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 <ashutosh.bapat.oss@gmail.com> Reviewed-by: Peter Eisentraut <peter@eisentraut.org> Discussion: https://www.postgresql.org/message-id/flat/CAExHW5uOykuTC+C6R1yDSp=o8Q83jr8xJdZxgPkxfZ1Ue5RRGg@mail.gmail.com
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