- Change vacuum_cleanup_index_scale_factor GUC to PGC_USERSET.
vacuum_cleanup_index_scale_factor GUC was defined as PGC_SIGHUP. But this
GUC affects not only autovacuum. So it might be useful to change it from user
session in order to influence manually runned VACUUM.
- Add missing tab-complete support for vacuum_cleanup_index_scale_factor
reloption.
- Fix condition for B-tree index cleanup.
Zero value of vacuum_cleanup_index_scale_factor means that user wants B-tree
index cleanup to be never skipped.
- Documentation and comment improvements
Authors: Justin Pryzby, Alexander Korotkov, Liudmila Mantrova
Reviewed by: all authors and Robert Haas
Discussion: https://www.postgresql.org/message-id/flat/
20180502023025.GD7631%40telsasoft.com
</term>
<listitem>
<para>
- When no tuples were deleted from the heap, B-tree indexes might still
- be scanned during <command>VACUUM</command> cleanup stage by two
- reasons. The first reason is that B-tree index contains deleted pages
- which can be recycled during cleanup. The second reason is that B-tree
- index statistics is stalled. The criterion of stalled index statistics
- is number of inserted tuples since previous statistics collection
- is greater than <varname>vacuum_cleanup_index_scale_factor</varname>
- fraction of total number of heap tuples.
+ Specifies the fraction of the total number of heap tuples counted in
+ the previous statistics collection that can be inserted without
+ incurring an index scan at the <command>VACUUM</command> cleanup stage.
+ This setting currently applies to B-tree indexes only.
</para>
+
+ <para>
+ If no tuples were deleted from the heap, B-tree indexes are still
+ scanned at the <command>VACUUM</command> cleanup stage when at least one
+ of the following conditions is met: the index statistics are stale, or
+ the index contains deleted pages that can be recycled during cleanup.
+ Index statistics are considered to be stale if the number of newly
+ inserted tuples exceeds the <varname>vacuum_cleanup_index_scale_factor</varname>
+ fraction of the total number of heap tuples detected by the previous
+ statistics collection. The total number of heap tuples is stored in
+ the index meta-page. Note that the meta-page does not include this data
+ until <command>VACUUM</command> finds no dead tuples, so B-tree index
+ scan at the cleanup stage can only be skipped if the second and
+ subsequent <command>VACUUM</command> cycles detect no dead tuples.
+ </para>
+
+ <para>
+ The value can range from <literal>0</literal> to <literal>100</literal>.
+ When <varname>vacuum_cleanup_index_scale_factor</varname> is set to
+ <literal>0</literal>, index scans are never skipped during
+ <command>VACUUM</command> cleanup. The default value is <literal>0.1</literal>.
+ </para>
+
</listitem>
</varlistentry>
</variablelist>
if (metad->btm_version < BTREE_VERSION)
_bt_upgrademetapage(metapg);
- /* update cleanup-related infromation */
+ /* update cleanup-related information */
metad->btm_oldest_btpo_xact = oldestBtpoXact;
metad->btm_last_cleanup_num_heap_tuples = numHeapTuples;
MarkBufferDirty(metabuf);
float8 cleanup_scale_factor;
/*
- * If table receives large enough amount of insertions and no cleanup
- * was performed, then index might appear to have stalled statistics.
- * In order to evade that, we perform cleanup when table receives
- * vacuum_cleanup_index_scale_factor fractions of insertions.
+ * If table receives enough insertions and no cleanup was performed,
+ * then index would appear have stale statistics. If scale factor
+ * is set, we avoid that by performing cleanup if the number of
+ * inserted tuples exceeds vacuum_cleanup_index_scale_factor fraction
+ * of original tuples count.
*/
relopts = (StdRdOptions *) info->index->rd_options;
cleanup_scale_factor = (relopts &&
? relopts->vacuum_cleanup_index_scale_factor
: vacuum_cleanup_index_scale_factor;
- if (cleanup_scale_factor < 0 ||
+ if (cleanup_scale_factor <= 0 ||
metad->btm_last_cleanup_num_heap_tuples < 0 ||
info->num_heap_tuples > (1.0 + cleanup_scale_factor) *
metad->btm_last_cleanup_num_heap_tuples)
&oldestBtpoXact);
/*
- * Update cleanup-related information in metapage. These information
- * is used only for cleanup but keeping up them to date can avoid
+ * Update cleanup-related information in metapage. This information
+ * is used only for cleanup but keeping them up to date can avoid
* unnecessary cleanup even after bulkdelete.
*/
_bt_update_meta_cleanup_info(info->index, oldestBtpoXact,
* If btbulkdelete was called, we need not do anything, just return the
* stats from the latest btbulkdelete call. If it wasn't called, we might
* still need to do a pass over the index, to recycle any newly-recyclable
- * pages and to obtain index statistics. _bt_vacuum_needs_cleanup checks
- * is there are newly-recyclable or stalled index statistics.
+ * pages or to obtain index statistics. _bt_vacuum_needs_cleanup
+ * determines if either are needed.
*
* Since we aren't going to actually delete any leaf items, there's no
* need to go through all the vacuum-cycle-ID pushups.
},
{
- {"vacuum_cleanup_index_scale_factor", PGC_SIGHUP, AUTOVACUUM,
+ {"vacuum_cleanup_index_scale_factor", PGC_USERSET, AUTOVACUUM,
gettext_noop("Number of tuple inserts prior to index cleanup as a fraction of reltuples."),
NULL
},
COMPLETE_WITH_CONST("(");
/* ALTER INDEX <foo> SET|RESET ( */
else if (Matches5("ALTER", "INDEX", MatchAny, "RESET", "("))
- COMPLETE_WITH_LIST7("fillfactor", "recheck_on_update",
+ COMPLETE_WITH_LIST8("fillfactor", "recheck_on_update",
+ "vacuum_cleanup_index_scale_factor", /* BTREE */
"fastupdate", "gin_pending_list_limit", /* GIN */
"buffering", /* GiST */
"pages_per_range", "autosummarize" /* BRIN */
);
else if (Matches5("ALTER", "INDEX", MatchAny, "SET", "("))
- COMPLETE_WITH_LIST7("fillfactor =", "recheck_on_update =",
+ COMPLETE_WITH_LIST8("fillfactor =", "recheck_on_update =",
+ "vacuum_cleanup_index_scale_factor =", /* BTREE */
"fastupdate =", "gin_pending_list_limit =", /* GIN */
"buffering =", /* GiST */
"pages_per_range =", "autosummarize =" /* BRIN */
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