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Re: json api WIP patch

From: james <james(at)mansionfamily(dot)plus(dot)com>
To: Andrew Dunstan <andrew(at)dunslane(dot)net>
Cc: Merlin Moncure <mmoncure(at)gmail(dot)com>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: json api WIP patch
Date: 2013-01-08 21:31:23
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Lists: pgsql-hackers
> You can use COPY from a stored procedure, but only to and from files.

I think that's in the chocolate fireguard realm though as far as 
efficiency for this sort of scenario goes, even if its handled by 
retaining an mmap'd file as workspace.

>> If SPI provided a way to perform a copy to a temp table and then some callback on an iterator that yields rows to it, that would do the trick I guess.
> SPI is useful, but it's certainly possible to avoid its use. After all, that what almost the whole backend does, including the COPY code. Of course, it's a lot harder to write that way, which is part of why SPI exists. Efficiency has its price.

So it is possible to use a lower level interface from a C stored proc? 
SPI is the (only) documented direct function extension API isn't it?

Is the issue with using the JSON data-to-record set that the parsing can 
be costly?  Perhaps it can be achieved with B64 of compressed protobuf, 
or such.  I don't mind if it seems a bit messy - the code can be 
generated from the table easily enough, especially if I can use C++.  I 
guess an allocator that uses SPI_palloc would solve issues with memory 
management on error?

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