Re: Declarative partitioning - another take

On Wed, Oct 26, 2016 at 3:04 PM, Amit Langote
<Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> On 2016/10/26 17:57, Amit Kapila wrote:
>> @@ -123,6 +123,9 @@ typedef struct RelationData
>> {
>> ..
>> MemoryContext rd_partkeycxt; /* private memory cxt for the below */
>> struct PartitionKeyData *rd_partkey; /* partition key, or NULL */
>> + MemoryContext rd_pdcxt; /* private context for partdesc */
>> + struct PartitionDescData *rd_partdesc; /* partitions, or NULL */
>> + List *rd_partcheck; /* partition CHECK quals */
>> ..
>> }
>>
>> I think one thing to consider here is the increase in size of relcache
>> due to PartitionDescData. I think it will be quite useful in some of
>> the cases like tuple routing. Isn't it feasible to get it in some
>> other way, may be by using relpartbound from pg_class tuple?
>
> Whereas pg_class.relpartbound stores partition bound of the *individual
> partitions* in Node form, the above relcache struct is associated with
> parent tables; it contains some efficient to use (and fairly compact)
> representation of bounds of *all* the partitions of the parent.
>

Okay, but still it will be proportional to number of partitions and
the partition keys. Is it feasible to store ranges only for
partitions that are actively accessed? For example, consider a table
with 100 partitions and the first access to table requires to access
5th partition, then we store ranges for first five partitions or
something like that. This could be helpful, if we consider cases that
active partitions are much less as compare to total partitions of a
table.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com