Re: why partition pruning doesn't work?

David Rowley <david.rowley@2ndquadrant.com>

From: David Rowley <david.rowley@2ndquadrant.com>

To: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>

Cc: Dmitry Dolgov <9erthalion6@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Jeff Janes <jeff.janes@gmail.com>, Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>, Pavel Stehule <pavel.stehule@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2018-06-06T09:52:04Z

Lists: pgsql-hackers

Attachments

run-time_pruning_for_exprs_v3.patch (application/octet-stream) patch v3

On 6 June 2018 at 18:05, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> wrote:
> On 2018/06/06 14:10, David Rowley wrote:
>> I then decided that
>> I didn't like the way we need to check which params are in the Expr
>> each time we call partkey_datum_from_expr. It seems better to prepare
>> this in advance when building the pruning steps. I started work on
>> that, but soon realised that I'd need to pass a List of Bitmapsets to
>> the executor. This is a problem as Bitmapset is not a Node type and
>> cannot be copied with COPY_NODE_FIELD(). Probably this could be
>> refactored to instead of passing 3 Lists in the PartitionPruneStepOp
>> we could invent a new node type that just has 3 fields and store a
>> single List.
>
> I wonder why we need to create those Bitmapsets in the planner?  Why not
> in ExecSetupPartitionPruneState()?  For example, like how
> context->exprstates is initialized.

That seems like a good idea.  Certainly much better than working them
out each time we prune.

v3 patch attached.

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

Commits

Fix up run-time partition pruning's use of relcache's partition data.
- e23bae82cf3d 11.0 landed
Fix access to just-closed relcache entry.
- bdc643e5e46f 11.0 landed
- b10edaf4bb44 10.5 landed
Improve ExecFindInitialMatchingSubPlans's subplan renumbering logic.
- 69025c5a07a1 11.0 landed
Improve commentary about run-time partition pruning data structures.
- 4e2323640333 11.0 landed
Fix run-time partition pruning code to handle NULL values properly.
- be3d90026a3c 11.0 landed
Assorted cosmetic cleanup of run-time-partition-pruning code.
- 321f648a312b 11.0 landed
Relocate partition pruning structs to a saner place.
- 939449de0e57 11.0 landed
Improve run-time partition pruning to handle any stable expression.
- 73b7f48f78d2 11.0 landed
Support partition pruning at execution time
- 499be013de65 11.0 cited