Prevent ActiveRecord errors when adding columns #725
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
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.
|
lfdebrux
approved these changes
Apr 4, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
What problem does this pull request solve?
Trello card: N/A
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 alphagov/forms-admin#1877).
Things to consider when reviewing