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Prevent ActiveRecord errors when adding columns#725
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DavidBiddle merged 1 commit intomainfrom Apr 4, 2025
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Rails uses [prepared statements](https://www.postgresql.org/docs/current/sql-prepare.html) to query the database. By default these use wildcard select statements. This commonly causes issues when adding new columns - the new column will cause postgres to throw an error `cached plan must not change result type`. In Rails 7, a new config setting, `enumerate_columns_in_select_statements`, was added. This replaces the wildcard select statements with explicit calls to each column. See [the Rails PR](rails/rails#41718) for details This means that the prepared statements will be regenerated every time a column is added, so postgres won't throw the error. This PR turns that config setting on for our ActiveRecord models.
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lfdebrux
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Apr 4, 2025
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What problem does this pull request solve?
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Rails uses prepared statements to query the database. By default these use wildcard select statements.
This commonly causes issues when adding new columns - the new column will cause postgres to throw an error cached plan must not change result type`.
In Rails 7, a new config setting,
enumerate_columns_in_select_statements, was added. This replaces the wildcard select statements with explicit calls to each column. See the Rails PR for details.This means that the prepared statements will be regenerated every time a column is added, so postgres won't throw the error.
This PR turns that config setting on for our ActiveRecord models.
We've already done this in forms-admin (see govuk-forms/forms-admin#1877).
Things to consider when reviewing