| From: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
|---|---|
| To: | "jacktby(at)gmail(dot)com" <jacktby(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Why the lp_len is 28 not 32? |
| Date: | 2023-02-26 15:07:21 |
| Message-ID: | fe359f0a-525e-0064-884f-0d09bc7047b6@enterprisedb.com |
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| Lists: | pgsql-hackers |
On 2/26/23 15:35, jacktby(at)gmail(dot)com wrote:
> use these sqls below:
> create table t(a int);
> insert into t values(1);
> select lp,lp_off,lp_len,t_data from heap_page_items(get_raw_page('t',0));
> lp | lp_off | lp_len | t_data
> ----+--------+--------+------------
> 1 | 8160 | 28 | \x01000000
> --------------------------------------------------------------------------------
Pretty sure this is because we align the data to MAXALIGN, and on x86_64
that's 8 bytes. 28 is not a multiple of 8 while 32 is.
regards
--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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