From: | Paul <Paul(at)abelian(dot)netcom(dot)co(dot)uk> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Trigger function, C, lookup of attribute type |
Date: | 2015-12-15 10:42:14 |
Message-ID: | 566FEE86.9020202@abelian.netcom.co.uk |
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Thread: | |
Lists: | pgsql-general |
I'm writing a trigger procedure in C to catch updates to a
table and write them to a log file.
The function must walk along trigdata->tg_trigtuple
pulling out the attributes, comparing them with those in
trigdata->tg_newtuple and writing the diffs to a flat ASCII
file.
I've got a loop over the attributes, and I can get the values
if I know the type, eg
Datum d = heap_getattr( trigdata->tg_trigtuple, ...
int32_t val = DatumGetInt32( d);
but I'm struggling to find how the function can determine the
attribute types. I'm only using the built-in scalar types.
Do I have to query the system catalogs? Or maybe there's a
function that works from a TupleDesc?
--
Paul Nicholson
--
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