Обсуждение: Schema design: user account deletion vs. keeping family tree data
Hi,
I’m designing a schema for a family‑tree web app on PostgreSQL. Users register accounts and can create one or more family trees. Each tree consists of persons (the user themself, relatives, ancestors). Many persons in a tree will never have an account (e.g. great‑grandparents). Because of GDPR, when a user deletes their account we must remove/anonymise their user profile, but we want to keep the family tree data intact so that other users can still reference those ancestors.
We expect hundreds of thousands to millions of persons and deep ancestry queries (N generations, inbreeding/relationship calculations).
I’m designing a schema for a family‑tree web app on PostgreSQL. Users register accounts and can create one or more family trees. Each tree consists of persons (the user themself, relatives, ancestors). Many persons in a tree will never have an account (e.g. great‑grandparents). Because of GDPR, when a user deletes their account we must remove/anonymise their user profile, but we want to keep the family tree data intact so that other users can still reference those ancestors.
We expect hundreds of thousands to millions of persons and deep ancestry queries (N generations, inbreeding/relationship calculations).
I’m hesitating between two schema designs:
Option A – Separate family_tree_node table
create table app_user (
id uuid primary key,
email text unique not null,
created_at timestamptz not null default now()
);
create table person (
id uuid primary key,
created_by_user_id uuid references app_user(id) on delete set null,
first_name text,
last_name text,
birth_date date
-- more non-account-specific attributes may be added her in future!
);
create table family_tree (
id uuid primary key,
owner_user_id uuid not null references app_user(id) on delete cascade,
created_at timestamptz not null default now()
);
create table family_tree_node (
id uuid primary key,
family_tree_id uuid not null references family_tree(id) on delete cascade,
person_id uuid references person(id) on delete set null,
father_node_id uuid references family_tree_node(id),
mother_node_id uuid references family_tree_node(id)
);
create index on family_tree_node (family_tree_id);
create index on family_tree_node (person_id);
create index on family_tree_node (father_node_id);
create index on family_tree_node (mother_node_id);
Here family_tree_node is the structural graph for a specific tree. A node may point to a person, but can also exist without one (minimal data only). If a user/account is deleted, we only drop/anonymise data in app_user (and optionally created_by_user_id), while person and family_tree_node remain.
Option B – Use person directly as the graph node (soft delete)
create table app_user (
id uuid primary key,
email text unique not null,
created_at timestamptz not null default now()
);
create table person (
id uuid primary key,
created_by_user_id uuid references app_user(id) on delete set null,
first_name text,
last_name text,
birth_date date,
father_id uuid references person(id),
mother_id uuid references person(id),
deleted_at timestamptz -- soft delete flag
);
create index on person (father_id);
create index on person (mother_id);
create index on person (deleted_at);
In this model, the pedigree graph is just a person(father_id, mother_id). When a user deletes their account we never hard‑delete persons; instead we set deleted_at and/or anonymise some fields. All queries must filter on deleted_at is null to hide soft‑deleted persons.
Question:
From a PostgreSQL point of view (database best practices, data integrity, performance and long‑term maintainability at millions of rows), which approach would you prefer, or is there a better pattern for this kind of “account can be deleted, but genealogy should remain” use case?
Regards and many thanks!
Christoph
 | Christoph Pieper fecra GmbH, Strelitzer Str. 63 10115 Berlin, Deutschland www.fecra.de | HRB 268518 B |
Option B would be fine with me, unless there is good reason to normalize it further. A query using recursive CTE would be able to find ancestors and descendants neatly and efficiently.
I deal with some tables in the billions of rows, and with that hat on, I would use int/bigint identity for the PKs instead of UUIDs (less storage, smaller indices, faster joins). I would have a boolean 'active' column to handle soft deletes, along with created_at and disabled_at timestamptz columns maintained by triggers. I would use composite partitioning, first level partition by list on 'active', and second level partition by range on the id PK with the range being a few million. If for some reason you have to use UUIDs, use time-based UUIDv7 (native on PostgreSQL v18) so you can range partition.
-- regards, Kiriakos Georgiou
On 11/24/25 6:27 AM, Christoph Pieper - christoph at fecra.de wrote:
Hi,
I’m designing a schema for a family‑tree web app on PostgreSQL. Users register accounts and can create one or more family trees. Each tree consists of persons (the user themself, relatives, ancestors). Many persons in a tree will never have an account (e.g. great‑grandparents). Because of GDPR, when a user deletes their account we must remove/anonymise their user profile, but we want to keep the family tree data intact so that other users can still reference those ancestors.
We expect hundreds of thousands to millions of persons and deep ancestry queries (N generations, inbreeding/relationship calculations).I’m hesitating between two schema designs:Option A – Separate family_tree_node table
create table app_user (
id uuid primary key,
email text unique not null,
created_at timestamptz not null default now()
);
create table person (
id uuid primary key,
created_by_user_id uuid references app_user(id) on delete set null,
first_name text,
last_name text,
birth_date date
-- more non-account-specific attributes may be added her in future!
);
create table family_tree (
id uuid primary key,
owner_user_id uuid not null references app_user(id) on delete cascade,
created_at timestamptz not null default now()
);
create table family_tree_node (
id uuid primary key,
family_tree_id uuid not null references family_tree(id) on delete cascade,
person_id uuid references person(id) on delete set null,
father_node_id uuid references family_tree_node(id),
mother_node_id uuid references family_tree_node(id)
);
create index on family_tree_node (family_tree_id);
create index on family_tree_node (person_id);
create index on family_tree_node (father_node_id);
create index on family_tree_node (mother_node_id);
Here family_tree_node is the structural graph for a specific tree. A node may point to a person, but can also exist without one (minimal data only). If a user/account is deleted, we only drop/anonymise data in app_user (and optionally created_by_user_id), while person and family_tree_node remain.Option B – Use person directly as the graph node (soft delete)
create table app_user (
id uuid primary key,
email text unique not null,
created_at timestamptz not null default now()
);
create table person (
id uuid primary key,
created_by_user_id uuid references app_user(id) on delete set null,
first_name text,
last_name text,
birth_date date,
father_id uuid references person(id),
mother_id uuid references person(id),
deleted_at timestamptz -- soft delete flag
);
create index on person (father_id);
create index on person (mother_id);
create index on person (deleted_at);
In this model, the pedigree graph is just a person(father_id, mother_id). When a user deletes their account we never hard‑delete persons; instead we set deleted_at and/or anonymise some fields. All queries must filter on deleted_at is null to hide soft‑deleted persons.
Question:From a PostgreSQL point of view (database best practices, data integrity, performance and long‑term maintainability at millions of rows), which approach would you prefer, or is there a better pattern for this kind of “account can be deleted, but genealogy should remain” use case?Regards and many thanks!Christoph--
Christoph Pieper
fecra GmbH, Strelitzer Str. 63 10115 Berlin, Deutschland
www.fecra.de | HRB 268518 B