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mirror of https://github.com/postgres/postgres.git synced 2026-10-23 13:29:09 +03:00
Álvaro Herrera 45da2c1d75 Fix REPACK (CONCURRENTLY) for columns added without a table rewrite
When applying the concurrent data changes, REPACK deformed the decoded
tuples with the descriptor of the transient relation.  That descriptor
has no "missing" values, because make_new_heap() gives the transient
relation none of the defaults and constraints of the source relation.  A
tuple written before an ALTER TABLE ... ADD COLUMN that did not rewrite
the table has fewer attributes than the descriptor, so the missing
values came out as NULL, even in a column declared NOT NULL.  If such a
value belongs to the replica identity, the key used to find the target
tuple was NULL too, so the tuple to modify cannot not be found.  The
scan key does not remember that a value is NULL, so a pass-by-reference
key would even crash the comparison function.  Such tuples will be rare,
because new row versions are normally formed with the current
descriptor.  A BEFORE ROW UPDATE trigger returning OLD is one way to
produce one.

Fix by deforming the decoded tuples with the descriptor of the source
relation, which does have the missing values.  Tuples formed with it are
still valid for the transient relation, whose attributes are a copy of
the source relation ones.  Commit 20d3fe9009 took the same approach
for INSERT and UPDATE in the executor.  Expanding the decoded tuple with
heap_expand_tuple() would be the other option, but that is the
workaround of commit ba9f18abd that 20d3fe9009 got rid of, so do not
bring it back.

Add an isolation test.

Author: Sami Imseih <samimseih.pg@gmail.com>
Reported-by: Shihao Zhong <zhong950419@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Backpatch-through: 19
Discussion: https://postgr.es/m/CAN12+Y+NJwr5EqKVrHpPD=5+b_NRAOzU9fhrVDO3H46x2WRxoA@mail.gmail.com
2026-09-25 14:07:59 +02:00
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PostgreSQL Database Management System

This directory contains the source code distribution of the PostgreSQL database management system.

PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.

Copyright and license information can be found in the file COPYRIGHT.

General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.

The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.

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