> 2023年9月27日 18:08，Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com> 写道：
>
> On Wed, 27 Sept 2023 at 05:03, jacktby jacktby <jacktby(at)gmail(dot)com <mailto:jacktby(at)gmail(dot)com>> wrote:
>>
>>
>>
>>> 2023年9月27日 00:45，Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com> 写道：
>>>
>>> On Tue, 26 Sept 2023 at 18:38, jacktby jacktby <jacktby(at)gmail(dot)com> wrote:
>>>>
>>>> typedef bool (*aminsert_function) (Relation indexRelation,
>>>> Datum *values,
>>>> bool *isnull,
>>>> ItemPointer heap_tid,
>>>> Relation heapRelation,
>>>> IndexUniqueCheck checkUnique,
>>>> bool indexUnchanged,
>>>> struct IndexInfo *indexInfo);
>>>>
>>>> Why is there a heap_tid, We haven’t inserted the value, so where does it from ?
>>>
>>> Index insertion only happens after the TableAM tuple has been
>>> inserted. As indexes refer to locations in the heap, this TID contains
>>> the TID of the table tuple that contains the indexed values, so that
>>> the index knows which tuple to refer to.
>>>
>>> Note that access/amapi.h describes only index AM APIs; it does not
>>> cover the table AM APIs descibed in access/tableam.h
>>>
>>> Kind regards,
>>>
>>> Matthias van de Meent
>> 1.Thanks, so if we insert a tuple into a table which has a index on itself, pg will insert tuple into heap firstly, and the give the heaptid form heap to the Index am api right?
>
> Correct. I think this is also detailed in various places of the
> documentation, yes.
>
>> 2. I’m trying to implement a new index, but I just need the data held in index table, I hope it’s not inserted into heap, because the all data I want can be in index table.
>
> In PostgreSQL, a table maintains the source of truth for the data, and
> indexes are ephemeral data structures that improve the speed of
> querying the data in their table. As such, dropping an index should
> not impact the availability of the table's data.
> If the only copy of your (non-derived) data is in the index, then it
> is likely that some normal table operations will result in failures
> due to the tableAM/indexAM breaking built-in assumptions about access
> methods and data availability.
>
> Kind regards,
>
> Matthias van de Meent
> Neon (https://neon.tech <https://neon.tech/>)
So do I need to free the ItemPointer and Values in the func implemented by myself?