Thread: GIN fast update technique and work_mem

Hi,

While going through the documentation for GIN fast update technique, I read -

"...or if the pending list becomes too large (larger than work_mem),
the entries are moved to the main GIN data structure using the same
bulk insert techniques used during initial index creation."

The "work_mem" links to work_mem setting documentation.

Whereas in the src/backend/access/gin/README, as one of the features
of GIN, I read  -

"...* Optimized index creation (Makes use of maintenance_work_mem to accumulate
    postings in memory.)"

So, which one is it - work_mem or maintenance_work_mem?

Or are these things unrelated?


--
Amit

On 2013-10-24 18:40:46 +0900, Amit Langote wrote:
> While going through the documentation for GIN fast update technique, I read -
>
> "...or if the pending list becomes too large (larger than work_mem),
> the entries are moved to the main GIN data structure using the same
> bulk insert techniques used during initial index creation."
>
> The "work_mem" links to work_mem setting documentation.
>
> Whereas in the src/backend/access/gin/README, as one of the features
> of GIN, I read  -
>
> "...* Optimized index creation (Makes use of maintenance_work_mem to accumulate
>     postings in memory.)"
>
> So, which one is it - work_mem or maintenance_work_mem?
>
> Or are these things unrelated?

Yes. One is about the initial index creation, the other about insertions
into an existing index.

Greetings,

Andres Freund

--
 Andres Freund                       http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

On Thu, Oct 24, 2013 at 7:26 PM, Andres Freund <andres@2ndquadrant.com> wrote:
> On 2013-10-24 18:40:46 +0900, Amit Langote wrote:
>> While going through the documentation for GIN fast update technique, I read -
>>
>> "...or if the pending list becomes too large (larger than work_mem),
>> the entries are moved to the main GIN data structure using the same
>> bulk insert techniques used during initial index creation."
>>
>> The "work_mem" links to work_mem setting documentation.
>>
>> Whereas in the src/backend/access/gin/README, as one of the features
>> of GIN, I read  -
>>
>> "...* Optimized index creation (Makes use of maintenance_work_mem to accumulate
>>     postings in memory.)"
>>
>> So, which one is it - work_mem or maintenance_work_mem?
>>
>> Or are these things unrelated?
>
> Yes. One is about the initial index creation, the other about insertions
> into an existing index.
>
> Greetings,
>

Hmm, okay. So, work_mem allocations are also involved in case of GIN
index updates (if FASTUPDATE is on)?

Thanks.

--
Amit