pageinspect: Support hash indexes.

Patch by Jesper Pedersen and Ashutosh Sharma, with some error handling
improvements by me.  Tests from Peter Eisentraut.  Reviewed by Álvaro
Herrera, Michael Paquier, Jesper Pedersen, Jeff Janes, Peter
Eisentraut, Amit Kapila, Mithun Cy, and me.

Discussion: http://postgr.es/m/e2ac6c58-b93f-9dd9-f4e6-d6d30add7fdf@redhat.com

1 files changed, 144 insertions, 0 deletions

diff --git a/doc/src/sgml/pageinspect.sgml b/doc/src/sgml/pageinspect.sgml
index d12dbac32db..4c201e75b0d 100644
--- a/doc/src/sgml/pageinspect.sgml
+++ b/doc/src/sgml/pageinspect.sgml
@@ -493,4 +493,148 @@ test=# SELECT first_tid, nbytes, tids[0:5] AS some_tids
   </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 | 4294967295
+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 * FROM hash_metapage_info(get_raw_page('con_hash_index', 0));
+-[ RECORD 1 ]-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+magic     | 105121344
+version   | 2
+ntuples   | 500500
+ffactor   | 40
+bsize     | 8152
+bmsize    | 4096
+bmshift   | 15
+maxbucket | 12512
+highmask  | 16383
+lowmask   | 8191
+ovflpoint | 14
+firstfree | 1204
+nmaps     | 1
+procid    | 450
+spares    | {0,0,0,0,0,0,1,1,1,1,1,4,59,704,1204,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
+mapp      | {65,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
+</screen>
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+ </sect2>
+
 </sect1>