On 6th of April 2020, Peter Eisentraut committed patch:
Add logical replication support to replicate into partitioned tables
Mainly, this adds support code in logical/worker.c for applying
replicated operations whose target is a partitioned table to its
Author: Amit Langote <email@example.com>
Reviewed-by: Rafia Sabih <firstname.lastname@example.org>
Reviewed-by: Peter Eisentraut <email@example.com>
Reviewed-by: Petr Jelinek <firstname.lastname@example.org>
Continue reading Waiting for PostgreSQL 13 – Add logical replication support to replicate into partitioned tables
On 3rd of October 2019, Amit Kapila committed patch:
pgbench: add --partitions and --partition-method options.
These new options allow users to partition the pgbench_accounts table by
specifying the number of partitions and partitioning method. The values
allowed for partitioning method are range and hash.
This feature allows users to measure the overhead of partitioning if any.
Author: Fabien COELHO
Continue reading Waiting for PostgreSQL 13 – pgbench: add –partitions and –partition-method options.
On 3rd of April 2019, Alvaro Herrera committed patch:
Support foreign keys that reference partitioned tables
Previously, while primary keys could be made on partitioned tables, it
was not possible to define foreign keys that reference those primary
keys. Now it is possible to do that.
Author: Álvaro Herrera
Continue reading Waiting for PostgreSQL 12 – Support foreign keys that reference partitioned tables
Recently someone asked, on irc, how to make table partitioned.
The thing is that it was supposed to be done with new partitioning, and not the old way.
The problem is that while we can create table that will be seen as partitioned – we can't alter table to become partitioned.
So. Is it possible?
Continue reading Migrating simple table to partitioned. How?
Previously I tested performance of pl/PgSQL coded foreign keys to partitioned table.
Now, let's see if I can make creation of them a bit easier.
Continue reading Foreign Key to partitioned table – part 3
Previously I wrote about how to create foreign key pointing to partitioned table.
Final solution in there required four separate functions and four triggers for each key between two tables.
Let's see how fast it is, and if it's possible to make it simpler.
Continue reading Foreign Key to partitioned table – part 2
On 30th of October 2018, Michael Paquier committed patch:
Add pg_partition_tree to display information about partitions
This new function is useful to display a full tree of partitions with a
partitioned table given in output, and avoids the need of any complex
WITH RECURSIVE query when looking at partition trees which are
deep multiple levels.
It returns a set of records, one for each partition, containing the
partition's name, its immediate parent's name, a boolean value telling
if the relation is a leaf in the tree and an integer telling its level
in the partition tree with given table considered as root, beginning at
zero for the root, and incrementing by one each time the scan goes one
Author: Amit Langote
Continue reading Waiting for PostgreSQL 12 – Add pg_partition_tree to display information about partitions
One of the long standing limitations of partitions is that you can't have foreign keys pointing to them.
Let's see if I can make it possible to have some kind of constraint that would do the same thing as fkey.
Continue reading Foreign Key to partitioned table
On 1st of August 2018, Peter Eisentraut committed patch:
Allow multi-inserts during COPY into a partitioned table
CopyFrom allows multi-inserts to be used for non-partitioned tables, but
this was disabled for partitioned tables. The reason for this appeared
to be that the tuple may not belong to the same partition as the
previous tuple did. Not allowing multi-inserts here greatly slowed down
imports into partitioned tables. These could take twice as long as a
copy to an equivalent non-partitioned table. It seems wise to do
something about this, so this change allows the multi-inserts by
flushing the so-far inserted tuples to the partition when the next tuple
does not belong to the same partition, or when the buffer fills. This
improves performance when the next tuple in the stream commonly belongs
to the same partition as the previous tuple.
In cases where the target partition changes on every tuple, using
multi-inserts slightly slows the performance. To get around this we
track the average size of the batches that have been inserted and
adaptively enable or disable multi-inserts based on the size of the
batch. Some testing was done and the regression only seems to exist
when the average size of the insert batch is close to 1, so let's just
enable multi-inserts when the average size is at least 1.3. More
performance testing might reveal a better number for, this, but since
the slowdown was only 1-2% it does not seem critical enough to spend too
much time calculating it. In any case it may depend on other factors
rather than just the size of the batch.
Allowing multi-inserts for partitions required a bit of work around the
per-tuple memory contexts as we must flush the tuples when the next
tuple does not belong the same partition. In which case there is no
good time to reset the per-tuple context, as we've already built the new
tuple by this time. In order to work around this we maintain two
per-tuple contexts and just switch between them every time the partition
changes and reset the old one. This does mean that the first of each
batch of tuples is not allocated in the same memory context as the
others, but that does not matter since we only reset the context once
the previous batch has been inserted.
Author: David Rowley <email@example.com>
Continue reading Waiting for PostgreSQL 12 – Allow multi-inserts during COPY into a partitioned table
On 10th of June 2018, Tom Lane committed patch:
Improve run-time partition pruning to handle any stable expression.
The initial coding of the run-time-pruning feature only coped with cases
where the partition key(s) are compared to Params. That is a bit silly;
we can allow it to work with any non-Var-containing stable expression, as
long as we take special care with expressions containing PARAM_EXEC Params.
The code is hardly any longer this way, and it's considerably clearer
(IMO at least). Per gripe from Pavel Stehule.
David Rowley, whacked around a bit by me
Continue reading Waiting for PostgreSQL 11 – Improve run-time partition pruning to handle any stable expression.