Horton

Re: Declarative partitioning - another take

Amit Langote <langote_amit_f8@lab.ntt.co.jp>

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From: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
To: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Date: 2016-08-25T06:52:55Z
Lists: pgsql-hackers 
On 2016/08/22 13:51, Ashutosh Bapat wrote:
> The parent-child relationship of multi-level partitioned tables is not
> retained when creating the AppendRelInfo nodes. We create RelOptInfo nodes
> for all the leaf and intermediate tables. The AppendRelInfo nodes created
> for these RelOptInfos set the topmost table as the parent of all the leaf
> and child tables. Since partitioning scheme/s at each level is/are
> associated with the parent/s at that level, we loose information about the
> immediate parents and thus it becomes difficult to identify which leaf node
> falls where in the partition hierarchy. This stops us from doing any
> lump-sum partition pruning where we can eliminate all the partitions under
> a given parent-partition if that parent-partition gets pruned. It also
> restricts partition-wise join technique from being applied to partial
> partition hierarchy when the whole partitioning scheme of joining tables
> does not match. Maintaining a RelOptInfo hierarchy should not create
> corresponding Append (all kinds) plan hierarchy since
> accumulate_append_subpath() flattens any such hierarchy while creating
> paths. Can you please consider this point in your upcoming patch?

I agree.  So there seem to be two things here:  a) when expanding a
partitioned table inheritance set, do it recursively such that resulting
AppendRelInfos preserve *immediate* parent-child relationship info.  b)
when accumulating append subpaths, do not flatten a subpath that is itself
an append when ((AppendPath *) subpath)->path.parent is a RelOptInfo with
non-NULL partitioning info.  Is the latter somehow necessary for
pairwise-join considerations?

I think I can manage to squeeze in (a) in the next version patch and will
also start working on (b), mainly the part about RelOptInfo getting some
partitioning info.

Thanks,
Amit

Commits

  1. Fix typo.

  2. Document trigger-firing behavior for inheritance/partitioning.

  3. Fire per-statement triggers on partitioned tables.

  4. Set ecxt_scantuple correctly for tuple routing.

  5. Fix interaction of partitioned tables with BulkInsertState.

  6. Avoid core dump for empty prepared statement in an aborted transaction.

  7. Fix some problems in check_new_partition_bound().

  8. Remove unnecessary arguments from partitioning functions.

  9. Fix reporting of constraint violations for table partitioning.

  10. Fix tuple routing in cases where tuple descriptors don't match.

  11. Invalid parent's relcache after CREATE TABLE .. PARTITION OF.

  12. Doc: improve documentation about inheritance.