--------------------
pg_autovacuum is a libpq client program that monitors all the
-databases associated with a postgresql server. It uses the stats
+databases associated with a PostgreSQL server. It uses the statistics
collector to monitor insert, update and delete activity.
-When a table exceeds its insert or delete threshold (more detail
-on thresholds below) then that table will be vacuumed or analyzed.
+When a table exceeds a insert or delete threshold (for more detail on
+thresholds, see "Vacuum and Analyze" below) then that table will be
+vacuumed and/or analyzed.
-This allows postgresql to keep the fsm and table statistics up to
-date, and eliminates the need to schedule periodic vacuums.
+This allows PostgreSQL to keep the FSM (Free Space Map) and table
+statistics up to date, and eliminates the need to schedule periodic
+vacuums.
The primary benefit of pg_autovacuum is that the FSM and table
-statistic information are updated as needed. When a table is actively
-changing, pg_autovacuum will perform the necessary vacuums and
-analyzes, whereas if a table remains static, no cycles will be wasted
-performing unnecessary vacuums/analyzes.
+statistic information are updated more nearly as frequently as needed.
+When a table is actively changing, pg_autovacuum will perform the
+VACUUMs and ANALYZEs that such a table needs, whereas if a table
+remains static, no cycles will be wasted performing this
+unnecessarily.
A secondary benefit of pg_autovacuum is that it ensures that a
-database wide vacuum is performed prior to xid wraparound. This is an
+database wide vacuum is performed prior to XID wraparound. This is an
important, if rare, problem, as failing to do so can result in major
-data loss.
-
+data loss. (See the section in the _Administrator's Guide_ entitled
+"Preventing transaction ID wraparound failures" for more details.)
KNOWN ISSUES:
-------------
-pg_autovacuum has been tested under Redhat Linux (by me) and Solaris (by
-Christopher B. Browne) and all known bugs have been resolved. Please report
-any problems to the hackers list.
-
-pg_autovacuum does not get started automatically by either the postmaster or
-by pg_ctl. Along the sames lines, when the postmaster exits no one tells
-pg_autovacuum. The result is that at the start of the next loop,
-pg_autovacuum fails to connect to the server and exits. Any time it fails
-to connect pg_autovacuum exits.
-
-pg_autovacuum requires that the stats system be enabled and reporting row
-level stats. The overhead of the stats system has been shown to be
-significant under certain workloads. For instance a tight loop of queries
-performing "select 1" was nearly 30% slower with stats enabled. However,
-in practice with more realistic workloads, the stats system overhead is
-usually nominal.
+pg_autovacuum has been tested under Redhat Linux (by me) and Debian
+GNU/Linux and Solaris (by Christopher B. Browne) and all known bugs
+have been resolved. Please report any problems to the hackers list.
+
+pg_autovacuum requires that the statistics system be enabled and
+reporting row level stats. The overhead of the stats system has been
+shown to be significant costly under certain workloads. For instance,
+a tight loop of queries performing "select 1" was found to run nearly
+30% slower when stats were enabled. However, in practice, with more
+realistic workloads, the stats system overhead is usually nominal.
+
+pg_autovacuum does not get started automatically by either the
+postmaster or by pg_ctl. Similarly, when the postmaster exits, no one
+tells pg_autovacuum. The result of that is that at the start of the
+next loop, pg_autovacuum will fail to connect to the server and
+exit(). Any time it fails to connect pg_autovacuum exit()s.
+
+While pg_autovacuum can manage vacuums for as many databases as you
+may have tied to a particular PostgreSQL postmaster, it can only
+connect to a single PostgreSQL postmaster. Thus, if you have multiple
+postmasters on a particular host, you will need multiple pg_autovacuum
+instances, and they have no way, at present, to coordinate between one
+another to ensure that they do not concurrently vacuum big tables.
+
+TODO:
+-----
+
+At present, there are no sample scripts to automatically start up
+pg_autovacuum along with the database. It would be desirable to have
+a SysV script to start up pg_autovacuum after PostgreSQL has been
+started.
+
+Some users have expressed interest in making pg_autovacuum more
+configurable so that certain tables known to be inactive could be
+excluded from being vacuumed. It would probably make sense to
+introduce this sort of functionality by providing arguments to specify
+the database and schema in which to find a configuration table.
INSTALL:
--------
-As of postgresql v7.4 pg_autovacuum is included in the main source tree
-under contrib. Therefore you just make && make install (similar to most other
-contrib modules) and it will be installed for you.
+As of postgresql v7.4 pg_autovacuum is included in the main source
+tree under contrib. Therefore you merely need to "make && make
+install" (similar to most other contrib modules) and it will be
+installed for you.
-If you are using an earlier version of postgresql just 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.
+If you are using an earlier version of PostgreSQL, uncompress the
+tar.gz file into the contrib directory and modify the contrib/Makefile
+to include the pg_autovacuum directory. pg_autovacuum will then be
+built as part of the standard postgresql install.
-make sure that the folowing are set in postgresql.conf
+make sure that the following are set in postgresql.conf:
stats_start_collector = true
stats_row_level = true
-start up the postmaster, then execute the pg_autovacuum executable.
+Start up the postmaster, then execute the pg_autovacuum executable.
+
+If you have a script that automatically starts up the PostgreSQL
+instance, you might add in, after that, something similar to the
+following:
+ sleep 10 # To give the database some time to start up
+ $PGBINS/pg_autovacuum -D -s $SBASE -S $SSCALE ... [other arguments]
Command line arguments:
-----------------------
pg_autovacuum has the following optional arguments:
-d debug: 0 silent, 1 basic info, 2 more debug info, etc...
--D dameonize: Detach from tty and run in background.
+-D daemonize: Detach from tty and run in background.
-s sleep base value: see "Sleeping" below.
-S sleep scaling factor: see "Sleeping" below.
-v vacuum base threshold: see Vacuum and Analyze.
-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.
+-H host: host name or IP to connect to.
-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 writing they are:
+Numerous arguments have default values defined in pg_autovacuum.h. At
+the time of writing they are:
-d 1
-v 1000
-V 2
--a 500 (half of -v is not specified)
--A 1 (half of -v is not specified)
+-a 500 (half of -v if not specified)
+-A 1 (half of -v if not specified)
-s 300 (5 minutes)
-S 2
Vacuum and Analyze:
-------------------
-pg_autovacuum performs either a vacuum analyze or just analyze depending
-on the quantity and type of table activity (insert, update, or delete):
+pg_autovacuum performs either a VACUUM ANALYZE or just ANALYZE
+depending on the mixture of table activity (insert, update, or
+delete):
- If the number of (inserts + updates + deletes) > AnalyzeThreshold, then
only an analyze is performed.
-- If the number of (deletes + updates ) > VacuumThreshold, then a
+- If the number of (deletes + updates) > VacuumThreshold, then a
vacuum analyze is performed.
deleteThreshold is equal to:
analyze_base_value + (analyze_scaling_factor * "number of tuples in the table")
The AnalyzeThreshold defaults to half of the VacuumThreshold since it
-represents a much less expensive operation (approx 5%-10% of vacuum), and
-running it more often should not substantially degrade system performance.
+represents a much less expensive operation (approx 5%-10% of vacuum),
+and running ANALYZE more often should not substantially degrade system
+performance.
Sleeping:
---------
pg_autovacuum sleeps for a while after it is done checking all the
databases. It does this in order to limit the amount of system
-resources it consumes. This also allows the system administrator to
+resources it consumes. This 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, whether they be database addition/removal, table
addition/removal, or just normal table activity.
-On the other hand, setting pg_autovaccum to sleep values to agressivly
-(for too short a period of time) can have a negative effect on server
-performance. If a table gets vacuumed 5 times during the course of a
-large update, this is likely to take much longer than if the table was
-vacuumed only once, at the end.
+On the other hand, setting pg_autovacuum to sleep values too
+aggressively (to too short periods of time) can have a negative effect
+on server performance. For instance, if a table gets vacuumed 5 times
+during the course of a large set of updates, this is likely to take a
+lot more work than if the table was vacuumed just once, at the end.
The total time it sleeps is equal to:
loop"
Note that timing measurements are made in seconds; specifying
-"pg_vacuum -s 1" means pg_autovacuum could poll the database upto 60 times
-minute. In a system with large tables where vacuums may run for several
-minutes, longer times between vacuums are likely to be appropriate.
+"pg_vacuum -s 1" means pg_autovacuum could poll the database up to 60
+times minute. In a system with large tables where vacuums may run for
+several minutes, rather longer times between vacuums are likely to be
+appropriate.
What pg_autovacuum monitors:
----------------------------
-pg_autovacuum dynamically generates a list of all databases and tables that
-exist on the server. It will dynamically add and remove databases and
-tables that are removed from the database server while pg_autovacuum is
-running. Overhead is fairly small per object. For example: 10 databases
-with 10 tables each appears to less than 10k of memory on my Linux box.
+pg_autovacuum dynamically generates a list of all databases and tables
+that exist on the server. It will dynamically add and remove
+databases and tables that are removed from the database server while
+pg_autovacuum is running. Overhead is fairly small per object. For
+example: 10 databases with 10 tables each appears to less than 10k of
+memory on my Linux box.
new_tbl->reltuples = atoi(PQgetvalue(res, row, PQfnumber(res, "reltuples")));
new_tbl->relpages = atoi(PQgetvalue(res, row, PQfnumber(res, "relpages")));
+ log_entry(PQgetvalue(res, row, PQfnumber(res, "relisshared")));
+ if (strcmp("t", PQgetvalue(res, row, PQfnumber(res, "relisshared"))))
+ new_tbl->relisshared = 0;
+ else
+ new_tbl->relisshared = 1;
+
new_tbl->analyze_threshold =
args->analyze_base_threshold + args->analyze_scaling_factor * new_tbl->reltuples;
new_tbl->vacuum_threshold =
* 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);
+ res = send_query((char *) TABLE_STATS_QUERY, dbi);
t = PQntuples(res);
/*
{
sprintf(logbuffer, " table name: %s.%s", tbl->dbi->dbname, tbl->table_name);
log_entry(logbuffer);
- sprintf(logbuffer, " relfilenode: %i", tbl->relfilenode);
+ sprintf(logbuffer, " relfilenode: %i; relisshared: %i", tbl->relfilenode, tbl->relisshared);
log_entry(logbuffer);
sprintf(logbuffer, " reltuples: %i; relpages: %i", tbl->reltuples, tbl->relpages);
log_entry(logbuffer);
/* 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;
-}
+/* Beginning of misc Functions */
/* Perhaps add some test to this function to make sure that the stats we need are available */
PGconn *
if (NULL == dbi->conn)
return NULL;
+ if (args->debug >= 4)
+ log_entry(query);
+
res = PQexec(dbi->conn, query);
if (!res)
int j = 0,
loops = 0;
-/* int numInserts, numDeletes, */
+ /* int numInserts, numDeletes, */
int sleep_secs;
Dllist *db_list;
Dlelem *db_elem,
if (0 == xid_wraparound_check(dbs));
{
- res = send_query(query_table_stats(dbs), dbs); /* Get an updated
+ res = send_query(TABLE_STATS_QUERY, dbs); /* Get an updated
* snapshot of this dbs
* table stats */
for (j = 0; j < PQntuples(res); j++)
*/
if ((tbl->curr_vacuum_count - tbl->CountAtLastVacuum) >= tbl->vacuum_threshold)
{
- snprintf(buf, sizeof(buf), "VACUUM ANALYZE \"%s\"", tbl->table_name);
+ /* if relisshared = t and database != template1 then only do an analyze */
+ if((tbl->relisshared > 0) && (strcmp("template1",dbs->dbname)))
+ snprintf(buf, sizeof(buf), "ANALYZE %s", tbl->table_name);
+ else
+ snprintf(buf, sizeof(buf), "VACUUM ANALYZE %s", tbl->table_name);
if (args->debug >= 1)
{
sprintf(logbuffer, "Performing: %s", buf);
}
else if ((tbl->curr_analyze_count - tbl->CountAtLastAnalyze) >= tbl->analyze_threshold)
{
- snprintf(buf, sizeof(buf), "ANALYZE \"%s\"", tbl->table_name);
+ snprintf(buf, sizeof(buf), "ANALYZE %s", tbl->table_name);
if (args->debug >= 1)
{
sprintf(logbuffer, "Performing: %s", buf);
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