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IlyaFaer merged 1 commit into from
Aug 18, 2022
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Update README.rst #233

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8 changes: 5 additions & 3 deletions README.rst
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Expand Up @@ -158,12 +158,14 @@ primary key:
)

As Spanner restricts changing a primary key value, not setting the flag
to ``False`` can cause migration problems.
to ``False`` can cause migration problems.

Also notice that DDL statements in Spanner are not transactional and will not be automatically reverted in case of a migration fail.
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@IlyaFaer IlyaFaer Aug 18, 2022 •
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Let's add a small note about DDLs into this section as well to make sure users understand the mechanism


| **Warning!**
| A migration script can produce a lot of DDL statements. If each of the
statements are executed separately, performance issues can occur. To
avoid these, it's highly recommended to use the `Alembic batch
statements is executed separately, performance issues can occur. To
avoid it, it's highly recommended to use the `Alembic batch
context <https://alembic.sqlalchemy.org/en/latest/batch.html>`__
feature to pack DDL statements into groups of statements.

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