From: Andrew Chernow <ac@esilo.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Merlin Moncure <mmoncure@gmail.com>
Cc: Andrew Dunstan <andrew@dunslane.net>
Cc: Alvaro Herrera <alvherre@commandprompt.com>
Cc: Patches (PostgreSQL) <pgsql-patches@postgresql.org>
Subject: Re: libpq object hooks
Date: Fri, 16 May 2008 20:00:07 -0400
Message-ID: <482E2007.6050502@esilo.com> (raw)
In-Reply-To: <20531.1210969396@sss.pgh.pa.us>
References: <b42b73150804301323i18b00019i62e765708abb65aa@mail.gmail.com>
<6044.1210867771@sss.pgh.pa.us>
<482C77E5.1060500@esilo.com>
<9458.1210875556@sss.pgh.pa.us>
<482C82BA.3090100@esilo.com>
<9867.1210877054@sss.pgh.pa.us>
<482CD76E.6000202@esilo.com>
<b42b73150805160628y3c175608hc383187951206448@mail.gmail.com>
<17177.1210949948@sss.pgh.pa.us>
<482DD3AC.9020207@esilo.com>
<b42b73150805161249wb67b065le957ef1c0cdaefec@mail.gmail.com>
<20531.1210969396@sss.pgh.pa.us>
Tom Lane wrote:
> Where
> exactly does the hook hand off the storage pointer to libpq? What
> are you going to do if the hook fails to create the storage
> (ie, out of memory during PGresult creation)?
The current submitted patch has 3 of its function callbacks returning a
void*, initHookData after the creation of a conn, resultCreate, and
resultCopy. We have recently changed this design so all hooks, now
called events, go through a single callback ... PGEventProc. The old
function callbacks are just eventIds now.
/////////////////////////////////
// The libpq side (looping registered event procs)
PGEventResultCreate info;
info.stateData = NULL; /* our event data ptr */
info.conn = conn;
info.result = result;
if(!result->evtState[i].proc(PGEVT_RESULTCREATE,
(void *)&info, result->evtState[i].passThrough)
{
PQclear(result); // destroy result? ... not sure
return error; // previously, we ignored it
}
// assign event data created by event proc.
result->evtState[i].data = info.stateData;
///////////////////////////////////////
// example of what the event proc does
int my_evtproc(PGEventId evtId, void *evtInfo, void *passThrough)
{
switch(eventId)
{
case PGEVT_RESULTCREATE:
{
void *data = makeresultdata(....)
if(!data)
return FALSE;
((PGEventResultCreate *)evtInfo)->stateData = data;
break;
}
}
return TRUE;
}
--
Andrew Chernow
eSilo, LLC
every bit counts
http://www.esilo.com/
--
Andrew Chernow
eSilo, LLC
every bit counts
http://www.esilo.com/
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To: pgsql-patches@postgresql.org
Cc: ac@esilo.com, tgl@sss.pgh.pa.us, mmoncure@gmail.com, andrew@dunslane.net, alvherre@commandprompt.com
Subject: Re: libpq object hooks
In-Reply-To: <482E2007.6050502@esilo.com>
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