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[Uid] Add a caution message about using UUIDs as primary keys #19783

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Apr 15, 2024
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[Uid] Add a caution message about using UUIDs as primary keys #19783

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16 changes: 15 additions & 1 deletion components/uid.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -344,6 +344,14 @@ entity primary keys::
// ...
}

.. caution::

Using UUIDs as primary keys is usually not recommended for performance reasons:
indexes are slower and take more space (because UUIDs in binary format take 128 bits
instead of 32/64 bits for auto-incremental integers) and the non-sequential nature of
UUIDs fragments indexes. UUID v7 is the only variant that solves the fragmentation
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WDYT to add anchor link on UUUD v7 ?

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Good idea! I did this while merging. Thanks.

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UUIDv6 are also fine from a fragmentation PoV

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I've updated the docs here: 2cbc55e Thanks!

issue (but the index size issue remains).

When using built-in Doctrine repository methods (e.g. ``findOneBy()``), Doctrine
knows how to convert these UUID types to build the SQL query
(e.g. ``->findOneBy(['user' => $user->getUuid()])``). However, when using DQL
Expand Down Expand Up @@ -530,9 +538,15 @@ entity primary keys::
}

// ...

}

.. caution::

Using ULIDs as primary keys is usually not recommended for performance reasons.
Although ULIDs don't suffer from index fragmentation issues (because the values
are sequential), their indexes are slower and take more space (because ULIDs
in binary format take 128 bits instead of 32/64 bits for auto-incremental integers).

When using built-in Doctrine repository methods (e.g. ``findOneBy()``), Doctrine
knows how to convert these ULID types to build the SQL query
(e.g. ``->findOneBy(['user' => $user->getUlid()])``). However, when using DQL
Expand Down
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