On Wed, Apr 6, 2022 at 6:56 AM Andy Fan <zhihui.fan1...@gmail.com> wrote: > > On Wed, Apr 6, 2022 at 12:41 AM Robert Haas <robertmh...@gmail.com> wrote: >> >> On Tue, Apr 5, 2022 at 10:10 AM Andy Fan <zhihui.fan1...@gmail.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. >> > > OK, Thanks for your confirmation!
Thanks all for your responses. Yes, using pg_logical_emit_message() is easy, but it might come in the way of logical decoding as those messages get decoded. PS: I wrote a small extension (just for fun) called pg_synthesize_wal [1] implementing functions to generate huge WAL records. I used the "Custom WAL Resource Managers" feature [2] that got committed to PG15. [1] https://github.com/BRupireddy/pg_synthesize_wal [2] https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=5c279a6d350205cc98f91fb8e1d3e4442a6b25d1 Regards, Bharath Rupireddy.
