Re: Query Performance / Planner estimate off

Thanks for your response Justin.

On 10/22/20 3:48 PM, Justin Pryzby wrote:
> On Thu, Oct 22, 2020 at 09:36:03AM +0200, Mats Olsen wrote:
>> On 10/22/20 8:37 AM, Justin Pryzby wrote:
>>> These look redundant (which doesn't matter for this the query):
>>>
>>> Partition key: RANGE (block_number)
>>> Indexes:
>>> "transactions_block_number_btree" btree (block_number DESC)
>>> "transactions_block_number_hash_key" UNIQUE CONSTRAINT, btree (block_number, hash)
>>> "transactions_block_number_time" btree (hash, block_number)
>>>
>>> Maybe that would be an index just on "hash", which might help here.
>>>
>>> Possibly you'd want to try to use a BRIN index on timestamp (or maybe
>>> block_number?).
>> Yeah this could be a good idea, but the size of this table doesn't let me
>> add any indexes while it's online. I'll revisit these the next time we
>> redeploy the database.
> Why not CREATE INDEX CONCURRENTLY ?
We could, but it would take forever on the `ethereum.transactions` table.
> It seems to me you could add BRIN on all correlated indexes. It's nearly free.
>
> 0.102922715 | Pair_evt_Mint | evt_block_time | f | 0 | -0.56466025 | 10000 | 10001 | 0.964666
> 0.06872191 | Pair_evt_Mint | evt_block_time | f | 0 | -0.8379525 | 500 | 501 | 0.99982
> 0.06872191 | Pair_evt_Mint | evt_block_number | f | 0 | -0.8379525 | 500 | 501 | 0.99982
> 0.032878816 | Pair_evt_Mint | evt_block_number | f | 0 | -0.56466025 | 2500 | 2501 | 0.964666
Agreed, could try to add BRIN's on these.
>
>>> Maybe you'd want to VACUUM the table to allow index-only scan on the hash
>>> columns ?
> Did you try it ? I think this could be a big win.
> Since it's append-only, autovacuum won't hit it (until you upgrade to pg13).

I vacuumed the uniswap_v2."Pair_evt_Mint", but still getting the same
plan, unfortunately.

>