pgstattuple: Add pgstathashindex.

Since pgstattuple v1.5 hasn't been released yet, no need for a new
extension version.  The new function exposes statistics about hash
indexes similar to what other pgstatindex functions return for other
index types.

Ashutosh Sharma, reviewed by Kuntal Ghosh.  Substantial further
revisions by me.

1 files changed, 95 insertions, 0 deletions

diff --git a/doc/src/sgml/pgstattuple.sgml b/doc/src/sgml/pgstattuple.sgml
index d2fa524d6ec..62b1a6f4794 100644
--- a/doc/src/sgml/pgstattuple.sgml
+++ b/doc/src/sgml/pgstattuple.sgml
@@ -355,6 +355,101 @@ pending_tuples | 0
    <varlistentry>
     <term>
      <indexterm>
+      <primary>pgstathashindex</primary>
+     </indexterm>
+     <function>pgstathashindex(regclass) returns record</>
+    </term>
+
+    <listitem>
+     <para>
+      <function>pgstathashindex</function> returns a record showing information
+      about a HASH index.  For example:
+<programlisting>
+test=&gt; select * from pgstathashindex('con_hash_index');
+-[ RECORD 1 ]--+-----------------
+version        | 2
+bucket_pages   | 33081
+overflow_pages | 0
+bitmap_pages   | 1
+zero_pages     | 32455
+live_items     | 10204006
+dead_items     | 0
+free_percent   | 61.8005949100872
+</programlisting>
+     </para>
+
+    <para>
+     The output columns are:
+
+    <informaltable>
+     <tgroup cols="3">
+      <thead>
+       <row>
+        <entry>Column</entry>
+        <entry>Type</entry>
+        <entry>Description</entry>
+       </row>
+      </thead>
+
+      <tbody>
+       <row>
+        <entry><structfield>version</structfield></entry>
+        <entry><type>integer</type></entry>
+        <entry>HASH version number</entry>
+       </row>
+
+       <row>
+        <entry><structfield>bucket_pages</structfield></entry>
+        <entry><type>bigint</type></entry>
+        <entry>Number of bucket pages</entry>
+       </row>
+
+       <row>
+        <entry><structfield>overflow_pages</structfield></entry>
+        <entry><type>bigint</type></entry>
+        <entry>Number of overflow pages</entry>
+       </row>
+
+       <row>
+        <entry><structfield>bitmap_pages</structfield></entry>
+        <entry><type>bigint</type></entry>
+        <entry>Number of bitmap pages</entry>
+       </row>
+
+       <row>
+        <entry><structfield>zero_pages</structfield></entry>
+        <entry><type>bigint</type></entry>
+        <entry>Number of new or zero pages</entry>
+       </row>
+
+       <row>
+        <entry><structfield>live_items</structfield></entry>
+        <entry><type>bigint</type></entry>
+        <entry>Number of live tuples</entry>
+       </row>
+
+       <row>
+        <entry><structfield>dead_tuples</structfield></entry>
+        <entry><type>bigint</type></entry>
+        <entry>Number of dead tuples</entry>
+       </row>
+
+       <row>
+        <entry><structfield>free_percent</structfield></entry>
+        <entry><type>float</type></entry>
+        <entry>Percentage of free space</entry>
+       </row>
+
+      </tbody>
+     </tgroup>
+    </informaltable>
+    </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term>
+     <indexterm>
       <primary>pg_relpages</primary>
      </indexterm>
      <function>pg_relpages(regclass) returns bigint</>