Re: Streaming replication and non-blocking I/O

On Mon, Dec 14, 2009 at 11:38 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Do we need a new "PQgetXLogData" function at all?  Seems like you could
> shove the data through the COPY protocol and not have to touch libpq
> at all, rather than duplicating a nontrivial amount of code there.

Yeah, I also think that all data (the WAL data itself, its LSN and
the flag bits) which the "PQgetXLogData" handles could be shoved
through the COPY protocol. But, outside libpq, it's somewhat messy
to extract the LSN and the flag bits from the data buffer which
"PQgetCopyData" returns, by using ntohs(). So I provided the new
libpq function only for replication. That is, I didn't want to expose
the low layer of network which libpq should handle.

I think that the friendly function would be useful to implement
the standby program (e.g., a stand-alone walreceiver tool) outside
the core.

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center