GIN fast update technique and work_mem

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

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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.

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Amit

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