mirror of
https://git.postgresql.org/git/postgresql.git
synced 2024-09-15 21:30:23 +02:00
620b49a16d
Per a report from AP, it's not that hard to exhaust the supply of bitmap pages if you create a table with a hash index and then insert a few billion rows - and then you start getting errors when you try to insert additional rows. In the particular case reported by AP, there's another fix that we can make to improve recycling of overflow pages, which is another way to avoid the error, but there may be other cases where this problem happens and that fix won't help. So let's buy ourselves as much headroom as we can without rearchitecting anything. The comments claim that the old limit was 64GB, but it was really only 32GB, because we didn't use all the bits in the page for bitmap bits - only the largest power of 2 that could fit after deducting space for the page header and so forth. Thus, we have 4kB per page for bitmap bits, not 8kB. The new limit is thus actually 8 times the old *real* limit but only 4 times the old *purported* limit. Since this breaks on-disk compatibility, bump HASH_VERSION. We've already done this earlier in this release cycle, so this doesn't cause any incremental inconvenience for people using pg_upgrade from releases prior to v10. However, users who use pg_upgrade to reach 10beta3 or later from 10beta2 or earlier will need to REINDEX any hash indexes again. Amit Kapila and Robert Haas Discussion: http://postgr.es/m/20170704105728.mwb72jebfmok2nm2@zip.com.au
721 lines
22 KiB
Plaintext
721 lines
22 KiB
Plaintext
<!-- doc/src/sgml/pageinspect.sgml -->
|
|
|
|
<sect1 id="pageinspect" xreflabel="pageinspect">
|
|
<title>pageinspect</title>
|
|
|
|
<indexterm zone="pageinspect">
|
|
<primary>pageinspect</primary>
|
|
</indexterm>
|
|
|
|
<para>
|
|
The <filename>pageinspect</> module provides functions that allow you to
|
|
inspect the contents of database pages at a low level, which is useful for
|
|
debugging purposes. All of these functions may be used only by superusers.
|
|
</para>
|
|
|
|
<sect2>
|
|
<title>General Functions</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>
|
|
<function>get_raw_page(relname text, fork text, blkno int) returns bytea</function>
|
|
<indexterm>
|
|
<primary>get_raw_page</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>get_raw_page</function> reads the specified block of the named
|
|
relation and returns a copy as a <type>bytea</> value. This allows a
|
|
single time-consistent copy of the block to be obtained.
|
|
<replaceable>fork</replaceable> should be <literal>'main'</literal> for
|
|
the main data fork, <literal>'fsm'</literal> for the free space map,
|
|
<literal>'vm'</literal> for the visibility map, or <literal>'init'</literal>
|
|
for the initialization fork.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>get_raw_page(relname text, blkno int) returns bytea</function>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
A shorthand version of <function>get_raw_page</function>, for reading
|
|
from the main fork. Equivalent to
|
|
<literal>get_raw_page(relname, 'main', blkno)</literal>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>page_header(page bytea) returns record</function>
|
|
<indexterm>
|
|
<primary>page_header</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>page_header</function> shows fields that are common to all
|
|
<productname>PostgreSQL</> heap and index pages.
|
|
</para>
|
|
|
|
<para>
|
|
A page image obtained with <function>get_raw_page</function> should be
|
|
passed as argument. For example:
|
|
<screen>
|
|
test=# SELECT * FROM page_header(get_raw_page('pg_class', 0));
|
|
lsn | checksum | flags | lower | upper | special | pagesize | version | prune_xid
|
|
-----------+----------+--------+-------+-------+---------+----------+---------+-----------
|
|
0/24A1B50 | 0 | 1 | 232 | 368 | 8192 | 8192 | 4 | 0
|
|
</screen>
|
|
The returned columns correspond to the fields in the
|
|
<structname>PageHeaderData</> struct.
|
|
See <filename>src/include/storage/bufpage.h</> for details.
|
|
</para>
|
|
|
|
<para>
|
|
The <structfield>checksum</structfield> field is the checksum stored in
|
|
the page, which might be incorrect if the page is somehow corrupted. If
|
|
data checksums are not enabled for this instance, then the value stored
|
|
is meaningless.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>page_checksum(page bytea, blkno int4) returns smallint</function>
|
|
<indexterm>
|
|
<primary>page_checksum</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>page_checksum</function> computes the checksum for the page, as if
|
|
it was located at the given block.
|
|
</para>
|
|
|
|
<para>
|
|
A page image obtained with <function>get_raw_page</function> should be
|
|
passed as argument. For example:
|
|
<screen>
|
|
test=# SELECT page_checksum(get_raw_page('pg_class', 0), 0);
|
|
page_checksum
|
|
---------------
|
|
13443
|
|
</screen>
|
|
Note that the checksum depends on the block number, so matching block
|
|
numbers should be passed (except when doing esoteric debugging).
|
|
</para>
|
|
|
|
<para>
|
|
The checksum computed with this function can be compared with
|
|
the <structfield>checksum</structfield> result field of the
|
|
function <function>page_header</function>. If data checksums are
|
|
enabled for this instance, then the two values should be equal.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>heap_page_items(page bytea) returns setof record</function>
|
|
<indexterm>
|
|
<primary>heap_page_items</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>heap_page_items</function> shows all line pointers on a heap
|
|
page. For those line pointers that are in use, tuple headers as well
|
|
as tuple raw data are also shown. All tuples are shown, whether or not
|
|
the tuples were visible to an MVCC snapshot at the time the raw page
|
|
was copied.
|
|
</para>
|
|
<para>
|
|
A heap page image obtained with <function>get_raw_page</function> should
|
|
be passed as argument. For example:
|
|
<screen>
|
|
test=# SELECT * FROM heap_page_items(get_raw_page('pg_class', 0));
|
|
</screen>
|
|
See <filename>src/include/storage/itemid.h</> and
|
|
<filename>src/include/access/htup_details.h</> for explanations of the fields
|
|
returned.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>tuple_data_split(rel_oid, t_data bytea, t_infomask integer, t_infomask2 integer, t_bits text [, do_detoast bool]) returns bytea[]</function>
|
|
<indexterm>
|
|
<primary>tuple_data_split</primary>
|
|
</indexterm>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
<function>tuple_data_split</function> splits tuple data into attributes
|
|
in the same way as backend internals.
|
|
<screen>
|
|
test=# SELECT tuple_data_split('pg_class'::regclass, t_data, t_infomask, t_infomask2, t_bits) FROM heap_page_items(get_raw_page('pg_class', 0));
|
|
</screen>
|
|
This function should be called with the same arguments as the return
|
|
attributes of <function>heap_page_items</function>.
|
|
</para>
|
|
<para>
|
|
If <parameter>do_detoast</parameter> is <literal>true</literal>,
|
|
attribute that will be detoasted as needed. Default value is
|
|
<literal>false</literal>.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>heap_page_item_attrs(rel_oid, t_data bytea, [, do_detoast bool]) returns bytea[]</function>
|
|
<indexterm>
|
|
<primary>heap_page_item_attrs</primary>
|
|
</indexterm>
|
|
</term>
|
|
<listitem>
|
|
<para>
|
|
<function>heap_page_item_attrs</function> is equivalent to
|
|
<function>heap_page_items</function> except that it returns
|
|
tuple raw data as an array of attributes that can optionally
|
|
be detoasted by <parameter>do_detoast</parameter> which is
|
|
<literal>false</literal> by default.
|
|
</para>
|
|
<para>
|
|
A heap page image obtained with <function>get_raw_page</function> should
|
|
be passed as argument. For example:
|
|
<screen>
|
|
test=# SELECT * FROM heap_page_item_attrs(get_raw_page('pg_class', 0), 'pg_class'::regclass);
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>fsm_page_contents(page bytea) returns text</function>
|
|
<indexterm>
|
|
<primary>fsm_page_contents</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>fsm_page_contents</function> shows the internal node structure
|
|
of a FSM page. The output is a multiline string, with one line per
|
|
node in the binary tree within the page. Only those nodes that are not
|
|
zero are printed. The so-called "next" pointer, which points to the
|
|
next slot to be returned from the page, is also printed.
|
|
</para>
|
|
<para>
|
|
See <filename>src/backend/storage/freespace/README</> for more
|
|
information on the structure of an FSM page.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>B-tree Functions</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>
|
|
<function>bt_metap(relname text) returns record</function>
|
|
<indexterm>
|
|
<primary>bt_metap</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>bt_metap</function> returns information about a B-tree
|
|
index's metapage. For example:
|
|
<screen>
|
|
test=# SELECT * FROM bt_metap('pg_cast_oid_index');
|
|
-[ RECORD 1 ]-----
|
|
magic | 340322
|
|
version | 2
|
|
root | 1
|
|
level | 0
|
|
fastroot | 1
|
|
fastlevel | 0
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>bt_page_stats(relname text, blkno int) returns record</function>
|
|
<indexterm>
|
|
<primary>bt_page_stats</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>bt_page_stats</function> returns summary information about
|
|
single pages of B-tree indexes. For example:
|
|
<screen>
|
|
test=# SELECT * FROM bt_page_stats('pg_cast_oid_index', 1);
|
|
-[ RECORD 1 ]-+-----
|
|
blkno | 1
|
|
type | l
|
|
live_items | 256
|
|
dead_items | 0
|
|
avg_item_size | 12
|
|
page_size | 8192
|
|
free_size | 4056
|
|
btpo_prev | 0
|
|
btpo_next | 0
|
|
btpo | 0
|
|
btpo_flags | 3
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>bt_page_items(relname text, blkno int) returns setof record</function>
|
|
<indexterm>
|
|
<primary>bt_page_items</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>bt_page_items</function> returns detailed information about
|
|
all of the items on a B-tree index page. For example:
|
|
<screen>
|
|
test=# SELECT * FROM bt_page_items('pg_cast_oid_index', 1);
|
|
itemoffset | ctid | itemlen | nulls | vars | data
|
|
------------+---------+---------+-------+------+-------------
|
|
1 | (0,1) | 12 | f | f | 23 27 00 00
|
|
2 | (0,2) | 12 | f | f | 24 27 00 00
|
|
3 | (0,3) | 12 | f | f | 25 27 00 00
|
|
4 | (0,4) | 12 | f | f | 26 27 00 00
|
|
5 | (0,5) | 12 | f | f | 27 27 00 00
|
|
6 | (0,6) | 12 | f | f | 28 27 00 00
|
|
7 | (0,7) | 12 | f | f | 29 27 00 00
|
|
8 | (0,8) | 12 | f | f | 2a 27 00 00
|
|
</screen>
|
|
In a B-tree leaf page, <structfield>ctid</> points to a heap tuple.
|
|
In an internal page, the block number part of <structfield>ctid</>
|
|
points to another page in the index itself, while the offset part
|
|
(the second number) is ignored and is usually 1.
|
|
</para>
|
|
<para>
|
|
Note that the first item on any non-rightmost page (any page with
|
|
a non-zero value in the <structfield>btpo_next</> field) is the
|
|
page's <quote>high key</quote>, meaning its <structfield>data</>
|
|
serves as an upper bound on all items appearing on the page, while
|
|
its <structfield>ctid</> field is meaningless. Also, on non-leaf
|
|
pages, the first real data item (the first item that is not a high
|
|
key) is a <quote>minus infinity</quote> item, with no actual value
|
|
in its <structfield>data</> field. Such an item does have a valid
|
|
downlink in its <structfield>ctid</> field, however.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>bt_page_items(page bytea) returns setof record</function>
|
|
<indexterm>
|
|
<primary>bt_page_items</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
It is also possible to pass a page to <function>bt_page_items</function>
|
|
as a <type>bytea</> value. A page image obtained
|
|
with <function>get_raw_page</function> should be passed as argument. So
|
|
the last example could also be rewritten like this:
|
|
<screen>
|
|
test=# SELECT * FROM bt_page_items(get_raw_page('pg_cast_oid_index', 1));
|
|
itemoffset | ctid | itemlen | nulls | vars | data
|
|
------------+---------+---------+-------+------+-------------
|
|
1 | (0,1) | 12 | f | f | 23 27 00 00
|
|
2 | (0,2) | 12 | f | f | 24 27 00 00
|
|
3 | (0,3) | 12 | f | f | 25 27 00 00
|
|
4 | (0,4) | 12 | f | f | 26 27 00 00
|
|
5 | (0,5) | 12 | f | f | 27 27 00 00
|
|
6 | (0,6) | 12 | f | f | 28 27 00 00
|
|
7 | (0,7) | 12 | f | f | 29 27 00 00
|
|
8 | (0,8) | 12 | f | f | 2a 27 00 00
|
|
</screen>
|
|
All the other details are the same as explained in the previous item.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>BRIN Functions</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>
|
|
<function>brin_page_type(page bytea) returns text</function>
|
|
<indexterm>
|
|
<primary>brin_page_type</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>brin_page_type</function> returns the page type of the given
|
|
<acronym>BRIN</acronym> index page, or throws an error if the page is
|
|
not a valid <acronym>BRIN</acronym> page. For example:
|
|
<screen>
|
|
test=# SELECT brin_page_type(get_raw_page('brinidx', 0));
|
|
brin_page_type
|
|
----------------
|
|
meta
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>brin_metapage_info(page bytea) returns record</function>
|
|
<indexterm>
|
|
<primary>brin_metapage_info</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>brin_metapage_info</function> returns assorted information
|
|
about a <acronym>BRIN</acronym> index metapage. For example:
|
|
<screen>
|
|
test=# SELECT * FROM brin_metapage_info(get_raw_page('brinidx', 0));
|
|
magic | version | pagesperrange | lastrevmappage
|
|
------------+---------+---------------+----------------
|
|
0xA8109CFA | 1 | 4 | 2
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>brin_revmap_data(page bytea) returns setof tid</function>
|
|
<indexterm>
|
|
<primary>brin_revmap_data</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>brin_revmap_data</function> returns the list of tuple
|
|
identifiers in a <acronym>BRIN</acronym> index range map page.
|
|
For example:
|
|
<screen>
|
|
test=# SELECT * FROM brin_revmap_data(get_raw_page('brinidx', 2)) LIMIT 5;
|
|
pages
|
|
---------
|
|
(6,137)
|
|
(6,138)
|
|
(6,139)
|
|
(6,140)
|
|
(6,141)
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>brin_page_items(page bytea, index oid) returns setof record</function>
|
|
<indexterm>
|
|
<primary>brin_page_items</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>brin_page_items</function> returns the data stored in the
|
|
<acronym>BRIN</acronym> data page. For example:
|
|
<screen>
|
|
test=# SELECT * FROM brin_page_items(get_raw_page('brinidx', 5),
|
|
'brinidx')
|
|
ORDER BY blknum, attnum LIMIT 6;
|
|
itemoffset | blknum | attnum | allnulls | hasnulls | placeholder | value
|
|
------------+--------+--------+----------+----------+-------------+--------------
|
|
137 | 0 | 1 | t | f | f |
|
|
137 | 0 | 2 | f | f | f | {1 .. 88}
|
|
138 | 4 | 1 | t | f | f |
|
|
138 | 4 | 2 | f | f | f | {89 .. 176}
|
|
139 | 8 | 1 | t | f | f |
|
|
139 | 8 | 2 | f | f | f | {177 .. 264}
|
|
</screen>
|
|
The returned columns correspond to the fields in the
|
|
<structname>BrinMemTuple</> and <structname>BrinValues</> structs.
|
|
See <filename>src/include/access/brin_tuple.h</> for details.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>GIN Functions</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>
|
|
<function>gin_metapage_info(page bytea) returns record</function>
|
|
<indexterm>
|
|
<primary>gin_metapage_info</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>gin_metapage_info</function> returns information about
|
|
a <acronym>GIN</acronym> index metapage. For example:
|
|
<screen>
|
|
test=# SELECT * FROM gin_metapage_info(get_raw_page('gin_index', 0));
|
|
-[ RECORD 1 ]----+-----------
|
|
pending_head | 4294967295
|
|
pending_tail | 4294967295
|
|
tail_free_size | 0
|
|
n_pending_pages | 0
|
|
n_pending_tuples | 0
|
|
n_total_pages | 7
|
|
n_entry_pages | 6
|
|
n_data_pages | 0
|
|
n_entries | 693
|
|
version | 2
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>gin_page_opaque_info(page bytea) returns record</function>
|
|
<indexterm>
|
|
<primary>gin_page_opaque_info</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>gin_page_opaque_info</function> returns information about
|
|
a <acronym>GIN</acronym> index opaque area, like the page type.
|
|
For example:
|
|
<screen>
|
|
test=# SELECT * FROM gin_page_opaque_info(get_raw_page('gin_index', 2));
|
|
rightlink | maxoff | flags
|
|
-----------+--------+------------------------
|
|
5 | 0 | {data,leaf,compressed}
|
|
(1 row)
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>gin_leafpage_items(page bytea) returns setof record</function>
|
|
<indexterm>
|
|
<primary>gin_leafpage_items</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>gin_leafpage_items</function> returns information about
|
|
the data stored in a <acronym>GIN</acronym> leaf page. For example:
|
|
<screen>
|
|
test=# SELECT first_tid, nbytes, tids[0:5] AS some_tids
|
|
FROM gin_leafpage_items(get_raw_page('gin_test_idx', 2));
|
|
first_tid | nbytes | some_tids
|
|
-----------+--------+----------------------------------------------------------
|
|
(8,41) | 244 | {"(8,41)","(8,43)","(8,44)","(8,45)","(8,46)"}
|
|
(10,45) | 248 | {"(10,45)","(10,46)","(10,47)","(10,48)","(10,49)"}
|
|
(12,52) | 248 | {"(12,52)","(12,53)","(12,54)","(12,55)","(12,56)"}
|
|
(14,59) | 320 | {"(14,59)","(14,60)","(14,61)","(14,62)","(14,63)"}
|
|
(167,16) | 376 | {"(167,16)","(167,17)","(167,18)","(167,19)","(167,20)"}
|
|
(170,30) | 376 | {"(170,30)","(170,31)","(170,32)","(170,33)","(170,34)"}
|
|
(173,44) | 197 | {"(173,44)","(173,45)","(173,46)","(173,47)","(173,48)"}
|
|
(7 rows)
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Hash Functions</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>
|
|
<function>hash_page_type(page bytea) returns text</function>
|
|
<indexterm>
|
|
<primary>hash_page_type</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>hash_page_type</function> returns page type of
|
|
the given <acronym>HASH</acronym> index page. For example:
|
|
<screen>
|
|
test=# SELECT hash_page_type(get_raw_page('con_hash_index', 0));
|
|
hash_page_type
|
|
----------------
|
|
metapage
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>hash_page_stats(page bytea) returns setof record</function>
|
|
<indexterm>
|
|
<primary>hash_page_stats</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>hash_page_stats</function> returns information about
|
|
a bucket or overflow page of a <acronym>HASH</acronym> index.
|
|
For example:
|
|
<screen>
|
|
test=# SELECT * FROM hash_page_stats(get_raw_page('con_hash_index', 1));
|
|
-[ RECORD 1 ]---+-----------
|
|
live_items | 407
|
|
dead_items | 0
|
|
page_size | 8192
|
|
free_size | 8
|
|
hasho_prevblkno | 4096
|
|
hasho_nextblkno | 8474
|
|
hasho_bucket | 0
|
|
hasho_flag | 66
|
|
hasho_page_id | 65408
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>hash_page_items(page bytea) returns setof record</function>
|
|
<indexterm>
|
|
<primary>hash_page_items</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>hash_page_items</function> returns information about
|
|
the data stored in a bucket or overflow page of a <acronym>HASH</acronym>
|
|
index page. For example:
|
|
<screen>
|
|
test=# SELECT * FROM hash_page_items(get_raw_page('con_hash_index', 1)) LIMIT 5;
|
|
itemoffset | ctid | data
|
|
------------+-----------+------------
|
|
1 | (899,77) | 1053474816
|
|
2 | (897,29) | 1053474816
|
|
3 | (894,207) | 1053474816
|
|
4 | (892,159) | 1053474816
|
|
5 | (890,111) | 1053474816
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>hash_bitmap_info(index oid, blkno int) returns record</function>
|
|
<indexterm>
|
|
<primary>hash_bitmap_info</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>hash_bitmap_info</function> shows the status of a bit
|
|
in the bitmap page for a particular overflow page of <acronym>HASH</acronym>
|
|
index. For example:
|
|
<screen>
|
|
test=# SELECT * FROM hash_bitmap_info('con_hash_index', 2052);
|
|
bitmapblkno | bitmapbit | bitstatus
|
|
-------------+-----------+-----------
|
|
65 | 3 | t
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>hash_metapage_info(page bytea) returns record</function>
|
|
<indexterm>
|
|
<primary>hash_metapage_info</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>hash_metapage_info</function> returns information stored
|
|
in meta page of a <acronym>HASH</acronym> index. For example:
|
|
<screen>
|
|
test=# SELECT magic, version, ntuples, ffactor, bsize, bmsize, bmshift,
|
|
test-# maxbucket, highmask, lowmask, ovflpoint, firstfree, nmaps, procid,
|
|
test-# regexp_replace(spares::text, '(,0)*}', '}') as spares,
|
|
test-# regexp_replace(mapp::text, '(,0)*}', '}') as mapp
|
|
test-# FROM hash_metapage_info(get_raw_page('con_hash_index', 0));
|
|
-[ RECORD 1 ]-------------------------------------------------------------------------------
|
|
spares | {0,0,0,0,0,0,1,1,1,1,1,1,1,1,3,4,4,4,45,55,58,59,508,567,628,704,1193,1202,1204}
|
|
magic | 105121344
|
|
version | 3
|
|
ntuples | 500500
|
|
ffactor | 40
|
|
bsize | 8152
|
|
bmsize | 4096
|
|
bmshift | 15
|
|
maxbucket | 12512
|
|
highmask | 16383
|
|
lowmask | 8191
|
|
ovflpoint | 28
|
|
firstfree | 1204
|
|
nmaps | 1
|
|
procid | 450
|
|
spares | {0,0,0,0,0,0,1,1,1,1,1,1,1,1,3,4,4,4,45,55,58,59,508,567,628,704,1193,1202,1204}
|
|
mapp | {65}
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
</sect1>
|