Обсуждение: Why do we expand tuples in execMain.c?
Hi,
I noticed
if (HeapTupleHeaderGetNatts(tuple.t_data) <
RelationGetDescr(erm->relation)->natts)
{
copyTuple = heap_expand_tuple(&tuple,
RelationGetDescr(erm->relation));
}
else
{
/* successful, copy tuple */
copyTuple = heap_copytuple(&tuple);
}
in EvalPlanQualFetchRowMarks, and I'm somewhat confused why it's there?
If it's required here, why isn't it required in dozens of other places?
Greetings,
Andres Freund
On 08/08/2018 12:20 AM, Andres Freund wrote:
> Hi,
>
> I noticed
> if (HeapTupleHeaderGetNatts(tuple.t_data) <
> RelationGetDescr(erm->relation)->natts)
> {
> copyTuple = heap_expand_tuple(&tuple,
> RelationGetDescr(erm->relation));
> }
> else
> {
> /* successful, copy tuple */
> copyTuple = heap_copytuple(&tuple);
> }
>
> in EvalPlanQualFetchRowMarks, and I'm somewhat confused why it's there?
> If it's required here, why isn't it required in dozens of other places?
>
>
Not dozens, I think, since you can't have short records for catalog
tables, which account for most of the calls to heap_copytuple().
I will look at the remainder of cases (less than 10) and reply in a day
or two.
cheers
andrew
--
Andrew Dunstan https://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
On August 9, 2018 1:33:17 AM GMT+05:30, Andrew Dunstan <andrew.dunstan@2ndquadrant.com> wrote:
>
>
>On 08/08/2018 12:20 AM, Andres Freund wrote:
>> Hi,
>>
>> I noticed
>> if (HeapTupleHeaderGetNatts(tuple.t_data) <
>> RelationGetDescr(erm->relation)->natts)
>> {
>> copyTuple = heap_expand_tuple(&tuple,
>> RelationGetDescr(erm->relation));
>> }
>> else
>> {
>> /* successful, copy tuple */
>> copyTuple = heap_copytuple(&tuple);
>> }
>>
>> in EvalPlanQualFetchRowMarks, and I'm somewhat confused why it's
>there?
>> If it's required here, why isn't it required in dozens of other
>places?
>>
>>
>
>
>
>Not dozens, I think, since you can't have short records for catalog
>tables, which account for most of the calls to heap_copytuple().
>
>I will look at the remainder of cases (less than 10) and reply in a day
>
>or two.
But why is it needed at all, and the deforming code at the site where we access the columns isn't sufficient?
Andres
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
On 08/08/2018 09:15 PM, Andres Freund wrote:
>
> On August 9, 2018 1:33:17 AM GMT+05:30, Andrew Dunstan <andrew.dunstan@2ndquadrant.com> wrote:
>>
>> On 08/08/2018 12:20 AM, Andres Freund wrote:
>>> Hi,
>>>
>>> I noticed
>>> if (HeapTupleHeaderGetNatts(tuple.t_data) <
>>> RelationGetDescr(erm->relation)->natts)
>>> {
>>> copyTuple = heap_expand_tuple(&tuple,
>>> RelationGetDescr(erm->relation));
>>> }
>>> else
>>> {
>>> /* successful, copy tuple */
>>> copyTuple = heap_copytuple(&tuple);
>>> }
>>>
>>> in EvalPlanQualFetchRowMarks, and I'm somewhat confused why it's
>> there?
>>> If it's required here, why isn't it required in dozens of other
>> places?
>>>
>>
>>
>> Not dozens, I think, since you can't have short records for catalog
>> tables, which account for most of the calls to heap_copytuple().
>>
>> I will look at the remainder of cases (less than 10) and reply in a day
>>
>> or two.
> But why is it needed at all, and the deforming code at the site where we access the columns isn't sufficient?
>
Yeah, I think you're right, and this is vestigial code that I neglected
to remove when cleaning up from development.
I'll fix it.
cheers
andrew
--
Andrew Dunstan https://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services