Horton

Re: [HACKERS] UPDATE of partition key

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Amit Khandekar <amitdkhan.pg@gmail.com>
Cc: David Rowley <david.rowley@2ndquadrant.com>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, pgsql-hackers <pgsql-hackers@postgresql.org>, Thomas Munro <thomas.munro@enterprisedb.com>
Date: 2018-01-09T21:00:39Z
Lists: pgsql-hackers 
On Fri, Jan 5, 2018 at 3:25 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> On Fri, Jan 5, 2018 at 7:12 AM, Amit Khandekar <amitdkhan.pg@gmail.com> wrote:
>> The above patch is to be applied over the last remaining preparatory
>> patch, now named (and attached) :
>> 0001-Refactor-CheckConstraint-related-code.patch
>
> Committed that one, too.

Some more comments on the main patch:

I don't really like the fact that ExecCleanupTupleRouting() now takes
a ModifyTableState as an argument, particularly because of the way
that is using that argument.  To figure out whether a ResultRelInfo
was pre-existing or one it created, it checks whether the pointer
address of the ResultRelInfo is >= mtstate->resultRelInfo and <
mtstate->resultRelInfo + mtstate->mt_nplans.  However, that means that
ExecCleanupTupleRouting() ends up knowing about the memory allocation
pattern used by ExecInitModifyTable(), which seems like a slightly
dangerous amount of action at a distance.  I think it would be better
for the PartitionTupleRouting structure to explicitly indicate which
ResultRelInfos should be closed, for example by storing a Bitmapset
*input_partitions.  (Here, by "input", I mean "provided from the
mtstate rather than created by the PartitionTupleRouting structure;
other naming suggestions welcome.)  When
ExecSetupPartitionTupleRouting latches onto a partition, it can do
proute->input_partitions = bms_add_member(proute->input_partitons, i).
In ExecCleanupTupleRouting, it can do if
(bms_is_member(proute->input_partitions, i)) continue.

We have a test, in the regression test suite for file_fdw, which
generates the message "cannot route inserted tuples to a foreign
table".  I think we should have a similar test for the case where an
UPDATE tries to move a tuple from a regular partition to a foreign
table partition.  I'm not sure if it should fail with the same error
or a different one, but I think we should have a test that it fails
cleanly and with a nice error message of some sort.

The comment for get_partitioned_child_rels() claims that it sets
is_partition_key_update, but it really sets *is_partition_key_update.
And I think instead of "is a partition key" it should say "is used in
the partition key either of the relation whose RTI is specified or of
any child relation."  I propose "used in" instead of "is" because
there can be partition expressions, and the rest is to clarify that
child partition keys matter.

create_modifytable_path uses partColsUpdated rather than
partKeyUpdated, which actually seems like better terminology.  I
propose partKeyUpdated -> partColsUpdated everywhere.  Also, why use
is_partition_key_update for basically the same thing in some other
places?  I propose changing that to partColsUpdated as well.

The capitalization of the first comment hunk in execPartition.h is strange.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Avoid referencing off the end of subplan_partition_offsets.

  2. Allow UPDATE to move rows between partitions.

  3. Remove useless lookup of root partitioned rel in ExecInitModifyTable().

  4. Factor error generation out of ExecPartitionCheck.

  5. Minor preparatory refactoring for UPDATE row movement.

  6. Simplify and encapsulate tuple routing support code.

  7. Avoid coercing a whole-row variable that is already coerced.

  8. Use ResultRelInfo ** rather than ResultRelInfo * for tuple routing.

  9. Make RelationGetPartitionDispatchInfo expand depth-first.

  10. Expand partitioned tables in PartDesc order.

  11. Use a real RT index when setting up partition tuple routing.

  12. Fix transition tables for partition/inheritance.

  13. Fix confusion about number of subplans in partitioned INSERT setup.

  14. Prevent BEFORE triggers from violating partitioning constraints.

  15. Fire per-statement triggers on partitioned tables.

  16. Fix reporting of violations in ExecConstraints, again.

  17. Don't scan partitioned tables.

  18. Allow FDWs to push down quals without breaking EvalPlanQual rechecks.