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e7bff46e50
Non-leaf pages of GiST indexes contain key attributes, leaf pages contain both key and non-key attributes, and gist_page_items() ignored the handling of non-key attributes. This caused a few problems when using gist_page_items() on a GiST index with INCLUDE: - On a non-leaf page, the function would crash. - On a leaf page, the function would work, but miss to display all the values for included attributes. This commit fixes gist_page_items() to handle such cases in a more appropriate way, and now displays the values of key and non-key attributes for each item separately in a style consistent with what ruleutils.c would generate for the attribute list, depending on the page type dealt with. In a way similar to how a record is displayed, values would be double-quoted for key or non-key attributes if required. ruleutils.c did not provide a routine able to control if non-key attributes should be displayed, so an extended() routine for index definitions is added to work around the leaf and non-leaf page differences. While on it, this commit fixes a third problem related to the amount of data reported for key attributes. The code originally relied on BuildIndexValueDescription() (used for error reports on constraints) that would not print all the data stored in the index but the index opclass's input type, so this limited the amount of information available. This switch makes gist_page_items() much cheaper as there is no need to run ACL checks for each item printed, which is not an issue anyway as superuser rights are required to execute the functions of pageinspect. Opclasses whose data cannot be displayed can rely on gist_page_items_bytea(). The documentation of this function was slightly incorrect for the output results generated on HEAD and v15, so adjust it on these branches. Author: Alexander Lakhin, Michael Paquier Discussion: https://postgr.es/m/17884-cb8c326522977acb@postgresql.org Backpatch-through: 14
963 lines
33 KiB
Plaintext
963 lines
33 KiB
Plaintext
<!-- doc/src/sgml/pageinspect.sgml -->
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<sect1 id="pageinspect" xreflabel="pageinspect">
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<title>pageinspect — low-level inspection of database pages</title>
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<indexterm zone="pageinspect">
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<primary>pageinspect</primary>
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</indexterm>
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<para>
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The <filename>pageinspect</filename> module provides functions that allow you to
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inspect the contents of database pages at a low level, which is useful for
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debugging purposes. All of these functions may be used only by superusers.
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</para>
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<sect2 id="pageinspect-general-funcs">
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<title>General Functions</title>
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<variablelist>
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<varlistentry>
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<term>
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<function>get_raw_page(relname text, fork text, blkno bigint) returns bytea</function>
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<indexterm>
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<primary>get_raw_page</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>get_raw_page</function> reads the specified block of the named
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relation and returns a copy as a <type>bytea</type> value. This allows a
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single time-consistent copy of the block to be obtained.
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<replaceable>fork</replaceable> should be <literal>'main'</literal> for
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the main data fork, <literal>'fsm'</literal> for the
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<link linkend="storage-fsm">free space map</link>,
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<literal>'vm'</literal> for the
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<link linkend="storage-vm">visibility map</link>, or
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<literal>'init'</literal> for the initialization fork.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>get_raw_page(relname text, blkno bigint) returns bytea</function>
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</term>
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<listitem>
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<para>
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A shorthand version of <function>get_raw_page</function>, for reading
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from the main fork. Equivalent to
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<literal>get_raw_page(relname, 'main', blkno)</literal>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>page_header(page bytea) returns record</function>
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<indexterm>
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<primary>page_header</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>page_header</function> shows fields that are common to all
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<productname>PostgreSQL</productname> heap and index pages.
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</para>
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<para>
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A page image obtained with <function>get_raw_page</function> should be
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passed as argument. For example:
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<screen>
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test=# SELECT * FROM page_header(get_raw_page('pg_class', 0));
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lsn | checksum | flags | lower | upper | special | pagesize | version | prune_xid
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-----------+----------+--------+-------+-------+---------+----------+---------+-----------
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0/24A1B50 | 0 | 1 | 232 | 368 | 8192 | 8192 | 4 | 0
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</screen>
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The returned columns correspond to the fields in the
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<structname>PageHeaderData</structname> struct.
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See <filename>src/include/storage/bufpage.h</filename> for details.
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</para>
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<para>
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The <structfield>checksum</structfield> field is the checksum stored in
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the page, which might be incorrect if the page is somehow corrupted. If
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data checksums are not enabled for this instance, then the value stored
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is meaningless.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>page_checksum(page bytea, blkno bigint) returns smallint</function>
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<indexterm>
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<primary>page_checksum</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>page_checksum</function> computes the checksum for the page, as if
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it was located at the given block.
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</para>
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<para>
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A page image obtained with <function>get_raw_page</function> should be
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passed as argument. For example:
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<screen>
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test=# SELECT page_checksum(get_raw_page('pg_class', 0), 0);
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page_checksum
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---------------
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13443
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</screen>
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Note that the checksum depends on the block number, so matching block
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numbers should be passed (except when doing esoteric debugging).
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</para>
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<para>
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The checksum computed with this function can be compared with
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the <structfield>checksum</structfield> result field of the
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function <function>page_header</function>. If data checksums are
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enabled for this instance, then the two values should be equal.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>fsm_page_contents(page bytea) returns text</function>
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<indexterm>
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<primary>fsm_page_contents</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>fsm_page_contents</function> shows the internal node structure
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of an <acronym>FSM</acronym> page. For example:
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<screen>
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test=# SELECT fsm_page_contents(get_raw_page('pg_class', 'fsm', 0));
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</screen>
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The output is a multiline string, with one line per node in the binary
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tree within the page. Only those nodes that are not zero are printed.
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The so-called "next" pointer, which points to the next slot to be
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returned from the page, is also printed.
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</para>
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<para>
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See <filename>src/backend/storage/freespace/README</filename> for more
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information on the structure of an <acronym>FSM</acronym> page.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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<sect2 id="pageinspect-heap-funcs">
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<title>Heap Functions</title>
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<variablelist>
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<varlistentry>
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<term>
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<function>heap_page_items(page bytea) returns setof record</function>
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<indexterm>
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<primary>heap_page_items</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>heap_page_items</function> shows all line pointers on a heap
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page. For those line pointers that are in use, tuple headers as well
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as tuple raw data are also shown. All tuples are shown, whether or not
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the tuples were visible to an MVCC snapshot at the time the raw page
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was copied.
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</para>
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<para>
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A heap page image obtained with <function>get_raw_page</function> should
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be passed as argument. For example:
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<screen>
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test=# SELECT * FROM heap_page_items(get_raw_page('pg_class', 0));
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</screen>
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See <filename>src/include/storage/itemid.h</filename> and
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<filename>src/include/access/htup_details.h</filename> for explanations of the fields
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returned.
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</para>
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<para>
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The <function>heap_tuple_infomask_flags</function> function can be
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used to unpack the flag bits of <structfield>t_infomask</structfield>
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and <structfield>t_infomask2</structfield> for heap tuples.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>tuple_data_split(rel_oid oid, t_data bytea, t_infomask integer, t_infomask2 integer, t_bits text [, do_detoast bool]) returns bytea[]</function>
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<indexterm>
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<primary>tuple_data_split</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>tuple_data_split</function> splits tuple data into attributes
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in the same way as backend internals.
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<screen>
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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));
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</screen>
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This function should be called with the same arguments as the return
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attributes of <function>heap_page_items</function>.
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</para>
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<para>
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If <parameter>do_detoast</parameter> is <literal>true</literal>,
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attributes will be detoasted as needed. Default value is
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<literal>false</literal>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>heap_page_item_attrs(page bytea, rel_oid regclass [, do_detoast bool]) returns setof record</function>
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<indexterm>
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<primary>heap_page_item_attrs</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>heap_page_item_attrs</function> is equivalent to
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<function>heap_page_items</function> except that it returns
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tuple raw data as an array of attributes that can optionally
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be detoasted by <parameter>do_detoast</parameter> which is
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<literal>false</literal> by default.
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</para>
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<para>
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A heap page image obtained with <function>get_raw_page</function> should
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be passed as argument. For example:
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<screen>
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test=# SELECT * FROM heap_page_item_attrs(get_raw_page('pg_class', 0), 'pg_class'::regclass);
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</screen>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>heap_tuple_infomask_flags(t_infomask integer, t_infomask2 integer) returns record</function>
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<indexterm>
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<primary>heap_tuple_infomask_flags</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>heap_tuple_infomask_flags</function> decodes the
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<structfield>t_infomask</structfield> and
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<structfield>t_infomask2</structfield> returned by
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<function>heap_page_items</function> into a human-readable
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set of arrays made of flag names, with one column for all
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the flags and one column for combined flags. For example:
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<screen>
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test=# SELECT t_ctid, raw_flags, combined_flags
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FROM heap_page_items(get_raw_page('pg_class', 0)),
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LATERAL heap_tuple_infomask_flags(t_infomask, t_infomask2)
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WHERE t_infomask IS NOT NULL OR t_infomask2 IS NOT NULL;
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</screen>
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This function should be called with the same arguments as the return
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attributes of <function>heap_page_items</function>.
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</para>
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<para>
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Combined flags are displayed for source-level macros that take into
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account the value of more than one raw bit, such as
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<literal>HEAP_XMIN_FROZEN</literal>.
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</para>
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<para>
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See <filename>src/include/access/htup_details.h</filename> for
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explanations of the flag names returned.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</sect2>
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<sect2 id="pageinspect-b-tree-funcs">
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<title>B-Tree Functions</title>
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<variablelist>
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<varlistentry>
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<term>
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<function>bt_metap(relname text) returns record</function>
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<indexterm>
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<primary>bt_metap</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>bt_metap</function> returns information about a B-tree
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index's metapage. For example:
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<screen>
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test=# SELECT * FROM bt_metap('pg_cast_oid_index');
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-[ RECORD 1 ]-------------+-------
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magic | 340322
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version | 4
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root | 1
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level | 0
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fastroot | 1
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fastlevel | 0
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last_cleanup_num_delpages | 0
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last_cleanup_num_tuples | 230
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allequalimage | f
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</screen>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>bt_page_stats(relname text, blkno bigint) returns record</function>
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<indexterm>
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<primary>bt_page_stats</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>bt_page_stats</function> returns summary information about
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a data page of a B-tree index. For example:
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<screen>
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test=# SELECT * FROM bt_page_stats('pg_cast_oid_index', 1);
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-[ RECORD 1 ]-+-----
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blkno | 1
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type | l
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live_items | 224
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dead_items | 0
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avg_item_size | 16
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page_size | 8192
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free_size | 3668
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btpo_prev | 0
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btpo_next | 0
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btpo_level | 0
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btpo_flags | 3
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</screen>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>bt_multi_page_stats(relname text, blkno bigint, blk_count bigint) returns setof record</function>
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<indexterm>
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<primary>bt_multi_page_stats</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>bt_multi_page_stats</function> returns the same information
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as <function>bt_page_stats</function>, but does so for each page of the
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range of pages beginning at <parameter>blkno</parameter> and extending
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for <parameter>blk_count</parameter> pages.
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If <parameter>blk_count</parameter> is negative, all pages
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from <parameter>blkno</parameter> to the end of the index are reported
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on. For example:
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<screen>
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test=# SELECT * FROM bt_multi_page_stats('pg_proc_oid_index', 5, 2);
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-[ RECORD 1 ]-+-----
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blkno | 5
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type | l
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live_items | 367
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dead_items | 0
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avg_item_size | 16
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page_size | 8192
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free_size | 808
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btpo_prev | 4
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btpo_next | 6
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btpo_level | 0
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btpo_flags | 1
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-[ RECORD 2 ]-+-----
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blkno | 6
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type | l
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live_items | 367
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dead_items | 0
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avg_item_size | 16
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page_size | 8192
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free_size | 808
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btpo_prev | 5
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btpo_next | 7
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btpo_level | 0
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btpo_flags | 1
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</screen>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<function>bt_page_items(relname text, blkno bigint) returns setof record</function>
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<indexterm>
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<primary>bt_page_items</primary>
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</indexterm>
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</term>
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<listitem>
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<para>
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<function>bt_page_items</function> returns detailed information about
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all of the items on a B-tree index page. For example:
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<screen>
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test=# SELECT itemoffset, ctid, itemlen, nulls, vars, data, dead, htid, tids[0:2] AS some_tids
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FROM bt_page_items('tenk2_hundred', 5);
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itemoffset | ctid | itemlen | nulls | vars | data | dead | htid | some_tids
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------------+-----------+---------+-------+------+-------------------------+------+--------+---------------------
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1 | (16,1) | 16 | f | f | 30 00 00 00 00 00 00 00 | | |
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2 | (16,8292) | 616 | f | f | 24 00 00 00 00 00 00 00 | f | (1,6) | {"(1,6)","(10,22)"}
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3 | (16,8292) | 616 | f | f | 25 00 00 00 00 00 00 00 | f | (1,18) | {"(1,18)","(4,22)"}
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4 | (16,8292) | 616 | f | f | 26 00 00 00 00 00 00 00 | f | (4,18) | {"(4,18)","(6,17)"}
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5 | (16,8292) | 616 | f | f | 27 00 00 00 00 00 00 00 | f | (1,2) | {"(1,2)","(1,19)"}
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6 | (16,8292) | 616 | f | f | 28 00 00 00 00 00 00 00 | f | (2,24) | {"(2,24)","(4,11)"}
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7 | (16,8292) | 616 | f | f | 29 00 00 00 00 00 00 00 | f | (2,17) | {"(2,17)","(11,2)"}
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8 | (16,8292) | 616 | f | f | 2a 00 00 00 00 00 00 00 | f | (0,25) | {"(0,25)","(3,20)"}
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9 | (16,8292) | 616 | f | f | 2b 00 00 00 00 00 00 00 | f | (0,10) | {"(0,10)","(0,14)"}
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10 | (16,8292) | 616 | f | f | 2c 00 00 00 00 00 00 00 | f | (1,3) | {"(1,3)","(3,9)"}
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11 | (16,8292) | 616 | f | f | 2d 00 00 00 00 00 00 00 | f | (6,28) | {"(6,28)","(11,1)"}
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12 | (16,8292) | 616 | f | f | 2e 00 00 00 00 00 00 00 | f | (0,27) | {"(0,27)","(1,13)"}
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13 | (16,8292) | 616 | f | f | 2f 00 00 00 00 00 00 00 | f | (4,17) | {"(4,17)","(4,21)"}
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(13 rows)
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</screen>
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This is a B-tree leaf page. All tuples that point to the table
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happen to be posting list tuples (all of which store a total of
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100 6 byte TIDs). There is also a <quote>high key</quote> tuple
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at <literal>itemoffset</literal> number 1.
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<structfield>ctid</structfield> is used to store encoded
|
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information about each tuple in this example, though leaf page
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tuples often store a heap TID directly in the
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<structfield>ctid</structfield> field instead.
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<structfield>tids</structfield> is the list of TIDs stored as a
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posting list.
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</para>
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<para>
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In an internal page (not shown), the block number part of
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<structfield>ctid</structfield> is a <quote>downlink</quote>,
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which is a block number of another page in the index itself.
|
|
The offset part (the second number) of
|
|
<structfield>ctid</structfield> stores encoded information about
|
|
the tuple, such as the number of columns present (suffix
|
|
truncation may have removed unneeded suffix columns). Truncated
|
|
columns are treated as having the value <quote>minus
|
|
infinity</quote>.
|
|
</para>
|
|
<para>
|
|
<structfield>htid</structfield> shows a heap TID for the tuple,
|
|
regardless of the underlying tuple representation. This value
|
|
may match <structfield>ctid</structfield>, or may be decoded
|
|
from the alternative representations used by posting list tuples
|
|
and tuples from internal pages. Tuples in internal pages
|
|
usually have the implementation level heap TID column truncated
|
|
away, which is represented as a NULL
|
|
<structfield>htid</structfield> value.
|
|
</para>
|
|
<para>
|
|
Note that the first item on any non-rightmost page (any page with
|
|
a non-zero value in the <structfield>btpo_next</structfield> field) is the
|
|
page's <quote>high key</quote>, meaning its <structfield>data</structfield>
|
|
serves as an upper bound on all items appearing on the page, while
|
|
its <structfield>ctid</structfield> field does not point to
|
|
another block. Also, on internal pages, the first real data
|
|
item (the first item that is not a high key) reliably has every
|
|
column truncated away, leaving no actual value in its
|
|
<structfield>data</structfield> field. Such an item does have a
|
|
valid downlink in its <structfield>ctid</structfield> field,
|
|
however.
|
|
</para>
|
|
<para>
|
|
For more details about the structure of B-tree indexes, see
|
|
<xref linkend="btree-structure"/>. For more details about
|
|
deduplication and posting lists, see <xref
|
|
linkend="btree-deduplication"/>.
|
|
</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</type> 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 itemoffset, ctid, itemlen, nulls, vars, data, dead, htid, tids[0:2] AS some_tids
|
|
FROM bt_page_items(get_raw_page('tenk2_hundred', 5));
|
|
itemoffset | ctid | itemlen | nulls | vars | data | dead | htid | some_tids
|
|
------------+-----------+---------+-------+------+-------------------------+------+--------+---------------------
|
|
1 | (16,1) | 16 | f | f | 30 00 00 00 00 00 00 00 | | |
|
|
2 | (16,8292) | 616 | f | f | 24 00 00 00 00 00 00 00 | f | (1,6) | {"(1,6)","(10,22)"}
|
|
3 | (16,8292) | 616 | f | f | 25 00 00 00 00 00 00 00 | f | (1,18) | {"(1,18)","(4,22)"}
|
|
4 | (16,8292) | 616 | f | f | 26 00 00 00 00 00 00 00 | f | (4,18) | {"(4,18)","(6,17)"}
|
|
5 | (16,8292) | 616 | f | f | 27 00 00 00 00 00 00 00 | f | (1,2) | {"(1,2)","(1,19)"}
|
|
6 | (16,8292) | 616 | f | f | 28 00 00 00 00 00 00 00 | f | (2,24) | {"(2,24)","(4,11)"}
|
|
7 | (16,8292) | 616 | f | f | 29 00 00 00 00 00 00 00 | f | (2,17) | {"(2,17)","(11,2)"}
|
|
8 | (16,8292) | 616 | f | f | 2a 00 00 00 00 00 00 00 | f | (0,25) | {"(0,25)","(3,20)"}
|
|
9 | (16,8292) | 616 | f | f | 2b 00 00 00 00 00 00 00 | f | (0,10) | {"(0,10)","(0,14)"}
|
|
10 | (16,8292) | 616 | f | f | 2c 00 00 00 00 00 00 00 | f | (1,3) | {"(1,3)","(3,9)"}
|
|
11 | (16,8292) | 616 | f | f | 2d 00 00 00 00 00 00 00 | f | (6,28) | {"(6,28)","(11,1)"}
|
|
12 | (16,8292) | 616 | f | f | 2e 00 00 00 00 00 00 00 | f | (0,27) | {"(0,27)","(1,13)"}
|
|
13 | (16,8292) | 616 | f | f | 2f 00 00 00 00 00 00 00 | f | (4,17) | {"(4,17)","(4,21)"}
|
|
(13 rows)
|
|
</screen>
|
|
All the other details are the same as explained in the previous item.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2 id="pageinspect-brin-funcs">
|
|
<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 | empty | value
|
|
------------+--------+--------+----------+----------+-------------+-------+--------------
|
|
137 | 0 | 1 | t | f | f | f |
|
|
137 | 0 | 2 | f | f | f | f | {1 .. 88}
|
|
138 | 4 | 1 | t | f | f | f |
|
|
138 | 4 | 2 | f | f | f | f | {89 .. 176}
|
|
139 | 8 | 1 | t | f | f | f |
|
|
139 | 8 | 2 | f | f | f | f | {177 .. 264}
|
|
</screen>
|
|
The returned columns correspond to the fields in the
|
|
<structname>BrinMemTuple</structname> and <structname>BrinValues</structname> structs.
|
|
See <filename>src/include/access/brin_tuple.h</filename> for details.
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2 id="pageinspect-gin-funcs">
|
|
<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 id="pageinspect-gist-funcs">
|
|
<title>GiST Functions</title>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>
|
|
<function>gist_page_opaque_info(page bytea) returns record</function>
|
|
<indexterm>
|
|
<primary>gist_page_opaque_info</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>gist_page_opaque_info</function> returns information from
|
|
a <acronym>GiST</acronym> index page's opaque area, such as the NSN,
|
|
rightlink and page type.
|
|
For example:
|
|
<screen>
|
|
test=# SELECT * FROM gist_page_opaque_info(get_raw_page('test_gist_idx', 2));
|
|
lsn | nsn | rightlink | flags
|
|
-----+-----+-----------+--------
|
|
0/1 | 0/0 | 1 | {leaf}
|
|
(1 row)
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>gist_page_items(page bytea, index_oid regclass) returns setof record</function>
|
|
<indexterm>
|
|
<primary>gist_page_items</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
<function>gist_page_items</function> returns information about
|
|
the data stored in a page of a <acronym>GiST</acronym> index. For example:
|
|
<screen>
|
|
test=# SELECT * FROM gist_page_items(get_raw_page('test_gist_idx', 0), 'test_gist_idx');
|
|
itemoffset | ctid | itemlen | dead | keys
|
|
------------+-----------+---------+------+-------------------------------
|
|
1 | (1,65535) | 40 | f | (p)=("(185,185),(1,1)")
|
|
2 | (2,65535) | 40 | f | (p)=("(370,370),(186,186)")
|
|
3 | (3,65535) | 40 | f | (p)=("(555,555),(371,371)")
|
|
4 | (4,65535) | 40 | f | (p)=("(740,740),(556,556)")
|
|
5 | (5,65535) | 40 | f | (p)=("(870,870),(741,741)")
|
|
6 | (6,65535) | 40 | f | (p)=("(1000,1000),(871,871)")
|
|
(6 rows)
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>
|
|
<function>gist_page_items_bytea(page bytea) returns setof record</function>
|
|
<indexterm>
|
|
<primary>gist_page_items_bytea</primary>
|
|
</indexterm>
|
|
</term>
|
|
|
|
<listitem>
|
|
<para>
|
|
Same as <function>gist_page_items</function>, but returns the key data
|
|
as a raw <type>bytea</type> blob. Since it does not attempt to decode
|
|
the key, it does not need to know which index is involved. For
|
|
example:
|
|
<screen>
|
|
test=# SELECT * FROM gist_page_items_bytea(get_raw_page('test_gist_idx', 0));
|
|
itemoffset | ctid | itemlen | dead | key_data
|
|
------------+-----------+---------+------+-----------------------------------------&zwsp;-------------------------------------------
|
|
1 | (1,65535) | 40 | f | \x00000100ffff28000000000000c0644000000000&zwsp;00c06440000000000000f03f000000000000f03f
|
|
2 | (2,65535) | 40 | f | \x00000200ffff28000000000000c0744000000000&zwsp;00c074400000000000e064400000000000e06440
|
|
3 | (3,65535) | 40 | f | \x00000300ffff28000000000000207f4000000000&zwsp;00207f400000000000d074400000000000d07440
|
|
4 | (4,65535) | 40 | f | \x00000400ffff28000000000000c0844000000000&zwsp;00c084400000000000307f400000000000307f40
|
|
5 | (5,65535) | 40 | f | \x00000500ffff28000000000000f0894000000000&zwsp;00f089400000000000c884400000000000c88440
|
|
6 | (6,65535) | 40 | f | \x00000600ffff28000000000000208f4000000000&zwsp;00208f400000000000f889400000000000f88940
|
|
7 | (7,65535) | 40 | f | \x00000700ffff28000000000000408f4000000000&zwsp;00408f400000000000288f400000000000288f40
|
|
(7 rows)
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
<sect2 id="pageinspect-hash-funcs">
|
|
<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 bigint) 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 the 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 ]-------------------------------------------------&zwsp;------------------------------
|
|
magic | 105121344
|
|
version | 4
|
|
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,&zwsp;508,567,628,704,1193,1202,1204}
|
|
mapp | {65}
|
|
</screen>
|
|
</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
</sect2>
|
|
|
|
</sect1>
|