On 16th of January 2024, Peter Eisentraut committed patch:
Support identity columns in partitioned tables
Previously, identity columns were disallowed on partitioned tables.
(The reason was mainly that no one had gotten around to working
through all the details to make it work.) This makes it work now.
Some details on the behavior:
* A newly created partition inherits identity property
The partitions of a partitioned table are integral part of the
partitioned table. A partition inherits identity columns from the
partitioned table. An identity column of a partition shares the
identity space with the corresponding column of the partitioned
table. In other words, the same identity column across all
partitions of a partitioned table share the same identity space.
This is effected by sharing the same underlying sequence.
When INSERTing directly into a partition, the sequence associated
with the topmost partitioned table is used to calculate the value of
the corresponding identity column.
In regular inheritance, identity columns and their properties in a
child table are independent of those in its parent tables. A child
table does not inherit identity columns or their properties
automatically from the parent. (This is unchanged.)
* Attached partition inherits identity column
A table being attached as a partition inherits the identity property
from the partitioned table. This should be fine since we expect
that the partition table's column has the same type as the
partitioned table's corresponding column. If the table being
attached is a partitioned table, the identity properties are
propagated down its partition hierarchy.
An identity column in the partitioned table is also marked as NOT
NULL. The corresponding column in the partition needs to be marked
as NOT NULL for the attach to succeed.
* Drop identity property when detaching partition
A partition's identity column shares the identity space
(i.e. underlying sequence) as the corresponding column of the
partitioned table. If a partition is detached it can longer share
the identity space as before. Hence the identity columns of the
partition being detached loose their identity property.
When identity of a column of a regular table is dropped it retains
the NOT NULL constraint that came with the identity property.
Similarly the columns of the partition being detached retain the NOT
NULL constraints that came with identity property, even though the
identity property itself is lost.
The sequence associated with the identity property is linked to the
partitioned table (and not the partition being detached). That
sequence is not dropped as part of detach operation.
* Partitions with their own identity columns are not allowed.
* The usual ALTER operations (add identity column, add identity
property to existing column, alter properties of an indentity
column, drop identity property) are supported for partitioned
tables. Changing a column only in a partitioned table or a
partition is not allowed; the change needs to be applied to the
whole partition hierarchy.
Author: Ashutosh Bapat <email@example.com>
Reviewed-by: Peter Eisentraut <firstname.lastname@example.org>
Continue reading Waiting for PostgreSQL 17 – Support identity columns in partitioned tables
A while ago someone wrote on irc that PostgreSQL has built in hard limit to number of partitions. This tweet was linked as a source of this information.
Decided to check it.
Continue reading Are there limits to partition counts?
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 18th of March 2020, Alvaro Herrera committed patch:
Enable BEFORE row-level triggers for partitioned tables
... with the limitation that the tuple must remain in the same
Reviewed-by: Ashutosh Bapat
Continue reading Waiting for PostgreSQL 13 – Enable BEFORE row-level triggers for 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
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