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Commit9cc2756

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Fix pgstattuple's handling of unused hash pages.
Hash indexes can contain both pages which are all-zeroes (i.e.PageIsNew()) and pages which have been initialized but currentlyaren't used. The latter category can happen either when a pagehas been reserved but not yet used or when it is used for a timeand then freed. pgstattuple was only prepared to deal with thepages that are actually-zeroes, which it called zero_pages.Rename the column to unused_pages (extension version 1.5 isas-yet-unreleased) and make it count both kinds of unused pages.Along the way, slightly tidy up the way we test for pages ofvarious types.Robert Haas and Ashutosh Sharma, reviewed by Amit KapilaDiscussion:http://postgr.es/m/CAE9k0PkTtKFB3YndOyQMjwuHx+-FtUP1ynK8E-nHtetoow3NtQ@mail.gmail.com
1 parent1d5fede commit9cc2756

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4 files changed

+22
-16
lines changed

4 files changed

+22
-16
lines changed

‎contrib/pgstattuple/expected/pgstattuple.out

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -132,9 +132,9 @@ select * from pgstatginindex('test_ginidx');
132132

133133
create index test_hashidx on test using hash (b);
134134
select * from pgstathashindex('test_hashidx');
135-
version | bucket_pages | overflow_pages | bitmap_pages |zero_pages | live_items | dead_items | free_percent
136-
---------+--------------+----------------+--------------+------------+------------+------------+--------------
137-
3 | 4 | 0 | 1 | 0 | 0 | 0 | 100
135+
version | bucket_pages | overflow_pages | bitmap_pages |unused_pages | live_items | dead_items | free_percent
136+
---------+--------------+----------------+--------------+--------------+------------+------------+--------------
137+
3 | 4 | 0 | 1 |0 | 0 | 0 | 100
138138
(1 row)
139139

140140
-- these should error with the wrong type

‎contrib/pgstattuple/pgstatindex.c

Lines changed: 15 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -119,7 +119,7 @@ typedef struct HashIndexStat
119119
BlockNumberbucket_pages;
120120
BlockNumberoverflow_pages;
121121
BlockNumberbitmap_pages;
122-
BlockNumberzero_pages;
122+
BlockNumberunused_pages;
123123

124124
int64live_items;
125125
int64dead_items;
@@ -634,7 +634,6 @@ pgstathashindex(PG_FUNCTION_ARGS)
634634
{
635635
Bufferbuf;
636636
Pagepage;
637-
HashPageOpaqueopaque;
638637

639638
CHECK_FOR_INTERRUPTS();
640639

@@ -644,7 +643,7 @@ pgstathashindex(PG_FUNCTION_ARGS)
644643
page= (Page)BufferGetPage(buf);
645644

646645
if (PageIsNew(page))
647-
stats.zero_pages++;
646+
stats.unused_pages++;
648647
elseif (PageGetSpecialSize(page)!=
649648
MAXALIGN(sizeof(HashPageOpaqueData)))
650649
ereport(ERROR,
@@ -654,19 +653,26 @@ pgstathashindex(PG_FUNCTION_ARGS)
654653
BufferGetBlockNumber(buf))));
655654
else
656655
{
656+
HashPageOpaqueopaque;
657+
intpagetype;
658+
657659
opaque= (HashPageOpaque)PageGetSpecialPointer(page);
658-
if (opaque->hasho_flag&LH_BUCKET_PAGE)
660+
pagetype=opaque->hasho_flag&LH_PAGE_TYPE;
661+
662+
if (pagetype==LH_BUCKET_PAGE)
659663
{
660664
stats.bucket_pages++;
661665
GetHashPageStats(page,&stats);
662666
}
663-
elseif (opaque->hasho_flag&LH_OVERFLOW_PAGE)
667+
elseif (pagetype==LH_OVERFLOW_PAGE)
664668
{
665669
stats.overflow_pages++;
666670
GetHashPageStats(page,&stats);
667671
}
668-
elseif (opaque->hasho_flag&LH_BITMAP_PAGE)
672+
elseif (pagetype==LH_BITMAP_PAGE)
669673
stats.bitmap_pages++;
674+
elseif (pagetype==LH_UNUSED_PAGE)
675+
stats.unused_pages++;
670676
else
671677
ereport(ERROR,
672678
(errcode(ERRCODE_INDEX_CORRUPTED),
@@ -680,8 +686,8 @@ pgstathashindex(PG_FUNCTION_ARGS)
680686
/* Done accessing the index */
681687
index_close(rel,AccessShareLock);
682688

683-
/* Countzero pages as free space. */
684-
stats.free_space+=stats.zero_pages*stats.space_per_page;
689+
/* Countunused pages as free space. */
690+
stats.free_space+=stats.unused_pages*stats.space_per_page;
685691

686692
/*
687693
* Total space available for tuples excludes the metapage and the bitmap
@@ -710,7 +716,7 @@ pgstathashindex(PG_FUNCTION_ARGS)
710716
values[1]=Int64GetDatum((int64)stats.bucket_pages);
711717
values[2]=Int64GetDatum((int64)stats.overflow_pages);
712718
values[3]=Int64GetDatum((int64)stats.bitmap_pages);
713-
values[4]=Int64GetDatum((int64)stats.zero_pages);
719+
values[4]=Int64GetDatum((int64)stats.unused_pages);
714720
values[5]=Int64GetDatum(stats.live_items);
715721
values[6]=Int64GetDatum(stats.dead_items);
716722
values[7]=Float8GetDatum(free_percent);

‎contrib/pgstattuple/pgstattuple--1.4--1.5.sql

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -125,7 +125,7 @@ CREATE OR REPLACE FUNCTION pgstathashindex(IN relname regclass,
125125
OUT bucket_pagesBIGINT,
126126
OUT overflow_pagesBIGINT,
127127
OUT bitmap_pagesBIGINT,
128-
OUTzero_pagesBIGINT,
128+
OUTunused_pagesBIGINT,
129129
OUT live_itemsBIGINT,
130130
OUT dead_itemsBIGINT,
131131
OUT free_percent FLOAT8)

‎doc/src/sgml/pgstattuple.sgml

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -372,7 +372,7 @@ version | 2
372372
bucket_pages | 33081
373373
overflow_pages | 0
374374
bitmap_pages | 1
375-
zero_pages | 32455
375+
unused_pages | 32455
376376
live_items | 10204006
377377
dead_items | 0
378378
free_percent | 61.8005949100872
@@ -418,9 +418,9 @@ free_percent | 61.8005949100872
418418
</row>
419419

420420
<row>
421-
<entry><structfield>zero_pages</structfield></entry>
421+
<entry><structfield>unused_pages</structfield></entry>
422422
<entry><type>bigint</type></entry>
423-
<entry>Number ofnew or zero pages</entry>
423+
<entry>Number ofunused pages</entry>
424424
</row>
425425

426426
<row>

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