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VACUUM VERBOSE: Count "newly deleted" index pages.

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Teach VACUUM VERBOSE to report on pages deleted by the _current_ VACUUM
operation -- these are newly deleted pages.  VACUUM VERBOSE continues to
report on the total number of deleted pages in the entire index (no
change there).  The former is a subset of the latter.

The distinction between each category of deleted index page only arises
with index AMs where page deletion is supported and is decoupled from
page recycling for performance reasons.

This is follow-up work to commit e5d8a999, which made nbtree store
64-bit XIDs (not 32-bit XIDs) in pages at the point at which they're
deleted.  Note that the btm_last_cleanup_num_delpages metapage field
added by that commit usually gets set to pages_newly_deleted.  The
exceptions (the scenarios in which they're not equal) all seem to be
tricky cases for the implementation (of page deletion and recycling) in
general.

Author: Peter Geoghegan <pg@bowt.ie>
Discussion: https://postgr.es/m/CAH2-WznpdHvujGUwYZ8sihX%3Dd5u-tRYhi-F4wnV2uN2zHpMUXw%40mail.gmail.com
This commit is contained in:
Peter Geoghegan
2021-02-25 14:32:18 -08:00
parent 301ed8812e
commit 2376361839
8 changed files with 86 additions and 54 deletions
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10
src/include/access/genam.h
View File

@@ -63,8 +63,11 @@ typedef struct IndexVacuumInfo
* of which this is just the first field; this provides a way for ambulkdelete
* to communicate additional private data to amvacuumcleanup.
*
* Note: pages_deleted and pages_free refer to free space within the index
* file. Some index AMs may compute num_index_tuples by reference to
* Note: pages_newly_deleted is the number of pages in the index that were
* deleted by the current vacuum operation. pages_deleted and pages_free
* refer to free space within the index file.
*
* Note: Some index AMs may compute num_index_tuples by reference to
* num_heap_tuples, in which case they should copy the estimated_count field
* from IndexVacuumInfo.
*/
@@ -74,7 +77,8 @@ typedef struct IndexBulkDeleteResult
bool estimated_count; /* num_index_tuples is an estimate */
double num_index_tuples; /* tuples remaining */
double tuples_removed; /* # removed during vacuum operation */
BlockNumber pages_deleted; /* # unused pages in index */
BlockNumber pages_newly_deleted; /* # pages marked deleted by us */
BlockNumber pages_deleted; /* # pages marked deleted (could be by us) */
BlockNumber pages_free; /* # pages available for reuse */
} IndexBulkDeleteResult;

16
src/include/access/nbtree.h
View File

@@ -312,6 +312,20 @@ BTPageIsRecyclable(Page page)
return false;
}
/*
* BTVacState is private nbtree.c state used during VACUUM. It is exported
* for use by page deletion related code in nbtpage.c.
*/
typedef struct BTVacState
{
IndexVacuumInfo *info;
IndexBulkDeleteResult *stats;
IndexBulkDeleteCallback callback;
void *callback_state;
BTCycleId cycleid;
MemoryContext pagedelcontext;
} BTVacState;
/*
* Lehman and Yao's algorithm requires a ``high key'' on every non-rightmost
* page. The high key is not a tuple that is used to visit the heap. It is
@@ -1181,7 +1195,7 @@ extern void _bt_delitems_vacuum(Relation rel, Buffer buf,
extern void _bt_delitems_delete_check(Relation rel, Buffer buf,
Relation heapRel,
TM_IndexDeleteOp *delstate);
extern uint32 _bt_pagedel(Relation rel, Buffer leafbuf);
extern void _bt_pagedel(Relation rel, Buffer leafbuf, BTVacState *vstate);
/*
* prototypes for functions in nbtsearch.c