From: | Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> |
---|---|
To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
Cc: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: PATCH: pageinspect / add page_checksum and bt_page_items(bytea) |
Date: | 2017-03-14 04:34:39 |
Message-ID: | CAE9k0PkvB4tAR6iFvF3CWtY0yHURxqD_n+7OicFW_4F7V8TYug@mail.gmail.com |
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Lists: | pgsql-hackers |
Hi,
>
>> 2) It seems like you have choosen wrong datatype for page_checksum. I
>> am getting negative checksum value when trying to run below query. I
>> think the return type for the SQL function page_checksum should be
>> 'integer' instead of 'smallint'.
>>
>> postgres=# SELECT page_checksum(get_raw_page('pg_class', 0), 100);
>> page_checksum
>> ---------------
>> -19532
>> (1 row)
>>
>> Above problem also exist in case of page_header. I am facing similar
>> problem with page_header as well.
>>
>> postgres=# SELECT page_header(get_raw_page('pg_class', 0));
>> page_header
>> ---------------------------------------------
>> (0/2891538,-28949,1,220,7216,8192,8192,4,0)
>> (1 row)
>>
>
> No. This is consistent with page_header() which is also using smallint for
> the checksum value.
>
Yes. But, as i said earlier I am getting negative checksum value for
page_header as well. Isn't that wrong. For eg. When I debug the
following query, i could pd_checksum value as '40074' in gdb where
page_header shows it as '-25462'.
SELECT page_header(get_raw_page('pg_class', 0));
(gdb) p page->pd_checksum
$2 = 40074
postgres=# SELECT page_header(get_raw_page('pg_class', 0));
page_header
---------------------------------------------
(0/304EDE0,-25462,1,220,7432,8192,8192,4,0)
(1 row)
I think pd_checksum in PageHeaderData is defined as uint16 (0 to
65,535) whereas in SQL function for page_header it is defined as
smallint (-32768 to +32767).
--
With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com
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