Horton

Re: [HACKERS] UPDATE of partition key

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: Amit Khandekar <amitdkhan.pg@gmail.com>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, Robert Haas <robertmhaas@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-11-14T16:52:05Z
Lists: pgsql-hackers 
David Rowley wrote:

> 5. Triggers. Do we need a new "TG_" tag to allow trigger functions to
> do something special when the DELETE/INSERT is a partition move? I
> have audit tables in mind here it may appear as though a user
> performed a DELETE when they actually performed an UPDATE giving
> visibility of this to the trigger function will allow the application
> to work around this.

+1  I think we do need a flag that can be inspected from the user
trigger function.

> 9. Also, this should likely be reworded:
> 
>  * 'num_update_rri' : number of UPDATE per-subplan result rels. For INSERT,
>  *      this is 0.
> 
>  'num_update_rri' number of elements in 'update_rri' array or zero for INSERT.

Also:

/pgsql/source/master/src/backend/executor/execMain.c: In function 'ExecSetupPartitionTupleRouting':
/pgsql/source/master/src/backend/executor/execMain.c:3401:18: warning: 'leaf_part_arr' may be used uninitialized in this function [-Wmaybe-uninitialized]
    leaf_part_rri = leaf_part_arr + i;
    ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~

I think using num_update_rri==0 as a flag to indicate INSERT is strange.
I suggest passing an additional boolean -- or maybe just split the whole
function in two, one for updates and another for inserts, say
ExecSetupPartitionTupleRoutingForInsert() and
ExecSetupPartitionTupleRoutingForUpdate().  They seem to
share almost no code, and the current flow is hard to read; maybe just
add a common subroutine for the lower bottom of the loop.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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.