From ca9c6a5680d7c7dece0f7209ee7ce20c9dfe0840 Mon Sep 17 00:00:00 2001 From: Melanie Plageman Date: Fri, 10 Jan 2025 18:20:16 -0500 Subject: [PATCH] Consolidate docs for vacuum-related GUCs in new subsection GUCs related to vacuum's freezing behavior were documented in a subsection of the Client Connection Defaults documentation. These GUCs don't belong there, as they affect the freezing behavior of all vacuums -- including autovacuums. There wasn't a clear alternative location, so this commit makes a new "Server Configuration" docs subsection, "Vacuuming", with a subsection for "Freezing". It also moves the "Automatic Vacuuming" subsection and the docs on GUCs controlling cost-based vacuum delay under the new "Vacuuming" subsection. The other vacuum-related GUCs under the "Resource Consumption" subsection have been left in their current location, as they seem to fit there. The GUCs' documentation was largely lifted and shifted. The only modification made was the addition of a few missing tags. Reviewed-by: Daniel Gustafsson Discussion: https://postgr.es/m/flat/CAAKRu_aQUOaMYrcjNuXeSkJtaX9oRUzKP57bsYbC0gVVWS%2BcbA%40mail.gmail.com --- doc/src/sgml/config.sgml | 1254 +++++++++++++++++++------------------- 1 file changed, 643 insertions(+), 611 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index f1ab614575..3f41a17b1f 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -2367,149 +2367,6 @@ include_dir 'conf.d' - - Cost-based Vacuum Delay - - - During the execution of - and - commands, the system maintains an - internal counter that keeps track of the estimated cost of the - various I/O operations that are performed. When the accumulated - cost reaches a limit (specified by - vacuum_cost_limit), the process performing - the operation will sleep for a short period of time, as specified by - vacuum_cost_delay. Then it will reset the - counter and continue execution. - - - - The intent of this feature is to allow administrators to reduce - the I/O impact of these commands on concurrent database - activity. There are many situations where it is not - important that maintenance commands like - VACUUM and ANALYZE finish - quickly; however, it is usually very important that these - commands do not significantly interfere with the ability of the - system to perform other database operations. Cost-based vacuum - delay provides a way for administrators to achieve this. - - - - This feature is disabled by default for manually issued - VACUUM commands. To enable it, set the - vacuum_cost_delay variable to a nonzero - value. - - - - - vacuum_cost_delay (floating point) - - vacuum_cost_delay configuration parameter - - - - - The amount of time that the process will sleep - when the cost limit has been exceeded. - If this value is specified without units, it is taken as milliseconds. - The default value is zero, which disables the cost-based vacuum - delay feature. Positive values enable cost-based vacuuming. - - - - When using cost-based vacuuming, appropriate values for - vacuum_cost_delay are usually quite small, perhaps - less than 1 millisecond. While vacuum_cost_delay - can be set to fractional-millisecond values, such delays may not be - measured accurately on older platforms. On such platforms, - increasing VACUUM's throttled resource consumption - above what you get at 1ms will require changing the other vacuum cost - parameters. You should, nonetheless, - keep vacuum_cost_delay as small as your platform - will consistently measure; large delays are not helpful. - - - - - - vacuum_cost_page_hit (integer) - - vacuum_cost_page_hit configuration parameter - - - - - The estimated cost for vacuuming a buffer found in the shared buffer - cache. It represents the cost to lock the buffer pool, lookup - the shared hash table and scan the content of the page. The - default value is one. - - - - - - vacuum_cost_page_miss (integer) - - vacuum_cost_page_miss configuration parameter - - - - - The estimated cost for vacuuming a buffer that has to be read from - disk. This represents the effort to lock the buffer pool, - lookup the shared hash table, read the desired block in from - the disk and scan its content. The default value is 2. - - - - - - vacuum_cost_page_dirty (integer) - - vacuum_cost_page_dirty configuration parameter - - - - - The estimated cost charged when vacuum modifies a block that was - previously clean. It represents the extra I/O required to - flush the dirty block out to disk again. The default value is - 20. - - - - - - vacuum_cost_limit (integer) - - vacuum_cost_limit configuration parameter - - - - - This is the accumulated cost that will cause the vacuuming process to sleep - for vacuum_cost_delay. The default is 200. - - - - - - - - There are certain operations that hold critical locks and should - therefore complete as quickly as possible. Cost-based vacuum - delays do not occur during such operations. Therefore it is - possible that the cost accumulates far higher than the specified - limit. To avoid uselessly long delays in such cases, the actual - delay is calculated as vacuum_cost_delay * - accumulated_balance / - vacuum_cost_limit with a maximum of - vacuum_cost_delay * 4. - - - Background Writer @@ -8590,14 +8447,22 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv; - - Automatic Vacuuming + + Vacuuming - autovacuum + vacuum configuration parameters + + These parameters control vacuuming behavior. For more information on the + purpose and responsibilities of vacuum, see . + + + + Automatic Vacuuming + These settings control the behavior of the autovacuum feature. Refer to for more information. @@ -8605,325 +8470,654 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv; basis; see . - - - - autovacuum (boolean) - - autovacuum configuration parameter - - - - - Controls whether the server should run the - autovacuum launcher daemon. This is on by default; however, - must also be enabled for - autovacuum to work. - This parameter can only be set in the postgresql.conf - file or on the server command line; however, autovacuuming can be - disabled for individual tables by changing table storage parameters. - - - Note that even when this parameter is disabled, the system - will launch autovacuum processes if necessary to - prevent transaction ID wraparound. See for more information. - - - + - - autovacuum_worker_slots (integer) - - autovacuum_worker_slots configuration parameter - - - - - Specifies the number of backend slots to reserve for autovacuum worker - processes. The default is typically 16 slots, but might be less if - your kernel settings will not support it (as determined during initdb). - This parameter can only be set at server start. - - - When changing this value, consider also adjusting - . - - - + + autovacuum (boolean) + + autovacuum configuration parameter + + + + + Controls whether the server should run the + autovacuum launcher daemon. This is on by default; however, + must also be enabled for + autovacuum to work. + This parameter can only be set in the postgresql.conf + file or on the server command line; however, autovacuuming can be + disabled for individual tables by changing table storage parameters. + + + Note that even when this parameter is disabled, the system + will launch autovacuum processes if necessary to + prevent transaction ID wraparound. See for more information. + + + - - autovacuum_max_workers (integer) - - autovacuum_max_workers configuration parameter - - - - - Specifies the maximum number of autovacuum processes (other than the - autovacuum launcher) that may be running at any one time. The default - is three. This parameter can only be set in the - postgresql.conf file or on the server command line. - - - Note that a setting for this value which is higher than - will have no effect, - since autovacuum workers are taken from the pool of slots established - by that setting. - - - + + autovacuum_worker_slots (integer) + + autovacuum_worker_slots configuration parameter + + + + + Specifies the number of backend slots to reserve for autovacuum worker + processes. The default is typically 16 slots, but might be less if + your kernel settings will not support it (as determined during initdb). + This parameter can only be set at server start. + + + When changing this value, consider also adjusting + . + + + - - autovacuum_naptime (integer) - - autovacuum_naptime configuration parameter - - - - - Specifies the minimum delay between autovacuum runs on any given - database. In each round the daemon examines the - database and issues VACUUM and ANALYZE commands - as needed for tables in that database. - If this value is specified without units, it is taken as seconds. - The default is one minute (1min). - This parameter can only be set in the postgresql.conf - file or on the server command line. - - - + + autovacuum_max_workers (integer) + + autovacuum_max_workers configuration parameter + + + + + Specifies the maximum number of autovacuum processes (other than the + autovacuum launcher) that may be running at any one time. The default + is 3. This parameter can only be set in the + postgresql.conf file or on the server command line. + + + Note that a setting for this value which is higher than + will have no effect, + since autovacuum workers are taken from the pool of slots established + by that setting. + + + - - autovacuum_vacuum_threshold (integer) - - autovacuum_vacuum_threshold - configuration parameter - - - - - Specifies the minimum number of updated or deleted tuples needed - to trigger a VACUUM in any one table. - The default is 50 tuples. - This parameter can only be set in the postgresql.conf - file or on the server command line; - but the setting can be overridden for individual tables by - changing table storage parameters. - - - + + autovacuum_naptime (integer) + + autovacuum_naptime configuration parameter + + + + + Specifies the minimum delay between autovacuum runs on any given + database. In each round the daemon examines the + database and issues VACUUM and ANALYZE commands + as needed for tables in that database. + If this value is specified without units, it is taken as seconds. + The default is one minute (1min). + This parameter can only be set in the postgresql.conf + file or on the server command line. + + + - - autovacuum_vacuum_insert_threshold (integer) - - autovacuum_vacuum_insert_threshold - configuration parameter - - - - - Specifies the number of inserted tuples needed to trigger a - VACUUM in any one table. - The default is 1000 tuples. If -1 is specified, autovacuum will not - trigger a VACUUM operation on any tables based on - the number of inserts. - This parameter can only be set in the postgresql.conf - file or on the server command line; - but the setting can be overridden for individual tables by - changing table storage parameters. - - - + + autovacuum_vacuum_threshold (integer) + + autovacuum_vacuum_threshold + configuration parameter + + + + + Specifies the minimum number of updated or deleted tuples needed + to trigger a VACUUM in any one table. + The default is 50 tuples. + This parameter can only be set in the postgresql.conf + file or on the server command line; + but the setting can be overridden for individual tables by + changing table storage parameters. + + + - - autovacuum_analyze_threshold (integer) - - autovacuum_analyze_threshold - configuration parameter - - - - - Specifies the minimum number of inserted, updated or deleted tuples - needed to trigger an ANALYZE in any one table. - The default is 50 tuples. - This parameter can only be set in the postgresql.conf - file or on the server command line; - but the setting can be overridden for individual tables by - changing table storage parameters. - - - + + autovacuum_vacuum_insert_threshold (integer) + + autovacuum_vacuum_insert_threshold + configuration parameter + + + + + Specifies the number of inserted tuples needed to trigger a + VACUUM in any one table. + The default is 1000 tuples. If -1 is specified, autovacuum will not + trigger a VACUUM operation on any tables based on + the number of inserts. + This parameter can only be set in the postgresql.conf + file or on the server command line; + but the setting can be overridden for individual tables by + changing table storage parameters. + + + - - autovacuum_vacuum_scale_factor (floating point) - - autovacuum_vacuum_scale_factor - configuration parameter - - - - - Specifies a fraction of the table size to add to - autovacuum_vacuum_threshold - when deciding whether to trigger a VACUUM. - The default is 0.2 (20% of table size). - This parameter can only be set in the postgresql.conf - file or on the server command line; - but the setting can be overridden for individual tables by - changing table storage parameters. - - - + + autovacuum_analyze_threshold (integer) + + autovacuum_analyze_threshold + configuration parameter + + + + + Specifies the minimum number of inserted, updated or deleted tuples + needed to trigger an ANALYZE in any one table. + The default is 50 tuples. + This parameter can only be set in the postgresql.conf + file or on the server command line; + but the setting can be overridden for individual tables by + changing table storage parameters. + + + - - autovacuum_vacuum_insert_scale_factor (floating point) - - autovacuum_vacuum_insert_scale_factor - configuration parameter - - - - - Specifies a fraction of the table size to add to - autovacuum_vacuum_insert_threshold - when deciding whether to trigger a VACUUM. - The default is 0.2 (20% of table size). - This parameter can only be set in the postgresql.conf - file or on the server command line; - but the setting can be overridden for individual tables by - changing table storage parameters. - - - + + autovacuum_vacuum_scale_factor (floating point) + + autovacuum_vacuum_scale_factor + configuration parameter + + + + + Specifies a fraction of the table size to add to + autovacuum_vacuum_threshold + when deciding whether to trigger a VACUUM. + The default is 0.2 (20% of table size). + This parameter can only be set in the postgresql.conf + file or on the server command line; + but the setting can be overridden for individual tables by + changing table storage parameters. + + + - - autovacuum_analyze_scale_factor (floating point) - - autovacuum_analyze_scale_factor - configuration parameter - - - - - Specifies a fraction of the table size to add to - autovacuum_analyze_threshold - when deciding whether to trigger an ANALYZE. - The default is 0.1 (10% of table size). - This parameter can only be set in the postgresql.conf - file or on the server command line; - but the setting can be overridden for individual tables by - changing table storage parameters. - - - + + autovacuum_vacuum_insert_scale_factor (floating point) + + autovacuum_vacuum_insert_scale_factor + configuration parameter + + + + + Specifies a fraction of the table size to add to + autovacuum_vacuum_insert_threshold + when deciding whether to trigger a VACUUM. + The default is 0.2 (20% of table size). + This parameter can only be set in the postgresql.conf + file or on the server command line; + but the setting can be overridden for individual tables by + changing table storage parameters. + + + - - autovacuum_freeze_max_age (integer) - - autovacuum_freeze_max_age - configuration parameter - - - - - Specifies the maximum age (in transactions) that a table's - pg_class.relfrozenxid field can - attain before a VACUUM operation is forced - to prevent transaction ID wraparound within the table. - Note that the system will launch autovacuum processes to - prevent wraparound even when autovacuum is otherwise disabled. - + + autovacuum_analyze_scale_factor (floating point) + + autovacuum_analyze_scale_factor + configuration parameter + + + + + Specifies a fraction of the table size to add to + autovacuum_analyze_threshold + when deciding whether to trigger an ANALYZE. + The default is 0.1 (10% of table size). + This parameter can only be set in the postgresql.conf + file or on the server command line; + but the setting can be overridden for individual tables by + changing table storage parameters. + + + - - Vacuum also allows removal of old files from the - pg_xact subdirectory, which is why the default - is a relatively low 200 million transactions. - This parameter can only be set at server start, but the setting - can be reduced for individual tables by - changing table storage parameters. - For more information see . - - - + + autovacuum_freeze_max_age (integer) + + autovacuum_freeze_max_age + configuration parameter + + + + + Specifies the maximum age (in transactions) that a table's + pg_class.relfrozenxid field can + attain before a VACUUM operation is forced + to prevent transaction ID wraparound within the table. + Note that the system will launch autovacuum processes to + prevent wraparound even when autovacuum is otherwise disabled. + - - autovacuum_multixact_freeze_max_age (integer) - - autovacuum_multixact_freeze_max_age - configuration parameter - - - - - Specifies the maximum age (in multixacts) that a table's - pg_class.relminmxid field can - attain before a VACUUM operation is forced to - prevent multixact ID wraparound within the table. - Note that the system will launch autovacuum processes to - prevent wraparound even when autovacuum is otherwise disabled. - + + Vacuum also allows removal of old files from the + pg_xact subdirectory, which is why the default + is a relatively low 200 million transactions. + This parameter can only be set at server start, but the setting + can be reduced for individual tables by + changing table storage parameters. + For more information see . + + + - - Vacuuming multixacts also allows removal of old files from the - pg_multixact/members and pg_multixact/offsets - subdirectories, which is why the default is a relatively low - 400 million multixacts. - This parameter can only be set at server start, but the setting can - be reduced for individual tables by changing table storage parameters. - For more information see . - - - + + autovacuum_multixact_freeze_max_age (integer) + + autovacuum_multixact_freeze_max_age + configuration parameter + + + + + Specifies the maximum age (in multixacts) that a table's + pg_class.relminmxid field can + attain before a VACUUM operation is forced to + prevent multixact ID wraparound within the table. + Note that the system will launch autovacuum processes to + prevent wraparound even when autovacuum is otherwise disabled. + - - autovacuum_vacuum_cost_delay (floating point) - - autovacuum_vacuum_cost_delay - configuration parameter - - - - - Specifies the cost delay value that will be used in automatic - VACUUM operations. If -1 is specified, the regular - value will be used. - If this value is specified without units, it is taken as milliseconds. - The default value is 2 milliseconds. - This parameter can only be set in the postgresql.conf - file or on the server command line; - but the setting can be overridden for individual tables by - changing table storage parameters. - - - + + Vacuuming multixacts also allows removal of old files from the + pg_multixact/members and pg_multixact/offsets + subdirectories, which is why the default is a relatively low + 400 million multixacts. + This parameter can only be set at server start, but the setting can + be reduced for individual tables by changing table storage parameters. + For more information see . + + + - - autovacuum_vacuum_cost_limit (integer) - - autovacuum_vacuum_cost_limit - configuration parameter - - - - - Specifies the cost limit value that will be used in automatic - VACUUM operations. If -1 is specified (which is the - default), the regular - value will be used. Note that - the value is distributed proportionally among the running autovacuum - workers, if there is more than one, so that the sum of the limits for - each worker does not exceed the value of this variable. - This parameter can only be set in the postgresql.conf - file or on the server command line; - but the setting can be overridden for individual tables by - changing table storage parameters. - - - + + autovacuum_vacuum_cost_delay (floating point) + + autovacuum_vacuum_cost_delay + configuration parameter + + + + + Specifies the cost delay value that will be used in automatic + VACUUM operations. If -1 is specified, the regular + value will be used. + If this value is specified without units, it is taken as milliseconds. + The default value is 2 milliseconds. + This parameter can only be set in the postgresql.conf + file or on the server command line; + but the setting can be overridden for individual tables by + changing table storage parameters. + + + - + + autovacuum_vacuum_cost_limit (integer) + + autovacuum_vacuum_cost_limit + configuration parameter + + + + + Specifies the cost limit value that will be used in automatic + VACUUM operations. If -1 + is specified (which is the default), the regular + value will be used. Note that + the value is distributed proportionally among the running autovacuum + workers, if there is more than one, so that the sum of the limits for + each worker does not exceed the value of this variable. + This parameter can only be set in the postgresql.conf + file or on the server command line; + but the setting can be overridden for individual tables by + changing table storage parameters. + + + + + + + + + Cost-based Vacuum Delay + + + During the execution of + and + commands, the system maintains an + internal counter that keeps track of the estimated cost of the + various I/O operations that are performed. When the accumulated + cost reaches a limit (specified by + vacuum_cost_limit), the process performing + the operation will sleep for a short period of time, as specified by + vacuum_cost_delay. Then it will reset the + counter and continue execution. + + + + The intent of this feature is to allow administrators to reduce + the I/O impact of these commands on concurrent database + activity. There are many situations where it is not + important that maintenance commands like + VACUUM and ANALYZE finish + quickly; however, it is usually very important that these + commands do not significantly interfere with the ability of the + system to perform other database operations. Cost-based vacuum + delay provides a way for administrators to achieve this. + + + + This feature is disabled by default for manually issued + VACUUM commands. To enable it, set the + vacuum_cost_delay variable to a nonzero + value. + + + + + vacuum_cost_delay (floating point) + + vacuum_cost_delay configuration parameter + + + + + The amount of time that the process will sleep when the cost + limit has been exceeded. If this value is specified without + units, it is taken as milliseconds. The default value is + 0, which disables the cost-based vacuum delay + feature. Positive values enable cost-based vacuuming. + + + + When using cost-based vacuuming, appropriate values for + vacuum_cost_delay are usually quite small, perhaps + less than 1 millisecond. While vacuum_cost_delay + can be set to fractional-millisecond values, such delays may not be + measured accurately on older platforms. On such platforms, + increasing VACUUM's throttled resource consumption + above what you get at 1ms will require changing the other vacuum cost + parameters. You should, nonetheless, + keep vacuum_cost_delay as small as your platform + will consistently measure; large delays are not helpful. + + + + + + vacuum_cost_page_hit (integer) + + vacuum_cost_page_hit configuration parameter + + + + + The estimated cost for vacuuming a buffer found in the shared + buffer cache. It represents the cost to lock the buffer pool, + lookup the shared hash table and scan the content of the page. + The default value is 1. + + + + + + vacuum_cost_page_miss (integer) + + vacuum_cost_page_miss configuration parameter + + + + + The estimated cost for vacuuming a buffer that has to be read from + disk. This represents the effort to lock the buffer pool, + lookup the shared hash table, read the desired block in from + the disk and scan its content. The default value is + 2. + + + + + + vacuum_cost_page_dirty (integer) + + vacuum_cost_page_dirty configuration parameter + + + + + The estimated cost charged when vacuum modifies a block that was + previously clean. It represents the extra I/O required to + flush the dirty block out to disk again. The default value is + 20. + + + + + + vacuum_cost_limit (integer) + + vacuum_cost_limit configuration parameter + + + + + This is the accumulated cost that will cause the vacuuming + process to sleep for vacuum_cost_delay. The + default is 200. + + + + + + + + There are certain operations that hold critical locks and should + therefore complete as quickly as possible. Cost-based vacuum + delays do not occur during such operations. Therefore it is + possible that the cost accumulates far higher than the specified + limit. To avoid uselessly long delays in such cases, the actual + delay is calculated as vacuum_cost_delay * + accumulated_balance / + vacuum_cost_limit with a maximum of + vacuum_cost_delay * 4. + + + + + + Freezing + + + To maintain correctness even after transaction IDs wrap around, + PostgreSQL marks rows that are sufficiently + old as frozen. These rows are visible to everyone; + other transactions do not need to examine their inserting XID to + determine visibility. VACUUM is responsible for + marking rows as frozen. The following settings control + VACUUM's freezing behavior and should be tuned based + on the XID consumption rate of the system and data access patterns of the + dominant workloads. See for more + information on transaction ID wraparound and tuning these parameters. + + + + + vacuum_freeze_table_age (integer) + + vacuum_freeze_table_age configuration parameter + + + + + VACUUM performs an aggressive scan if the table's + pg_class.relfrozenxid field has reached + the age specified by this setting. An aggressive scan differs from + a regular VACUUM in that it visits every page that might + contain unfrozen XIDs or MXIDs, not just those that might contain dead + tuples. The default is 150 million transactions. Although users can + set this value anywhere from zero to two billion, VACUUM + will silently limit the effective value to 95% of + , so that a + periodic manual VACUUM has a chance to run before an + anti-wraparound autovacuum is launched for the table. For more + information see + . + + + + + + vacuum_freeze_min_age (integer) + + vacuum_freeze_min_age configuration parameter + + + + + Specifies the cutoff age (in transactions) that + VACUUM should use to decide whether to + trigger freezing of pages that have an older XID. + The default is 50 million transactions. Although + users can set this value anywhere from zero to one billion, + VACUUM will silently limit the effective value to half + the value of , so + that there is not an unreasonably short time between forced + autovacuums. For more information see . + + + + + + vacuum_failsafe_age (integer) + + vacuum_failsafe_age configuration parameter + + + + + Specifies the maximum age (in transactions) that a table's + pg_class.relfrozenxid + field can attain before VACUUM takes + extraordinary measures to avoid system-wide transaction ID + wraparound failure. This is VACUUM's + strategy of last resort. The failsafe typically triggers + when an autovacuum to prevent transaction ID wraparound has + already been running for some time, though it's possible for + the failsafe to trigger during any VACUUM. + + + When the failsafe is triggered, any cost-based delay that is + in effect will no longer be applied, further non-essential + maintenance tasks (such as index vacuuming) are bypassed, and any + Buffer Access Strategy + in use will be disabled resulting in VACUUM being + free to make use of all of + shared buffers. + + + The default is 1.6 billion transactions. Although users can + set this value anywhere from zero to 2.1 billion, + VACUUM will silently adjust the effective + value to no less than 105% of . + + + + + + vacuum_multixact_freeze_table_age (integer) + + vacuum_multixact_freeze_table_age configuration parameter + + + + + VACUUM performs an aggressive scan if the table's + pg_class.relminmxid field has reached + the age specified by this setting. An aggressive scan differs from + a regular VACUUM in that it visits every page that might + contain unfrozen XIDs or MXIDs, not just those that might contain dead + tuples. The default is 150 million multixacts. + Although users can set this value anywhere from zero to two billion, + VACUUM will silently limit the effective value to 95% of + , so that a + periodic manual VACUUM has a chance to run before an + anti-wraparound is launched for the table. + For more information see . + + + + + + vacuum_multixact_freeze_min_age (integer) + + vacuum_multixact_freeze_min_age configuration parameter + + + + + Specifies the cutoff age (in multixacts) that VACUUM + should use to decide whether to trigger freezing of pages with + an older multixact ID. The default is 5 million multixacts. + Although users can set this value anywhere from zero to one billion, + VACUUM will silently limit the effective value to half + the value of , + so that there is not an unreasonably short time between forced + autovacuums. + For more information see . + + + + + + vacuum_multixact_failsafe_age (integer) + + vacuum_multixact_failsafe_age configuration parameter + + + + + Specifies the maximum age (in multixacts) that a table's + pg_class.relminmxid + field can attain before VACUUM takes + extraordinary measures to avoid system-wide multixact ID + wraparound failure. This is VACUUM's + strategy of last resort. The failsafe typically triggers when + an autovacuum to prevent transaction ID wraparound has already + been running for some time, though it's possible for the + failsafe to trigger during any VACUUM. + + + When the failsafe is triggered, any cost-based delay that is + in effect will no longer be applied, and further non-essential + maintenance tasks (such as index vacuuming) are bypassed. + + + The default is 1.6 billion multixacts. Although users can set + this value anywhere from zero to 2.1 billion, + VACUUM will silently adjust the effective + value to no less than 105% of . + + + + + + @@ -9595,168 +9789,6 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv; - - vacuum_freeze_table_age (integer) - - vacuum_freeze_table_age configuration parameter - - - - - VACUUM performs an aggressive scan if the table's - pg_class.relfrozenxid field has reached - the age specified by this setting. An aggressive scan differs from - a regular VACUUM in that it visits every page that might - contain unfrozen XIDs or MXIDs, not just those that might contain dead - tuples. The default is 150 million transactions. Although users can - set this value anywhere from zero to two billion, VACUUM - will silently limit the effective value to 95% of - , so that a - periodic manual VACUUM has a chance to run before an - anti-wraparound autovacuum is launched for the table. For more - information see - . - - - - - - vacuum_freeze_min_age (integer) - - vacuum_freeze_min_age configuration parameter - - - - - Specifies the cutoff age (in transactions) that - VACUUM should use to decide whether to - trigger freezing of pages that have an older XID. - The default is 50 million transactions. Although - users can set this value anywhere from zero to one billion, - VACUUM will silently limit the effective value to half - the value of , so - that there is not an unreasonably short time between forced - autovacuums. For more information see . - - - - - - vacuum_failsafe_age (integer) - - vacuum_failsafe_age configuration parameter - - - - - Specifies the maximum age (in transactions) that a table's - pg_class.relfrozenxid - field can attain before VACUUM takes - extraordinary measures to avoid system-wide transaction ID - wraparound failure. This is VACUUM's - strategy of last resort. The failsafe typically triggers - when an autovacuum to prevent transaction ID wraparound has - already been running for some time, though it's possible for - the failsafe to trigger during any VACUUM. - - - When the failsafe is triggered, any cost-based delay that is - in effect will no longer be applied, further non-essential - maintenance tasks (such as index vacuuming) are bypassed, and any - Buffer Access Strategy - in use will be disabled resulting in VACUUM being - free to make use of all of - shared buffers. - - - The default is 1.6 billion transactions. Although users can - set this value anywhere from zero to 2.1 billion, - VACUUM will silently adjust the effective - value to no less than 105% of . - - - - - - vacuum_multixact_freeze_table_age (integer) - - vacuum_multixact_freeze_table_age configuration parameter - - - - - VACUUM performs an aggressive scan if the table's - pg_class.relminmxid field has reached - the age specified by this setting. An aggressive scan differs from - a regular VACUUM in that it visits every page that might - contain unfrozen XIDs or MXIDs, not just those that might contain dead - tuples. The default is 150 million multixacts. - Although users can set this value anywhere from zero to two billion, - VACUUM will silently limit the effective value to 95% of - , so that a - periodic manual VACUUM has a chance to run before an - anti-wraparound is launched for the table. - For more information see . - - - - - - vacuum_multixact_freeze_min_age (integer) - - vacuum_multixact_freeze_min_age configuration parameter - - - - - Specifies the cutoff age (in multixacts) that VACUUM - should use to decide whether to trigger freezing of pages with - an older multixact ID. The default is 5 million multixacts. - Although users can set this value anywhere from zero to one billion, - VACUUM will silently limit the effective value to half - the value of , - so that there is not an unreasonably short time between forced - autovacuums. - For more information see . - - - - - - vacuum_multixact_failsafe_age (integer) - - vacuum_multixact_failsafe_age configuration parameter - - - - - Specifies the maximum age (in multixacts) that a table's - pg_class.relminmxid - field can attain before VACUUM takes - extraordinary measures to avoid system-wide multixact ID - wraparound failure. This is VACUUM's - strategy of last resort. The failsafe typically triggers when - an autovacuum to prevent transaction ID wraparound has already - been running for some time, though it's possible for the - failsafe to trigger during any VACUUM. - - - When the failsafe is triggered, any cost-based delay that is - in effect will no longer be applied, and further non-essential - maintenance tasks (such as index vacuuming) are bypassed. - - - The default is 1.6 billion multixacts. Although users can set - this value anywhere from zero to 2.1 billion, - VACUUM will silently adjust the effective - value to no less than 105% of . - - - - bytea_output (enum) -- 2.39.5