Solved

How can i gather Histogram stats on a column?

Posted on 2011-09-07
4
338 Views
Last Modified: 2012-05-12
I have a "select' statment with a column in where clause and that column has indexed.
But in explain plan it is not using that index may be because of uneven distribution of values.
So i want to update histogram stats on that column only.

How can i update Histogram stats on that column?
0
Comment
Question by:ajaybelde
  • 2
4 Comments
 
LVL 76

Expert Comment

by:slightwv (䄆 Netminder)
ID: 36495819
I've not read of anyway to gather stats for a single column only.

I suggest regenerating stats on the specific index with dbms_stats.gather_index_stats

http://download.oracle.com/docs/cd/E11882_01/appdev.112/e16760/d_stats.htm#i1036276
0
 

Author Comment

by:ajaybelde
ID: 36495860
BEGIN
  DBMS_STATS.GATHER_table_STATS (OWNNAME => 'OE', TABNAME => 'INVENTORIES',
  METHOD_OPT => 'FOR COLUMNS SIZE 20 warehouse_id');
END;
/

Can i Use this for histograms stats on warehouse_id column?

I found that in fallowing link
http://download.oracle.com/docs/cd/B19306_01/server.102/b14211/stats.htm
0
 
LVL 76

Expert Comment

by:slightwv (䄆 Netminder)
ID: 36495896
>>Can i Use this for histograms stats on warehouse_id column?

Based on how I read it, it looks like you can actually generate stats on a specific column after all?

But will those stats be applied over to the index in question?  You will likely need to regenerate stats on the index anyway.

I would look at the last_analyzed columns for the column and index to see how stale they are.

for the column: user_tab_columns
for the index: user_indexes
0
 
LVL 15

Accepted Solution

by:
Devinder Singh Virdi earned 500 total points
ID: 36503212
Just curious about:-
>> But in explain plan it is not using that index may be because of uneven distribution of values.

1. It is possible that runtime explain plan may or may not equal to show plan.
2. Execution plan of production may or may not equal to Development env.
3. If table is partitioned and somehow stats are not updated on partitions, then you can see this problem, where query working fine with certain values. (I had that problem earlier and need Oracle help to understand the scenario).
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Queries 15 45
sort a spool into file output in oracle 1 44
Extract Currency data from a string and put them in a new field 3 42
Help with Oracle IF statment 5 23
How to Unravel a Tricky Query Introduction If you browse through the Oracle zones or any of the other database-related zones you'll come across some complicated solutions and sometimes you'll just have to wonder how anyone came up with them.  …
Using SQL Scripts we can save all the SQL queries as files that we use very frequently on our database later point of time. This is one of the feature present under SQL Workshop in Oracle Application Express.
Via a live example show how to connect to RMAN, make basic configuration settings changes and then take a backup of a demo database
This video shows how to Export data from an Oracle database using the Datapump Export Utility.  The corresponding Datapump Import utility is also discussed and demonstrated.

809 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question