/*
* suppress_redundant_updates_trigger
*
* This trigger function will inhibit an update from being done
* if the OLD and NEW records are identical.
*/
Datum
suppress_redundant_updates_trigger(PG_FUNCTION_ARGS)
{
TriggerData *trigdata = (TriggerData *) fcinfo->context;
HeapTuple newtuple,
oldtuple,
rettuple;
HeapTupleHeader newheader,
oldheader;
/* make sure it's called as a trigger */
if (!CALLED_AS_TRIGGER(fcinfo))
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("suppress_redundant_updates_trigger: must be called as trigger")));
/* and that it's called on update */
if (!TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("suppress_redundant_updates_trigger: must be called on update")));
/* and that it's called before update */
if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("suppress_redundant_updates_trigger: must be called before update")));
/* and that it's called for each row */
if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("suppress_redundant_updates_trigger: must be called for each row")));
/* get tuple data, set default result */
rettuple = newtuple = trigdata->tg_newtuple;
oldtuple = trigdata->tg_trigtuple;
newheader = newtuple->t_data;
oldheader = oldtuple->t_data;
/*
* We are called before the OID, if any, has been transcribed from the old
* tuple to the new (in heap_update). To avoid a bogus compare failure,
* copy the OID now. But check that someone didn't already put another
* OID value into newtuple. (That's not actually possible at present, but
* maybe someday.)
*/
if (trigdata->tg_relation->rd_rel->relhasoids &&
!OidIsValid(HeapTupleHeaderGetOid(newheader)))
HeapTupleHeaderSetOid(newheader, HeapTupleHeaderGetOid(oldheader));
/* if the tuple payload is the same ... */
if (newtuple->t_len == oldtuple->t_len &&
newheader->t_hoff == oldheader->t_hoff &&
(HeapTupleHeaderGetNatts(newheader) ==
HeapTupleHeaderGetNatts(oldheader)) &&
((newheader->t_infomask & ~HEAP_XACT_MASK) ==
(oldheader->t_infomask & ~HEAP_XACT_MASK)) &&
memcmp(((char *) newheader) + offsetof(HeapTupleHeaderData, t_bits),
((char *) oldheader) + offsetof(HeapTupleHeaderData, t_bits),
newtuple->t_len - offsetof(HeapTupleHeaderData, t_bits)) == 0)
{
/* ... then suppress the update */
rettuple = NULL;
}
return PointerGetDatum(rettuple);
}
/*
* heap_form_tuple
* construct a tuple from the given values[] and isnull[] arrays,
* which are of the length indicated by tupleDescriptor->natts
*
* The result is allocated in the current memory context.
*/
HeapTuple
heaptuple_form_to(TupleDesc tupleDescriptor, Datum *values, bool *isnull, HeapTuple dst, uint32 *dstlen)
{
HeapTuple tuple; /* return tuple */
HeapTupleHeader td; /* tuple data */
unsigned long len, predicted_len, actual_len;
int hoff;
bool hasnull = false;
Form_pg_attribute *att = tupleDescriptor->attrs;
int numberOfAttributes = tupleDescriptor->natts;
int i;
if (numberOfAttributes > MaxTupleAttributeNumber)
ereport(ERROR,
(errcode(ERRCODE_TOO_MANY_COLUMNS),
errmsg("number of columns (%d) exceeds limit (%d)",
numberOfAttributes, MaxTupleAttributeNumber)));
/*
* Check for nulls and embedded tuples; expand any toasted attributes in
* embedded tuples. This preserves the invariant that toasting can only
* go one level deep.
*
* We can skip calling toast_flatten_tuple_attribute() if the attribute
* couldn't possibly be of composite type. All composite datums are
* varlena and have alignment 'd'; furthermore they aren't arrays. Also,
* if an attribute is already toasted, it must have been sent to disk
* already and so cannot contain toasted attributes.
*/
for (i = 0; i < numberOfAttributes; i++)
{
if (isnull[i])
hasnull = true;
else if (att[i]->attlen == -1 &&
att[i]->attalign == 'd' &&
att[i]->attndims == 0 &&
!VARATT_IS_EXTENDED_D(values[i]))
{
values[i] = toast_flatten_tuple_attribute(values[i],
att[i]->atttypid,
att[i]->atttypmod);
}
}
/*
* Determine total space needed
*/
len = offsetof(HeapTupleHeaderData, t_bits);
if (hasnull)
len += BITMAPLEN(numberOfAttributes);
if (tupleDescriptor->tdhasoid)
len += sizeof(Oid);
hoff = len = MAXALIGN(len); /* align user data safely */
predicted_len = heap_compute_data_size(tupleDescriptor, values, isnull);
len += predicted_len;
if(dstlen && (*dstlen) < (HEAPTUPLESIZE + len))
{
*dstlen = HEAPTUPLESIZE + len;
return NULL;
}
if(dstlen)
{
*dstlen = HEAPTUPLESIZE + len;
tuple = dst;
}
else
tuple = (HeapTuple) palloc(HEAPTUPLESIZE + len);
/*
* Allocate and zero the space needed. Note that the tuple body and
* HeapTupleData management structure are allocated in one chunk.
*/
tuple->t_data = td = (HeapTupleHeader) ((char *) tuple + HEAPTUPLESIZE);
/*
* And fill in the information. Note we fill the Datum fields even though
* this tuple may never become a Datum.
*/
tuple->t_len = len;
ItemPointerSetInvalid(&(tuple->t_self));
/*
* The following 3 calls will setup the first 12 bytes of td (tuple->t_data)
*/
HeapTupleHeaderSetDatumLength(td, len);
HeapTupleHeaderSetTypeId(td, tupleDescriptor->tdtypeid);
HeapTupleHeaderSetTypMod(td, tupleDescriptor->tdtypmod);
/* t_ctid does not matter */
/* num of attrs are stored in t_infomask2. Clear the other flags first */
td->t_infomask2 = 0;
HeapTupleHeaderSetNatts(td, numberOfAttributes);
/*
* Set up t_hoff. This need to be done before set up t_infomask
* because HeapTupleHeaderSetOid will use t_hoff
*/
td->t_hoff = hoff;
if (tupleDescriptor->tdhasoid)
{
td->t_infomask = HEAP_HASOID;
HeapTupleHeaderSetOid(td, InvalidOid);
}
else
td->t_infomask = 0;
/* Really fill in the data. */
actual_len =
heap_fill_tuple(tupleDescriptor,
values,
isnull,
(char *) td + hoff,
&td->t_infomask,
(hasnull ? td->t_bits : NULL));
Assert(predicted_len == actual_len);
Assert(!is_heaptuple_memtuple(tuple));
return tuple;
}
