Re: A bad behavior under autocommit off mode

Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Tom, did you have any thought of adding the ability to ask for reports
> > on GUC variables on every query return?
> 
> That seems excessive.  There is a case for reporting autocommit (if
> we don't decide to remove it altogether, which is still an open
> argument).  I have not heard any complaints suggesting that we need any
> others.

Well, the jdbc guys like SET, and I haven't seen any proposal that
explains how applications would control a client-based autocommit API
from the client.

> A fixed commitment to report xact status will cost us one byte added to
> Z messages.  If we add a commitment to report autocommit status, we
> could choose to pack that bit into the same byte as xact status (still
> only three bits used...).  A slightly more forward-looking approach
> would be to decree that Z messages carry labeled status bytes, ie, pairs
> of <label> <status> bytes, which makes total cost 4 bytes to transmit
> xact state and autocommit state.  But if we want to say that we'll
> transmit *any* darn random GUC variable you want to hear about, I don't
> think we can use a compact encoding of this sort; instead we're talking
> about sending the whole GUC variable name and string value as label and
> value.  In other words the Z message starts to look like
>     Z X a c t s t a t u s \0 i d l e \0 a u t o c o m m i t \0 o f f \0
> and somewhere around here my concern for connection bandwidth kicks in.
> A 10X increase in bytes sent is a bit much to cater to hypothetical
> needs.

Very true.  The only other environment variable I have heard about was
client encoding.  As I remember right now, we do have a problem with SET
changing the client encoding, and the client not realizing that.

My idea may be overdesign.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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