How to know detailed information about HOT(Heap-Only Tuples)?

On Thu, Aug 22, 2013 at 4:20 AM, 高健 <luckyjackgao@gmail.com> wrote:

according to a table, How many tuples are heap only tuples , and how many
are not?

I believe there are not "hot tuples", a tuple is updated using HOT
depending on the indexes defined and the type of update itself.
Anyway, you can get an information of how many tuples have been
hot-touched via pg_stat_user_tables.n_tup_hot_upd

And also , Is there any options which can influence HOT occurrance?

The storage setting (fillfactor) will change the hotness of your
tables, but of course this depends on the workload.

Luca

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On 08/21/2013 07:20 PM, 高健 wrote:

Hi:

I have heard that Heap-Only Tuples is introduce from 8.3.
And I am searching information for it.

How can I get a detailed information of HOT?

http://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/access/heap/README.HOT;hb=HEAD

For example:
according to a table, How many tuples are heap only tuples , and how
many are not?

And also , Is there any options which can influence HOT occurrance?

Best Regards

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Adrian Klaver
adrian.klaver@gmail.com

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Hi:

Thank you all for kindly replying.

I think that I need this: pg_stat_user_tables.n_tup_hot_upd

And Adrian's information is a pretty good material for me to understand
the internal.

Best regards

2013/8/22 Adrian Klaver <adrian.klaver@gmail.com>