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RE: Parallel Apply

Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Tomas Vondra <tomas@vondra.me>, Amit Kapila <amit.kapila16@gmail.com>, 'Dilip Kumar' <dilipbalaut@gmail.com>, 'Andrei Lepikhov' <lepihov@gmail.com>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, 'wenhui qiu' <qiuwenhuifx@gmail.com>
Date: 2026-01-30T11:18:07Z
Lists: pgsql-hackers

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Dear Hackers,

Here is a rebased version, plus 0009 patch.

0009 contains changes to handle dependencies based on the foreign keys. Without
this, parallel apply can violate foreign key constraints if referenced tuples
are committed after referencing tuples, leading to replication failures.

This patch extends the dependency hash to track dependencies via FKs. Since
referenced columns must be unique, information must be already stored to the
hash if they have been modified. Based on the point, the leader apply worker
checks to determine whether values in referencing columns have already been
registered or not if applying tuples refer some columns, and regards that there
is a dependency if found.

Best regards,
Hayato Kuroda
FUJITSU LIMITED