode,reltuples,relpages from pg_class where relfilenode=%i",tbl->relfilenode);
+    res=send_query(query,dbi);
+    if(NULL!=res)
+    {
+    	tbl->reltuples = atoi(PQgetvalue(res,0,PQfnumber(res,"reltuples")));
+    	tbl->relpages = atoi(PQgetvalue(res,0,PQfnumber(res,"relpages")));
+      tbl->deleteThreshold = (args->tuple_base_threshold + args->tuple_scaling_factor*tbl->reltuples);
+      tbl->insertThreshold = (0.5 * tbl->deleteThreshold);
+      PQclear(res);
+    }
+	}
+  if(disconnect)	db_disconnect(dbi);
+}
+
+void update_table_list(db_info *dbi)
+{
+	int disconnect=0;
+	PGresult *res=NULL;
+	tbl_info *tbl=NULL;
+	Dlelem *tbl_elem=DLGetHead(dbi->table_list);
+	int i=0,t=0,found_match=0;
+	
+  if(NULL==dbi->conn)
+  {	dbi->conn=db_connect(dbi);   disconnect=1;}
+
+  if(NULL != dbi->conn)
+  {
+    /* Get a result set that has all the information
+    	 we will need to both remove tables from the list
+       that no longer exist and add tables to the list
+       that are new */
+		res=send_query(query_table_stats(dbi),dbi);
+		t=PQntuples(res);
+   
+		/* First: use the tbl_list as the outer loop and
+				the result set as the inner loop, this will
+				determine what tables should be removed */
+    while(NULL != tbl_elem)
+		{
+			tbl=((tbl_info *)DLE_VAL(tbl_elem));
+			found_match=0;
+			
+			for(i=0;i<t;i++) /* loop through result set looking for a match */
+			{
+				if(tbl->relfilenode==atoi(PQgetvalue(res,i,PQfnumber(res,"relfilenode"))))
+				{
+					found_match=1;
+					break;
+				}
+			}
+			if(0==found_match) /*then we didn't find this tbl_elem in the result set */
+			{
+				Dlelem *elem_to_remove=tbl_elem;
+				tbl_elem=DLGetSucc(tbl_elem);
+				remove_table_from_list(elem_to_remove);
+			}
+			else
+				tbl_elem=DLGetSucc(tbl_elem);
+		} /* Done removing dropped tables from the table_list */
+
+		/* Then loop use result set as outer loop and
+				tbl_list as the inner loop to determine
+				what tables are new */
+		for(i=0;i<t;i++)
+		{
+			tbl_elem=DLGetHead(dbi->table_list);
+			found_match=0;
+			while(NULL != tbl_elem)
+			{
+				tbl=((tbl_info *)DLE_VAL(tbl_elem));
+				if(tbl->relfilenode==atoi(PQgetvalue(res,i,PQfnumber(res,"relfilenode"))))
+				{
+					found_match=1;
+					break;
+				}
+				tbl_elem=DLGetSucc(tbl_elem);
+			}
+			if(0==found_match) /*then we didn't find this result now in the tbl_list */
+			{
+				DLAddTail(dbi->table_list,DLNewElem(init_table_info(res,i)));
+				if(args->debug >= 1) {printf("added table: %s.%s\n",dbi->dbname,((tbl_info *)DLE_VAL(DLGetTail(dbi->table_list)))->table_name);}
+			}
+		} /* end of for loop that adds tables */
+		PQclear(res); res=NULL;
+		if(args->debug >= 3)	{print_table_list(dbi->table_list);}
+		if(disconnect) db_disconnect(dbi);
+	}
+}
+
+/* Free memory, and remove the node from the list */
+void remove_table_from_list(Dlelem *tbl_to_remove)
+{
+  tbl_info *tbl=((tbl_info *)DLE_VAL(tbl_to_remove));
+
+  if(args->debug >= 1) {printf("Removing table: %s from list.\n",tbl->table_name);}
+  DLRemove(tbl_to_remove);
+
+	if(tbl->schema_name)
+	{	free(tbl->schema_name); tbl->schema_name=NULL;}
+	if(tbl->table_name)
+	{	free(tbl->table_name); tbl->table_name=NULL;}
+	if(tbl)
+	{	free(tbl); tbl=NULL;}
+  DLFreeElem(tbl_to_remove);
+}
+
+/* Free the entire table list */
+void free_tbl_list(Dllist *tbl_list)
+{
+	Dlelem *tbl_elem=DLGetHead(tbl_list);
+	Dlelem *tbl_elem_to_remove=NULL;
+	while(NULL != tbl_elem)
+	{
+		tbl_elem_to_remove=tbl_elem;
+		tbl_elem=DLGetSucc(tbl_elem);
+		remove_table_from_list(tbl_elem_to_remove);
+	}
+	DLFreeList(tbl_list);
+}
+
+void print_table_list(Dllist *table_list)
+{
+  Dlelem *table_elem=DLGetHead(table_list);
+  while (NULL != table_elem)
+  {
+    print_table_info(((tbl_info *)DLE_VAL(table_elem)));
+    table_elem=DLGetSucc(table_elem);
+  }
+}
+
+void print_table_info(tbl_info *tbl)
+{
+  printf("  table name:     %s\n",tbl->table_name);
+  printf("     iThresh: %i; Delete Thresh %i\n",tbl->insertThreshold,tbl->deleteThreshold);
+  printf("     relfilenode: %i; reltuples: %i;  relpages: %i\n",tbl->relfilenode,tbl->reltuples,tbl->relpages);
+  printf("     InsertsAtLastAnalyze: %li; DeletesAtLastVacuum: %li\n",tbl->InsertsAtLastAnalyze,tbl->DeletesAtLastVacuum);
+}
+
+/* End of table Management Functions */
+
+/* Beginning of DB Management Functions */
+
+/* init_db_list() creates the db_list and initalizes template1 */
+Dllist *init_db_list()
+{
+  Dllist   *db_list=DLNewList();
+  db_info  *dbs=NULL;
+  PGresult *res=NULL;
+
+  DLAddHead(db_list,DLNewElem(init_dbinfo((char *)"template1",0,0)));
+  if(NULL == DLGetHead(db_list)) /* Make sure init_dbinfo was successful */
+  { printf("init_db_list(): Error creating db_list for db: template1.\n"); return NULL; }
+
+  /* We do this just so we can set the proper oid for the template1 database */
+  dbs = ((db_info *)DLE_VAL(DLGetHead(db_list)));
+  dbs->conn=db_connect(dbs);
+
+  if(NULL != dbs->conn)
+  {
+    res=send_query("select oid,age(datfrozenxid) from pg_database where datname = 'template1'",dbs);
+    dbs->oid=atoi(PQgetvalue(res,0,PQfnumber(res,"oid")));
+    dbs->age=atoi(PQgetvalue(res,0,PQfnumber(res,"age")));
+    if(res)
+      PQclear(res);
+
+    if(args->debug >= 2) {print_db_list(db_list,0);}
+	}
+  return db_list;
+}
+
+/* Simple function to create an instance of the dbinfo struct
+    Initalizes all the pointers and connects to the database  */
+db_info *init_dbinfo(char *dbname, int oid, int age)
+{
+  db_info *newdbinfo=(db_info *)malloc(sizeof(db_info));
+  newdbinfo->insertThreshold=args->tuple_base_threshold;
+  newdbinfo->deleteThreshold=args->tuple_base_threshold;
+  newdbinfo->dbname=(char *)malloc(strlen(dbname)+1);
+  strcpy(newdbinfo->dbname,dbname);
+  newdbinfo->username=NULL;
+  if(NULL != args->user)
+  {
+  	newdbinfo->username=(char *)malloc(strlen(args->user)+1);
+  	strcpy(newdbinfo->username,args->user);
+  }
+  newdbinfo->password=NULL;
+  if(NULL != args->password)
+  {
+  	newdbinfo->password=(char *)malloc(strlen(args->password)+1);
+  	strcpy(newdbinfo->password,args->password);
+  }
+  newdbinfo->oid=oid;
+  newdbinfo->age=age;
+  newdbinfo->table_list=DLNewList();
+	newdbinfo->conn=NULL;
+	
+  if(args->debug >= 2) {print_table_list(newdbinfo->table_list);}
+
+  return newdbinfo;
+}
+
+/* Function adds and removes databases from the db_list as appropriate */
+void update_db_list(Dllist *db_list)
+{
+	int disconnect=0;
+	PGresult *res=NULL;
+	Dlelem *db_elem=DLGetHead(db_list);
+	db_info *dbi=NULL;
+	db_info *dbi_template1=DLE_VAL(db_elem);
+	int i=0,t=0,found_match=0;
+
+  if(args->debug >= 2) {printf("updating the database list\n");}
+
+  if(NULL==dbi_template1->conn)
+  {	dbi_template1->conn=db_connect(dbi_template1);   disconnect=1;}
+
+  if(NULL != dbi_template1->conn)
+  {
+    /* 	Get a resu22lt set that has all the information
+		we will need to both remove databasews from the list
+		that no longer exist and add databases to the list
+		that are new */
+		res=send_query("select oid,datname,age(datfrozenxid) from pg_database where datname!='template0'",dbi_template1);
+		t=PQntuples(res);
+
+		/* First: use the db_list as the outer loop and
+				the result set as the inner loop, this will
+				determine what databases should be removed */
+		while(NULL != db_elem)
+		{
+			dbi=((db_info *)DLE_VAL(db_elem));
+			found_match=0;
+
+			for(i=0;i<t;i++) /* loop through result set looking for a match */
+			{
+				if(dbi->oid==atoi(PQgetvalue(res,i,PQfnumber(res,"oid"))))
+				{
+					found_match=1;
+					/* update the dbi->age so that we ensure xid_wraparound won't happen */
+					dbi->age=atoi(PQgetvalue(res,i,PQfnumber(res,"age")));
+					break;
+				}
+			}
+			if(0==found_match) /*then we didn't find this db_elem in the result set */
+			{
+				Dlelem *elem_to_remove=db_elem;
+				db_elem=DLGetSucc(db_elem);
+				remove_db_from_list(elem_to_remove);
+			}
+			else
+				db_elem=DLGetSucc(db_elem);
+		} /* Done removing dropped databases from the table_list */
+
+		/* Then loop use result set as outer loop and
+				db_list as the inner loop to determine
+				what databases are new */
+		for(i=0;i<t;i++)
+		{
+			db_elem=DLGetHead(db_list);
+			found_match=0;
+			while(NULL != db_elem)
+			{
+				dbi=((db_info *)DLE_VAL(db_elem));
+				if(dbi->oid==atoi(PQgetvalue(res,i,PQfnumber(res,"oid"))))
+				{
+					found_match=1;
+					break;
+				}
+				db_elem=DLGetSucc(db_elem);
+			}
+			if(0==found_match) /*then we didn't find this result now in the tbl_list */
+			{
+				DLAddTail(db_list,DLNewElem(init_dbinfo(PQgetvalue(res,i,PQfnumber(res,"datname")),
+									atoi(PQgetvalue(res,i,PQfnumber(res,"oid"))),atoi(PQgetvalue(res,i,PQfnumber(res,"age"))))));
+				if(args->debug >= 1) {printf("added database: %s\n",((db_info *)DLE_VAL(DLGetTail(db_list)))->dbname);}
+			}
+		} /* end of for loop that adds tables */
+		PQclear(res); res=NULL;
+		if(args->debug >= 3)	{print_db_list(db_list,0);}
+		if(disconnect) db_disconnect(dbi_template1);
+	}
+}
+
+/* xid_wraparound_check
+
+From the docs:
+
+With the standard freezing policy, the age column will start at one billion for a
+freshly-vacuumed database. When the age approaches two billion, the database must
+be vacuumed again to avoid risk of wraparound failures. Recommended practice is
+to vacuum each database at least once every half-a-billion (500 million) transactions,
+so as to provide plenty of safety margin.
+
+So we do a full database vacuum if age > 1.5billion
+return 0 if nothing happened,
+return 1 if the database needed a database wide vacuum
+*/
+int xid_wraparound_check(db_info *dbi)
+{
+  /* FIXME: should probably do something better here so that we don't vacuum all the
+  databases on the server at the same time.  We have 500million xacts to work with so
+  we should be able to spread the load of full database vacuums a bit */
+	if(1500000000 < dbi->age)
+	{
+		PGresult *res=NULL;
+		res=send_query("vacuum",dbi);
+		/* FIXME: Perhaps should add a check for PQ_COMMAND_OK */
+		PQclear(res);
+		return 1;
+	}
+	return 0;
+}
+
+/* Close DB connection, free memory, and remove the node from the list */
+void  remove_db_from_list(Dlelem *db_to_remove)
+{
+  db_info *dbi=((db_info *)DLE_VAL(db_to_remove));
+
+	if(args->debug >= 1) {printf("Removing db: %s from list.\n",dbi->dbname);}
+  DLRemove(db_to_remove);
+  if(dbi->conn)
+		db_disconnect(dbi);
+  if(dbi->dbname)
+	{	free(dbi->dbname); dbi->dbname=NULL;}
+  if(dbi->username)
+	{	free(dbi->username); dbi->username=NULL;}
+  if(dbi->password)
+	{	free(dbi->password); dbi->password=NULL;}
+  if(dbi->table_list)
+	{	free_tbl_list(dbi->table_list); dbi->table_list=NULL;}
+  if(dbi)
+	{	free(dbi); dbi=NULL;}
+  DLFreeElem(db_to_remove);
+}
+
+/* Function is called before program exit to free all memory
+		mostly it's just to keep valgrind happy */
+void free_db_list(Dllist *db_list)
+{
+	Dlelem *db_elem=DLGetHead(db_list);
+	Dlelem *db_elem_to_remove=NULL;
+	while(NULL != db_elem)
+	{
+    db_elem_to_remove=db_elem;
+		db_elem=DLGetSucc(db_elem);
+		remove_db_from_list(db_elem_to_remove);
+		db_elem_to_remove=NULL;
+	}
+	DLFreeList(db_list);
+}
+
+void print_db_list(Dllist *db_list, int print_table_lists)
+{
+  Dlelem *db_elem=DLGetHead(db_list);
+  while(NULL != db_elem)
+  {
+    print_db_info(((db_info *)DLE_VAL(db_elem)),print_table_lists);
+    db_elem=DLGetSucc(db_elem);
+  }
+}
+
+void print_db_info(db_info *dbi, int print_tbl_list)
+{
+  printf("dbname: %s\n Username %s\n Passwd %s\n",dbi->dbname,dbi->username,dbi->password);
+  printf(" oid %i\n InsertThresh: %i\n DeleteThresh: %i\n",dbi->oid,dbi->insertThreshold,dbi->deleteThreshold);
+  if(NULL!=dbi->conn)
+    printf(" conn is valid, we are connected\n");
+  else
+    printf(" conn is null, we are not connected.\n");
+
+  if(0 < print_tbl_list)
+    print_table_list(dbi->table_list);
+}
+
+/* End of DB List Management Function */
+
+/* Begninning of misc Functions */
+
+
+char *query_table_stats(db_info *dbi)
+{
+  if(!strcmp(dbi->dbname,"template1")) /* Use template1 to monitor the system tables */
+    return (char*)TABLE_STATS_ALL;
+  else
+    return (char*)TABLE_STATS_USER;
+}
+
+/* Perhaps add some test to this function to make sure that the stats we need are availalble */
+PGconn *db_connect(db_info *dbi)
+{
+  PGconn *db_conn=PQsetdbLogin(args->host, args->port, NULL, NULL, dbi->dbname, dbi->username, dbi->password);
+  
+  if(CONNECTION_OK != PQstatus(db_conn))
+  {
+    fprintf(stderr,"Failed connection to database %s with error: %s.\n",dbi->dbname,PQerrorMessage(db_conn));
+    PQfinish(db_conn);
+    db_conn=NULL;
+  }
+  return db_conn;
+} /* end of db_connect() */
+
+void db_disconnect(db_info *dbi)
+{
+  if(NULL != dbi->conn)
+  {
+    PQfinish(dbi->conn);
+    dbi->conn=NULL;
+  }
+}
+
+int	check_stats_enabled(db_info *dbi)
+{
+	PGresult *res=NULL;
+	int ret=0;
+	res=send_query("show stats_row_level",dbi);
+	ret = strcmp("on",PQgetvalue(res,0,PQfnumber(res,"stats_row_level")));
+	PQclear(res);
+	return ret;
+}
+
+PGresult *send_query(const char *query,db_info *dbi)
+{
+  PGresult *res;
+
+  if(NULL==dbi->conn)
+    return NULL;
+
+  res=PQexec(dbi->conn,query);
+
+  if(!res)
+  {
+    fprintf(stderr,"Fatal error occured while sending query (%s) to database %s\n",query,dbi->dbname);
+    fprintf(stderr,"The error is \n%s\n",PQresultErrorMessage(res));
+    return NULL;
+  }
+  if(PQresultStatus(res)!=PGRES_TUPLES_OK && PQresultStatus(res)!=PGRES_COMMAND_OK)
+  {
+    fprintf(stderr,"Can not refresh statistics information from the database %s.\n",dbi->dbname);
+    fprintf(stderr,"The error is \n%s\n",PQresultErrorMessage(res));
+    PQclear(res);
+    return NULL;
+  }
+  return res;
+} /* End of send_query() */
+
+
+void free_cmd_args()
+{
+  if(NULL!=args)
+  {
+    if(NULL!=args->user)
+      free(args->user);
+    if(NULL!=args->user)
+      free(args->password);
+  free(args);
+  }
+}
+
+cmd_args *get_cmd_args(int argc,char *argv[])
+{
+  int c;
+
+  args=(cmd_args *)malloc(sizeof(cmd_args));
+  args->sleep_base_value=SLEEPVALUE;
+  args->sleep_scaling_factor=SLEEPSCALINGFACTOR;
+  args->tuple_base_threshold=BASETHRESHOLD;
+  args->tuple_scaling_factor=SCALINGFACTOR;
+  args->debug=AUTOVACUUM_DEBUG;
+  args->user=NULL;
+  args->password=NULL;
+  args->host=NULL;
+  args->port=NULL;
+  while (-1 != (c = getopt(argc, argv, "s:S:t:T:d:U:P:H:p:h")))
+	{
+		switch (c)
+		{
+			case 's':
+				args->sleep_base_value=atoi(optarg);
+				break;
+			case 'S':
+				args->sleep_scaling_factor = atof(optarg);
+				break;
+			case 't':
+				args->tuple_base_threshold = atoi(optarg);
+				break;
+			case 'T':
+				args->tuple_scaling_factor = atof(optarg);
+				break;
+			case 'd':
+				args->debug = atoi(optarg);
+				break;
+			case 'U':
+				args->user=optarg;
+				break;
+			case 'P':
+				args->password=optarg;
+				break;
+			case 'H':
+				args->host=optarg;
+				break;
+			case 'p':
+				args->port=optarg;
+				break;
+			case 'h':
+			default:
+				fprintf(stderr, "usage: pg_autovacuum [-d debug][-s sleep base value][-S sleep scaling factor]\n[-t tuple base threshold][-T tulple scaling factor]\n[-U username][-P password][-H host][-p port][-h help]\n");
+				exit(1);
+				break;
+		}
+  }
+
+  return args;
+}
+
+void print_cmd_args()
+{
+	printf("Printing command_args\n");
+	printf("  args->host=%s\n",args->host);
+	printf("  args->port=%s\n",args->port);
+	printf("	args->user=%s\n",args->user);
+	printf("	args->password=%s\n",args->password);
+	printf("	args->sleep_base_value=%i\n",args->sleep_base_value);
+	printf("	args->sleep_scaling_factor=%f\n",args->sleep_scaling_factor);
+	printf("	args->tuple_base_threshold=%i\n",args->tuple_base_threshold);
+	printf("	args->tuple_scaling_factor=%f\n",args->tuple_scaling_factor);
+	printf("	args->debug=%i\n",args->debug);
+}
+
+/* Beginning of AutoVacuum Main Program */
+int main(int argc, char *argv[])
+{
+  char buf[256];
+  int j=0, loops=0;
+  int numInserts, numDeletes, sleep_secs;
+  Dllist    *db_list;
+  Dlelem    *db_elem,*tbl_elem;
+  db_info   *dbs;
+  tbl_info  *tbl;
+  PGresult  *res;
+  long long       diff=0;
+  struct timeval now,then;
+
+  args=get_cmd_args(argc,argv); /* Get Command Line Args and put them in the args struct */
+
+  if(args->debug >= 2)	{print_cmd_args();}
+
+  db_list=init_db_list();   /* Init the db list with template1 */
+  if(NULL == db_list)
+    return 1;
+
+	if(0!=check_stats_enabled(((db_info*)DLE_VAL(DLGetHead(db_list)))))
+	{
+		printf("Error: GUC variable stats_row_level must be enabled.\n       Please fix the problems and try again.\n");
+		exit(1);
+	}
+
+	gettimeofday(&then, 0); /* for use later to caluculate sleep time */
+
+	while(1)   /* Main Loop */
+	{
+		db_elem=DLGetHead(db_list); /* Reset cur_db_node to the beginning of the db_list */
+
+		dbs=((db_info *)DLE_VAL(db_elem)); /* get pointer to cur_db's db_info struct */
+		if(NULL==dbs->conn) 
+		{
+			dbs->conn=db_connect(dbs);
+			if(NULL==dbs->conn) /* Serious problem: We can't connect to template1 */
+			{
+				printf("Error: Cannot connect to template1, exiting.\n");
+				exit(1);
+			}	
+		}
+
+		if(0==(loops % UPDATE_INTERVAL)) /* Update the list if it's time */
+			update_db_list(db_list); /* Add new databases to the list to be checked, and remove databases that no longer exist */
+
+		while(NULL != db_elem) /* Loop through databases in list */
+		{
+      dbs=((db_info *)DLE_VAL(db_elem)); /* get pointer to cur_db's db_info struct */
+      if(NULL==dbs->conn)
+        dbs->conn=db_connect(dbs);
+
+      if(NULL!=dbs->conn)
+      {
+				if(0==(loops % UPDATE_INTERVAL)) /* Update the list if it's time */
+					update_table_list(dbs); /* Add new databases to the list to be checked, and remove databases that no longer exist */
+
+				if(0==xid_wraparound_check(dbs));
+				{
+          res=send_query(query_table_stats(dbs),dbs);  /* Get an updated snapshot of this dbs table stats */
+          for(j=0;j < PQntuples(res);j++) /* loop through result set */
+          {
+            tbl_elem = DLGetHead(dbs->table_list); /* Reset tbl_elem to top of dbs->table_list */
+            while(NULL!=tbl_elem)	/* Loop through tables in list */
+            {
+              tbl=((tbl_info *)DLE_VAL(tbl_elem)); /* set tbl_info = current_table */
+              if(tbl->relfilenode == atoi(PQgetvalue(res,j,PQfnumber(res,"relfilenode"))))
+              {
+                numInserts=(atol(PQgetvalue(res,j,PQfnumber(res,"n_tup_ins"))) + atol(PQgetvalue(res,j,PQfnumber(res,"n_tup_upd"))));
+                numDeletes=(atol(PQgetvalue(res,j,PQfnumber(res,"n_tup_del"))) + atol(PQgetvalue(res,j,PQfnumber(res,"n_tup_upd"))));
+
+                /* Check numDeletes to see if we need to vacuum, if so:
+                Run vacuum analyze (adding analyze is small so we might as well)
+                Update table thresholds and related information
+                if numDeletes is not big enough for vacuum then check numInserts for analyze */
+                if((numDeletes - tbl->DeletesAtLastVacuum) >= tbl->deleteThreshold)
+                {
+                  snprintf(buf,sizeof(buf),"vacuum %s",tbl->table_name);
+                  if(args->debug >= 1) {printf("Performing: %s\n",buf);}
+                  send_query(buf,dbs);
+                  tbl->DeletesAtLastVacuum=numDeletes;
+    							update_table_thresholds(dbs,tbl);
+                  if(args->debug >= 2)	{print_table_info(tbl);}
+                }
+                else if((numInserts - tbl->InsertsAtLastAnalyze) >= tbl->insertThreshold)
+                {
+                  snprintf(buf,sizeof(buf),"analyze %s",tbl->table_name);
+                  if(args->debug >= 1) {printf("Performing: %s\n",buf);}
+                  send_query(buf,dbs);
+                  tbl->InsertsAtLastAnalyze=numInserts;
+                  tbl->reltuples=atoi(PQgetvalue(res,j,PQfnumber(res,"reltuples")));
+                  tbl->insertThreshold = (args->tuple_base_threshold + args->tuple_scaling_factor*tbl->reltuples);
+                  if(args->debug >= 2)	{print_table_info(tbl);}
+                }
+
+                /* If the stats collector is reporting fewer updates then we have on record
+                then the stats were probably reset, so we need to reset also */
+                if((numInserts < tbl->InsertsAtLastAnalyze)||(numDeletes < tbl->DeletesAtLastVacuum))
+                {
+                  tbl->InsertsAtLastAnalyze=numInserts;
+                  tbl->DeletesAtLastVacuum=numDeletes;
+                }
+                break; /* once we have found a match, no need to keep checking. */
+              }
+              /* Advance the table pointers for the next loop */
+              tbl_elem=DLGetSucc(tbl_elem);
+
+            } /* end for table while loop */
+          } /* end for j loop (tuples in PGresult) */
+				} /* close of if(xid_wraparound_check()) */
+        /* Done working on this db, Clean up, then advance cur_db */
+        PQclear(res);  res=NULL;
+        db_disconnect(dbs);
+			}
+			db_elem=DLGetSucc(db_elem); /* move on to next DB regardless */
+    } /* end of db_list while loop */
+
+    /* Figure out how long to sleep etc ... */
+    gettimeofday(&now, 0);
+    diff = (now.tv_sec - then.tv_sec) * 1000000 + (now.tv_usec - then.tv_usec);
+
+    sleep_secs = args->sleep_base_value + args->sleep_scaling_factor*diff/1000000;
+    loops++;
+    if(args->debug >= 2)
+    {	printf("%i All DBs checked in: %lld usec, will sleep for %i secs.\n",loops,diff,sleep_secs);}
+
+    sleep(sleep_secs); /* Larger Pause between outer loops */
+
+    gettimeofday(&then, 0);	/* Reset time counter */
+
+  } /* end of while loop */
+
+  /* 	program is exiting, this should never run, but is here to make compiler / valgrind happy */
+  free_db_list(db_list);
+  free_cmd_args();
+  return EXIT_SUCCESS;
+}

contrib/pg_autovacuum/pg_autovacuum.h

+/* pg_autovacuum.h
+ * Header file for pg_autovacuum.c
+ * (c) 2003 Matthew T. O'Connor
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+/* Includes that I added */
+#include <string.h>
+#include <unistd.h>
+#include <getopt.h>
+#include <sys/time.h>
+#include "../../interfaces/libpq/libpq-fe.h"
+#include "lib/dllist.h"
+
+#define AUTOVACUUM_DEBUG    1
+#define BASETHRESHOLD       100
+#define SCALINGFACTOR       2
+#define SLEEPVALUE          1
+#define SLEEPSCALINGFACTOR	0
+#define UPDATE_INTERVAL     2
+#define TABLE_STATS_ALL     "select a.relfilenode,a.relname,a.relnamespace,a.relpages,a.reltuples,b.schemaname,b.n_tup_ins,b.n_tup_upd,b.n_tup_del from pg_class a, pg_stat_all_tables b where a.relfilenode=b.relid"
+#define TABLE_STATS_USER    "select a.relfilenode,a.relname,a.relnamespace,a.relpages,a.reltuples,b.schemaname,b.n_tup_ins,b.n_tup_upd,b.n_tup_del from pg_class a, pg_stat_user_tables b where a.relfilenode=b.relid"
+#define FRONTEND
+
+struct cmdargs{
+  int tuple_base_threshold,sleep_base_value,debug;
+  float tuple_scaling_factor,sleep_scaling_factor;
+  char *user, *password, *host, *port;
+}; typedef struct cmdargs cmd_args;
+
+/* define cmd_args as global so we can get to them everywhere */
+cmd_args  *args;
+
+struct tableinfo{
+  char *schema_name,*table_name;
+  int insertThreshold,deleteThreshold;
+  int relfilenode,reltuples,relpages;
+  long InsertsAtLastAnalyze; /* equal to: inserts + updates as of the last analyze or initial values at startup */
+  long DeletesAtLastVacuum; /* equal to: deletes + updates as of the last vacuum or initial values at startup */
+  }; typedef struct tableinfo tbl_info;
+
+/* Might need to add a time value for last time the whold database was vacuumed.
+    I think we need to guarantee this happens approx every 1Million TX's  */
+struct dbinfo{
+  int			oid,age;
+  int			insertThreshold,deleteThreshold; /* Use these as defaults for table thresholds */
+  PGconn  *conn;
+  char    *dbname,*username,*password;
+  Dllist  *table_list;
+  }; typedef struct dbinfo db_info;
+
+/* Functions for dealing with command line arguements */
+static cmd_args *get_cmd_args(int argc,char *argv[]);
+static void print_cmd_args(void);
+static void free_cmd_args(void);
+
+/* Functions for managing database lists */
+static Dllist *init_db_list(void);
+static db_info *init_dbinfo(char *dbname,int oid,int age);
+static void update_db_list(Dllist *db_list);
+static void remove_db_from_list(Dlelem *db_to_remove);
+static void print_db_info(db_info *dbi,int print_table_list);
+static void print_db_list(Dllist *db_list,int print_table_lists);
+static int  xid_wraparound_check(db_info *dbi);
+static void free_db_list(Dllist *db_list);
+
+/* Functions for managing table lists */
+static tbl_info *init_table_info(PGresult *conn, int row);
+static void update_table_list(db_info *dbi);
+static void remove_table_from_list(Dlelem *tbl_to_remove);
+static void print_table_list(Dllist *tbl_node);
+static void print_table_info(tbl_info *tbl);
+static void update_table_thresholds(db_info *dbi,tbl_info *tbl);
+static void free_tbl_list(Dllist *tbl_list);
+
+/* A few database helper functions */
+static int	check_stats_enabled(db_info *dbi);
+static PGconn *db_connect(db_info *dbi);
+static void db_disconnect(db_info *dbi);
+static PGresult *send_query(const char *query,db_info *dbi);
+static char *query_table_stats(db_info *dbi);
+
+