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Add vacuum_truncate reloption.

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vacuum_truncate controls whether vacuum tries to truncate off
any empty pages at the end of the table. Previously vacuum always
tried to do the truncation. However, the truncation could cause
some problems; for example, ACCESS EXCLUSIVE lock needs to
be taken on the table during the truncation and can cause
the query cancellation on the standby even if hot_standby_feedback
is true. Setting this reloption to false can be helpful to avoid
such problems.

Author: Tsunakawa Takayuki
Reviewed-By: Julien Rouhaud, Masahiko Sawada, Michael Paquier, Kirk Jamison and Fujii Masao
Discussion: https://postgr.es/m/CAHGQGwE5UqFqSq1=kV3QtTUtXphTdyHA-8rAj4A=Y+e4kyp3BQ@mail.gmail.com
This commit is contained in:
Fujii Masao
2019-04-08 16:43:57 +09:00
parent e3865c3754
commit 119dcfad98
7 changed files with 112 additions and 5 deletions
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18
src/backend/access/common/reloptions.c
View File

@@ -89,6 +89,11 @@
* Setting parallel_workers is safe, since it acts the same as
* max_parallel_workers_per_gather which is a USERSET parameter that doesn't
* affect existing plans or queries.
*
* vacuum_truncate can be set at ShareUpdateExclusiveLock because it
* is only used during VACUUM, which uses a ShareUpdateExclusiveLock,
* so the VACUUM will not be affected by in-flight changes. Changing its
* value has no affect until the next VACUUM, so no need for stronger lock.
*/
static relopt_bool boolRelOpts[] =
@@ -147,6 +152,15 @@ static relopt_bool boolRelOpts[] =
},
true
},
{
{
"vacuum_truncate",
"Enables vacuum to truncate empty pages at the end of this table",
RELOPT_KIND_HEAP | RELOPT_KIND_TOAST,
ShareUpdateExclusiveLock
},
true
},
/* list terminator */
{{NULL}}
};
@@ -1399,7 +1413,9 @@ default_reloptions(Datum reloptions, bool validate, relopt_kind kind)
{"vacuum_cleanup_index_scale_factor", RELOPT_TYPE_REAL,
offsetof(StdRdOptions, vacuum_cleanup_index_scale_factor)},
{"vacuum_index_cleanup", RELOPT_TYPE_BOOL,
offsetof(StdRdOptions, vacuum_index_cleanup)}
offsetof(StdRdOptions, vacuum_index_cleanup)},
{"vacuum_truncate", RELOPT_TYPE_BOOL,
offsetof(StdRdOptions, vacuum_truncate)}
};
options = parseRelOptions(reloptions, validate, kind, &numoptions);

12
src/backend/access/heap/vacuumlazy.c
View File

@@ -165,7 +165,7 @@ static void lazy_cleanup_index(Relation indrel,
LVRelStats *vacrelstats);
static int lazy_vacuum_page(Relation onerel, BlockNumber blkno, Buffer buffer,
int tupindex, LVRelStats *vacrelstats, Buffer *vmbuffer);
static bool should_attempt_truncation(LVRelStats *vacrelstats);
static bool should_attempt_truncation(Relation rel, LVRelStats *vacrelstats);
static void lazy_truncate_heap(Relation onerel, LVRelStats *vacrelstats);
static BlockNumber count_nondeletable_pages(Relation onerel,
LVRelStats *vacrelstats);
@@ -306,7 +306,7 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params,
/*
* Optionally truncate the relation.
*/
if (should_attempt_truncation(vacrelstats))
if (should_attempt_truncation(onerel, vacrelstats))
lazy_truncate_heap(onerel, vacrelstats);
/* Report that we are now doing final cleanup */
@@ -660,7 +660,7 @@ lazy_scan_heap(Relation onerel, VacuumParams *params, LVRelStats *vacrelstats,
/* see note above about forcing scanning of last page */
#define FORCE_CHECK_PAGE() \
(blkno == nblocks - 1 && should_attempt_truncation(vacrelstats))
(blkno == nblocks - 1 && should_attempt_truncation(onerel, vacrelstats))
pgstat_progress_update_param(PROGRESS_VACUUM_HEAP_BLKS_SCANNED, blkno);
@@ -1869,10 +1869,14 @@ lazy_cleanup_index(Relation indrel,
* careful to depend only on fields that lazy_scan_heap updates on-the-fly.
*/
static bool
should_attempt_truncation(LVRelStats *vacrelstats)
should_attempt_truncation(Relation rel, LVRelStats *vacrelstats)
{
BlockNumber possibly_freeable;
if (rel->rd_options != NULL &&
((StdRdOptions *) rel->rd_options)->vacuum_truncate == false)
return false;
possibly_freeable = vacrelstats->rel_pages - vacrelstats->nonempty_pages;
if (possibly_freeable > 0 &&
(possibly_freeable >= REL_TRUNCATE_MINIMUM ||