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: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, pgsql-hackers <pgsql-hackers@postgresql.org>, Thomas Munro <thomas.munro@enterprisedb.com>
Date: 2018-01-15T12:09:40Z
Lists: pgsql-hackers 
On Sun, Jan 14, 2018 at 6:57 AM, Amit Khandekar <amitdkhan.pg@gmail.com> wrote:
> Even where partitions are present, in the usual case where there are
> no transition tables we won't require per-leaf map at all [1]. So I
> think we should keep mt_per_sub_plan_maps only for the case where
> per-leaf map is not allocated. And we will not allocate
> mt_per_sub_plan_maps when mt_per_leaf_maps is needed. In other words,
> exactly one of the two maps will be allocated.
>
> This is turning out to be close to what's already there in the last
> patch versions: use a single map array, and an offsets array. The
> difference is : in the patch I am using the *same* variable for the
> two maps. Where as, now we are talking about two different array
> variables for maps, but only allocating one of them.
>
> Are you ok with this ? I think the thing you were against was to have
> a common *variable* for two purposes. But above, I am saying we have
> two variables but assign a map array to only *one* of them and leave
> the other unused.

Yes, I'm OK with that.

> Regarding the on-demand map allocation ....
> Where mt_per_sub_plan_maps is allocated, we won't have the on-demand
> allocation: all the maps will be allocated initially. The reason is
> becaues the map_is_required array is only per-leaf. Or else, again, we
> need to keep another map_is_required array for per-subplan. May be we
> can support the on-demand stuff for subplan maps also, but only as a
> separate change after we are done with update-partition-key.

Sure.

> Regarding mt_per_leaf_tupconv_required, I am thinking we can make it a
> bool array, and name it : mt_per_leaf_map_not_required. When it is
> true for a given index, it means, we have already called
> convert_tuples_by_name() and it returned NULL; i.e. it means we are
> sure that map is not required. A false value means we need to call
> convert_tuples_by_name() if it is NULL, and then set
> mt_per_leaf_map_not_required to (map == NULL).

OK.

> Instead of a bool array, we can even make it a Bitmapset. But I think
> access would become slower as compared to array, particularly because
> it is going to be a heavily used function.

It probably makes little difference -- the Bitmapset will be more
compact (which saves time) but involve function calls (which cost
time).

-- 
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.