Re: [HACKERS] Add pgstathashindex() to get hash index table statistics.

On Wed, Dec 21, 2016 at 7:22 PM, Ashutosh Sharma <ashu.coek88@gmail.com> wrote:
> Hi All,
>
> I have introduced a new function 'pgstathashindex()' inside pgstatuple
> extension to view the statistics related to hash index table.
>
I think this feature is going to be helpful. I've some initial review
for the patch.
I've not applied the patch yet.

+        buf = ReadBufferExtended(rel, MAIN_FORKNUM, blkno, RBM_NORMAL, NULL);
Use ReadBuffer() instead.

+    /*
+     * Let us ignore metapage and bitmap page when calculating
+     * free space percentage for tuples in a table.
+     */
+    table_len = (stats.total_pages - 2) * BLCKSZ;
+
+    free_percent = 100.0 * stats.free_space / table_len;
I think the calculation for max available spcae is wrong here. You
should subtract the page header and special area from the total page size.
A check for non-zero denominator should be added while calculating the
percentage.
There can be multiple bitmap pages. Right?

+    values[10] = Float8GetDatum(free_percent);
Some precision should be added.

+       <row>
+        <entry><structfield>ffactor</structfield></entry>
+        <entry><type>integer</type></entry>
+        <entry>Average number of tuples per bucket</entry>
+       </row>
I feel that either the column name should be changed or it should
just output how full the index method is in percentage.

+   </varlistentry>
+
+
+   <varlistentry>
Please remove extra spaces.

And, please add some test cases for regression tests.

-- 
Thanks & Regards,
Kuntal Ghosh
EnterpriseDB: http://www.enterprisedb.com