| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Andy Fan <zhihui(dot)fan1213(at)gmail(dot)com> |
| Cc: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: How to generate a WAL record spanning multiple WAL files? |
| Date: | 2022-04-05 16:40:52 |
| Message-ID: | CA+TgmoY0PMy-h4SSr3LU=YhbeD05VY+x=f=KeQtt-Sa0A5ZATA@mail.gmail.com |
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On Tue, Apr 5, 2022 at 10:10 AM Andy Fan <zhihui(dot)fan1213(at)gmail(dot)com> wrote:
>> > I wanted to have a WAL record spanning multiple WAL files of size, say
>> > 16MB. I'm wondering if the Full Page Images (FPIs) of a TOAST table
>> > would help here. Please let me know if there's any way to generate
>> > such large WAL records.
>>
>> It's easier to use pg_logical_emit_message().
>
> Not sure I understand the question correctly here. What if I use the below code
> where the len might be very large? like 64MB.
>
> XLogBeginInsert();
> XLogRegisterData((char *)&xl_append, sizeof(xl_cstore_append));
> XLogRegisterData((char *)data, len);
>
> XLogInsert(..);
Well, that's how to do it from C. And pg_logical_emit_message() is how
to do it from SQL.
--
Robert Haas
EDB: http://www.enterprisedb.com
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